mir138-1: MIR138-1 is a micro-RNA encoded by a specific genomic locus on chromosome 9, distinct from its homolog MIR138-2, and is implicated in various biological processes [PMC6836737]. It is expressed in the nervous system and has been identified as one of the brain-enriched microRNA-coding long non-coding RNAs (lncRNAs) [PMC4468152]. Notably, MIR138-1 does not appear to be associated with a deficit in Schwann cell (SC) differentiation, as indicated by studies on MIR138-1 conditional knockout (cKO) nerves [PMC5830491]. In the context of ischemic chronic heart disease (iCHD), Mendelian randomization analysis has identified DNA methylation levels at two CpG sites near MIR138-1 that may exert causal effects on the disease [PMC8501606]. Additionally, this micro-RNA is situated in an intergenic region with no other nearby annotated miRNAs or mRNAs, suggesting a unique regulatory role [PMC4057207]. Research using Bru-seq technology has revealed that the primary transcription start site (TSS) for MIR138-1 may be located significantly upstream from its annotated mature DNA sequence [PMC4675984]. Furthermore, quantitative RT-PCR results support an accumulation of miRNA 5′ leader sequences relative to primary miRNA for MIR138-1, indicating post-transcriptional regulatory mechanisms at play [PMC4057207].