Katanin-like 2 (KATNAL2) functions in multiple aspects of haploid male germ cell development in the mouse
Fig 5
Tubulobulbar complex and residual body formation requires KATNAL2.
(a–e) Electron microscopy showing elongated spermatid morphology during spermiation in Katnal2WT/WT and Katnal2Y86C/Y86C mice. Detachment of the acrosome (red arrowheads) from the nucleus was frequently observed in Katnal2Y86C/Y86C (b) but not Katnal2WT/WT (a) spermatids. Retention of cytoplasm was frequently seen in Katnal2Y86C/Y86C spermatids that had failed spermiation (c). Within the cytoplasm of retained spermatids, disorganised outer dense fibres (red arrowheads) were frequently observed (c). Ectoplasmic specializations (black arrowheads) showed normal morphology in Katnal2Y86C/Y86C (d) and Katnal2WT/WT (a) spermatids, and were absent in Katnal2Y86C/Y86C retained spermatids (e) indicating they were disassembled normally prior to spermiation. Tubulobulbar complexes (asterisks) were present in Katnal2WT/WT (a) spermatids but were absent in Katnal2Y86C/Y86C spermatids (d). Scale bars in a–e = 1 μm. Immunostaining of seminiferous tubules for the ectoplasmic specialization marker espin confirmed ectoplasmic specialisations were disassembled normally in Katnal2WT/WT and Katnal2Y86C/Y86C spermatids (f–k). Ectoplasmic specializations were present in early step 16 (stage VII) Katnal2WT/WT (f) and Katnal2Y86C/Y86C spermatids (i), but were absent from late step 16 (stage VIII) Katnal2WT/WT (g) and Katnal2Y86C/Y86C spermatids (j) and from retained (stage IX) Katnal2Y86C/Y86C spermatids (k). Immunostaining of seminiferous tubules for the tubulobulbar complex markers dynamin-2 and ARP2 confirmed the absence of tubulobulbar complexes from Katnal2Y86C/Y86C (o–p) but not Katnal2WT/WT (l–m) spermatids. Residual body (arrowheads) formation in Katnal2WT/WT (n) versus Katnal2Y86C/Y86C (q) mice. Residual bodies were absent in Katnal2Y86C/Y86C (q) mice. Scale bars in f–q = 10 μm. Primary antibody negative controls for (f–m) and (o–p) are included in S7 Fig.