Lack of CCDC146 causes centriole duplication and mislocalization in Ccdc146 KO spermatids.
Ultrastructural analysis of centrioles in adult mouse WT (A, B) and Ccdc146 KO (C-H) testis sections. (A) In WT spermatids, the axoneme is attached to the base of the compacting nucleus (Nu) through the basal plate (BP) and the capitulum (Ca), and the distal centriole (DC) is embedded in the segmented column (SC). These sperm-specific cytoskeletal structures make up the head-to-tail coupling apparatus (HTCA). (B) In WT elongated spermatids, the different components of the axonemal structures (Ax) and outer dense fibers (ODF) were visible downstream the distal centriole. (C) In Ccdc146 KO elongating spermatids, the overall structure of the HTCA was conserved, with the presence of the centrioles and the accessory cytoskeletal structures. However, the HTCAs were often duplicated (C, E, F) and separated from their usual nuclear attachment site (C-F, H), and sometimes misplaced far away from the nucleus (F), the red arrow in F indicating the misplaced centrioles at the end of the manchette. The axoneme is missing (C-F). In elongated spermatids with condensed nucleus, malformed and detached centrioles with poorly-assembled or missing flagella compared to the WT (B) can be seen. Manchette (Ma), Adjunct (Ad), proximal centriole (PC). Scale bars 1µm.