Familial cortical myoclonic tremor with epilepsy is an autosomal dominant neurodegenerative disease, characterized by cortical tremor and epileptic seizures. Although four subtypes (types 1-4) mapped on different chromosomes (8q24, 2p11.1-q12.2, 5p15.31-p15.1 and 3q26.32-3q28) have been reported, the causative gene has not yet been identified. Here, we report the genetic study in a cohort of 20 Chinese pedigrees with familial cortical myoclonic tremor with epilepsy. Linkage and haplotype analysis in 11 pedigrees revealed maximum two-point logarithm of the odds (LOD) scores from 1.64 to 3.77 (LOD scores in five pedigrees were >3.0) in chromosomal region 8q24 and narrowed the candidate region to an interval of 4.9 Mb. Using whole-genome sequencing, long-range polymerase chain reaction and repeat-primed polymerase chain reaction, we identified an intronic pentanucleotide (TTTCA)n insertion in the SAMD12 gene as the cause, which co-segregated with the disease among the 11 pedigrees mapped on 8q24 and additional seven unmapped pedigrees. Only two pedigrees did not contain the (TTTCA)n insertion. Repeat-primed polymerase chain reaction revealed that the sizes of (TTTCA)n insertion in all affected members were larger than 105 repeats. The same pentanucleotide insertion (ATTTCATTTC)58 has been reported to form RNA foci resulting in neurotoxicity in spinocerebellar ataxia type 37, which suggests the similar pathogenic process in familial cortical myoclonic tremor with epilepsy type 1.

Schizophrenia and bipolar disorder are complex mental disorders with risks contributed by multiple genes. Dysregulation of gene expression has been implicated, but little is known about such regulation systems in the human brain. We analyzed three transcriptome datasets using 394 brain tissue samples from patients with schizophrenia or bipolar disorder and healthy control individuals without known history of psychiatric disorders. We built genome wide co-expression networks that included microRNAs (miRNAs). We identified a co-expression network module that was differentially expressed between patients and control individuals. This module contained genes that were principally involved in glial and neural cell genesis and glial cell differentiation, and included schizophrenia risk genes carrying rare variants. This module included five miRNAs and 545 mRNAs, with six transcription factors serving as hub genes in this module. We found that the most connected transcription factor POU3F2, a gene also identified on a GWAS for bipolar disorder, could regulate hsa-miR-320e and other putative target mRNAs. These regulatory relationships were replicated by PsychENCODE/BrainGVEX data and validated by knockdown and overexpression experiments in the SH-SY5Y and neural progenitor cell lines in vitro. We identified a psychosis-associated brain gene expression module that was enriched for rare coding variants in genes associated with schizophrenia and contained the putative bipolar disorder risk gene POU3F2 as a key regulator of gene expression in this module.

Many psychiatric disorders are characterized by a strong sex difference, but the mechanisms behind sex-bias are not fully understood. DNA methylation plays important roles in regulating gene expression, ultimately impacting sexually different characteristics of the human brain. Most previous literature focused on DNA methylation alone without considering the regulatory network and its contribution to sex-bias of psychiatric disorders. Since DNA methylation acts in a complex regulatory network to connect genetic and environmental factors with high-order brain functions, we investigated the regulatory networks associated with different DNA methylation and assessed their contribution to the risks of psychiatric disorders. We compiled data from 1408 postmortem brain samples in 3 collections to identify sex-differentially methylated positions (DMPs) and regions (DMRs). We identified and replicated thousands of DMPs and DMRs. The DMR genes were enriched in neuronal related pathways. We extended the regulatory networks related to sex-differential methylation and psychiatric disorders by integrating methylation quantitative trait loci (meQTLs), gene expression, and protein-protein interaction data. We observed significant enrichment of sex-associated genes in psychiatric disorder-associated gene sets. We prioritized 2080 genes that were sex-biased and associated with psychiatric disorders, such as NRXN1, NRXN2, NRXN3, FDE4A, and SHANK2. These genes are enriched in synapse-related pathways and signaling pathways, suggesting that sexdifferential genes of these neuronal pathways may cause the sex-bias of psychiatric disorders.

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A number of studies indicate that rare copy number variations (CNVs) contribute to the risk of schizophrenia (SCZ). Most of these studies have focused on protein-coding genes residing in the CNVs. Here, we investigated long non-coding RNAs (lncRNAs) within ten SCZ risk-associated CNV deletion regions (CNV-lncRNAs) and examined their potential contribution to SCZ risk. We used RNA-Seq transcriptomics data derived from postmortem brain tissue from control individuals without psychiatric disease as part of the PsychENCODE BrainGVEX and Developmental Capstone projects. We carried out weighted gene coexpression network analysis (WGCNA) to identify protein-coding genes coexpressed with CNV-lncRNAs in the human brain. We identified one neuronal function-related coexpression module shared by both data sets. This module contained a lncRNA within the 22q11.2 CNV region called DGCR5, which was identified as a hub gene. Protein-coding genes associated with SCZ GWAS signals, de novo mutations or differential expression were also contained in this neuronal module. Using DGCR5 knockdown and overexpression experiments in human neural progenitor cells derived from human induced pluripotent stem cells, we identified a potential role for DGCR5 in regulating certain SCZ-related genes.