Fig. 4.

Male sterility in sys mice is due to mutation of Fndc3a. (A) PAS-hematoxylin stained testis histology of an adult Fndc3a^sys/+ mouse. The seminiferous epithelium has a normal appearance, with heads (arrow) and flagella (arrowhead) of elongate spermatids. (B) Testis histology of Fndc3a^sys homozygote mouse, with the absence of elongate spermatids and the presence of symplasts of round spermatids (arrows). (C) Testis histology of Fndc3a^RRP208/+ adult male mouse, with normal appearance of the seminiferous epithelium. (D) Testis histology of Fndc3a^RRP208/Fndc3a^sys compound heterozygote adult male mouse. The histology is essentially identical to that observed in Fndc3a^sys homozygotes, having symplasts (arrows) but no elongate spermatids. (E–H) Contents of epididymides of (E) Fndc3a^sys/+, (F) Fndc3a^sys homozygote, (G) Fndc3a^RRP208/+, and (H) Fndc3a^RRP208/Fndc3a^sys compound heterozygote mice. Mature spermatozoa are present in the lumen (asterisks) of the epididymis in control (E, G) but neither sys homozygous (F) nor Fndc3a^RRP208/Fndc3a^sys compound heterozygous mutant mice (H). (I–N) Analysis of contents of vasa deferentia from homozygous (I–K) and heterozygous (L–N) Fndc3a^sys mice. (I, L) DAPI staining; (K, N) DIC image; (J, M) merged. Arrows indicate example of a symplast of spermatids (I–K) or a mature spermatozoon (L–N). The contents of the vasa deferentia from homozygous animal contain acellular material in addition to symplasts. Magnification=A–H, L–N 200×; I–N, 100×.