Men: Your Biological Clocks are Ticking

Men: Your Biological Clocks are Ticking!
by Whitney Rhodes on January 30, 2010

For many years, it was tacitly assumed that while women have a “Sell By” date when it comes to fertility, men become fertile at puberty and remain so until a ripe old age.

Actually, although there is some truth in that myth, to the extent that males do not have a hormonal menopause as women do; the fact is that fertility in men does begin to decline after a certain age.

Men don’t completely stop being fertile at any age.

However, older fathers are prone to problems that younger fathers usually don’t experience.

What are Some of the Problems Experienced by Older Fathers?

A study that was conducted recently at the University of California, Berkeley, on a test group of men aged 22 to 80 showed that the sperm of older men are fewer in number with less mobility, as well as being less able to move in a straight line.

This research also showed an increased risk of achondroplasia, a genetic mutation that produces a kind of dwarfism.

Nor was this the only risk.

Older fathers were shown to have an increased risk of siring children with autism, or who were mentally retarded, or have behavioral problems with conditions such as schizophrenia.

Downs Syndrome, although associated with older mothers, doesn’t seem so far to be one of the risks of older fathers, but testing is still in progress.

It is believed that many times, male fertility problems caused by age and/or a medical condition might be mistaken as a potency issue, and mistakenly treated with a prescription for Viagra or a similar medication.

Investigating male infertility, and research of male sperm is gaining much new ground these days, as specialists recognize that infertility is not any more likely to rest with the female half of a couple than the male.

Today, more than ever, men and women alike are waiting longer to start families. This has given rise to an increasing frequency of fertility problems encountered with older parents.

So, although men are never completely infertile due to age, research has shown that the quality and quantity of sperm decrease with age.

Advanced paternal age is associated with alterations in discrete behavioural domains and cortical neuroanatomy of C57BL/6J mice.

Eur J Neurosci. 2010 Jan 25. [Epub ahead of print]

Advanced paternal age is associated with alterations in discrete behavioural domains and cortical neuroanatomy of C57BL/6J mice.
Foldi CJ, Eyles DW, McGrath JJ, Burne TH.

Queensland Brain Institute, The University of Queensland, St Lucia, Qld 4072, Australia.

Abstract Advanced paternal age (APA) is associated with an increased risk of neurodevelopmental disorders such as autism and schizophrenia. A previous study in mice suggested that the offspring of aged sires have altered locomotion and avoidance learning. The aim of the current study was to conduct a comprehensive behavioural screen in adult offspring of mice of APA. We also examined brain morphology in neonate and adult mice. The adult offspring of 12- to18-month-old (APA) and 4-month-old (control) male C57BL/6J mice underwent a behavioural test battery comprising tests for locomotion, anxiety, exploration, social behaviour, learned helplessness and sensorimotor gating. The brains of these mice were collected at 3 months and imaged ex vivo using a 16.4T MRI scanner to assess gross neuroanatomy. Neuroanatomy was also examined at birth in a separate cohort of animals. Overall, the APA mouse model was associated with subtle behavioural changes and altered cortical morphology. The behavioural phenotype of female APA mice included increased anxiety-related behaviour, increased exploration and decreased learned helplessness compared to control females. Male APA mice had thinner cortices at birth and increased cortical volume as adults. This animal model may assist in exploring the mechanism of action linking APA with disorders such as schizophrenia and autism.

PMID: 20105239 [PubMed - as supplied by publisher]

Our findings suggest that paternal age may be a risk factor for some multifactorial birth defects

Ann Epidemiol. 2010 Jan 5. [Epub ahead of print]

Association of Paternal Age and Risk for Major Congenital Anomalies From the National Birth Defects Prevention Study, 1997 to 2004.
Green RF, Devine O, Crider KS, Olney RS, Archer N, Olshan AF, Shapira SK; The National Birth Defects Prevention Study.

National Center on Birth Defects and Developmental Disabilities; Centers for Disease Control and Prevention; Atlanta, GA (R.F.G., O.D., K.S.C., R.S.O., S.K.S.); Texas Department of State Health Services; Austin, TX (N.A.); and Department of Epidemiology; University of North Carolina; Chapel Hill, NC (A.F.O.).

PURPOSE: The objective of this study was to examine the associations between paternal age and birth defects of unknown etiologies while carefully controlling for maternal age. METHODS: By using 1997 to 2004 data from the National Birth Defects Prevention Study, we fit logistic regression models with paternal and maternal age as continuous variables while adjusting for demographic and other factors. RESULTS: Elevated odds ratios (ORs) for each year increase in paternal age were found for cleft palate (OR. 1.02, 95% confidence interval [95% CI], 1.00-1.04), diaphragmatic hernia (OR, 1.04; 95% CI, 1.02-1.06), right ventricular outflow tract obstruction (OR, 1.03; 95% CI, 1.01-1.04), and pulmonary valve stenosis (OR, 1.02, 95% CI, 1.01-1.04). At younger paternal ages, each year increase in paternal age correlated with increased odds of having offspring with encephalocele, cataract, esophageal atresia, anomalous pulmonary venous return, and coarctation of the aorta, but these increased odds were not observed at older paternal ages. The effect of paternal age was modified by maternal age for gastroschisis, omphalocele, spina bifida, all orofacial clefts, and septal heart defects. CONCLUSIONS: Our findings suggest that paternal age may be a risk factor for some multifactorial birth defects. Published by Elsevier Inc.

PMID: 20056435 [PubMed - as supplied by publisher]

Paternal Age and Schizophrenia

Paternal Age and Schizophrenia
Research Date:
03/23/2006
An Expert Interview with Dolores Malaspina, M.D., M.P.H.

Great Neck, NY - March 23, 2006) — Scientists have linked paternal age to genetic diseases since the 1950s, and some have suggested an association between the age of the father and the risk for schizophrenia. In 2001, Dolores Malaspina, M.D., M.P.H., and her colleagues reported their research identifying a relationship between paternal age and the occurrence of schizophrenia. On behalf of Medscape* Jessica Gould interviewed Dr. Malaspina, Professor of Clinical Psychiatry at Columbia University and Research Psychiatrist at New York State Psychiatric Institute in New York City. Dr. Malaspina elaborates on her research and speaks about new directions in genetic research on schizophrenia. (NARSAD NOTE: Dr. Malaspina was a NARSAD 1993 and 1995 Young Investigator and a 2001 Independent Investigator.)

Medscape: Tell me about your research on paternal age and schizophrenia.

Dolores Malaspina: I have been compelled by the idea that schizophrenia is not a single disease. The consensus in the field is that schizophrenia is a syndrome, and a syndrome is a collection of different disorders. Yet there is still some controversy over whether or not there are variants of schizophrenia that might have separate causes and respond differently to various medications.

Since beginning my research in the late 1980s, I have focused on this heterogeneity, and one way that I've done that is by examining aspects of the disease in people who come from densely affected families, where two or more relatives have schizophrenia, and comparing them with cases of schizophrenia that have no family history of any chronic psychosis.

Now, in genetic research, it's known that for human genetic diseases, when a new case presents itself in a family, the mutation almost always arises during spermatogenesis. We have known for almost 100 years that the late born children in a family have more new genetic diseases. In the 1950s, a scientist named Penrose showed that only the age of the father predicts these genetic diseases. Over the last decade, it was shown that the risk for many complex genetic diseases was also correlated with paternal age. I thought that if schizophrenia cases with no family history were due to new genetic events, maybe they would also be correlated with the father's age.

I have the good fortune to be funded by the National Institutes of Health to study a very special birth cohort in Israel of about 100,000 pregnancies. We have a rich amount of demographic and clinical data on the parents, including the age of the father. The analysis showed what we considered to be a striking effect of the age of the father on the risk for schizophrenia.

Medscape: Could you tell me more about this group of research subjects from Israel?

Dr. Malaspina: The offspring were born between 1964 and 1976, and the original birth cohort was designed to examine the health of women during pregnancy as well as fetal outcomes. Israel maintains a high-quality psychiatric case registry. Working with the people at the Ministry of Health in Israel, my colleagues linked the birth cohort data to the psychiatric case registry data. The results showed that the risk of schizophrenia was tripled for the offspring of the oldest group of fathers.

We found that paternal age explained over a quarter of the risk for schizophrenia in the population. At the time, people were skeptical. But the findings have been replicated many times now, and not a single study has failed to find this strong relationship between father's age and the risk for schizophrenia. And at this point, other explanations for the relationship have been ruled out, including social factors in the family, prenatal care, and parental psychiatric ailments. There simply seems to be a relationship between paternal age and schizophrenia risk.

Medscape: Can you explain why the relationship between paternal age and schizophrenia exists?

Dr. Malaspina: When Penrose found that paternal age predicted new human genetic diseases, he proposed the Copy Error Theory. He said that each time the spermatozoa are copied there's an opportunity for a new mutation. Sperm cells divide every 16 days after puberty, so the DNA in the sperm of a 20-year-old father has been copied 100 times, but sperm DNA from a 50-year-old father has been copied more than 800 times. By comparison, egg cells from the mother only undergo a few dozen cell divisions all together. It is clear that there are many more opportunities for mutations to occur during spermatogenesis and that these increase with the age of the father. That is why new mutations are introduced in mammals in proportion to paternal age.

To further establish that paternal age is associated with schizophrenia risk, we went back to examine if paternal age is related to other factors associated with schizophrenia risk. We looked at intellectual functioning at age 17 in our birth cohort. Those data were available because adolescents in Israel are screened for military service. Working with personnel at the Israeli Defense Force, we examined whether intelligence was related to paternal age. And what we found was a very strong specific effect of paternal age on performance IQ. Very young mothers and very old mothers had offspring with impairments in verbal and performance intelligence. While there was no effect of late fathers' age on verbal IQ, there was a strong effect on performance intelligence, or nonverbal intelligence, which we have published.

In a parallel study, we examined the effect of late paternal age in a mouse model. Working with my colleague, Jay Gingrich, we studied several cohorts of inbred mice to compare offspring with younger and older fathers. The mouse model demonstrated striking effects of paternal age on the behavior of mice.

Those three lines of evidence provide converging data that paternal age does influence neural functioning and that paternal age is a plausible risk factor for schizophrenia.

Medscape: Could you describe what is meant by sporadic schizophrenia and how that relates to paternal age?

Dr. Malaspina: This goes along with the issue of whether schizophrenia is one single disease or several different variants, several different diseases. If it is several diseases, we could make much more progress if we knew how to separate individuals who have one variant of the disease from individuals who have the other variant, such as for treatment studies.

So, we have this finding that father's age predicts schizophrenia, but we don't know if the genetic changes are in the same genes that cause familial schizophrenia or if they occur at a different place. Some of the birth cohorts have actually looked to see how the risk of schizophrenia with paternal age is related to the family history of schizophrenia. The finding is that father's age is not connected to the risk of schizophrenia when it runs in families, but only for cases with no family history. That is called sporadic schizophrenia.

We have also looked at patients, with the help of funding from the National Alliance for Research on Schizophrenia and Depression, and we have examined whether or not cases with late paternal age and no family history have different symptoms and brain abnormalities from those of other cases. That work is under way.

Medscape: You also looked at the duration of the parents' marriage.

Dr. Malaspina: Yes, and we found that the duration of marriage was protective against the risk for schizophrenia. This goes in the opposite direction of paternal age, but it's an independent factor. Couples that have a very long marriage are less likely to have offspring with schizophrenia. One possibility is that parents who have mental disorders themselves may have shorter marriages. Another possibility is that there is an increased risk of schizophrenia when there is a marital separation.

Medscape: A variety of environmental factors can influence the development of schizophrenia. How do you control for that?

Dr. Malaspina: On the one hand, there may be scores of different intrauterine exposures that increase the risk for schizophrenia through different pathways. Another possibility, though, is that there are only a few final common pathways through which various intrauterine adversities are linked to the risk for schizophrenia.

The Barker hypothesis deals with the area of fetal programming. Research shows that the risk for many adult-onset chronic diseases, such as cardiovascular disease, obesity, diabetes, and hypertension, is related to fetal development. The mechanism may be that an adverse fetal environment compromises the development of organs and tissues and changes lifelong gene expression. The fetus survives, but its health is compromised. Effects on the developing nervous system could contribute to schizophrenia risk. So that's a possible pathway for the risk for schizophrenia, through a variety of prenatal exposures.

The benefit of our study in Israel is that we had such a wealth of obstetric data. The birth cohort involved early pregnancy interviews with the mom. It also involved evaluations of the progress of the pregnancy and records of the delivery. Our study was able to show that other prenatal exposures did not explain the linkage of paternal age to the risk of schizophrenia. Also, there have been many excellent studies after ours was conducted that have looked at numerous fetal exposures and found that those also do not explain the risk of paternal age for schizophrenia.

I do, however, believe that many fetal exposures can increase the risk of schizophrenia. I would suggest that the mechanism of these events may be via changes in lifelong gene expression.

Medscape: What about the influence of environmental factors after birth, during childhood and adolescence?

Dr. Malaspina: I think three of the interesting factors that have been linked to the risk of schizophrenia are severe stress in a stress-sensitive person who has underlying genes for schizophrenia, traumatic brain injury in those with underlying genes for schizophrenia, and, very importantly, cannabis exposure in early adolescence.

Medscape: Your research about paternal age became public in 2001. Do you think fewer men over a certain age might choose to have children as a result?

Dr. Malaspina: I haven't heard that. I would personally not discourage anyone from having a child at any age. People weigh their own risks. For the offspring of older fathers, the risk of schizophrenia is about 3 percent. That means that 97percent of the offspring do not have schizophrenia. Other cognitive diseases linked to paternal age include mental retardation of unknown etiology and Alzheimer's disease, and there is a strong relationship between paternal age and autism.

Medscape: What do you expect to be the future of your research in this area?

Dr. Malaspina: The genes for schizophrenia that we have identified lately are very interesting; they explain a large degree of the risk of the disease. Attention probably should turn toward factors that affect the expression of these genes and other genes. This is the area of epigenetics, the code that determines whether or not genes will be expressed.

We're pursuing a gene expression hypothesis for paternal age and schizophrenia. Humans have dozens or hundreds of genes that are expressed, not on the basis of being dominant or recessive, but on the basis of which parent we have inherited them from. So genes that control the growth of the fetus tend to be expressed on the basis of inheritance from the father. Other genes are expressed only on the basis of inheritance from the mother. These are called "parent of origin genes" or "parentally-imprinted genes." In these genes, the father's copy is expressed and the mother's is silenced, or vice versa. We are interested in this mechanism of gene-silencing. For the male parent, the silencing, or the activation/expression of genes from dad, takes place late in spermatogenesis. So our hypothesis and model right now for how paternal age affects the risk for schizophrenia is that it has altered the expression of genes inherited from the father.

Even exposures that interact with genetic susceptibility may act by changing gene expression, such as traumatic brain injury, cannabis, and stress. Maybe we can integrate our understanding of the many exposures tied to schizophrenia and the many genes tied to schizophrenia with the understanding that certain exposures may act by changing gene expression.

Meanwhile, some individuals who develop schizophrenia have a good outcome and stability without much deterioration -- but not as many as we would like. If we can't prevent the disease, perhaps we can learn the risk factors for deterioration and how to prevent it.

Although I see schizophrenia as a syndrome of separate illness variants, I think the field has benefited from considering it as a single disease. From here forwards, we may be diluting our ability to find risk factors and optimize outcome by considering the disease as a whole. To go forward in schizophrenia, we need to better understand how similar symptoms may arise from abnormalities in different neural circuits; that the set of symptoms we call schizophrenia could reflect a common pathway, but that the underlying biology may differ for groups of people, and that those differences may explain which medications they should receive, or which factors are more adverse for them. I think the field needs to move toward a finer understanding of the variants that exist. The identified genes may be clearly explanatory for some cases but not for others.

Funding Information

This interview is published in collaboration with NARSAD: The Mental Health Research Association, and is supported by an educational grant from Pfizer.

Dolores Malaspina, M.D., Professor of Clinical Psychiatry, Columbia University, New York, NY;
Director of Clinical Neurobiology, New York State Psychiatric Institute and Columbia University Medical Center, New York, N.Y.

Disclosure: Jessica Gould has disclosed no relevant financial relationships.

Disclosure: Dolores Malaspina, MD, has disclosed no relevant financial relationships.

*Reprinted with permission from Medscape Psychiatry & Mental Health 2006:11(1) http://www.medscape.com/viewarticle/520009 © 2006, Medscape. Please be advised that Medscape requires free registration to view articles.

Advancing Paternal Age Is Associated with Deficits in Social and Exploratory Behaviors in the Offspring: A Mouse Model

Open Access

Research Article

Advancing Paternal Age Is Associated with Deficits in Social and Exploratory Behaviors in the Offspring: A Mouse Model

Accumulating evidence from epidemiological research has demonstrated an association between advanced paternal age and risk for several psychiatric disorders including autism, schizophrenia and early-onset bipolar disorder. In order to establish causality, this study used an animal model to investigate the effects of advanced paternal age on behavioural deficits in the offspring.

C57BL/6J offspring (n = 12 per group) were bred from fathers of two different ages, 2 months (young) and 10 months (old), and mothers aged 2 months (n = 6 breeding pairs per group). Social and exploratory behaviors were examined in the offspring.

The offspring of older fathers were found to engage in significantly less social (p = 0.02) and exploratory (p = 0.02) behaviors than the offspring of younger fathers. There were no significant differences in measures of motor activity.

Given the well-controlled nature of this study, this provides the strongest evidence for deleterious effects of advancing paternal age on social and exploratory behavior. De-novo chromosomal changes and/or inherited epigenetic changes are the most plausible explanatory factors.


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Abstract
Introduction
Results
Discussion
Methods
Author Contributions
References
Rebecca G. Smith1#, Rachel L. Kember1#, Jonathan Mill1, Cathy Fernandes2*, Leonard C. Schalkwyk1, Joseph D. Buxbaum3,4, Abraham Reichenberg1,3

1 Medical Research Council Social Genetic and Developmental Psychiatry Centre, King's College London, London, United Kingdom, 2 Department of Psychological Medicine and Psychiatry, King's College London, London, United Kingdom, 3 Department of Psychiatry, Mount Sinai School of Medicine, New York, New York, United States of America, 4 Laboratory of Molecular Neuropsychiatry, and the Seaver Autism Center for Research and Treatment, Mount Sinai School of Medicine, New York, New York, United States of America

Abstract Top
Background
Accumulating evidence from epidemiological research has demonstrated an association between advanced paternal age and risk for several psychiatric disorders including autism, schizophrenia and early-onset bipolar disorder. In order to establish causality, this study used an animal model to investigate the effects of advanced paternal age on behavioural deficits in the offspring.

Methods
C57BL/6J offspring (n = 12 per group) were bred from fathers of two different ages, 2 months (young) and 10 months (old), and mothers aged 2 months (n = 6 breeding pairs per group). Social and exploratory behaviors were examined in the offspring.

Principal Findings
The offspring of older fathers were found to engage in significantly less social (p = 0.02) and exploratory (p = 0.02) behaviors than the offspring of younger fathers. There were no significant differences in measures of motor activity.

Conclusions
Given the well-controlled nature of this study, this provides the strongest evidence for deleterious effects of advancing paternal age on social and exploratory behavior. De-novo chromosomal changes and/or inherited epigenetic changes are the most plausible explanatory factors.

Citation: Smith RG, Kember RL, Mill J, Fernandes C, Schalkwyk LC, et al. (2009) Advancing Paternal Age Is Associated with Deficits in Social and Exploratory Behaviors in the Offspring: A Mouse Model. PLoS ONE 4(12): e8456. doi:10.1371/journal.pone.0008456

Editor: Kenji Hashimoto, Chiba University Center for Forensic Mental Health, Japan


Received: October 28, 2009; Accepted: December 2, 2009; Published: December 30, 2009

Copyright: © 2009 Smith et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: This study was supported by the Beatrice and Samuel A. Seaver Foundation, by a British Medical Association Margaret Temple Award, and National Institute of Health Research (NIHR) Biomedical Research Centre (BRC) for Mental Health at the South London and Maudsley National Health Service (NHS) Foundation Trust and Institute of Psychiatry, King's College London (KCL) Pilot Award to Drs. Jonathan Mill and Abraham (Avi) Reichenberg. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

* E-mail: cathy.fernandes@kcl.ac.uk

# These authors contributed equally to this work.

Introduction Top
Accumulating evidence from epidemiological research has demonstrated an association between advanced paternal age and risk for several psychiatric disorders including autism [1], schizophrenia [2] and early-onset bipolar disorder [3]. Despite the methodological advantages of epidemiological research, a major limitation is that techniques are limited to observation. In order to establish causality, experimental evidence in the form of randomized-controlled trials or the development of animal models is required [4]. Animal models are particularly important as they allow environmental and genetic confounds to be controlled.

The lack of complete specificity in the association between advancing paternal age and psychiatric disorders may suggest that advancing paternal age is related to phenotypes shared across disorders. One phenotype in-common to schizophrenia, autism and bipolar disorder is abnormalities in social cognition broadly defined severe social deficit [5], [6], [7], [8]. A recent epidemiological study found an association between advancing paternal age and impaired social functioning in male offspring in the general population [9].

In this study we examined the effect of older paternal age on social and non-social behavior in mice. To the best of our knowledge this is the first fully-controlled animal study of the effects of paternal age on these behaviors.

Results Top
Social Behavior
Offspring of old fathers engaged in less social activity than the offspring of young fathers, spending less time socially-interacting with the conspecific mice (t = 2.23, d.f. = 22, p = 0.02, one-tailed test, Figure 1). This result was consistently observed across all measures of social behavior. There were no significant differences in overall locomotor activity.

Figure 1. Results of social behavioral data from male offspring of young fathers (n = 12) and old fathers (n = 12).

* shows a p-value of less than 0.05, † shows p-value of 0.06. A. Mean time (±SEM) displaying all social behaviors toward a conspecific mouse (broken down into components in B, C and D). B. Mean time (±SEM) displaying allogrooming behavior towards a conspecific mouse. C. Mean time (±SEM) displaying anogenital sniffing behavior towards a conspecific mouse. D. Mean time (±SEM) displaying sniffing behavior towards a conspecific mouse.

doi:10.1371/journal.pone.0008456.g001
Exploration in the Holeboard
Offspring of old fathers demonstrated reduced exploration in the holeboard, making fewer nose pokes and spending less time nose poking than offspring of young fathers (t = −2.21, d.f. = 22, p = 0.02; Figure 2A). No significant differences were evident in distance moved or time spent in the centre of the Holeboard arena.

Figure 2. Results of holeboard and open field data from male offspring of young fathers (n = 12) and old fathers (n = 12).

* shows a p-value of less than 0.05. A. Mean number of nose pokes (±SEM) into holes in the holeboard trial. B. Mean time spent in each area of arena (±SEM) in the open field task.

doi:10.1371/journal.pone.0008456.g002
Exploration in the Open Field
Offspring of old fathers were less exploratory in the Open Field, taking longer to enter the central zone of the arena (t = 1.7837, d.f. = 22, p = 0.04). However, there were no significant differences inthe time spent in the middle (t = −0.9548, d.f. = 22, p = 0.1785) or central zones (t = −1.3166, d.f. = 22, p = 0.1056) (Figure 2B) or in overall locomotor activity between offspring of old fathers and offspring of young fathers in the open field.

To further explore these findings we examined the same set of behaviors in a small group of mice that were the offspring of very old fathers (aged >12 months, n = 9 male offspring generated from 7 breeding pairs). The behavioral results of reduced social behavior and exploration were seen in the offspring of very old fathers, but the numbers are too small to allow for a reliable statistical test (data not shown).

Discussion Top
Using a mouse model we documented deleterious effects of advancing paternal age on offspring behavior. Male offspring of older fathers engaged in less social behavior and exhibited less exploration in a novel environment. These effects were not confounded by differences in overall locomotor activity. Abnormalities in social behavior characterize psychiatric disorders previously linked to advancing paternal age, suggesting a common phenotype affected by paternal age.

There are several advantages for the mouse model used in this study. First, given the tractable nature of animal work, the environment was tightly controlled, minimizing any environmental confounds. Second, the age of all the mothers of the offspring was standard such that differences observed in the offspring cannot be accounted for by maternal age.

Finally, the most common reference inbred strain of mouse was used (C57BL/6J), reducing genetic variation.

In men, it is thought that the spermatogonial stem cell divisions occurring over the life-course of males result in higher mutational rates and cytogenetic abnormalities in the sperm of older men [10], [11]. Numerous neurological and psychiatric disorders have been related to genomic alterations [12]. A number of studies have uncovered an increased prevalence of de-novo copy-number variants (CNVs), and other forms of genomic alterations in autistic and in schizophrenia cases [13], [14].

An alternative explanation is that epigenetic dysfunction underlies some paternal age effects. Epigenetic dysfunction has been associated with several neuropsychiatric disorders, including schizophrenia and bipolar disorder [15]. A study by Flanagan and colleagues [16] reported intra- and inter-individual epigenetic variability in the male germline, and found a number of genes that demonstrated age-related DNA-methylation changes. Epigenetic signals are generally reprogrammed in the germline, although it appears that such reprogramming may not be fully complete across all regions of the genome [17]. In particular, repetitive and transposable elements in the genome, which are generally hypermethylated, are often not efficiently reprogrammed [18]. It is thus plausible that de novo structural mutations, which are often associated with repetitive DNA sequence motifs, may also be subjected to differential epigenetic reprogramming implicating both mutagenic and epigenetic processes in the phenotypic manifestation of increased paternal age.

Despite the advantages of this model, the results of this study should be interpreted in light of some limitations. We only examined one strain of male mice. This was a-priori decided in order to follow common practice in animal research aimed at limiting variation caused by sex differences in behaviors. Hence, findings should not be generalized across sexes. In addition, behavior was assessed at one developmental stage (12 weeks, young adulthood). Thus, the developmental nature of these differences could not be determined.

In conclusion, this study provides the strongest evidence to date for the behavioral effects of advancing paternal age on the offspring. Studies are ongoing to investigate the role of molecular changes in mediating the effects of advancing paternal age on social and exploratory behaviors in offspring, by assessing de-novo CNV events and alterations in DNA methylation.

Methods Top
Breeding Strategy
C57BL/6J mice were bred and maintained in the Biological Services Unit at the Institute of Psychiatry, Kings College London using stocks purchased from Charles River Laboratories. All housing and experimental procedures were performed in accordance with the UK Home Office Animals (Scientific Procedures) Act 1986. Typical breeding age for mice starts at 2 months. Male breeders are generally retired after 7–8 months. Therefore, females aged 2 months were bred with males of two different ages; young males of 2 months (n = 6 breeding pairs), and old males of 10 months (n = 6 breeding pairs). The average litter size within each age group was 7 (male to female ratio 1:1) and total progeny generated was 40 mice in the young fathers group and 44 mice in the old fathers group. Two males were randomly selected from each litter (n = 12 males per group) and weaned aged 4–5 weeks and pair housed with their siblings and then individually housed for two weeks prior to testing. Mice were housed in standard cages measuring 30.5×13×11 cm, with food and water available ad libitum. The housing room was maintained on a standard light/dark cycle with white lights on from 08:00 to 20:00. Ambient temperature in all rooms was maintained at 21±2°C with 45% humidity.

Offspring Behavioral Testing
Offspring were aged 12 weeks at the start of testing and all testing took place during the light phase with a light level <30 lux in the test room. Each apparatus was wiped clean with 1% Trigene® between subjects to avoid olfactory cueing behaviors. Behaviors for all tests were recorded on videotapes for further detailed analysis. Mice were returned to their home cage at the end of each test.

Social Behavior
The social behavior of the test mice towards a juvenile conspecific was assessed in a 5 minute trial [19]. The test mouse is habituated in an arena (36×20×14 cm) for 5 minutes, after which a male juvenile conspecific of the same strain (aged 4 weeks) was introduced for a further 5 minutes. During this trial, social behavior (including social sniffing, anogenital sniffing and allogrooming) by the test mouse towards the conspecific were scored from videotape by an observer blind to the group factor of paternal age.

Holeboard
The holeboard test is used to measure activity and exploration in a novel arena [20]. The Truscan Photo Beam Activity System (Coulbourn Instruments, Whitehall, PA) was used, which consists of an arena (25.4 cm square) and a nose poke floor with 16 holes (4×4 array) with sensor rings to track movement. The beams are spaced 1.52 cm apart providing a 0.76 cm spatial resolution. Animals were placed in the arena and the movement, the number of nose pokes and the time spent nose poking were recorded automatically by beam breaks for 5 minutes using the Truscan program.

Open Field
The open field [21] used a square white acrylic box with dimensions 72×72×33 cm. The animal was placed in the outer part of the arena facing an outer wall and allowed to freely explore the arena for 5 minutes. A video camera placed above the arena allowed movement to be tracked using an automated tracking system (Ethovision, Noldus Information Technologies). The number of faecal boli and urination were recorded at the end of the test. A square of equal distance from the periphery (36×36 cm) was defined in Ethovision as the ‘outer’, ‘middle’ and ‘central’ zones in order to determine the number of entries into, and time spent in, these zones in the arena. In addition, the latency to enter the inner zones as well as locomotor activity in all three zones of the arena were measured by the tracking system.

Statistical Analysis
Behavioral performances of offspring of young fathers and offspring of old fathers in the social interaction task, holeboard and open field were compared using unpaired, one-tailed Students t-tests. Significance level was set at 0.05.

Author Contributions Top
Conceived and designed the experiments: JM CF LCS AR. Performed the experiments: RGS RLK. Analyzed the data: RGS RLK CF. Contributed reagents/materials/analysis tools: JDB. Wrote the paper: RGS RLK JM CF LCS AR.

References Top
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Frans EM, Sandin S, Reichenberg A, Lichtenstein P, Langstrom N, et al. (2008) Advancing paternal age and bipolar disorder. Arch Gen Psychiatry 65: 1034–1040. Find this article online
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Limb malformations with associated congenital constriction rings in two unrelated Egyptian males

Clin Dysmorphol. 2009 Nov 24. [Epub ahead of print]

Limb malformations with associated congenital constriction rings in two unrelated Egyptian males, one with a disorganization-like spectrum and the other with a probable distinct type of septo-optic dysplasia.
Temtamy SA, Aglan MS, Ashour AM, El-Badry TH.

Departments of aClinical Genetics bOrodental Genetics, Division of Human Genetics and Genome Research, National Research Centre, Cairo, Egypt.

In this report, we describe two unrelated Egyptian male infants with limb malformations and constriction rings. The first case is developing normally but has severe limb anomalies, congenital constriction rings, scoliosis because of vertebral anomalies, a left accessory nipple, a small tumor-like swelling on his lower back with tiny skin tubular appendages, a hypoplastic scrotum, and an anchored penis. The second case is developmentally delayed with limb malformations, congenital constriction rings, a lumbar myelomeningeocele, hemangioma, and tiny tubular skin appendages on the back. The patient also had bilateral optic atrophy. The constellation of features in our patients cannot be fully explained by the amniotic disruption complex. The first patient may represent an additional case of the human homolog of the mouse disorganization mutant. The presence of bilateral optic atrophy in the second case, although without an absent septum pellucidum nor other brain anomalies resembles the infrequently reported disorder of septo-optic dysplasia with limb anomalies. Both cases were sporadic and could be caused by a new dominant mutation because of the high paternal age of case 1 and the history of paternal occupational exposure to heat for both fathers. We draw attention to the phenotypic overlap between the disorganization-like syndrome and septo-optic dysplasia with limb anomalies.

PMID: 19940763 [PubMed - as supplied by publisher]

"The biological clock for men and women is really the same," says Dr. Dolores Malaspina

According to a study released last March in the Public Library of Science Medicine, children born to fathers who were 20 scored an average of 2 points higher on an IQ test than children born to 50-year-old fathers. And that's not all. Recent studies from Israel, California and Sweden have connected "late paternal age" with any number of serious medical conditions: The longer you wait, the more likely it is that your kid will be affected by schizophrenia, dwarfism, bipolar disorder, autism, Marfan syndrome, certain childhood cancers, or even, later in life, Alzheimer's. In some cases, the risk factors skyrocket. A 2005 study conducted by the University of California, Los Angeles, found a fourfold rise in Down syndrome among babies born to men 50 and older. Worse still, those risk factors aren't limited to your tweed-sporting years: Statistically, "late paternal age" starts at 30, as in Zack's age. A 2006 study conducted by Mount Sinai School of Medicine found that fathers in their 30s have children with about 1.5 times the risk of developing autism compared with fathers in their teens and 20s. That factor jumps to five times for dads in their 40s. The cherry on the cake? The American Society for Reproductive Medicine recommends that sperm banks do not accept specimens from men over 40.

"The biological clock for men and women is really the same," says Dr. Dolores Malaspina of Bellevue Hospital Center in New York City and New York University, who conducted one of the first studies. "It's just that men can keep having babies."