GAD1 alternative transcripts and DNA methylation in human prefrontal cortex and hippocampus in brain development,...

Area of Science:

• Neuroscience
• Genetics
• Psychiatry

Background:

• Schizophrenia risk is linked to abnormal brain development from genetic and environmental factors.
• Gamma-aminobutyric acid (GABA) is crucial for brain development, synthesized by glutamic acid decarboxylase (GAD) enzymes.
• GAD1 (GAD67) transcript is implicated in schizophrenia, but its full structure and regulation remain unclear.

Purpose of the Study:

• To characterize the GAD1 transcript structure in the human brain.
• To investigate the role of novel GAD1 transcripts and their expression patterns.
• To explore the association between GAD1, epigenetic factors, and schizophrenia.

Main Methods:

• RNA sequencing and PCR technologies were employed.
• Analysis of GAD1 transcript expression across lifespan.
• Investigation of CpG methylation in the GAD1 promoter and its relation to schizophrenia risk SNPs and gene expression.
• Comparison of GAD1 expression in schizophrenia patients (including those with suicide history or nicotine exposure) versus controls in the dorsolateral prefrontal cortex (DLPFC).

Main Results:

• Ten novel GAD1 transcripts were identified in the human brain.
• Four novel transcripts (8A, 8B, I80, I86) exhibited lifespan expression patterns inversely correlated with full-length GAD1.
• CpG methylation in the GAD1 promoter associated with schizophrenia risk SNP rs3749034 and GAD2 expression in DLPFC.
• Elevated full-length GAD1 expression was observed in DLPFC of schizophrenia patients with suicide history and/or nicotine exposure.

Conclusions:

• Alternative splicing of GAD1 and epigenetic modifications influence its developmental expression profile.
• These GAD1 alterations may contribute to GABAergic dysfunction in the prefrontal cortex and hippocampus of schizophrenia patients.
• The findings highlight novel GAD1 transcripts and regulatory mechanisms potentially involved in schizophrenia pathogenesis.