DNMT1 Y495C mutation interferes with maintenance methylation of imprinting control regions.

Hereditary Sensory and Autonomic Neuropathy Type 1E (HSAN1E) is a rare autosomal dominant neurological disorder due to missense mutations in DNA methyltransferase 1 (DNMT1). To investigate the nature of the dominant effect, we compared methylomes of transgenic R1 and R1 mouse embryonic stem cells (mESCs) overexpressing WT and the mutant mouse proteins respectively, with the R1 (wild-type) cells. In case of R1, 15 out of the 20 imprinting control regions were hypomethylated with transcript level dysregulation of multiple imprinted genes in ESCs and neurons.

DNMT1 downregulation as well as its overexpression distinctly affect mostly overlapping genes implicated in schizophrenia, autism spectrum, epilepsy, and bipolar disorders.

Data on schizophrenia (SZ), epilepsy (EPD) and bipolar disorders (BPD) suggested an association of DNMT1 overexpression whereas certain variants of the gene were predicted to result in its increased expression in autism spectrum disorder (ASD). In addition, loss of DNMT1 in frontal cortex resulted in behavioral abnormalities in mice. Here we investigated the effects of increased as well as lack of DNMT1 expression using neurons as a model for abnormal neurogenesis and 10,861 genes showing transcript level dysregulation in datasets from the four disorders.

Somatic Variants and Exon-Level Copy Number Changes in Five Hyperplastic Oral Leukoplakias.

Oral leukoplakia (OL), an oral potentially malignant disorder, begins with a hyperplastic/hyperkeratotic stage at which no genome-scale somatic single nucleotide variant profiles have been described so far. We performed exome sequencing of five cases at this stage with no evidence of dysplasia to identify genetic alterations (exon-level copy number alterations, indels, and single nucleotide variants), their association with transcript levels, and relationship with oral cancer susceptibility. Pathway enrichment analysis of genes associated with tobacco chewing and age-related mutation signatures, transcripts with variants predicted to be functionally damaging and those with significantly altered levels all indicated the involvement of focal adhesion, ECM-receptor interactions, regulation of cytoskeleton, and DNA repair.

Comparative Somatic Variant Analysis of a Rare Case with Concurrent Oral Leukoplakia and Oral Submucosal Fibrosis.

Oral leukoplakia (OL) and oral submucosal fibrosis (OSMF) are precancerous conditions with common etiologies but with different risks for oral cancer (OC) progression. In rare cases, both conditions occur in the same patient and provide an opportunity for understanding the common and distinctive variants upon exposure of genetically identical normal cells to the same carcinogen(s). We performed exome sequencing of a patient with OL (hyperplasia, but no dysplasia) and OSMF (grade II) in the opposite cheeks using blood DNA as the reference genome.

Genome-wide methylation analysis of post-mortem cerebellum samples supports the role of peroxisomes in autism spectrum disorder.

We tested the hypothesis that a subset of patients with autism spectrum disorder (ASD) contains candidate genes with high DNA methylation differences (effective values) that potentially affect one of the two alleles. Genome-wide DNA methylation comparisons were made on cerebellum samples from 30 patients and 45 controls. 12 genes with high effective values, including , , and , implicated in ASD and other neuropsychiatric disorders were identified.

DNMT1: catalytic and non-catalytic roles in different biological processes.

DNMT1 is the main enzyme that uses the information on DNA methylation patterns in the parent strand and methylates the daughter strand in freshly replicated hemimethylated DNA. It is widely known that DNMT1 is a component of the epigenetic machinery mediating gene repression via increased promoter methylation. However, recent data suggest that DNMT1 can also modulate gene expression independent of its catalytic activity and participates in multiple processes including the cell cycle, DNA damage repair and stem cell function.

Dysregulation of schizophrenia-associated genes and genome-wide hypomethylation in neurons overexpressing DNMT1.

To study the effects of DNMT1 overexpression on transcript levels of genes dysregulated in schizophrenia and on genome-wide methylation patterns. Transcriptome and DNA methylome comparisons were made between (wild-type) and mouse embryonic stem cells and neurons overexpressing DNMT1. Genes dysregulated in both cells and schizophrenia patients were studied further.

Analysis of 15q11.2 CNVs in an Indian population with schizophrenia.

Copy number variants (CNVs) of 15q11.2 yielded conflicting reports on their association with schizophrenia (SZ), indicating the need for replication studies. Because there are no 15q11.

Improved Multiplex Ligation-dependent Probe Amplification (i-MLPA) for rapid copy number variant (CNV) detection.

Background: In Multiplex Ligation-dependent Probe Amplification (MLPA), copy number variants (CNVs) for specific genes are identified after normalization of the amounts of PCR products from ligated reference probes hybridized to genomic regions that are ideally free from normal variation. However, we observed ambiguous calls for two reference probes in an investigation of the human 15q11.2 region by MLPA among 20 controls, due to the presence of single nucleotide polymorphisms (SNPs) in the probe-binding regions.

Modest impact on risk for autism spectrum disorder of rare copy number variants at 15q11.2, specifically breakpoints 1 to 2.

The proximal region of chromosome 15 is one of the genomic hotspots for copy number variants (CNVs). Among the rearrangements observed in this region, CNVs from the interval between the common breakpoints 1 and 2 (BP1 and BP2) have been reported cosegregating with autism spectrum disorder (ASD). Although evidence supporting an association between BP1-BP2 CNVs and autism accumulates, the magnitude of the effect of BP1-BP2 CNVs remains elusive, posing a great challenge to recurrence-risk counseling.

Characterization of TTAGG telomeric repeats, their interstitial occurrence and constitutively active telomerase in the mealybug Planococcus lilacinus (Homoptera; Coccoidea).

We confirmed the occurrence of the insect TTAGG telomeric repeats in the mealybug Planococcus lilacinus, a radiation-resistant coccid, by single primer polymerase chain reaction (PCR) and Southern hybridization. Analysis of Bal31 nuclease-digested DNA by Southern hybridization and chromosomes by FISH suggests that these repeats occur mainly at the ends of the chromosomes. However, sequence analysis of the PCR products of TTAGG-associated sequences from genomic DNA showed their interstitial occurrence and association with certain unrelated low-copy repeats.