Genome-wide analysis of TMEM38 family revealed functional roles of TMEM38B in fat deposition and its miRNA-mediated regulation in chicken

Transmembrane protein 38 (TMEM38) gene family, including TMEM38A and TMEM38B, is responsible for facilitating trimeric intracellular cation transport across the membrane and regulating key cellular processes, such as muscle contraction and cell differentiation in mammals. However, a genome-wide analysis of the chicken TMEM38 gene family, as well as investigations into their biological roles and post-transcriptional expression regulation in fat deposition have not yet been conducted. In this study, we investigated the genome-wide characteristics of chicken TMEM38 gene family, elucidated the regulatory roles of the TMEM38B gene in both abdominal and intramuscular adipogenesis, and explored its miRNA-mediated expression regulatory mechanisms. We found that chicken TMEM38A and TMEM38B exhibited notable conservation in gene structure and motifs across diverse species. Principal component analysis based on SNPs showed that genetic variations in the TMEM38B gene contributed to the selective breeding of commercial broilers. Moreover, gene expression profiling demonstrated that TMEM38A and TMEM38B showed the positive expression in chicken abdominal adipose and muscle tissues, and overall increased expression during the proliferation and adipogenic differentiation of both chicken abdominal and intramuscular preadipocytes. Functionally, TMEM38B overexpression significantly enhanced viability, proliferation, cell cycle progression as well as intracellular triglyceride content and lipid droplet accumulation of both chicken abdominal and intramuscular preadipocytes, paralleling with the expression of proliferative and adipogenic marker genes. Target miRNA prediction identified 37 potential miRNAs targeting the TMEM38B gene. Of these, a dual-luciferase reporter system verified that miR-20b-3p could directly bind to the 3'UTR of the TMEM38B gene and thus inhibit its post-transcriptional expression. Gain-of-function assays showed that miR-20b-3p could suppress the viability, proliferation, and cell cycle progression of chicken abdominal and intramuscular preadipocytes, as well as the adipogenic differentiation of chicken abdominal preadipocytes. Collectively, we demonstrated the promotive effects of TMEM38B in regulating abdominal and intramuscular fat deposition, as well as its post-transcriptional expression inhibition mediated by miR-20b-3p. These findings shed novel lights into the functional role and expression regulation of the miR-20b-3p-TMEM38B axis in adipogenesis, and may provide valuable biomarkers for the genetic improvement of fat traits in chickens.