Rate of de novo mutations and the importance of father's age to disease risk. Kong A, Frigge ML, Masson G, Besenbacher S, Sulem P, Magnusson G, Gudjonsson SA, Sigurdsson A, Jonasdottir A, Jonasdottir A, Wong WS, Sigurdsson G, Walters GB, Steinberg S, Helgason H, Thorleifsson G, Gudbjartsson DF, Helgason A, Magnusson OT, Thorsteinsdottir U, Stefansson K. Nature. 2012 Aug 22;488(7412):471-5. doi: 10.1038/nature11396. PMID: 22914163 [PubMed - in process]

Rate of de novo mutations and the importance of father's age to disease risk. Kong A, Frigge ML, Masson G, Besenbacher S, Sulem P, Magnusson G, Gudjonsson SA, Sigurdsson A, Jonasdottir A, Jonasdottir A, Wong WS, Sigurdsson G, Walters GB, Steinberg S, Helgason H, Thorleifsson G, Gudbjartsson DF, Helgason A, Magnusson OT, Thorsteinsdottir U, Stefansson K. Nature. 2012 Aug 22;488(7412):471-5. doi: 10.1038/nature11396. PMID: 22914163 [PubMed - in process]

James Crow Dies

James Crow Dies

January 11, 2012







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James Crow, who was a population geneticist at the University of Wisconsin-Madison, has died, reports The New York Times. He was 95. Crow studied mutational load, and was part of on a National Academy of Sciences committee that assessed mutational damage to the populations of Hiroshima and Nagasaki following the use of atomic bombs there. He also was on a committee that paved the way for using DNA forensics in court. The Times notes that when Crow began teaching in the 1940s and 1950s, the field of genetics underwent rapid changes. "When anxious students asked Dr. Crow what would be in the exams, he would tell them that the questions were the same every year but that the answers were different," the Times says.

High Frequencies of De Novo CNVs in Bipolar Disorder and Schizophrenia.

Neuron. 2011 Dec 22;72(6):951-63.

High Frequencies of De Novo CNVs in Bipolar Disorder and Schizophrenia.

Malhotra D, McCarthy S, Michaelson JJ, Vacic V, Burdick KE, Yoon S, Cichon S, Corvin A, Gary S, Gershon ES, Gill M, Karayiorgou M, Kelsoe JR, Krastoshevsky O, Krause V, Leibenluft E, Levy DL, Makarov V, Bhandari A, Malhotra AK, McMahon FJ, Nöthen MM, Potash JB, Rietschel M, Schulze TG, Sebat J.


Source

Beyster Center for Genomics of Psychiatric Diseases, University of California, San Diego, La Jolla, CA 92093, USA; Department of Psychiatry, University of California, San Diego, La Jolla, CA 92093, USA; Stanley Institute for Cognitive Genomics, Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 12824, USA.


Abstract

While it is known that rare copy-number variants (CNVs) contribute to risk for some neuropsychiatric disorders, the role of CNVs in bipolar disorder is unclear. Here, we reasoned that a contribution of CNVs to mood disorders might be most evident for de novo mutations. We performed a genome-wide analysis of de novo CNVs in a cohort of 788 trios. Diagnoses of offspring included bipolar disorder (n = 185), schizophrenia (n = 177), and healthy controls (n = 426). Frequencies of de novo CNVs were significantly higher in bipolar disorder as compared with controls (OR = 4.8 [1.4,16.0], p = 0.009). De novo CNVs were particularly enriched among cases with an age at onset younger than 18 (OR = 6.3 [1.7,22.6], p = 0.006). We also confirmed a significant enrichment of de novo CNVs in schizophrenia (OR = 5.0 [1.5,16.8], p = 0.007). Our results suggest that rare spontaneous mutations are an important contributor to risk for bipolar disorder and other major neuropsychiatric diseases.

Copyright © 2011 Elsevier Inc. All rights reserved.

Cereb Cortex. 2011 Aug 4. [Epub ahead of print]

http://www.ncbi.nlm.nih.gov/pubmed/21817090

Cereb Cortex. 2011 Aug 4. [Epub ahead of print]
Parental Age Effects on Cortical Morphology in Offspring.
Shaw P, Gilliam M, Malek M, Rodriguez N, Greenstein D, Clasen L, Evans A, Rapoport J, Giedd J.
SourceChild Psychiatry Branch, Intramural Program of the National Institute of Mental Health.

Abstract
The age at which a parent has a child impacts the child's cognition and risk for mental illness. It appears that this risk is curvilinear, with both age extremes associated with lower intelligence and increased prevalence of some neuropsychiatric disorders. Little is known of the neural mechanisms underpinning this phenomenon. We extracted lobar volumes, surface areas, and cortical thickness from 489 neuroanatomic magnetic resonance images acquired on 171 youth. Using linear mixed model regression, we determined the association between parental age and offspring's neuroanatomy, adjusting for offspring's age, sex, intelligence, and parental socioeconomic class. For gray matter volumes, quadratic paternal and maternal age terms contributed significantly (maternal quadratic age effect: t = -2.2, P = 0.03; paternal quadratic age effect: t = -2.4, P = 0.02) delineating an inverted "U" relationship between parental age and gray matter volume. Cortical volume increased with both advancing paternal and maternal age until around the early 30s after which it fell. Paternal age effects were more pronounced on cortical surface area, whereas maternal age impacted more on cortical thickness. There were no significant effects of parental age on white matter volumes. These parental age effects on cerebral morphology may form part of the link between parental age extremes and suboptimal neurocognitive outcomes.

PMID:21817090[PubMed - as supplied by publisher]

A Strategy to Identify de Novo Mutations in Common Disorders such as Autism and Schizophrenia.

http://www.ncbi.nlm.nih.gov/pubmed/21712793

Vis Exp. 2011 Jun 15;(52). pii: 2534. doi: 10.3791/2534.
A Strategy to Identify de Novo Mutations in Common Disorders such as Autism and Schizophrenia.
Julie G, Hamdan FF, Rouleau GA.
SourceCentre of Excellence in Neuromics, CHUM Research Center and the Department of Medicine, Universite de Montreal.

Abstract
There are several lines of evidence supporting the role of de novo mutations as a mechanism for common disorders, such as autism and schizophrenia. First, the de novo mutation rate in humans is relatively high, so new mutations are generated at a high frequency in the population. However, de novo mutations have not been reported in most common diseases. Mutations in genes leading to severe diseases where there is a strong negative selection against the phenotype, such as lethality in embryonic stages or reduced reproductive fitness, will not be transmitted to multiple family members, and therefore will not be detected by linkage gene mapping or association studies. The observation of very high concordance in monozygotic twins and very low concordance in dizygotic twins also strongly supports the hypothesis that a significant fraction of cases may result from new mutations. Such is the case for diseases such as autism and schizophrenia. Second, despite reduced reproductive fitness(1) and extremely variable environmental factors, the incidence of some diseases is maintained worldwide at a relatively high and constant rate. This is the case for autism and schizophrenia, with an incidence of approximately 1% worldwide. Mutational load can be thought of as a balance between selection for or against a deleterious mutation and its production by de novo mutation. Lower rates of reproduction constitute a negative selection factor that should reduce the number of mutant alleles in the population, ultimately leading to decreased disease prevalence. These selective pressures tend to be of different intensity in different environments. Nonetheless, these severe mental disorders have been maintained at a constant relatively high prevalence in the worldwide population across a wide range of cultures and countries despite a strong negative selection against them(2). This is not what one would predict in diseases with reduced reproductive fitness, unless there was a high new mutation rate. Finally, the effects of paternal age: there is a significantly increased risk of the disease with increasing paternal age, which could result from the age related increase in paternal de novo mutations. This is the case for autism and schizophrenia(3). The male-to-female ratio of mutation rate is estimated at about 4-6:1, presumably due to a higher number of germ-cell divisions with age in males. Therefore, one would predict that de novo mutations would more frequently come from males, particularly older males(4). A high rate of new mutations may in part explain why genetic studies have so far failed to identify many genes predisposing to complexes diseases genes, such as autism and schizophrenia, and why diseases have been identified for a mere 3% of genes in the human genome. Identification for de novo mutations as a cause of a disease requires a targeted molecular approach, which includes studying parents and affected subjects. The process for determining if the genetic basis of a disease may result in part from de novo mutations and the molecular approach to establish this link will be illustrated, using autism and schizophrenia as examples.

PMID:21712793[PubMed - in process]

Influence of paternal age in schizophrenia

Encephale. 2011 Jun;37(3):199-206. Epub 2011 Apr 2.
[Influence of paternal age in schizophrenia.]
[Article in French]
Hubert A, Szöke A, Leboyer M, Schürhoff F.
SourcePôle de psychiatrie du CHU de Créteil, groupe hospitalier Henri-Mondor-Albert-Chenevier, AP-HP, 40, rue Mesly, 94000 Créteil, France; Inserm unité 955, IMRB, département de génétique, équipe 15, 94000 Créteil, France; Faculté de médecine, université Paris-Est Créteil, IFR10, 94000 Créteil, France; Fondation Fondamental, fondation de coopération scientifique, hôpital Chenevier, 40, rue Mesly, 94000 Créteil, France.

Abstract
BACKGROUND: Schizophrenia is an aetiologically heterogeneous syndrome, with a strong genetic component. Despite a reduced fertility in this disorder, its prevalence is maintained and could be explained by de novo genetic mutations. Advanced paternal age (APA) is a major source of new mutations in human beings and could thus be associated with an increased risk of developing schizophrenia in offspring. New mutations related to APA have been implicated as a cause of sporadic cases in several autosomal dominant diseases and also in neurodevelopmental diseases, autism, intellectual disabilities, and social functioning. The aim of the present study was to summarize the results of studies investigating the role of APA, and to discuss some interpretations.

METHODS: All relevant studies were identified through the National Library of Medicine (PubMed(®) database). Keywords used for research were "age" and "schizophrenia" linked to "paternal or father". We have identified and analysed eight cohort studies, five case-control studies, two meta-analyses, and one review concerning different father's mutations potentially transmitted, two studies comparing paternal age at conception between sporadic versus familial cases of schizophrenia. All studies selected have been published between 2000 and 2009.

RESULTS: After controlling for several confounding factors including maternal age, the relative risk of schizophrenia increased from 1.84 to 4.62 in offspring of fathers with an older age of fatherhood. Mother's age showed no significant effects after adjusting for paternal age. There was a significant association between paternal age and risk of developing schizophrenia, there was a weaker association with psychosis.

DISCUSSION: The results of these different studies are confirmed by two recent meta-analyses which found an increased risk of schizophrenia in offspring of fathers older than 35 years. Two main hypotheses could explain these results. The first one is based on the presence of new mutations in the spermatogonia, possibly because of accumulating replication errors in spermatogonial cell lines. This hypothesis is confirmed by Malaspina et al. (2002) [19], who found that patients without a family history of schizophrenia had significantly older fathers than probands with a positive family history of schizophrenia. However, this result has not been confirmed by other studies, and paternal age effect could be also explained by a mechanism called imprinting, which is a form of gene regulation. The second hypothesis is based on the fact that fathers with schizophrenia spectrum personality disorder, known to be genetically related to schizophrenia, could have an advanced age at conception. However, regarding this hypothesis, advanced maternal age at conception should be a risk factor for schizophrenia, and this is not the case. Thus, the first hypothesis seems more plausible than the second. APA has been identified as a risk factor for other psychiatric disorders such as autism, bipolar disorder, obsessive-compulsive disorder, and phobia, and thus seems to be a non-specific risk factor. Furthermore, its association with impaired neurocognitive outcomes during infancy and childhood in normal populations raises the question of the phenotype linked to APA.

CONCLUSION: APA at conception appears to be a risk factor for schizophrenia. This risk factor probably interacts with genetic factors in a gene-environment interaction. To date, there is no validated cut-off at which the risk is significantly increased in offspring. In the future, studies could benefit from analyzing the phenotype related to APA.

Copyright © 2010 L’Encéphale, Paris. Published by Elsevier Masson SAS. All rights reserved.

PMID:21703435[PubMed - as supplied by publisher]

Delayed fathering and risk of mental disorders in adult offspring.

Early Hum Dev. 2011 Jan 8. [Epub ahead of print]

Delayed fathering and risk of mental disorders in adult offspring.
Krishnaswamy S, Subramaniam K, Ramachandran P, Indran T, Abdul Aziz J.

University of New England, Locked bag 4, NSW 2351, Australia.

Abstract
INTRODUCTION: Delayed parenting and child bearing at a very young age impose various risks to development of the offspring.

OBJECTIVE: This study aims to investigate the association between disparities in parental age and increased risk factor for common mental disorders in the progenies during adulthood.

METHODOLOGY: The Malaysian Mental Health Survey (MMHS) was analysed for this study. Respondents were asked to estimate the age of their parents at their birth. Presence of common mental disorders (CMD) was determined by referring to the diagnosis given by the Clinical Interview Schedule-Revised (CIS-R) instrument in the Programmed Questionnaire System (PROQSY) format. The association between parental age disparities and CMD was studied using logistic regression.

RESULT: Fifty three percent (n=1972) of the MMHS respondents (N=3666) knew the age of both parents and were included in the study. Three percent (n=53) had significant disparity in parental age, or a difference of 11years or more. Respondents born to parents with significant age disparity had a prevalence rate of 24% (95% CI=22.12-25.89) for CMD in comparison to 6% (95% CI=5.99-6.11) in their counterparts and 3.4 times higher risk for CMD, after adjusting for demographic factors, paternal age at birth and presence of family history of mental disorders. Amongst those born to older fathers aged 50 and above, the presence of disparity increased the rate for CMD to 42% (95% CI=39.82-44.18).

DISCUSSION: Disparity in parental age was significantly associated with increased risk for CMD. Various psychosocial factors contributing to age disparity in both the father and the mother could predispose to stress and mental health problems.

Copyright © 2010 Elsevier Ltd. All rights reserved.