SRR intronic variation inhibits expression of its neighbouring SMG6 gene and protects against temporal lobe epilepsy

Physiology, Pathophysiology and Clinical Relevance of D-Amino Acids Dynamics: From Neurochemistry to Pharmacotherapy

Over three decades ago, two independent groups of investigators identified free D-aspartic and later D-serine in specific brain nuclei and endocrine glands. This finding revealed a novel, non-proteinogenic role of these molecules. Moreover, the finding that aged proteins from the human eye crystallin, teeth, bone, blood vessels or the brain incorporate D-aspartic acids to specific primary protein sequences fostered the hypothesis that aging might be related to D-amino acid isomerization of body proteins. The experimental confirmation that schizophrenia and neurodegenerative diseases modify plasma free D-amino acids or tissue levelsnurtured the opportunity of using D-amino acids as therapeutic agents for several disease treatments, a strategy that prompted the successful current application of D-amino acids to human medicine.

d-Amino acids: new clinical pathways for brain diseases

Free d-amino acids (d-AAs) are emerging as a novel and important class of signaling molecules in many organs, including the brain and endocrine systems. There has been considerable progress in our understanding of the fundamental roles of these atypical messengers, with increasingly recognized implications in a wide range of neuropathologies, including schizophrenia (SCZ), epilepsy, Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), substance abuse, and chronic pain, among others. Research has enabled the discovery that d-serine, d-aspartate and more recently d-cysteine are essential for the healthy development and function of the central nervous system (CNS). We discuss recent progress that has profoundly transformed our vision of numerous physiological processes but has also shown how d-AAs are now offering therapeutic promise in clinical settings for several human diseases.

DNA Methylation Signature of Epileptic Encephalopathy-Related Pathogenic Genes Encoding Ion Channels in Temporal Lobe Epilepsy

Epilepsy is characterized by highly abnormal synchronous discharge of brain neurons, and ion channels are fundamental in the generation and modulation of neural excitability. Considering that abnormal methylation can either activate or repress genes, this study was designed to explore the DNA methylation signature of pathogenic genes encoding ion channels in temporal lobe epilepsy (TLE). In total, 38 TLE patients and 38 healthy controls were enrolled in the study, and genomic DNA and total protein of the lymphocytes were extracted from peripheral blood samples to assess methylation and protein levels. The DNA methylation levels of all 12 genes examined were significantly lower in the TLE group than in the control group. After false-positive correction, 83.3% (10/12) of these genes, namely, gamma-aminobutyric acid type A receptor subunit beta1 (GABRB1), gamma-aminobutyric acid type A receptor subunit beta2 (GABRB2), gamma-aminobutyric acid type A receptor subunit beta1 (GABRB3), glutamate ionotropic receptor NMDA type subunit 1 (GRIN1), glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A), glutamate ionotropic receptor NMDA type subunit 2B (GRIN2B), hyperpolarization activated cyclic nucleotide gated potassium channel 1 (HCN1), potassium voltage-gated channel subfamily A member 2 (KCNA2), potassium voltage-gated channel subfamily B member 1 (KCNB1), and potassium sodium-activated channel subfamily T member 1 (KCNT1), were still differentially expressed. Among these ion channels, HCN1 and KCNA2 were selected to evaluate the effects of DNA methylation, and the levels of these proteins were inversely upregulated in the TLE group compared to the control group. As the genes identified as having differential methylation levels are involved in both excitatory and inhibitory ion channels, this study observed by binary logistic regression that hypermethylated GARAB1 was an independent risk factor for TLE, indicating that the overwhelming effect of ion channels on TLE is probably inhibitory from the perspective of DNA methylation. All these findings support the involvement of DNA methylation in TLE pathologies, but the mechanisms need to be further investigated.

Genetic Effects of the Schizophrenia-Related Gene DTNBP1 in Temporal Lobe Epilepsy

Recent studies have reported patients who concurrently exhibit conditions of epilepsy and schizophrenia, indicating certain shared pathologies between them. This study aimed to investigate the genetic effects of the schizophrenia-related gene DTNBP1 in temporal lobe epilepsy (TLE). A total of 496 TLE patients and 528 healthy individuals were successfully genotyped for six DTNBP1 polymorphisms (rs760665, rs1011313, rs2619528, rs2619522, rs909706, and rs2619538), including 335 TLE patients and 325 healthy controls in cohort 1, and 161 TLE patients and 203 healthy controls in cohort 2. The frequency of the TT genotype at rs909706 T > C was lower in TLE patients than in normal controls in the initial cohort (cohort 1), which was confirmed in an independent cohort (cohort 2). However, the intronic T allele failed to be in linkage disequilibrium (LD) with any functional variations nearby; thus, together with the CCAC and TCAT haplotypes (rs1011313-rs2619528-rs2619522-rs909706) observed in the study, this allele acts only as a protective factor against susceptibility to TLE. Meanwhile, a novo mutant allele rs2619538 T > A was exclusively observed in TLE patients, and a dual-luciferase assay revealed that the mutant allele was increased by approximately 22% in the DTNBP2 promoter compared with the wild-type allele. Together with the trend of increasing DTNBP1 expression in epilepsy patients and animal models in this study, these are the first findings to demonstrate the genetic association of DTNBP1 with TLE. Homozygous mutation of rs2619538 T > A likely promotes DTNBP1 expression and facilitates subsequent processes in epilepsy pathologies. Thus, the role of DTNBP1 in TLE deserves further exploration in the future.

FABP1 Polymorphisms Contribute to Hepatocellular Carcinoma Susceptibility in Chinese Population with Liver Cirrhosis: A Case-Control Study

Purpose: Single nucleotide variations in the liver fatty acid binding protein (L-FABP, FABP1) gene lead to changes in cellular signaling pathways and lipid metabolism. FABP1 polymorphisms were associated with some liver diseases, like steatotic hepatocellular carcinoma. However, the association between FABP1 rs1545224 and rs2241883 polymorphisms and hepatitis B virus-related liver cirrhosis (LC) and hepatocellular carcinoma (HCC) has not been reported. We performed this study to explore their relationship.

Methods: One thousand individuals (250 healthy controls, 250 chronic HBV (CHB), 250 LC, and 250 HCC patients) were recruited. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were applied to assess the difference in allele and genotype frequencies. Cochran-Armitage trend test was used to evaluate the cumulative effect. Significant difference would be defined when the P value was less than 0.05.

Results: The distribution of rs1545224 GG, AG and AA genotypes in healthy controls or CHB carriers was not significant when compared to LC or HCC patients (P>0.05). LC patients carrying at least one A allele are more likely to develop HCC in contrast with those with G allele (P<0.05). After adjustment for confounders, meaningful results were only seen in the comparison between rs1545224 AG+AA genotype carriers and GG genotype carriers among the LC patients (P<0.05). Rs2241883 polymorphism did not influence the risk of developing LC or HCC in healthy and CHB individuals, nor did it influence the risk of HCC in LC patients (P>0.05).

Conclusions: Taken together, FABP1 rs1545224 polymorphism might increase HCC risk in LC patients, indicating that FABP1 rs1545224 polymorphism may be related to the process of developing HCC in Chinese patients with LC.