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Identification of Human Neuronal Protein Complexes Reveals Biochemical Activities and Convergent Mechanisms of Action in Autism Spectrum Disorders.

March 8, 2016 - 7:21am

Identification of Human Neuronal Protein Complexes Reveals Biochemical Activities and Convergent Mechanisms of Action in Autism Spectrum Disorders.

Cell Syst. 2015 Nov 25;1(5):361-374

Authors: Li J, Ma Z, Shi M, Malty RH, Aoki H, Minic Z, Phanse S, Jin K, Wall DP, Zhang Z, Urban AE, Hallmayer J, Babu M, Snyder M

Abstract
The prevalence of autism spectrum disorders (ASDs) is rapidly growing, yet its molecular basis is poorly understood. We used a systems approach in which ASD candidate genes were mapped onto the ubiquitous human protein complexes and the resulting complexes were characterized. The studies revealed the role of histone deacetylases (HDAC1/2) in regulating the expression of ASD orthologs in the embryonic mouse brain. Proteome-wide screens for the co-complexed subunits with HDAC1 and six other key ASD proteins in neuronal cells revealed a protein interaction network, which displayed preferential expression in fetal brain development, exhibited increased deleterious mutations in ASD cases, and were strongly regulated by FMRP and MECP2 causal for Fragile X and Rett syndromes, respectively. Overall, our study reveals molecular components in ASD, suggests a shared mechanism between the syndromic and idiopathic forms of ASDs, and provides a systems framework for analyzing complex human diseases.

PMID: 26949739 [PubMed - as supplied by publisher]

Neocortical Neurogenesis and the Etiology of Autism Spectrum Disorder.

March 8, 2016 - 7:21am

Neocortical Neurogenesis and the Etiology of Autism Spectrum Disorder.

Neurosci Biobehav Rev. 2016 Mar 3;

Authors: Packer A

Abstract
Researchers have now identified many highly penetrant genetic risk factors for autism spectrum disorder (ASD). Some of these genes encode synaptic proteins, lending support to the hypothesis that ASD is a disorder of synaptic homeostasis. Less attention, however, has been paid to the genetic risk factors that converge on events that precede synaptogenesis, including the proliferation of neural progenitor cells and the migration of neurons to the appropriate layers of the developing neocortex. Here I review this evidence, focusing on studies of mutant mouse phenotypes, human postmortem data, systems biological analyses, and non-genetic risk factors. These findings highlight embryonic neurogenesis as a potentially important locus of pathology in ASD. In some instances, this pathology may be driven by alterations in chromatin biology and canonical Wnt signaling, which in turn affect fundamental cellular processes such as cell-cycle length and cell migration. This view of ASD suggests the need for a better understanding of the relationship between variation in neuron number, laminar composition, and the neural circuitry most relevant to the disorder.

PMID: 26949225 [PubMed - as supplied by publisher]

Males are from Mars, females are from Venus: sex-specific fetal brain gene expression signatures in a mouse model of maternal diet-induced obesity.

March 8, 2016 - 7:21am
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Males are from Mars, females are from Venus: sex-specific fetal brain gene expression signatures in a mouse model of maternal diet-induced obesity.

Am J Obstet Gynecol. 2016 Mar 2;

Authors: Edlow AG, Guedj F, Pennings JL, Sverdlov D, Neri C, Bianchi DW

Abstract
BACKGROUND: Maternal obesity is associated with adverse neurodevelopmental outcomes in children, including autism spectrum disorders, developmental delay, and attention deficit hyperactivity disorder. The underlying mechanisms remain unclear. We previously identified second trimester amniotic fluid and term cord blood gene expression patterns suggesting dysregulated brain development in fetuses of obese compared to lean women.
OBJECTIVES: We sought to investigate the biological significance of these findings in a mouse model of maternal diet-induced obesity. We evaluated sex-specific differences in fetal growth, brain gene expression signatures and associated pathways.
STUDY DESIGN: Female C57BL/6J mice were fed a 60% high-fat diet or 10% fat control diet for 12-14 weeks prior to mating. During pregnancy, obese dams continued on the high-fat diet (HFD/HFD), or transitioned to the CD (HFD/CD). Lean dams stayed on the control diet. On embryonic day 17.5, embryos were weighed and fetal brains were snap frozen. RNA was extracted from male and female forebrains (10/diet group/sex) and hybridized to whole genome expression arrays. Significantly differentially expressed genes were identified using Welch's t-test with the Benjamini-Hochberg correction. Functional analyses were performed using Ingenuity Pathways Analysis and Gene Set Enrichment Analysis.
RESULTS: Embryos of HFD/HFD dams were significantly smaller than controls, with males more severely affected than females (p=0.01). Maternal obesity and maternal obesity with dietary change in pregnancy resulted in significantly more dysregulated genes in male versus female fetal brains (386 vs 66, p<0.001). Maternal obesity with and without dietary change in pregnancy was associated with unique brain gene expression signatures for each sex, with overlap of only one gene. Changing obese dams to a control diet in pregnancy resulted in more differentially expressed genes in the fetal brain than maternal obesity alone. Functional analyses identified common dysregulated pathways in both sexes, but maternal obesity and maternal dietary change affected different aspects of brain development in males compared to females.
CONCLUSIONS: Maternal obesity is associated with sex-specific differences in fetal size and fetal brain gene expression signatures. Male fetal growth and brain gene expression may be more sensitive to environmental influences during pregnancy. Maternal diet during pregnancy significantly impacts the embryonic brain transcriptome. It is important to consider both fetal sex and maternal diet when evaluating the effects of maternal obesity on fetal neurodevelopment.

PMID: 26945603 [PubMed - as supplied by publisher]

Sequential ionic and conformational signaling by calcium channels drives neuronal gene expression.

March 8, 2016 - 7:21am
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Sequential ionic and conformational signaling by calcium channels drives neuronal gene expression.

Science. 2016 Feb 19;351(6275):863-7

Authors: Li B, Tadross MR, Tsien RW

Abstract
Voltage-gated CaV1.2 channels (L-type calcium channel α1C subunits) are critical mediators of transcription-dependent neural plasticity. Whether these channels signal via the influx of calcium ion (Ca(2+)), voltage-dependent conformational change (VΔC), or a combination of the two has thus far been equivocal. We fused CaV1.2 to a ligand-gated Ca(2+)-permeable channel, enabling independent control of localized Ca(2+) and VΔC signals. This revealed an unexpected dual requirement: Ca(2+) must first mobilize actin-bound Ca(2+)/calmodulin-dependent protein kinase II, freeing it for subsequent VΔC-mediated accumulation. Neither signal alone sufficed to activate transcription. Signal order was crucial: Efficiency peaked when Ca(2+) preceded VΔC by 10 to 20 seconds. CaV1.2 VΔC synergistically augmented signaling by N-methyl-d-aspartate receptors. Furthermore, VΔC mistuning correlated with autistic symptoms in Timothy syndrome. Thus, nonionic VΔC signaling is vital to the function of CaV1.2 in synaptic and neuropsychiatric processes.

PMID: 26912895 [PubMed - indexed for MEDLINE]

Walking on multiple disease-gene networks to prioritize candidate genes.

March 8, 2016 - 7:21am
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Walking on multiple disease-gene networks to prioritize candidate genes.

J Mol Cell Biol. 2015 Jun;7(3):214-30

Authors: Jiang R

Abstract
Uncovering causal genes for human inherited diseases, as the primary step toward understanding the pathogenesis of these diseases, requires a combined analysis of genetic and genomic data. Although bioinformatics methods have been designed to prioritize candidate genes resulting from genetic linkage analysis or association studies, the coverage of both diseases and genes in existing methods is quite limited, thereby preventing the scan of causal genes for a significant proportion of diseases at the whole-genome level. To overcome this limitation, we propose a method named pgWalk to prioritize candidate genes by integrating multiple phenomic and genomic data. We derive three types of phenotype similarities among 7719 diseases and nine types of functional similarities among 20327 genes. Based on a pair of phenotype and gene similarities, we construct a disease-gene network and then simulate the process that a random walker wanders on such a heterogeneous network to quantify the strength of association between a candidate gene and a query disease. A weighted version of the Fisher's method with dependent correction is adopted to integrate 27 scores obtained in this way, and a final q-value is calibrated for prioritizing candidate genes. A series of validation experiments are conducted to demonstrate the superior performance of this approach. We further show the effectiveness of this method in exome sequencing studies of autism and epileptic encephalopathies. An online service and the standalone software of pgWalk can be found at http://bioinfo.au.tsinghua.edu.cn/jianglab/pgwalk.

PMID: 25681405 [PubMed - indexed for MEDLINE]

Multimodal brain imaging in autism spectrum disorder and the promise of twin research.

March 8, 2016 - 7:21am
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Multimodal brain imaging in autism spectrum disorder and the promise of twin research.

Autism. 2015 Jul;19(5):527-41

Authors: Mevel K, Fransson P, Bölte S

Abstract
Current evidence suggests the phenotype of autism spectrum disorder to be driven by a complex interaction of genetic and environmental factors impacting onto brain maturation, synaptic function, and cortical networks. However, findings are heterogeneous, and the exact neurobiological pathways of autism spectrum disorder still remain poorly understood. The co-twin control or twin-difference design is a potentially powerful tool to disentangle causal genetic and environmental contributions on neurodevelopment in autism spectrum disorder. To this end, monozygotic twins discordant for this condition provide unique means for the maximum control of potentially confounding factors. Unfortunately, only few studies of a rather narrow scope, and limited sample size, have been conducted. In an attempt to highlight the great potential of combining the brain connectome approach with monozygotic twin design, we first give an overview of the existing neurobiological evidence for autism spectrum disorder and its cognitive correlates. Then, a special focus is made onto the brain imaging findings reported within populations of monozygotic twins phenotypically discordant for autism spectrum disorder. Finally, we introduce the brain connectome model and describe an ongoing project using this approach among the largest cohort of monozygotic twins discordant for autism spectrum disorder ever recruited.

PMID: 24916451 [PubMed - indexed for MEDLINE]

Developmental role of the cell adhesion molecule Contactin-6 in the cerebral cortex and hippocampus.

March 5, 2016 - 7:01am

Developmental role of the cell adhesion molecule Contactin-6 in the cerebral cortex and hippocampus.

Cell Adh Migr. 2016 Mar 3;:0

Authors: Zuko A, Oguro-Ando A, Van Dijk R, Gregorio-Jordan S, Van Der Zwaag B, Burbach JP

Abstract
The gene encoding the neural cell adhesion molecule Contactin-6 (Cntn6 a.k.a. NB-3) has been implicated as an autism risk gene, suggesting that its mutation is deleterious to brain development. Due to its GPI-anchoring at Cntn6 may exert cell adhesion/receptor functions in complex with other membrane proteins, or serve as a ligand. We aimed to uncover novel phenotypes related to Cntn6 functions during development in the cerebral cortex of adult Cntn6(-/-) mice. We first determined Cntn6 protein and mRNA expression in the cortex, thalamic nuclei and the hippocampus at P14, which decreased specifically in the cortex at adult stages. Neuroanatomical analysis demonstrated a significant decrease of Cux1+ projection neurons in layers II-IV and an increase of FoxP2+ projection neurons in layer VI in the visual cortex of adult Cntn6(-/-) mice compared to wild-type controls. Furthermore, the number of parvalbumin+ (PV) interneurons was decreased in Cntn6(-/-) mice, while the amount of NPY+ interneurons remained unchanged. In the hippocampus the delineation and outgrowth of mossy fibers remained largely unchanged, except for the observation of a larger suprapyramidal bundle. The observed abnormalities in the cerebral cortex and hippocampus of Cntn6(-/-) mice suggests that Cntn6 serves developmental functions involving cell survival, migration and fasciculation. Furthermore, hese data suggest that Cntn6 engages in both trans- and cis-interactions and may be involved in larger protein interaction networks.

PMID: 26939565 [PubMed - as supplied by publisher]

Genetic Studies in Autism.

March 5, 2016 - 7:01am
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Genetic Studies in Autism.

Indian J Pediatr. 2016 Mar 3;

Authors: Sudarshan S, Gupta N, Kabra M

Abstract
Autism is a complex neurodevelopmental disorder, which has captured the attention of not only pediatricians but also the parents. From the symptoms until the final diagnosis, parents undergo a diagnostic odyssey that involves a battery of tests without much yield. This has led to an increase in the referrals to the clinical geneticists to rule out the possible genetic etiology that can have implications for the parents for future pregnancy. This chapter focuses on the various genetic causes and their appropriate application in the evaluation of a child with Autism Spectrum Disorders (ASDs).

PMID: 26935198 [PubMed - as supplied by publisher]

Autism Linked to Increased Oncogene Mutations but Decreased Cancer Rate.

March 5, 2016 - 7:01am
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Autism Linked to Increased Oncogene Mutations but Decreased Cancer Rate.

PLoS One. 2016;11(3):e0149041

Authors: Darbro BW, Singh R, Zimmerman MB, Mahajan VB, Bassuk AG

Abstract
Autism spectrum disorder (ASD) is one phenotypic aspect of many monogenic, hereditary cancer syndromes. Pleiotropic effects of cancer genes on the autism phenotype could lead to repurposing of oncology medications to treat this increasingly prevalent neurodevelopmental condition for which there is currently no treatment. To explore this hypothesis we sought to discover whether autistic patients more often have rare coding, single-nucleotide variants within tumor suppressor and oncogenes and whether autistic patients are more often diagnosed with neoplasms. Exome-sequencing data from the ARRA Autism Sequencing Collaboration was compared to that of a control cohort from the Exome Variant Server database revealing that rare, coding variants within oncogenes were enriched for in the ARRA ASD cohort (p<1.0x10-8). In contrast, variants were not significantly enriched in tumor suppressor genes. Phenotypically, children and adults with ASD exhibited a protective effect against cancer, with a frequency of 1.3% vs. 3.9% (p<0.001), but the protective effect decreased with age. The odds ratio of neoplasm for those with ASD relative to controls was 0.06 (95% CI: 0.02, 0.19; p<0.0001) in the 0 to 14 age group; 0.35 (95% CI: 0.14, 0.87; p = 0.024) in the 15 to 29 age group; 0.41 (95% CI: 0.15, 1.17; p = 0.095) in the 30 to 54 age group; and 0.49 (95% CI: 0.14, 1.74; p = 0.267) in those 55 and older. Both males and females demonstrated the protective effect. These findings suggest that defects in cellular proliferation, and potentially senescence, might influence both autism and neoplasm, and already approved drugs targeting oncogenic pathways might also have therapeutic value for treating autism.

PMID: 26934580 [PubMed - in process]

Synaptic vesicle dynamic changes in a model of fragile X.

March 5, 2016 - 7:01am
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Synaptic vesicle dynamic changes in a model of fragile X.

Mol Autism. 2016;7:17

Authors: Broek JA, Lin Z, de Gruiter HM, van 't Spijker H, Haasdijk ED, Cox D, Ozcan S, van Cappellen GW, Houtsmuller AB, Willemsen R, de Zeeuw CI, Bahn S

Abstract
BACKGROUND: Fragile X syndrome (FXS) is a single-gene disorder that is the most common heritable cause of intellectual disability and the most frequent monogenic cause of autism spectrum disorders (ASD). FXS is caused by an expansion of trinucleotide repeats in the promoter region of the fragile X mental retardation gene (Fmr1). This leads to a lack of fragile X mental retardation protein (FMRP), which regulates translation of a wide range of messenger RNAs (mRNAs). The extent of expression level alterations of synaptic proteins affected by FMRP loss and their consequences on synaptic dynamics in FXS has not been fully investigated.
METHODS: Here, we used an Fmr1 knockout (KO) mouse model to investigate the molecular mechanisms underlying FXS by monitoring protein expression changes using shotgun label-free liquid-chromatography mass spectrometry (LC-MS(E)) in brain tissue and synaptosome fractions. FXS-associated candidate proteins were validated using selected reaction monitoring (SRM) in synaptosome fractions for targeted protein quantification. Furthermore, functional alterations in synaptic release and dynamics were evaluated using live-cell imaging, and interpretation of synaptic dynamics differences was investigated using electron microscopy.
RESULTS: Key findings relate to altered levels of proteins involved in GABA-signalling, especially in the cerebellum. Further exploration using microscopy studies found reduced synaptic vesicle unloading of hippocampal neurons and increased vesicle unloading in cerebellar neurons, which suggests a general decrease of synaptic transmission.
CONCLUSIONS: Our findings suggest that FMRP is a regulator of synaptic vesicle dynamics, which supports the role of FMRP in presynaptic functions. Taken together, these studies provide novel insights into the molecular changes associated with FXS.

PMID: 26933487 [PubMed]

The sodium-activated potassium channel Slack is required for optimal cognitive flexibility in mice.

March 5, 2016 - 7:01am
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The sodium-activated potassium channel Slack is required for optimal cognitive flexibility in mice.

Learn Mem. 2015 Jul;22(7):323-35

Authors: Bausch AE, Dieter R, Nann Y, Hausmann M, Meyerdierks N, Kaczmarek LK, Ruth P, Lukowski R

Abstract
Kcnt1 encoded sodium-activated potassium channels (Slack channels) are highly expressed throughout the brain where they modulate the firing patterns and general excitability of many types of neurons. Increasing evidence suggests that Slack channels may be important for higher brain functions such as cognition and normal intellectual development. In particular, recent findings have shown that human Slack mutations produce very severe intellectual disability and that Slack channels interact directly with the Fragile X mental retardation protein (FMRP), a protein that when missing or mutated results in Fragile X syndrome (FXS), the most common form of inherited intellectual disability and autism in humans. We have now analyzed a recently developed Kcnt1 null mouse model in several behavioral tasks to assess which aspects of memory and learning are dependent on Slack. We demonstrate that Slack deficiency results in mildly altered general locomotor activity, but normal working memory, reference memory, as well as cerebellar control of motor functions. In contrast, we find that Slack channels are required for cognitive flexibility, including reversal learning processes and the ability to adapt quickly to unfamiliar situations and environments. Our data reveal that hippocampal-dependent spatial learning capabilities require the proper function of Slack channels.

PMID: 26077685 [PubMed - indexed for MEDLINE]

Deciphering discord: How Drosophila research has enhanced our understanding of the importance of FMRP in different spatial and temporal contexts.

March 5, 2016 - 7:01am
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Deciphering discord: How Drosophila research has enhanced our understanding of the importance of FMRP in different spatial and temporal contexts.

Exp Neurol. 2015 Dec;274(Pt A):14-24

Authors: Weisz ED, Monyak RE, Jongens TA

Abstract
Fragile X Syndrome (FXS) is the most common heritable form of intellectual impairment as well as the leading monogenetic cause of autism. In addition to its canonical definition as a neurodevelopmental disease, recent findings in the clinic suggest that FXS is a systemic disorder that is characterized by a variety of heterogeneous phenotypes. Efforts to study FXS pathogenesis have been aided by the development and characterization of animal models of the disease. Research efforts in Drosophila melanogaster have revealed key insights into the mechanistic underpinnings of FXS. While much remains unknown, it is increasingly apparent that FXS involves a myriad of spatially and temporally specific alterations in cellular function. Consequently, the literature is filled with numerous discordant findings. Researchers and clinicians alike must be cognizant of this dissonance, as it will likely be important for the design of preclinical studies to assess the efficacy of therapeutic strategies to improve the lives of FXS patients.

PMID: 26026973 [PubMed - indexed for MEDLINE]

Developmental trajectories in 22q11.2 deletion.

March 5, 2016 - 7:01am
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Developmental trajectories in 22q11.2 deletion.

Am J Med Genet C Semin Med Genet. 2015 Jun;169(2):172-81

Authors: Swillen A, McDonald-McGinn D

Abstract
Chromosome 22q11.2 deletion syndrome (22q11.2DS), a neurogenetic condition, is the most common microdeletion syndrome affecting 1 in 2,000-4,000 live births and involving haploinsufficiency of ∼50 genes resulting in a multisystem disorder. Phenotypic expression is highly variable and ranges from severe life-threatening conditions to only a few associated features. Most common medical problems include: congenital heart disease, in particular conotruncal anomalies; palatal abnormalities, most frequently velopharyngeal incompetence (VPI); immunodeficiency; hypocalcemia due to hypoparathyroidism; genitourinary anomalies; severe feeding/gastrointestinal differences; and subtle dysmorphic facial features. The neurocognitive profile is also highly variable, both between individuals and during the course of development. From infancy onward, motor delays (often with hypotonia) and speech/language deficits are commonly observed. During the preschool and primary school ages, learning difficulties are very common. The majority of patients with 22q11.2DS have an intellectual level that falls in the borderline range (IQ 70-84), and about one-third have mild to moderate intellectual disability. More severe levels of intellectual disability are uncommon in children and adolescents but are more frequent in adults. Individuals with 22q11.2DS are at an increased risk for developing several psychiatric disorders including attention deficit with hyperactivity disorder (ADHD), autism spectrum disorder (ASD), anxiety and mood disorders, and psychotic disorders and schizophrenia. In this review, we will focus on the developmental phenotypic transitions regarding cognitive development in 22q11.2DS from early preschool to adulthood, and on the changing behavioral/psychiatric phenotype across age, on a background of frequently complex medical conditions.

PMID: 25989227 [PubMed - indexed for MEDLINE]

Developmental trajectories in cognitive-behavioral phenotypes: Introduction.

March 5, 2016 - 7:01am
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Developmental trajectories in cognitive-behavioral phenotypes: Introduction.

Am J Med Genet C Semin Med Genet. 2015 Jun;169(2):131-4

Authors: Fisch GS

Abstract
Developmental trajectories in behavioral phenotypes are important areas for systematic research and have been for more than 30 years. They interweave several important strands related to human growth: that of individuals born with some form of intellectual impairment or disability (ID); second, the genetics associated with intellectual ability and disability; and third, at the behavioral level, the dynamic expression and variability of specific abnormalities as individuals age. ID, and the genetic disorders that produce ID, were often not well-received by earlier societies. While the inheritance of behavior and intellectual ability has probably been observed throughout human history, the systematic investigation of the inheritance of intellectual ability probably begins with Sir Francis Galton, in his treatise Hereditary Genius in 1869. The dynamic features of ID have its roots in late 19th century developmental psychology and early 20th century pediatrics. Alfred Binet, along with his colleague Theodore Simon, created the first methods of formal intelligence testing of children for the French school system. Scores based on the items administered would then be used to distinguish children who were prepared for enrollment in a standard educational program from those who were not. The confluence of these research topics brings us to the subject of our Special Issue.

PMID: 25959524 [PubMed - indexed for MEDLINE]

Unusual retrospective prenatal findings in a male newborn with Timothy syndrome type 1.

March 5, 2016 - 7:01am
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Unusual retrospective prenatal findings in a male newborn with Timothy syndrome type 1.

Eur J Med Genet. 2015 Jun-Jul;58(6-7):332-5

Authors: Corona-Rivera JR, Barrios-Prieto E, Nieto-García R, Bloise R, Priori S, Napolitano C, Bobadilla-Morales L, Corona-Rivera A, Zapata-Aldana E, Peña-Padilla C, Rivera-Vargas J, Chavana-Naranjo E

Abstract
Timothy syndrome 1 (TS1) is a multisystem disorder characterized by severe QT prolongation and potentially lethal ventricular arrhythmias in the first years of life, plus other cardiac and extracardiac manifestations caused by mutation in the CACNA1C gene, a CaV1.2 L-type calcium channel. Here, we report retrospectively an unusual fetal presentation on a second patient with TS1 with fetal hydrops due to a congenital AV block and its postnatal diagnosis by a marked prolongation of the corrected QTc interval of 570 ms and a missense mutation, p.Gly406Arg, in exon 8A of CACNA1C gene. The observed manifestations in our patient during fetal period indicate a severe form and they were probably exacerbated by the maternal use of amitriptyline during the first 4 months of pregnancy. Unfortunately, he died at 3 months-old due a ventricular tachycardia and fibrillation related to a septic event. Although difficult to diagnose, possibly most fetuses with TS1 have symptoms of long QT syndrome. Despite the fatal outcome for our patient, an early diagnosis of TS may help to prevent life-threatening events or early death in future patients, especially in developing countries where availability of therapies such as cardioverter defibrillator are very limited, or require time for its funding.

PMID: 25882468 [PubMed - indexed for MEDLINE]

Novel rare missense variations and risk of autism spectrum disorder: whole-exome sequencing in two families with affected siblings and a two-stage follow-up study in a Japanese population.

March 5, 2016 - 7:01am
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Novel rare missense variations and risk of autism spectrum disorder: whole-exome sequencing in two families with affected siblings and a two-stage follow-up study in a Japanese population.

PLoS One. 2015;10(3):e0119413

Authors: Egawa J, Watanabe Y, Wang C, Inoue E, Sugimoto A, Sugiyama T, Igeta H, Nunokawa A, Shibuya M, Kushima I, Orime N, Hayashi T, Okada T, Uno Y, Ozaki N, Someya T

Abstract
Rare inherited variations in multiplex families with autism spectrum disorder (ASD) are suggested to play a major role in the genetic etiology of ASD. To further investigate the role of rare inherited variations, we performed whole-exome sequencing (WES) in two families, each with three affected siblings. We also performed a two-stage follow-up case-control study in a Japanese population. WES of the six affected siblings identified six novel rare missense variations. Among these variations, CLN8 R24H was inherited in one family by three affected siblings from an affected father and thus co-segregated with ASD. In the first stage of the follow-up study, we genotyped the six novel rare missense variations identified by WES in 241 patients and 667 controls (the Niigata sample). Only CLN8 R24H had higher mutant allele frequencies in patients (1/482) compared with controls (1/1334). In the second stage, this variation was further genotyped, yet was not detected in a sample of 309 patients and 350 controls (the Nagoya sample). In the combined Niigata and Nagoya samples, there was no significant association (odds ratio = 1.8, 95% confidence interval = 0.1-29.6). These results suggest that CLN8 R24H plays a role in the genetic etiology of ASD, at least in a subset of ASD patients.

PMID: 25806950 [PubMed - indexed for MEDLINE]

Increased female autosomal burden of rare copy number variants in human populations and in autism families.

March 5, 2016 - 7:01am
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Increased female autosomal burden of rare copy number variants in human populations and in autism families.

Mol Psychiatry. 2015 Feb;20(2):170-5

Authors: Desachy G, Croen LA, Torres AR, Kharrazi M, Delorenze GN, Windham GC, Yoshida CK, Weiss LA

Abstract
Autosomal genetic variation is presumed equivalent in males and females and makes a major contribution to disease risk. We set out to identify whether maternal copy number variants (CNVs) contribute to autism spectrum disorders (ASDs). Surprisingly, we observed a higher autosomal burden of large, rare CNVs in females in the population, reflected in, but not unique to, ASD families. Meta-analysis across control data sets confirms female excess in CNV number (P=2.1 × 10(-5)) and gene content (P=4.1 × 10(-3)). We additionally observed CNV enrichment in ASD mothers compared with control mothers (P=0.03). We speculate that tolerance for CNV burden contributes to decreased female fetal loss in the population and that ASD-specific maternal CNV burden may contribute to high sibling recurrence. These data emphasize the need for study of familial CNV risk factors in ASDs and the requirement of sex-matched comparisons.

PMID: 25582617 [PubMed - indexed for MEDLINE]

Proteomic analysis and identification of cellular interactors of the giant ubiquitin ligase HERC2.

March 5, 2016 - 7:01am
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Proteomic analysis and identification of cellular interactors of the giant ubiquitin ligase HERC2.

J Proteome Res. 2015 Feb 6;14(2):953-66

Authors: Galligan JT, Martinez-Noël G, Arndt V, Hayes S, Chittenden TW, Harper JW, Howley PM

Abstract
HERC2 is a large E3 ubiquitin ligase with multiple structural domains that has been implicated in an array of cellular processes. Mutations in HERC2 are linked to developmental delays and impairment caused by nervous system dysfunction, such as Angelman Syndrome and autism-spectrum disorders. However, HERC2 cellular activity and regulation remain poorly understood. We used a broad proteomic approach to survey the landscape of cellular proteins that interact with HERC2. We identified nearly 300 potential interactors, a subset of which we validated binding to HERC2. The potential HERC2 interactors included the eukaryotic translation initiation factor 3 complex, the intracellular transport COPI coatomer complex, the glycogen regulator phosphorylase kinase, beta-catenin, PI3 kinase, and proteins involved in fatty acid transport and iron homeostasis. Through a complex bioinformatic analysis of potential interactors, we linked HERC2 to cellular processes including intracellular protein trafficking and transport, metabolism of cellular energy, and protein translation. Given its size, multidomain structure, and association with various cellular activities, HERC2 may function as a scaffold to integrate protein complexes and bridge critical cellular pathways. This work provides a significant resource with which to interrogate HERC2 function more deeply and evaluate its contributions to mechanisms governing cellular homeostasis and disease.

PMID: 25476789 [PubMed - indexed for MEDLINE]

Early pragmatic language difficulties in siblings of children with autism: implications for DSM-5 social communication disorder?

March 5, 2016 - 7:01am
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Early pragmatic language difficulties in siblings of children with autism: implications for DSM-5 social communication disorder?

J Child Psychol Psychiatry. 2015 Jul;56(7):774-81

Authors: Miller M, Young GS, Hutman T, Johnson S, Schwichtenberg AJ, Ozonoff S

Abstract
BACKGROUND: We evaluated early pragmatic language skills in preschool-age siblings of children with autism spectrum disorder (ASD), and examined correspondence between pragmatic language impairments and general language difficulties, autism symptomatology, and clinical outcomes.
METHODS: Participants were younger siblings of children with ASD (high-risk, n = 188) or typical development (low-risk, n = 119) who were part of a prospective study of infants at risk for ASD; siblings without ASD outcomes were included in analyses. Pragmatic language skills were measured via the Language Use Inventory (LUI).
RESULTS: At 36 months, the high-risk group had significantly lower parent-rated pragmatic language scores than the low-risk group. When defining pragmatic language impairment (PLI) as scores below the 10(th) percentile on the LUI, 35% of the high-risk group was identified with PLI versus 10% of the low-risk group. Children with PLI had higher rates of general language impairment (16%), defined as scores below the 10(th) percentile on the Receptive or Expressive Language subscales of the Mullen Scales of Early Learning, relative to those without PLI (3%), but most did not evidence general language impairments. Children with PLI had significantly higher ADOS scores than those without PLI and had higher rates of clinician-rated atypical clinical best estimate outcomes (49%) relative to those without PLI (15%).
CONCLUSIONS: Pragmatic language problems are present in some siblings of children with ASD as early as 36 months of age. As the new DSM-5 diagnosis of Social (Pragmatic) Communication Disorder (SCD) is thought to occur more frequently in family members of individuals with ASD, it is possible that some of these siblings will meet criteria for SCD as they get older. Close monitoring of early pragmatic language development in young children at familial risk for ASD is warranted.

PMID: 25315782 [PubMed - indexed for MEDLINE]

Adenylosuccinate lyase deficiency.

March 5, 2016 - 7:01am
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Adenylosuccinate lyase deficiency.

J Inherit Metab Dis. 2015 Mar;38(2):231-42

Authors: Jurecka A, Zikanova M, Kmoch S, Tylki-Szymańska A

Abstract
Adenylosuccinate lyase ADSL) deficiency is a defect of purine metabolism affecting purinosome assembly and reducing metabolite fluxes through purine de novo synthesis and purine nucleotide recycling pathways. Biochemically this defect manifests by the presence in the biologic fluids of two dephosphorylated substrates of ADSL enzyme: succinylaminoimidazole carboxamide riboside (SAICAr) and succinyladenosine (S-Ado). More than 80 individuals with ADSL deficiency have been identified, but incidence of the disease remains unknown. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The fatal neonatal form has onset from birth and presents with fatal neonatal encephalopathy with a lack of spontaneous movement, respiratory failure, and intractable seizures resulting in early death within the first weeks of life. Patients with type I (severe form) present with a purely neurologic clinical picture characterized by severe psychomotor retardation, microcephaly, early onset of seizures, and autistic features. A more slowly progressing form has also been described (type II, moderate or mild form), as having later onset, usually within the first years of life, slight to moderate psychomotor retardation and transient contact disturbances. Diagnosis is facilitated by demonstration of SAICAr and S-Ado in extracellular fluids such as plasma, cerebrospinal fluid and/or followed by genomic and/or cDNA sequencing and characterization of mutant proteins. Over 50 ADSL mutations have been identified and their effects on protein biogenesis, structural stability and activity as well as on purinosome assembly were characterized. To date there is no specific and effective therapy for ADSL deficiency.

PMID: 25112391 [PubMed - indexed for MEDLINE]

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