Mutation screening and association study of the UBE2H gene on chromosome 7q32 in autistic disorder

Multisite phosphorylation dictates selective E2-E3 pairing as revealed by Ubc8/UBE2H-GID/CTLH assemblies

Ubiquitylation is catalyzed by coordinated actions of E3 and E2 enzymes. Molecular principles governing many important E3-E2 partnerships remain unknown, including those for RING-family GID/CTLH E3 ubiquitin ligases and their dedicated E2, Ubc8/UBE2H (yeast/human nomenclature). GID/CTLH-Ubc8/UBE2H-mediated ubiquitylation regulates biological processes ranging from yeast metabolic signaling to human development. Here, cryoelectron microscopy (cryo-EM), biochemistry, and cell biology reveal this exquisitely specific E3-E2 pairing through an unconventional catalytic assembly and auxiliary interactions 70-100 Å away, mediated by E2 multisite phosphorylation. Rather than dynamic polyelectrostatic interactions reported for other ubiquitylation complexes, multiple Ubc8/UBE2H phosphorylation sites within acidic CK2-targeted sequences specifically anchor the E2 C termini to E3 basic patches. Positions of phospho-dependent interactions relative to the catalytic domains correlate across evolution. Overall, our data show that phosphorylation-dependent multivalency establishes a specific E3-E2 partnership, is antagonistic with dephosphorylation, rigidifies the catalytic centers within a flexing GID E3-substrate assembly, and facilitates substrate collision with ubiquitylation active sites.

Genome-Wide Association Analysis of Heat Tolerance in F2 Progeny from the Hybridization between Two Congeneric Oyster Species

As the world's largest farmed marine animal, oysters have enormous economic and ecological value. However, mass summer mortality caused by high temperature poses a significant threat to the oyster industry. To investigate the molecular mechanisms underlying heat adaptation and improve the heat tolerance ability in the oyster, we conducted genome-wide association analysis (GWAS) analysis on the F2 generation derived from the hybridization of relatively heat-tolerant Crassostrea angulata ♀ and heat-sensitive Crassostrea gigas ♂, which are the dominant cultured species in southern and northern China, respectively. Acute heat stress experiment (semi-lethal temperature 42 °C) demonstrated that the F2 population showed differentiation in heat tolerance, leading to extremely differentiated individuals (approximately 20% of individuals die within the first four days with 10% survival after 14 days). Genome resequencing and GWAS of the two divergent groups had identified 18 significant SNPs associated with heat tolerance, with 26 candidate genes located near these SNPs. Eleven candidate genes that may associate with the thermal resistance were identified, which were classified into five categories: temperature sensor (Trpm2), transcriptional factor (Gata3), protein ubiquitination (Ube2h, Usp50, Uchl3), heat shock subfamily (Dnajc17, Dnaja1), and transporters (Slc16a9, Slc16a14, Slc16a9, Slc16a2). The expressional differentiation of the above genes between C. gigas and C. angulata under sublethal temperature (37 °C) further supports their crucial role in coping with high temperature. Our results will contribute to understanding the molecular mechanisms underlying heat tolerance, and provide genetic markers for heat-resistance breeding in the oyster industry.

A heterozygous mutation in UBE2H in a patient with developmental delay leads to an aberrant brain development in zebrafish

BACKGROUND

Ubiquitin-related rare diseases are generally characterized by developmental delays and mental retardation, but the exact incidence or prevalence is not yet fully understood. The clinical application of next-generation sequencing for pediatric seizures and developmental delay of unknown causes has become common in studies aimed at identification of a causal gene in patients with ubiquitin-related rare diseases that cannot be diagnosed using conventional fluorescence in situ hybridization or chromosome microarray tests. Our study aimed to investigate the effects of ubiquitin-proteasome system on ultra-rare neurodevelopmental diseases, through functional identification of candidate genes and variants.

METHODS

In our present work, we carried out genome analysis of a patient with clinical phenotypes of developmental delay and intractable convulsion, to identify causal mutations. Further characterization of the candidate gene was performed using zebrafish, through gene knockdown approaches. Transcriptomic analysis using whole embryos of zebrafish knockdown morphants and additional functional studies identified downstream pathways of the candidate gene affecting neurogenesis.

RESULTS

Through trio-based whole-genome sequencing analysis, we identified a de novo missense variant of the ubiquitin system-related gene UBE2H (c.449C>T; p.Thr150Met) in the proband. Using zebrafish, we found that Ube2h is required for normal brain development. Differential gene expression analysis revealed activation of the ATM-p53 signaling pathway in the absence of Ube2h. Moreover, depletion of ube2h led to induction of apoptosis, specifically in the differentiated neural cells. Finally, we found that a missense mutation in zebrafish, ube2h (c.449C>T; p.Thr150Met), which mimics a variant identified in a patient with neurodevelopmental defects, causes aberrant Ube2h function in zebrafish embryos.

CONCLUSION

A de novo heterozygous variant in the UBE2H c.449C>T (p.Thr150Met) has been identified in a pediatric patient with global developmental delay and UBE2H is essential for normal neurogenesis in the brain.

Construction of a circRNA-Mediated ceRNA Network Reveals Novel Biomarkers for Aortic Dissection

Background

Aortic dissection (AD) is a rare and lethal disorder with its genetic basis remains largely unknown. Many studies have confirmed that circRNAs play important roles in various physiological and pathological processes. However, the roles of circRNAs in AD are still unclear and need further investigation. The present study aimed to elucidate the underlying molecular mechanisms of circRNAs regulation in AD based on the circRNA-associated competing endogenous RNA (ceRNA) network.

Methods

Expression profiles of circRNAs (GSE97745), miRNAs (GSE92427), and mRNAs (GSE52093) were downloaded from Gene Expression Omnibus (GEO) databases, and the differentially expressed RNAs (DERNAs) were subsequently identified by bioinformatics analysis. CircRNA–miRNA–mRNA ceRNA network, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were used to predict the potential functions of circRNA-associated ceRNA network. RNA was isolated from human arterial blood samples after which qRT-PCR was performed to confirm the DERNAs.

Results

We identified 14 (5 up-regulated and 9 down-regulated) differentially expressed circRNAs (DEcircRNAs), 17 (8 up-regulated and 9 down-regulated) differentially expressed miRNAs (DEmiRNAs) and 527 (297 up-regulated and 230 down-regulated) differentially expressed mRNAs (DEmRNAs) (adjusted P-value <0.05 and | log2FC | > 1.0). KEGG pathway analysis indicated that DEmRNAs were related to focal adhesion and extracellular matrix receptor interaction signaling pathways. Simultaneously, the present study constructed a ceRNA network based on 1 circRNAs (hsa_circRNA_082317), 1 miRNAs (hsa-miR-149-3p) and 10 mRNAs (MLEC, ENTPD7, SLC16A3, SLC7A8, TBC1D16, PAQR4, MAPK13, PIK3R2, ITGA5, SERPINA1). qRT-PCR demonstrated that hsa_circRNA_082317 and ITGA5 were significantly up-regulated, and hsa-miR-149-3p was dramatically down-regulated in AD (n = 3).

Conclusion

This is the first study to demonstrate the circRNA-associated ceRNA network is altered in AD, implying that circRNAs may play important roles in regulating the onset and progression and thus may serve as potential biomarkers for the diagnosis and treatment of AD.

Pierre C, Bimschleger H, Gao J, Cheng R, Polesskaya O, Solberg Woods LC, Palmer AA, Chen H. Genome-Wide Association Study on Three Behaviors Tested in an Open Field in Heterogeneous Stock Rats Identifies Multiple Loci Implicated in Psychiatric Disorders

Many personality traits are influenced by genetic factors. Rodents models provide an efficient system for analyzing genetic contribution to these traits. Using 1,246 adolescent heterogeneous stock (HS) male and female rats, we conducted a genome-wide association study (GWAS) of behaviors measured in an open field, including locomotion, novel object interaction, and social interaction. We identified 30 genome-wide significant quantitative trait loci (QTL). Using multiple criteria, including the presence of high impact genomic variants and co-localization of cis-eQTL, we identified 17 candidate genes (Adarb2, Ankrd26, Cacna1c, Cacng4, Clock, Ctu2, Cyp26b1, Dnah9, Gda, Grxcr1, Eva1a, Fam114a1, Kcnj9, Mlf2, Rab27b, Sec11a, and Ube2h) for these traits. Many of these genes have been implicated by human GWAS of various psychiatric or drug abuse related traits. In addition, there are other candidate genes that likely represent novel findings that can be the catalyst for future molecular and genetic insights into human psychiatric diseases. Together, these findings provide strong support for the use of the HS population to study psychiatric disorders.

The Molecular Basis of Ubiquitin-Conjugating Enzymes (E2s) as a Potential Target for Cancer Therapy

Ubiquitin-conjugating enzymes (E2s) are one of the three enzymes required by the ubiquitin-proteasome pathway to connect activated ubiquitin to target proteins via ubiquitin ligases. E2s determine the connection type of the ubiquitin chains, and different types of ubiquitin chains regulate the stability and activity of substrate proteins. Thus, E2s participate in the regulation of a variety of biological processes. In recent years, the importance of E2s in human health and diseases has been particularly emphasized. Studies have shown that E2s are dysregulated in variety of cancers, thus it might be a potential therapeutic target. However, the molecular basis of E2s as a therapeutic target has not been described systematically. We reviewed this issue from the perspective of the special position and role of E2s in the ubiquitin-proteasome pathway, the structure of E2s and biological processes they are involved in. In addition, the inhibitors and microRNAs targeting E2s are also summarized. This article not only provides a direction for the development of effective drugs but also lays a foundation for further study on this enzyme in the future.

Predictive Potential of Circulating Ube2h mRNA as an E2 Ubiquitin-Conjugating Enzyme for Diagnosis or Treatment of Alzheimer's Disease

Neurodegenerative disorders are caused by neuronal cell death, miscommunications between synapse, and abnormal accumulations of proteins in the brain. Alzheimer’s disease (AD) is one of the age-related disorders, which are the most common degenerative disorders today, and strongly affects memory consolidation and cognitive function in the brain. Amyloid-β and tau proteins are triggers for AD pathogenesis, and usually used as AD candidate biomarkers in the clinical research. Especially, clinical exam, brain imaging and molecular biological methods are being used to diagnosis for AD. Genome-wide association study (GWAS) is a new biomedical method, and its use contributes to understanding many human diseases, including brain diseases. Here, we identified ubiquitin conjugating enzyme E2 (Ube2) gene expression in neurons through GWAS. The subfamilies of Ube2’s genetic expression and inborn errors affect the ubiquitin proteasome system (UPS), leading to protein degradation in the brain. We found that only Ube2h mRNA transcription was significantly increased in the blood from AD, however we did not find any change of Ube2 subfamily genes’ expression in the blood and brain tissue. These data may provide information for diagnosis or clinical approach, and suggest that cell-free circulating Ube2h mRNA is a novel potential biomarker for AD.

New Insights into the Role of E2s in the Pathogenesis of Diseases: Lessons Learned from UBE2O

Intracellular communication via ubiquitin (Ub) signaling impacts all aspects of cell biology and regulates pathways critical to human development and viability; therefore aberrations or defects in Ub signaling can contribute to the pathogenesis of human diseases. Ubiquitination consists of the addition of Ub to a substrate protein via coordinated action of E1-activating, E2-conjugating and E3-ligating enzymes. Approximately 40 E2s have been identified in humans, and most are thought to be involved in Ub transfer; although little information is available regarding the majority of them, emerging evidence has highlighted their importance to human health and disease. In this review, we focus on recent insights into the pathogenetic roles of E2s (particularly the ubiquitin-conjugating enzyme E2O [UBE2O]) in debilitating diseases and cancer, and discuss the tantalizing prospect that E2s may someday serve as potential therapeutic targets for human diseases.

Neuronal Proteomic Analysis of the Ubiquitinated Substrates of the Disease-Linked E3 Ligases Parkin and Ube3a

Both Parkin and UBE3A are E3 ubiquitin ligases whose mutations result in severe brain dysfunction. Several of their substrates have been identified using cell culture models in combination with proteasome inhibitors, but not in more physiological settings. We recently developed the ^bioUb strategy to isolate ubiquitinated proteins in flies and have now identified by mass spectrometry analysis the neuronal proteins differentially ubiquitinated by those ligases. This is an example of how flies can be used to provide biological material in order to reveal steady state substrates of disease causing genes. Collectively our results provide new leads to the possible physiological functions of the activity of those two disease causing E3 ligases. Particularly, in the case of Parkin the novelty of our data originates from the experimental setup, which is not overtly biased by acute mitochondrial depolarisation. In the case of UBE3A, it is the first time that a nonbiased screen for its neuronal substrates has been reported.

Language Impairment Resulting from a de novo Deletion of 7q32.1q33

We report on a girl who presents with hearing loss, behavioral disturbances (according to the Inventory for Client and Agency Planning) as well as motor and cognitive delay (according to Battelle Developmental Inventories) which have a significant impact on her speech and language abilities [according to the Peabody Picture Vocabulary Test (ed 3), and the Prueba de Lenguaje Oral de Navarra-Revisada (Navarra Oral Language Test, Revised)]. Five copy number variations (CNVs) were identified in the child: arr[hg18] 7q32.1q33(127109685-132492196)×1, 8p23.1(7156900-7359099) ×1, 15q13.1(26215673-26884937)×1, Xp22.33(17245- 102434)×3, and Xp22.33(964441-965024)×3. The pathogenicity of similar CNVs is mostly reported as unknown. The largest deletion is found in a hot spot for cognitive disease and language impairment and contains several genes involved in brain development and function, many of which have been related to developmental disorders encompassing language deficits (dyslexia, speech-sound disorder, and autism). Some of these genes interact with FOXP2. The proband's phenotype may result from a reduced expression of some of these genes.

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

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.

Meta-Analysis of Differential Connectivity in Gene Co-Expression Networks in Multiple Sclerosis

Differential gene expression analyses to investigate multiple sclerosis (MS) molecular pathogenesis cannot detect genes harboring genetic and/or epigenetic modifications that change the gene functions without affecting their expression. Differential co-expression network approaches may capture changes in functional interactions resulting from these alterations. We re-analyzed 595 mRNA arrays from publicly available datasets by studying changes in gene co-expression networks in MS and in response to interferon (IFN)-β treatment. Interestingly, MS networks show a reduced connectivity relative to the healthy condition, and the treatment activates the transcription of genes and increases their connectivity in MS patients. Importantly, the analysis of changes in gene connectivity in MS patients provides new evidence of association for genes already implicated in MS by single-nucleotide polymorphism studies and that do not show differential expression. This is the case of amiloride-sensitive cation channel 1 neuronal (ACCN1) that shows a reduced number of interacting partners in MS networks, and it is known for its role in synaptic transmission and central nervous system (CNS) development. Furthermore, our study confirms a deregulation of the vitamin D system: among the transcription factors that potentially regulate the deregulated genes, we find TCF3 and SP1 that are both involved in vitamin D3-induced p27Kip1 expression. Unveiling differential network properties allows us to gain systems-level insights into disease mechanisms and may suggest putative targets for the treatment.

Bergmann Glia, Long-Term Depression, and Autism Spectrum Disorder

Bergmann glia (BG), a specific type of radial astrocytes in the cerebellum, play a variety of vital functions in the development of this structure. However, the possible role of BG in the development of abnormalities observed in individuals with autism spectrum disorder (ASD) seems to be underestimated. One of the most consistent findings observed in ASD patients is loss of Purkinje cells (PCs). Such a defect may be caused by dysregulation of glutamate homeostasis, which is maintained mainly by BG. Moreover, these glial cells are involved in long-term depression (LTD), a form of plasticity which can additionally subserve neuroprotective functions. The aim of presented review is to summarize the current knowledge about interactions which occur between PC and BG, with special emphasis on those which are relevant to the survival and proper functioning of cerebellar neurons.

Variants in several genomic regions associated with asperger disorder

Asperger disorder (ASP) is one of the autism spectrum disorders (ASD) and is differentiated from autism largely on the absence of clinically significant cognitive and language delays. Analysis of a homogenous subset of families with ASP may help to address the corresponding effect of genetic heterogeneity on identifying ASD genetic risk factors. To examine the hypothesis that common variation is important in ASD, we performed a genome-wide association study (GWAS) in 124 ASP families in a discovery data set and 110 ASP families in a validation data set. We prioritized the top 100 association results from both cohorts by employing a ranking strategy. Novel regions on 5q21.1 (P = 9.7 × 10(-7) ) and 15q22.1-q22.2 (P = 7.3 × 10(-6) ) were our most significant findings in the combined data set. Three chromosomal regions showing association, 3p14.2 (P = 3.6 × 10(-6) ), 3q25-26 (P = 6.0 × 10(-5) ) and 3p23 (P = 3.3 × 10(-4) ) overlapped linkage regions reported in Finnish ASP families, and eight association regions overlapped ASD linkage areas. Our findings suggest that ASP shares both ASD-related genetic risk factors, as well as has genetic risk factors unique to the ASP phenotype.

Association study of the ubiquitin conjugating enzyme gene UBE2H in sporadic ALS

Ubiquitin inclusions represent a cytopathological hallmark of ALS. The ubiquitin-dependent protein degradation pathway may also be involved in the pathophysiology of SOD1 mutated ALS cases as demonstrated in transgenic animals. UBE2H is an ubiquitin conjugating enzyme known to act on histones and cytoskeletal proteins, both involved in the degenerative pathway of the motor neuron. We screened the whole coding sequence of the UBE2H gene in 24 sporadic ALS (SALS) patients using single strand conformation polymorphism (SSCP). All variants detected by SSCP were analysed by genomic DNA sequencing. We found one known polymorphism (rs12539800) and two new synonymous single nucleotide polymorphisms (SNP) (nG78A and nG501A). The allele distribution of the rs12539800 (A336G) SNP were tested for association in 252 SALS patients and 357 controls. The allele and genotype distributions were identical in the two groups. The UBE2H gene is not implicated in SALS; however, the ubiquitin pathway is worthy of further investigation in ALS.

A review of gene linkage, association and expression studies in autism and an assessment of convergent evidence

Autism is a neurodevelopmental disorder with high heritability and a likely complex genetic architecture. Much genetic evidence has accumulated in the last 20 years but no gene has been unequivocally identified as containing risk variants for autism. In this article we review the past and present literature on neuro-pathological, genetic linkage, genetic association, and gene expression studies in this disorder. We sought convergent evidence to support particular genes or chromosomal regions that might be likely to contain risk DNA variants. The convergent evidence from these studies supports the current hypotheses that there are multiple genetic loci predisposing to autism, and that genes involved in neurodevelopment are especially important for future genetic studies. Convergent evidence suggests the chromosome regions 7q21.2-q36.2, 16p12.1-p13.3, 6q14.3-q23.2, 2q24.1-q33.1, 17q11.1-q21.2, 1q21-q44 and 3q21.3-q29, are likely to contain risk genes for autism. Taken together with results from neuro-pathological studies, genes involved in brain development located at the above regions should be prioritized for future genetic research.

Imbalanced genomic imprinting in brain development: an evolutionary basis for the aetiology of autism

We describe a new hypothesis for the development of autism, that it is driven by imbalances in brain development involving enhanced effects of paternally expressed imprinted genes, deficits of effects from maternally expressed genes, or both. This hypothesis is supported by: (1) the strong genomic-imprinting component to the genetic and developmental mechanisms of autism, Angelman syndrome, Rett syndrome and Turner syndrome; (2) the core behavioural features of autism, such as self-focused behaviour, altered social interactions and language, and enhanced spatial and mechanistic cognition and abilities, and (3) the degree to which relevant brain functions and structures are altered in autism and related disorders. The imprinted brain theory of autism has important implications for understanding the genetic, epigenetic, neurological and cognitive bases of autism, as ultimately due to imbalances in the outcomes of intragenomic conflict between effects of maternally vs. paternally expressed genes.

Identification of novel autism candidate regions through analysis of reported cytogenetic abnormalities associated with autism

The identification of the candidate genes for autism through linkage and association studies has proven to be a difficult enterprise. An alternative approach is the analysis of cytogenetic abnormalities associated with autism. We present a review of all studies to date that relate patients with cytogenetic abnormalities to the autism phenotype. A literature survey of the Medline and Pubmed databases was performed, using multiple keyword searches. Additional searches through cited references and abstracts from the major genetic conferences from 2000 onwards completed the search. The quality of the phenotype (i.e. of the autism spectrum diagnosis) was rated for each included case. Available specific probe and marker information was used to define optimally the boundaries of the cytogenetic abnormalities. In case of recurrent deletions or duplications on chromosome 15 and 22, the positions of the low copy repeats that are thought to mediate these rearrangements were used to define the most likely boundaries of the implicated 'Cytogenetic Regions Of Interest' (CROIs). If no molecular data were available, the sequence position of the relevant chromosome bands was used to obtain the approximate molecular boundaries of the CROI. The findings of the current review indicate: (1) several regions of overlap between CROIs and known loci of significant linkage and/or association findings, and (2) additional regions of overlap among multiple CROIs at the same locus. Whereas the first finding confirms previous linkage/association findings, the latter may represent novel, not previously identified regions containing genes that contribute to autism. This analysis not only has confirmed the presence of several known autism risk regions but has also revealed additional previously unidentified loci, including 2q37, 5p15, 11q25, 16q22.3, 17p11.2, 18q21.1, 18q23, 22q11.2, 22q13.3 and Xp22.2-p22.3.

The genetics of autism

Autism spectrum disorders (ASD) are among the most heritable of all neuropsychiatric disorders. Discovery of autism susceptibility genes has been the focus of intense research efforts over the last 10 years, and current estimates suggest that 10 to 20 different interacting genes are involved. Evidence from twin and family studies demonstrates increased risk in family members not only for autistic disorder, but also for a milder constellation of similar symptoms referred to as the broader phenotype. In addition, several genetic syndromes and chromosomal anomalies have been associated with ASD. Large family studies using linkage-analysis techniques have demonstrated several chromosomal regions thought to harbor genes related to the disorder. Finally, specific candidate genes based on function and location have been explored; these studies are reviewed here.