Drosophilaasterlessand Vertebrate Cep152 Are Orthologs Essential for Centriole Duplication

Abstract

The centriole is the core structure of centrosome and cilium. Failure to restrict centriole duplication to once per cell cycle has serious consequences and is commonly observed in cancer. Despite its medical importance, the mechanism of centriole formation is poorly understood. Asl was previously reported to be a centrosomal protein essential for centrosome function. Here we identify mecD, a severe loss-of-function allele of the asl gene, and demonstrate that it is required for centriole and cilia formation. Similarly, Cep152, the Asl ortholog in vertebrates, is essential for cilia formation and its function can be partially rescued by the Drosophila Asl. The study of Asl localization suggests that it is closely associated with the centriole wall, but is not part of the centriole structure. By analyzing the biogenesis of centrosomes in cells depleted of Asl, we found that, while pericentriolar material (PCM) function is mildly affected, Asl is essential for daughter centriole formation. The clear absence of several centriolar markers in mecD mutants suggests that Asl is critical early in centriole duplication.

DrosophilaBld10 Is a Centriolar Protein That Regulates Centriole, Basal Body, and Motile Cilium Assembly

“…These data indicate that Bld10 is likely a ubiquitous component of centrioles throughout development. Two recent reports corroborated the centriole localization of Bld10 (Blachon et al, 2008;Dobbelaere et al, 2008).…”

“…These data indicate that Bld10 is likely a ubiquitous component of centrioles throughout development. Two recent reports corroborated the centriole localization of Bld10 (Blachon et al, 2008;Dobbelaere et al, 2008).In Drosophila spermatocytes, where the centrioles are ϳ10-fold longer than in somatic cells (Gonzalez et al, 1998), the centriole-specific marker YFP-Asl (Varmark et al, 2007) colocalized with Bld10 at centrioles throughout spermatocyte development. In mature spermatocytes and throughout the two meiotic divisions, Bld10 was concentrated at the proximal end of the centrioles, a subregion of the centriole where YFP-Asl and Bld10 localization overlapped ( Figure 2B).…”

“…In Drosophila several approaches have identified evolutionarily conserved centriole proteins required for centriole biogenesis including Sak, Sas4, Sas6, Ana1, Ana2, and Asterless (Bettencourt-Dias et al, 2005;Basto et al, 2006;Goshima et al, 2007;Rodrigues-Martins et al, 2007;Blachon et al, 2008). In flies, mutations in these genes abolish centrosome and cilium/flagellum assembly (except mutations in ana1 and ana2, which have not been described yet).…”

“…In most differentiated cell types, centrioles transform into basal bodies, membrane-embedded centrioles that template cilium and flagellum axoneme assembly. The requirement of cilia and flagella for many developmental and physiological processes, together with the growing list of human diseases that result from defects in basal bodies and cilia (Badano et al, 2006;Bisgrove and Yost, 2006;Bettencourt-Dias and Glover, 2007;Fliegauf et al, 2007;Marshall, 2008), drives the need to understand the basic processes involved in centriole, basal body, cilium assembly, and motility.In Drosophila several approaches have identified evolutionarily conserved centriole proteins required for centriole biogenesis including Sak, Sas4, Sas6, Ana1, Ana2, and Asterless (Bettencourt-Dias et al, 2005;Basto et al, 2006;Goshima et al, 2007;Rodrigues-Martins et al, 2007;Blachon et al, 2008). In flies, mutations in these genes abolish centrosome and cilium/flagellum assembly (except mutations in ana1 and ana2, which have not been described yet).…”

Centrobin-mediated Regulation of the Centrosomal Protein 4.1-associated Protein (CPAP) Level Limits Centriole Length during Elongation Stage

“…The duplication process involves three stages: initiation, elongation, and maturation. Initiation process includes the recruitment of essential centriolar proteins such as CEP152, PLK4, hSAS-6, STIL, CPAP 2 , CEP135, CP110, ␥-tubulin, and centrobin to the proximal end of preexisting mother centrioles (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36). Once this pro-centriolar protein complex is formed, centrioles are elongated to achieve a maximum length of ϳ500 nm and width of ϳ200 nm by the addition of ␣/␤-tubulin heterodimers onto it (37).…”