Atypical septate junctions maintain the somatic enclosure around maturing spermatids and prevent premature sperm release in Drosophila testis

• Published in: Biology open 2019-02, Vol.8 (2)
• Main Authors: Dubey, Pankaj, Kapoor, Tushna, Gupta, Samir, Shirolikar, Seema, Ray, Krishanu
• Format: Article
• Language: English
• Subjects: Discs-large-1; Drosophila; Neurexin-IV; Septate junctions; Somatic cyst cells; Spermiation
• ISSN: 2046-6390; 2046-6390
• DOI: 10.1242/bio.036939

Tight junctions prevent paracellular flow and maintain cell polarity in an epithelium. These junctions are also required for maintaining the blood-testis-barrier, which is essential for sperm differentiation. Septate junctions in insects are orthologous to the tight junctions. In testis, major septate junction components co-localize at the interface of germline and somatic cells initially and then condense between the two somatic cells in a cyst after germline meiosis. Their localization is extensively remodeled in subsequent stages. We find that characteristic septate junctions are formed between the somatic cyst cells at the elongated spermatid stage. Consistent with previous reports, knockdown of essential junctional components- Discs-large-1 and Neurexin-IV- during the early stages, disrupted sperm differentiation beyond the spermatocyte stage. Knockdown of these proteins during the final stages of spermatid maturation caused premature release of spermatids inside the testes, resulting in partial loss of male fertility. These results indicate the importance of maintaining the integrity of the somatic enclosure during spermatid coiling and release in testis. It also highlights the functional similarity with the tight junction proteins during mammalian spermatogenesis.