The Microtubule-Depolymerizing Kinesin-13 Klp10A Is Enriched in the Transition Zone of the Ciliary Structures of Drosophila melanogaster.

Veronica Persico,Giuliano Callaini,Maria Giovanna Riparbelli

doi:10.3389/fcell.2019.00173

Abstract

The precursor of the flagellar axoneme is already present in the primary spermatocytes of Drosophila melanogaster. During spermatogenesis each primary spermatocyte shows a centriole pair that moves to the cell membrane and organizes an axoneme-based structure, the cilium-like region (CLR). The CLRs persist through the meiotic divisions and are inherited by young spermatids. During spermatid differentiation the ciliary caps elongate giving rise to the sperm axoneme. Mutations in Klp10A, a kinesin-13 of Drosophila, results in defects of centriole/CLR organization in spermatocytes and of ciliary cap assembly in elongating spermatids. Reduced Klp10A expression also results in strong structural defects of sensory type I neurons. We show, here, that this protein displays a peculiar localization during male gametogenesis. The Klp10A signal is first detected at the distal ends of the centrioles when they dock to the plasma membrane of young primary spermatocytes. At the onset of the first meiotic prometaphase, when the CLRs reach their full size, Klp10A is enriched in a distinct narrow area at the distal end of the centrioles and persists in elongating spermatids at the base of the ciliary cap. We conclude that Klp10A could be a core component of the ciliary transition zone in Drosophila.

Highlights

Gametes are specialized cells that give rise to the offspring
Staining of control testes with an antibody against Spd2, a widely conserved centriole associated protein involved in centrosome organization (Varadarajan and Rusan, 2018), shows that dotlike centrioles were typically found in stem cells (Figure 1A) and spermatogones (Figure 1A’), whereas elongating rodlike centrioles were observed during spermatocyte maturation (Figure 1A”)
That 64.4% of the centrioles (56/87) examined in mature primary spermatocytes at the ultrastructural level were elongated with reduced cilium-like region (CLR) (Figure 1B”’)

Summary

Introduction

Gametes are specialized cells that give rise to the offspring. Male and female gametes are produced by spermatogenesis and oogenesis occurring in testis and ovary, respectively. The spermatogonial cells undergo mitotic divisions from which originate the spermatocytes that give rise to the haploid spermatids. Spermatids are round cells that differentiate during the final phase of spermatogenesis, called spermiogenesis, undergoing morphological changes to become mature sperm. Several sperm dysfunctions cause infertility due to axoneme anomalies. Axonemal defects in primary cilia are often observed in human diseases, ciliopathies, in which genetic mutations affect ciliary assembly

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