Mouse genome engineering uncovers 18 genes dispensable for male reproduction.

Abstract

Background: Male infertility is an intricate multifactorial disease involving the interplay between genetic and environmental factors. Genetic anomalies account for more than 15% of all male infertility cases; however, diagnosing them exhibits enormous challenges due to variable symptomatic presentations and limited knowledge of gene functions. Therefore, a thorough investigation into gene regulatory networks underlying male reproduction is demanded to improve patient counseling and infertility treatment.

Objective: In this study, we aimed to identify testis-expressed genes essential for male fertility.

Methods: We searched public databases, such as the National Center for Biotechnology Information (NCBI), Ensembl genome browser, the Human Protein Atlas (HPA), and the Mammalian Reproductive Genetics Database V2 (MRGDv2), to identify genes predominantly expressed in male reproductive tissues. Genetically engineered mouse lines lacking individual genes of interest were generated using either targeted gene replacement or the CRISPR/Cas9 system. To determine the gene functions, we analyzed fertility, testis weight, testis and epididymis histology, and sperm motility and morphology in adult knockout (KO) male mice.

Results: Through the in silico screen, we identified 18 testis-expressed genes, including coiled-coil domain containing 182 (Ccdc182), EF-hand calcium-binding domain 15 (Efcab15), family with sequence similarity 187, member B (Fam187b), family with sequence similarity 24, member A (Fam24a), family with sequence similarity 24, member B (Fam24b), glial cell line derived neurotrophic factor family receptor alpha 2 (Gfra2), GLI pathogenesis-related 1 like 1, 2, and 3 (Glipr1l1-3), interleukin 3 (Il3), IZUMO family member 4 (Izumo4), peptidyl-prolyl cis/trans isomerase, NIMA-interacting 1, retrogene 1 (Pin1rt1), solute carrier family 22 (organic cation transporter), member 16 (Slc22a16), sperm microtubule inner protein 2 (Spmip2), testis expressed 51 (Tex51), transmembrane and coiled-coil domains 2 (Tmco2), and tripartite motif family-like 1 and 2 (Triml1/2). The KO males displayed no obvious health problems, and normal mating behavior, fecundity, testis and epididymis histology, and sperm morphology and motility.

Discussion and conclusion: Our findings indicate that these 18 testis-expressed genes are individually dispensable for male reproduction in mice. Disseminating such genes would promote our understanding of male reproduction and expedite the discovery of novel key male factors. Although we anticipate that mutations in these genes may not impair fertility in men, their enrichment in male germ cells makes them potential biomarkers for sperm count, quality, and morphological anomalies.