Abstract
TSLC1/IGSF4, an immunoglobulin superfamily molecule, is predominantly expressed in the brain, lungs, and testes and plays important roles in epithelial cell adhesion, cancer invasion, and synapse formation. We generated Tslc1/Igsf4-deficient mice by disrupting exon 1 of the gene and found that Tslc1(-/-) mice were born with the expected Mendelian ratio but that Tslc1(-/-) male mice were infertile. In 11-week-old adult Tslc1(-/-) mice, the weight of a testis was 88% that in Tslc1(+/+) mice, and the number of sperm in the semen was approximately 0.01% that in Tslc1(+/+) mice. Histological analysis revealed that the round spermatids and the pachytene spermatocytes failed to attach to the Sertoli cells in the seminiferous tubules and sloughed off into the lumen with apoptosis in the Tslc1(-/-) mice. On the other hand, the spermatogonia and the interstitial cells, including Leydig cells, were essentially unaffected. In the Tslc1(+/+) mice, TSLC1/IGSF4 expression was observed in the spermatogenic cells from the intermediate spermatogonia to the early pachytene spermatocytes and from spermatids at step 7 or later. These findings suggest that TSLC1/IGSF4 expression is indispensable for the adhesion of spermatocytes and spermatids to Sertoli cells and for their normal differentiation into mature spermatozoa.