Letter from the editor: CFTR and male fertility-Impact beyond cystic fibrosis

Update on the cellular and molecular aspects of cystic fibrosis transmembrane conductance regulator (CFTR) and male fertility

CFTR protein regulates electrolyte and fluid transport in almost all tissues with exocrine function, including male reproductive tract. Mutation of CFTR gene causes cystic fibrosis (CF), which affects the function of several organs, and impairs male fertility. The role of CFTR protein in different compartments of male reproductive tract (testis, epididymis, sperm) as well as an impact of CFTR mutation(s) on male fertility phenotype is discussed in relation with the choice of optimal technique for Assisted Reproductive Techniques (ART) management.

Localization of epithelial sodium channel (ENaC) and CFTR in the germinal epithelium of the testis, Sertoli cells, and spermatozoa

Spermatogenesis starts within the seminiferous tubules of the testis by mitotic division of spermatogonia that produces spermatocytes. Meiotic division of these spermatocytes produces haploid spermatids that differentiate into spermatozoa. In this study, we examined the expression of ENaC and CFTR (a Cl^- channel) in rat testicular sections using confocal microscopic immunofluorescence. The structural integrity of the seminiferous tubule sections was verified by precise phalloidin staining of the actin fibers located abundantly at both basal and adluminal tight junctions. The acrosome forming regions in the round spermatids were stained using an FITC coupled lectin (wheat germ agglutinin). In all phases of the germ cells (spermatogonia, spermatocytes, and spermatids) ENaC was localized in cytoplasmic pools. Prior to spermiation, ENaC immunofluorescence appeared along the tails of the spermatids. In spermatozoa isolated from the epididymis, ENaC was localized at the acrosome and a central region of the sperm flagellum. The mature sperm are transcriptionally silent. Hence, we suggest that ENaC subunits in cytoplasmic pools in germ cells serve as the source of ENaC subunits located along the tail of spermatozoa. The locations of ENaC is compatible with a possible role in the acrosomal reaction and sperm mobility. In contrast to ENaC, CFTR immunofluorescence was most strongly observed specifically within the Sertoli cell nuclei. Based on the nuclear localization of CFTR we suggest that, in addition to its role as an ion channel, CFTR may have an independent role in gene regulation within the nuclei.