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Phylogenetic Analysis Supports a Link between DUF1220 Domain Number and Primate Brain Expansion.

June 25, 2016 - 6:50am
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Phylogenetic Analysis Supports a Link between DUF1220 Domain Number and Primate Brain Expansion.

Genome Biol Evol. 2015 Aug;7(8):2083-8

Authors: Zimmer F, Montgomery SH

Abstract
The expansion of DUF1220 domain copy number during human evolution is a dramatic example of rapid and repeated domain duplication. Although patterns of expression, homology, and disease associations suggest a role in cortical development, this hypothesis has not been robustly tested using phylogenetic methods. Here, we estimate DUF1220 domain counts across 12 primate genomes using a nucleotide Hidden Markov Model. We then test a series of hypotheses designed to examine the potential evolutionary significance of DUF1220 copy number expansion. Our results suggest a robust association with brain size, and more specifically neocortex volume. In contradiction to previous hypotheses, we find a strong association with postnatal brain development but not with prenatal brain development. Our results provide further evidence of a conserved association between specific loci and brain size across primates, suggesting that human brain evolution may have occurred through a continuation of existing processes.

PMID: 26112965 [PubMed - indexed for MEDLINE]

Aging in Fragile X Premutation Carriers.

June 24, 2016 - 6:49am

Aging in Fragile X Premutation Carriers.

Cerebellum. 2016 Jun 22;

Authors: Lozano R, Saito N, Reed D, Eldeeb M, Schneider A, Hessl D, Tassone F, Beckett L, Hagerman R

Abstract
It is now recognized that FMR1 premutation carriers (PC) are at risk to develop a range of neurological, psychiatric, and immune-mediated disorders during adulthood. There are conflicting findings regarding the incidence of hypertension, hypothyroidism, diabetes, and cancer in these patients that warrant further study. A retrospective controlled study was performed in a convenience sample of 248 controls (130 men, 118 women) and 397 FMR1 PC with and without fragile X-associated tremor ataxia syndrome (FXTAS) (176 men, 221 women); all participants were at least 45 years old (men: mean 62.4, SD 9.5; women: mean 62.8, SD 9.9; p = 0.63). Memory and cognitive assessments (Wechsler Adult Intelligence Scale (WAIS-III), Wechsler Memory Scale (WMS-III)) and molecular testing (CGG repeats and FMR1-mRNA levels) were performed. Additional data included body mass index (BMI), cholesterol levels, blood pressure, hemoglobin A1c (HbA1c) levels, and medical history. A higher percentage of PC subjects self-reported having a diagnosis of hypertension (50.0 vs. 35.0 %, p = 0.006) and thyroid problems (20.4 vs. 10.0 %, p = 0.012) than control subjects. When comparing controls versus PC with FXTAS, the association was higher for diabetes (p = 0.043); however, the effect was not significant after adjusting for demographic predictors. Blood pressure, blood glucose levels, HbA1c, and BMI values were not significantly different between the two groups. The PC with FXTAS group performed consistently lower in neuropsychological testing compared with the PC without FXTAS group, but the differences were very small for all but the WAIS full-scale IQ. Based on these findings, it appears that the risk for hypertension, thyroid problems, and diabetes may be more frequent in PC with FXTAS, which will require verification in future studies.

PMID: 27334385 [PubMed - as supplied by publisher]

Risk factors for autism spectrum disorder in the Thai population.

June 24, 2016 - 6:49am
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Risk factors for autism spectrum disorder in the Thai population.

Eur J Pediatr. 2015 Oct;174(10):1365-72

Authors: Khaiman C, Onnuam K, Photchanakaew S, Chonchaiya W, Suphapeetiporn K

Abstract
UNLABELLED: Autism spectrum disorder (ASD) is a heterogeneous neurodevelopmental disorder commonly prevalent in children worldwide including Thailand. However, there are very few studies thus far addressing risk factors for ASD in Thai children. This case-control study aims to investigate whether various risk factors especially socioeconomic status, advanced parental age (age >35 years), perinatal factors, maternal autoimmune diseases, and family history of neuropsychiatric illnesses were associated with the risk of having an offspring with ASD. There were 235 children with ASD (age 8.44 ± 3.37 years) and 235 controls (age 8.39 ± 3.37 years) enrolled in this study. The risk of developing ASD in these children included advanced paternal age (adjusted odds ratio (AOR) = 3.49, 95 % confidence interval (CI) = 2.05-5.96), family history of neuropsychiatric illnesses particularly if such disorders came from the paternal side of the child's family (AOR = 2.87, 95 % CI = 1.29-6.39), and having unemployed mothers (AOR = 1.65, 95 % CI = 1.08-2.54).
CONCLUSION: This study supports previous findings of Western countries where risk factors for ASD tend to occur in children whose fathers were of advanced paternal age and in the families with neuropsychiatric illnesses particularly if such disorders came from the paternal side of the child's family.
WHAT IS KNOWN: • Family history of neuropsychiatric disorders and advanced paternal age are risk factors for ASD in the offspring previously identified in the studies in Europe and North America. What is New: • To our knowledge, this is the first study documenting risk factors for ASD in the Asian population. • Our study supports previous findings of Western countries where risk factors for ASD tend to occur in the families with neuropsychiatric illnesses particularly if such disorders came from the paternal side of the child's family.

PMID: 26226890 [PubMed - indexed for MEDLINE]

Gene discovery and functional assessment of rare copy-number variants in neurodevelopmental disorders.

June 24, 2016 - 6:49am
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Gene discovery and functional assessment of rare copy-number variants in neurodevelopmental disorders.

Brief Funct Genomics. 2015 Sep;14(5):315-28

Authors: Iyer J, Girirajan S

Abstract
Rare copy-number variants (CNVs) are a significant cause of neurodevelopmental disorders. The sequence architecture of the human genome predisposes certain individuals to deletions and duplications within specific genomic regions. While assessment of individuals with different breakpoints has identified causal genes for certain rare CNVs, deriving gene-phenotype correlations for rare CNVs with similar breakpoints has been challenging. We present a comprehensive review of the literature related to genetic architecture that is predisposed to recurrent rearrangements, and functional evaluation of deletions, duplications and candidate genes within rare CNV intervals using mouse, zebrafish and fruit fly models. It is clear that phenotypic assessment and complete genetic evaluation of large cohorts of individuals carrying specific CNVs and functional evaluation using multiple animal models are necessary to understand the molecular genetic basis of neurodevelopmental disorders.

PMID: 25971441 [PubMed - indexed for MEDLINE]

Human Pluripotent Stem Cell-derived Cortical Neurons for High Throughput Medication Screening in Autism: A Proof of Concept Study in SHANK3 Haploinsufficiency Syndrome.

June 23, 2016 - 6:46am

Human Pluripotent Stem Cell-derived Cortical Neurons for High Throughput Medication Screening in Autism: A Proof of Concept Study in SHANK3 Haploinsufficiency Syndrome.

EBioMedicine. 2016 May 27;

Authors: Darville H, Poulet A, Rodet-Amsellem F, Chatrousse L, Pernelle J, Boissart C, Héron D, Nava C, Perrier A, Jarrige M, Cogé F, Millan MJ, Bourgeron T, Peschanski M, Delorme R, Benchoua A

Abstract
Autism spectrum disorders affect millions of individuals worldwide, but their heterogeneity complicates therapeutic intervention that is essentially symptomatic. A versatile yet relevant model to rationally screen among hundreds of therapeutic options would help improving clinical practice. Here we investigated whether neurons differentiated from pluripotent stem cells can provide such a tool using SHANK3 haploinsufficiency as a proof of principle. A library of compounds was screened for potential to increase SHANK3 mRNA content in neurons differentiated from control human embryonic stem cells. Using induced pluripotent stem cell technology, active compounds were then evaluated for efficacy in correcting dysfunctional networks of neurons differentiated from individuals with deleterious point mutations of SHANK3. Among 202 compounds tested, lithium and valproic acid showed the best efficacy at corrected SHANK3 haploinsufficiency associated phenotypes in cellulo. Lithium pharmacotherapy was subsequently provided to one patient and, after one year, an encouraging decrease in autism severity was observed. This demonstrated that pluripotent stem cell-derived neurons provide a novel cellular paradigm exploitable in the search for specific disease-modifying treatments.

PMID: 27333044 [PubMed - as supplied by publisher]

Episodic ataxia associated with a de novo SCN2A mutation.

June 23, 2016 - 6:46am

Episodic ataxia associated with a de novo SCN2A mutation.

Eur J Paediatr Neurol. 2016 Jun 14;

Authors: Leach EL, van Karnebeek CD, Townsend KN, Tarailo-Graovac M, Hukin J, Gibson WT

Abstract
INTRODUCTION: Episodic ataxia (EA) is characterized by paroxysmal attacks of ataxia interspersed by asymptomatic periods. Dominant mutations or copy number variants in CACNA1A are a well-known cause of EA.
CLINICAL PRESENTATION: This boy presented with clinical features of episodic ataxia, and also showed cerebellar atrophy, hypotonia, autism and global developmental delay at age 4 years. Acetazolamide prevented further episodes of ataxia, dystonia and encephalopathy. Extensive biochemical and genetic tests were unrevealing; whole exome sequencing found a previously unreported variant in SCN2A, proven to be de novo and predicted to be protein-damaging.
CONCLUSION: Considered alongside previous reports of episodic ataxia in SCN2A mutation-positive patients, our case further illustrates the genetic heterogeneity of episodic ataxia. In addition, this case suggests that acetazolamide may be an effective treatment for some aspects of the phenotype in a broader range of channelopathy-related conditions.

PMID: 27328862 [PubMed - as supplied by publisher]

The impact of genotype calling errors on family-based studies.

June 23, 2016 - 6:46am

The impact of genotype calling errors on family-based studies.

Sci Rep. 2016;6:28323

Authors: Yan Q, Chen R, Sutcliffe JS, Cook EH, Weeks DE, Li B, Chen W

Abstract
Family-based sequencing studies have unique advantages in enriching rare variants, controlling population stratification, and improving genotype calling. Standard genotype calling algorithms are less likely to call rare variants correctly, often mistakenly calling heterozygotes as reference homozygotes. The consequences of such non-random errors on association tests for rare variants are unclear, particularly in transmission-based tests. In this study, we investigated the impact of genotyping errors on rare variant association tests of family-based sequence data. We performed a comprehensive analysis to study how genotype calling errors affect type I error and statistical power of transmission-based association tests using a variety of realistic parameters in family-based sequencing studies. In simulation studies, we found that biased genotype calling errors yielded not only an inflation of type I error but also a power loss of association tests. We further confirmed our observation using exome sequence data from an autism project. We concluded that non-symmetric genotype calling errors need careful consideration in the analysis of family-based sequence data and we provided practical guidance on ameliorating the test bias.

PMID: 27328765 [PubMed - in process]

Cyfip1 Regulates Presynaptic Activity during Development.

June 23, 2016 - 6:46am
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Cyfip1 Regulates Presynaptic Activity during Development.

J Neurosci. 2016 Feb 3;36(5):1564-76

Authors: Hsiao K, Harony-Nicolas H, Buxbaum JD, Bozdagi-Gunal O, Benson DL

Abstract
UNLABELLED: Copy number variations encompassing the gene encoding Cyfip1 have been associated with a variety of human diseases, including autism and schizophrenia. Here we show that juvenile mice hemizygous for Cyfip1 have altered presynaptic function, enhanced protein translation, and increased levels of F-actin. In developing hippocampus, reduced Cyfip1 levels serve to decrease paired pulse facilitation and increase miniature EPSC frequency without a change in amplitude. Higher-resolution examination shows these changes to be caused primarily by an increase in presynaptic terminal size and enhanced vesicle release probability. Short hairpin-mediated knockdown of Cyfip1 coupled with expression of mutant Cyfip1 proteins indicates that the presynaptic alterations are caused by dysregulation of the WAVE regulatory complex. Such dysregulation occurs downstream of Rac1 as acute exposure to Rac1 inhibitors rescues presynaptic responses in culture and in hippocampal slices. The data serve to highlight an early and essential role for Cyfip1 in the generation of normally functioning synapses and suggest a means by which changes in Cyfip1 levels could impact the generation of neural networks and contribute to abnormal and maladaptive behaviors.
SIGNIFICANCE STATEMENT: Several developmental brain disorders have been associated with gene duplications and deletions that serve to increase or decrease levels of encoded proteins. Cyfip1 is one such protein, but the role it plays in brain development is poorly understood. We asked whether decreased Cyfip1 levels altered the function of developing synapses. The data show that synapses with reduced Cyfip1 are larger and release neurotransmitter more rapidly. These effects are due to Cyfip1's role in actin polymerization and are reversed by expression of a Cyfip1 mutant protein retaining actin regulatory function or by inhibiting Rac1. Thus, Cyfip1 has a more prominent early role regulating presynaptic activity during a stage of development when activity helps to define neural pathways.

PMID: 26843638 [PubMed - indexed for MEDLINE]

Autism-associated R451C mutation in neuroligin3 leads to activation of the unfolded protein response in a PC12 Tet-On inducible system.

June 23, 2016 - 6:46am
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Autism-associated R451C mutation in neuroligin3 leads to activation of the unfolded protein response in a PC12 Tet-On inducible system.

Biochem J. 2016 Feb 15;473(4):423-34

Authors: Ulbrich L, Favaloro FL, Trobiani L, Marchetti V, Patel V, Pascucci T, Comoletti D, Marciniak SJ, De Jaco A

Abstract
Several forms of monogenic heritable autism spectrum disorders are associated with mutations in the neuroligin genes. The autism-linked substitution R451C in neuroligin3 induces local misfolding of its extracellular domain, causing partial retention in the ER (endoplasmic reticulum) of expressing cells. We have generated a PC12 Tet-On cell model system with inducible expression of wild-type or R451C neuroligin3 to investigate whether there is activation of the UPR (unfolded protein response) as a result of misfolded protein retention. As a positive control for protein misfolding, we also expressed the mutant G221R neuroligin3, which is known to be completely retained within the ER. Our data show that overexpression of either R451C or G221R mutant proteins leads to the activation of all three signalling branches of the UPR downstream of the stress sensors ATF6 (activating transcription factor 6), IRE1 (inositol-requiring enzyme 1) and PERK [PKR (dsRNA-dependent protein kinase)-like endoplasmic reticulum kinase]. Each branch displayed different activation profiles that partially correlated with the degree of misfolding caused by each mutation. We also show that up-regulation of BiP (immunoglobulin heavy-chain-binding protein) and CHOP [C/EBP (CCAAT/enhancer-binding protein)-homologous protein] was induced by both mutant proteins but not by wild-type neuroligin3, both in proliferative cells and cells differentiated to a neuron-like phenotype. Collectively, our data show that mutant R451C neuroligin3 activates the UPR in a novel cell model system, suggesting that this cellular response may have a role in monogenic forms of autism characterized by misfolding mutations.

PMID: 26621873 [PubMed - indexed for MEDLINE]

Comorbidity of intellectual disability confounds ascertainment of autism: implications for genetic diagnosis.

June 23, 2016 - 6:46am
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Comorbidity of intellectual disability confounds ascertainment of autism: implications for genetic diagnosis.

Am J Med Genet B Neuropsychiatr Genet. 2015 Oct;168(7):600-8

Authors: Polyak A, Kubina RM, Girirajan S

Abstract
While recent studies suggest a converging role for genetic factors towards risk for nosologically distinct disorders including autism, intellectual disability (ID), and epilepsy, current estimates of autism prevalence fail to take into account the impact of comorbidity of these disorders on autism diagnosis. We aimed to assess the effect of comorbidity on the diagnosis and prevalence of autism by analyzing 11 years (2000-2010) of special education enrollment data on approximately 6.2 million children per year. We found a 331% increase in the prevalence of autism from 2000 to 2010 within special education, potentially due to a diagnostic recategorization from frequently comorbid features such as ID. The decrease in ID prevalence equaled an average of 64.2% of the increase of autism prevalence for children aged 3-18 years. The proportion of ID cases potentially undergoing recategorization to autism was higher (P = 0.007) among older children (75%) than younger children (48%). Some US states showed significant negative correlations between the prevalence of autism compared to that of ID while others did not, suggesting state-specific health policy to be a major factor in categorizing autism. Further, a high frequency of autistic features was observed when individuals with classically defined genetic syndromes were evaluated for autism using standardized instruments. Our results suggest that current ascertainment practices are based on a single facet of autism-specific clinical features and do not consider associated comorbidities that may confound diagnosis. Longitudinal studies with detailed phenotyping and deep molecular genetic analyses are necessary to completely understand the cause of this complex disorder.

PMID: 26198689 [PubMed - indexed for MEDLINE]

[Children's hearing behavior observations and high risk individual genetic screening for late-onset hearing loss early detection and intervention exploring a basic-level hospitals model].

June 22, 2016 - 6:35am
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[Children's hearing behavior observations and high risk individual genetic screening for late-onset hearing loss early detection and intervention exploring a basic-level hospitals model].

Lin Chung Er Bi Yan Hou Tou Jing Wai Ke Za Zhi. 2015 Sep;29(18):1618-21

Authors: Guo Y, Zeng X, Liu T, Zou Y, Ye Y

Abstract
OBJECTIVE: To explore the methods to detect and intervene children's late-onset hearing loss early which are suitable for basic-level hospitals.
METHOD: Udiology and imaging diagnosis had been given to the children who passed the newborn hearing screening but showed auditory behavior disorders in the growth process, and individualized interventions were given according to the results of diagnosis. Seven children with high risk for hereditary deafness were sent to superior hospital and had molecular screening of common mutations of inherited deafness carried out, then corresponding prevention guidance and intervention were given to them.
RESULT: Fifty-two cases with late-onset hearing loss or verbal disorders were detected by auditory behavior observations,including 4 cases of auditory neuropathy, 4 cases of unilateral sensorineural deafness, 27 cases of secretory otitis media. 13 cases of bilateral sensorineural deafness and 4 cases of autism. Seven newborns with high risk of hereditary deafness were sent to the Third Affiliated Hospital of Sun Yat-Sen University and received molecular screening of common mutations of inherited deafness. One case with GJB2 compound heterozygous mutations was detected and followed up to 4 years old, he was found bilateral moderate hearing loss and accepted the hearing aids at 2 years old. Mitochondrial DNA 1555 a > G heterogeneity mutation in 2 cases and GJB2 235 delC single heterozygous mutations in 3 cases, no mutation in 1 case, all these 6 cases have been followed-up until now, their hearing are normal.
CONCLUSION: Children's auditory behavior observations and the superior hospitals referral performing high risk individual screening for newborns with high risk for hereditary deafness can detect children's late-onset hearing loss in time, this model is suitable for basic-level hospitals.

PMID: 26790261 [PubMed - indexed for MEDLINE]

A2BP1 gene polymorphisms association with olanzapine-induced weight gain.

June 22, 2016 - 6:35am
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A2BP1 gene polymorphisms association with olanzapine-induced weight gain.

Pharmacol Res. 2015 Sep;99:155-61

Authors: Dong L, Yan H, Huang X, Hu X, Yang Y, Ma C, Du B, Lu T, Jin C, Wang L, Yu H, Dong Z, Li W, Ruan Y, Zhang H, Zhang H, Mi W, Ma W, Li K, Lv L, Zhang D, Yue W

Abstract
The ataxin-2 binding protein 1 (A2BP1) gene is reported to be one of the susceptibility genes in schizophrenia, autism, and obesity. The aim of this study was to explore the association of A2BP1 gene polymorphisms with antipsychotic induced weight gain (AIWG) in Chinese Han population. Three hundred and twenty-eight patients with schizophrenia were followed-up for an 8-week period of treatment with olanzapine. The fasting weights of 328 patients were measured before and after the 8-week course of treatment. Four single nucleotide polymorphisms (SNPs: rs8048076, rs1478697, rs10500331, and rs4786847) of the A2BP1 gene were genotyped by polymerase chain reaction (PCR). We analyzed putative association of A2BP1 polymorphisms with AIWG of olanzapine using linear regression analysis and found that SNP rs1478697 was significantly associated with AIWG caused by olanzapine (p=0.0012; Bonferroni corrected p=0.0048). The association was replicated in another independent sample including 208 first-episode and drug-naïve patients presenting with schizophrenia after a 4-week treatment with olanzapine (p=0.0092; Bonferroni corrected p=0.0368; meta p=5.33×10(-5)). To explore the biological plausibility of A2BP1 in the pathogenesis of AIWG, we made expression analyses and eQTL analyses; these analyses showed that A2BP1 was highly expressed in whole brain tissues using the HBT database, and that rs1478697 has an expression quantitative trait locus effect in human cerebellar cortex tissues using the BRAINEAC database (p=2.50E-04). In conclusion, the rs1478697 in A2BP1 may be associated with AIWG induced by 8-week treatment with olanzapine.

PMID: 26092620 [PubMed - indexed for MEDLINE]

Genomic structural variants are linked with intellectual disability.

June 22, 2016 - 6:35am
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Genomic structural variants are linked with intellectual disability.

J Neural Transm (Vienna). 2015 Sep;122(9):1289-301

Authors: Bulayeva K, Lesch KP, Bulayev O, Walsh C, Glatt S, Gurgenova F, Omarova J, Berdichevets I, Thompson PM

Abstract
Mutations in more than 500 genes have been associated with intellectual disability (ID) and related disorders of cognitive function, such as autism and schizophrenia. Here we aimed to unravel the molecular epidemiology of non-specific ID in a genetic isolate using a combination of population and molecular genetic approaches. A large multigenerational pedigree was ascertained within a Dagestan Genetic Heritage research program in a genetic isolate of indigenous ethnics. Clinical characteristics of the affected members were based on combining diagnoses from regional psychiatric hospitals with our own clinical assessment, using a Russian translation of the structured psychiatric interviews, the Diagnostic Interview for Genetic Studies and the Family Interview for Genetic Studies, based on DSM-IV criteria. Weber/CHLC 9.0 STRs set was used for multipoint parametric linkage analyses (Simwalk2.91). Next, we checked CNVs and LOH (based on Affymetrix SNP 5.0 data) in the linked with ID genomic regions with the aim to identify candidate genes associated with mutations in linked regions. The number of statistically significant (p ≤ 0.05) suggestive linkage peaks with 1.3 < LOD < 3.0 we detected in a total of 10 genomic regions: 1q41, 2p25.3-p24.2, 3p13-p12.1, 4q13.3, 10p11, 11q23, 12q24.22-q24.31, 17q24.2-q25.1, 21q22.13 and 22q12.3-q13.1. Three significant linkage signals with LOD >3 were obtained at 2p25.3-p24.2 under the dominant model, with a peak at 21 cM flanked by loci D2S2976 and D2S2952; at 12q24.22-q24.31 under the recessive model, with a peak at -120 cM flanked by marker D12S2070 and D12S395 and at 22q12.3 under the dominant model, with a peak at 32 cM flanked by marker D22S683 and D22S445. After a set of genes had been designated as possible candidates in these specific chromosomal regions,we conducted an exploratory search for LOH and CNV based on microarray data to detect structural genomic variants within five ID-linked regions with LOD scores between 2.0 and 3.9. In these selected regions we obtained 173 ROH segments and 98 CN segments. Further analysis of region 2p25.3-p24.2 revealed deletions within genes encoding MYTL, SNTG2 and TPO among five of 21 affected cases at 2p25.3-p24.2. In the ID-linked region at 12q24.22-12q24.31 19 out of 21 ID cases carried segmental CNV and 20 of 21 them displayed ROH segments with mean size lengths for ID cases 2512 kb (500-6,472 kb) and for healthy control 682 kb (531-986 kb), including the genes MED13L, HRK, FBXW8, TESC, CDK2AP1 and SBNO1. Seven of 21 affected pedigree members displayed segmental deletions at 22q12.3 that includes the gene LARGE. Eight affected pedigree members carried ROH segments and 6 CN segments at 10p11.23-p11.21 containing the genes ZEB1, c10orf68 and EPC1. Our linkage and structural genomic variation analyses in a remote highland genetic isolate with aggregation of ID demonstrated that even highly isolated single kindred ID has oligo/polygenic pathogenesis. The results obtained implicate 10 genomic regions linked with ID that contain some of previously reported candidate genes, including HRK, FBXW8, TESC, CDK2AP1 and SBNO1 at 12q24 that were shown in recent studies as associated with brain measures derived from MRI scans.

PMID: 25626716 [PubMed - indexed for MEDLINE]

Comprehensive molecular testing in patients with high functioning autism spectrum disorder.

June 21, 2016 - 6:33am
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Comprehensive molecular testing in patients with high functioning autism spectrum disorder.

Mutat Res. 2016 Feb-Mar;784-785:46-52

Authors: Alvarez-Mora MI, Calvo Escalona R, Puig Navarro O, Madrigal I, Quintela I, Amigo J, Martinez-Elurbe D, Linder-Lucht M, Aznar Lain G, Carracedo A, Mila M, Rodriguez-Revenga L

Abstract
Autism spectrum disorders (ASD) include a range of complex neurodevelopmental disorders with extreme genetic heterogeneity. Exome and target sequencing studies have shown to be an effective tool for the discovery of new ASD genes. The aim of this study was to design an ASD candidate gene panel that covers 44 of the top ASD candidate genes. As a pilot study we performed comprehensive molecular diagnostic testing, including the study of the FMR1 and FMR2 repeat regions, copy number variant analysis in a collection of 50 Spanish ASD cases and mutation screening using targeted next generation sequencing-based techniques in 44 out of the total cohort. We evaluated and clinically selected our cohort, with most of the cases having high functioning ASD without facial dysmorphic features. The results of the present study allowed the detection of copy number and single nucleotide variants not yet identified. In addition, our results underscore the difficulty of the molecular diagnosis of ASD and confirm its genetic heterogeneity. The information gained from this and other genetic screenings is necessary to unravel the clinical interpretation of novel variants.

PMID: 26845707 [PubMed - indexed for MEDLINE]

Accumulated common variants in the broader fragile X gene family modulate autistic phenotypes.

June 21, 2016 - 6:33am
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Accumulated common variants in the broader fragile X gene family modulate autistic phenotypes.

EMBO Mol Med. 2015 Dec;7(12):1565-79

Authors: Stepniak B, Kästner A, Poggi G, Mitjans M, Begemann M, Hartmann A, Van der Auwera S, Sananbenesi F, Krueger-Burg D, Matuszko G, Brosi C, Homuth G, Völzke H, Benseler F, Bagni C, Fischer U, Dityatev A, Grabe HJ, Rujescu D, Fischer A, Ehrenreich H

Abstract
Fragile X syndrome (FXS) is mostly caused by a CGG triplet expansion in the fragile X mental retardation 1 gene (FMR1). Up to 60% of affected males fulfill criteria for autism spectrum disorder (ASD), making FXS the most frequent monogenetic cause of syndromic ASD. It is unknown, however, whether normal variants (independent of mutations) in the fragile X gene family (FMR1, FXR1, FXR2) and in FMR2 modulate autistic features. Here, we report an accumulation model of 8 SNPs in these genes, associated with autistic traits in a discovery sample of male patients with schizophrenia (N = 692) and three independent replicate samples: patients with schizophrenia (N = 626), patients with other psychiatric diagnoses (N = 111) and a general population sample (N = 2005). For first mechanistic insight, we contrasted microRNA expression in peripheral blood mononuclear cells of selected extreme group subjects with high- versus low-risk constellation regarding the accumulation model. Thereby, the brain-expressed miR-181 species emerged as potential "umbrella regulator", with several seed matches across the fragile X gene family and FMR2. To conclude, normal variation in these genes contributes to the continuum of autistic phenotypes.

PMID: 26612855 [PubMed - indexed for MEDLINE]

The Chromatin Regulator CHD8 Is a Context-Dependent Mediator of Cell Survival in Murine Hematopoietic Malignancies.

June 21, 2016 - 6:33am
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The Chromatin Regulator CHD8 Is a Context-Dependent Mediator of Cell Survival in Murine Hematopoietic Malignancies.

PLoS One. 2015;10(11):e0143275

Authors: Shingleton JR, Hemann MT

Abstract
Aberrant chromatin regulation is a frequent driver of leukemogenesis. Mutations in chromatin regulators often result in more stem-like cells that seed a bulk leukemic population. Inhibitors targeting these proteins represent an emerging class of therapeutics, and identifying further chromatin regulators that promote disease progression may result in additional drug targets. We identified the chromatin-modifying protein CHD8 as necessary for cell survival in a mouse model of BCR-Abl+ B-cell acute lymphoblastic leukemia. This disease has a poor prognosis despite treatment with kinase inhibitors targeting BCR-Abl. Although implicated as a risk factor in autism spectrum disorder and a tumor suppressor in prostate and lung cancer, the mechanism of CHD8's activity is still unclear and has never been studied in the context of hematopoietic malignancies. Here we demonstrate that depletion of CHD8 in B-ALL cells leads to cell death. While multiple B cell malignancies were dependent on CHD8 expression for survival, T cell malignancies displayed milder phenotypes upon CHD8 knockdown. In addition, ectopic expression of the Notch1 intracellular domain in a T cell malignancy partially alleviated the detrimental effect of CHD8 depletion. Our results demonstrate that CHD8 has a context-dependent role in cell survival, and its inhibition may be an effective treatment for B lymphoid malignancies.

PMID: 26588464 [PubMed - indexed for MEDLINE]

Mutation screening of the ubiquitin ligase gene RNF135 in French patients with autism.

June 21, 2016 - 6:33am
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Mutation screening of the ubiquitin ligase gene RNF135 in French patients with autism.

Psychiatr Genet. 2015 Dec;25(6):263-7

Authors: Tastet J, Decalonne L, Marouillat S, Malvy J, Thépault RA, Toutain A, Paubel A, Tabagh R, Bénédetti H, Laumonnier F, Barthélémy C, Bonnet-Brilhault F, Andres CR, Vourc'h P

Abstract
Many genes are now thought to confer susceptibility to autism. Despite the fact that this neuropsychiatric disease appears to be related to several different causes, common cellular and molecular pathways have emerged and point to synaptic dysfunction or cellular growth. Several studies have indicated the importance of the ubiquitin pathway in synaptic function and the aetiology of autism. Here, we focused on the ring finger protein 135 (RNF135) gene, encoding an E3 ubiquitin ligase expressed in the cortex and cerebellum, and located in the NF1 gene locus in 17q11.2, a region linked to autism. We carried out a genetic analysis of the coding sequence of RFN135 in a French cohort of patients with autism and observed a significantly increased frequency of genotypes carrying the rare allele of the rs111902263 (p.R115K) missense variant in patients (P=0.0019, odds ratio: 4.23, 95% confidence interval: 1.87-9.57). Particularly, three unrelated patients showed a homozygous genotype for K115, a situation not observed in the 1812 control individuals. Further cellular and molecular studies are required to elucidate the role of this gene and the variant K115 in brain development and neuronal function.

PMID: 26368817 [PubMed - indexed for MEDLINE]

Variant Rett syndrome in a girl with a pericentric X-chromosome inversion leading to epigenetic changes and overexpression of the MECP2 gene.

June 21, 2016 - 6:33am
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Variant Rett syndrome in a girl with a pericentric X-chromosome inversion leading to epigenetic changes and overexpression of the MECP2 gene.

Int J Dev Neurosci. 2015 Nov;46:82-7

Authors: Vieira JP, Lopes F, Silva-Fernandes A, Sousa MV, Moura S, Sousa S, Costa BM, Barbosa M, Ylstra B, Temudo T, Lourenço T, Maciel P

Abstract
Rett syndrome is a neurodevelopmental disorder caused by mutations in the MECP2 gene. We investigated the genetic basis of disease in a female patient with a Rett-like clinical. Karyotype analysis revealed a pericentric inversion in the X chromosome -46,X,inv(X)(p22.1q28), with breakpoints in the cytobands where the MECP2 and CDKL5 genes are located. FISH analysis revealed that the MECP2 gene is not dislocated by the inversion. However, and in spite of a balanced pattern of X inactivation, this patient displayed hypomethylation and an overexpression of the MECP2 gene at the mRNA level in the lymphocytes (mean fold change: 2.55±0.38) in comparison to a group of control individuals; the expression of the CDKL5 gene was similar to that of controls (mean fold change: 0.98±0.10). No gains or losses were detected in the breakpoint regions encompassing known or suspected transcription regulatory elements. We propose that the de-regulation of MECP2 expression in this patient may be due to alterations in long-range genomic interactions caused by the inversion and hypothesize that this type of epigenetic de-regulation of the MECP2 may be present in other RTT-like patients.

PMID: 26287660 [PubMed - indexed for MEDLINE]

Diagnosis of autism, abortion and the ethics of childcare in Yoruba culture.

June 21, 2016 - 6:33am
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Diagnosis of autism, abortion and the ethics of childcare in Yoruba culture.

Indian J Med Ethics. 2014 Oct-Dec;11(4):245-8

Authors: Fayemi AK

Abstract
This paper examines the ethics of childcare in Yoruba culture in the contexts of autism and abortion. The traditional Yoruba moral principles of ibikojuibi (equality of humans at birth) and ajowapo (solidarity) have been theoretically developed to establish the personhood of autistic children and provide a justification for not aborting foetuses with autism. Despite these justifications, this paper argues that there is a need for contextual rethinking, which would allow for: (i) prenatal genetic testing, as well as abortion of foetuses with a high risk of the autism mutation, and (ii) early clinical diagnosis and treatment of autistic children in contemporary Yoruba society.

PMID: 25377038 [PubMed - indexed for MEDLINE]

Fragile X Premutation Carrier Epidemiology and Symptomatology in Israel-Results from a Tertiary Child Developmental Center.

June 18, 2016 - 6:28am

Fragile X Premutation Carrier Epidemiology and Symptomatology in Israel-Results from a Tertiary Child Developmental Center.

Cerebellum. 2016 Jun 17;

Authors: Gabis LV, Gruber N, Berkenstadt M, Shefer S, Attia OL, Mula D, Cohen Y, Elizur SE

Abstract
Fragile X syndrome (FXS) is the most prevalent known genetically inherited cause for autism and intellectual disability. Premutation state can cause several clinical disorders as well. We aimed to perform a nesting approach to acquire data with regard to first degree relatives of index fragile X cases at the largest child development center in Israel in order to map characteristics of Israeli FXS permutation women carriers. Seventy-nine women were referred due to a related fragile X syndrome patient, mainly an offspring or sibling. General information regarding demographics, ethnicity, and associated medical conditions were collected using interviews and structured questionnaires. Thirteen (17 %) of the women who were referred as "carrier" were proven to be actually full mutation. The mean years of education were 14 (±1.51, range 12-17). Twenty-one women (27 %) originated from Tunisia (mainly from the island of Djerba). Ten women (13 %) reported delivery of their affected offspring beyond 41 gestational weeks. Twenty-two percent of women with premutation reported symptoms consistent with learning difficulties, mainly dyscalculia, and 14 % reported ADHD symptoms. Awareness about clinical disorders of the carriers was existent only in 25 % of the patients. Increased awareness and knowledge dissemination concerning premutation symptomatology and associated medical conditions are warranted. We suggest a national registry to be installed in different countries in order to identify fragile X premutation carriers at increased risk for various medical complications.

PMID: 27312842 [PubMed - as supplied by publisher]

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