Asterless Is a Centriolar Protein Required for Centrosome Function and Embryo Development in Drosophila

Background: Centrosomes, the major organizers of the microtubule network in most animal cells, are com-posed of centrioles embedded in a web of pericentriolar material (PCM). Recruitment and stabilization of PCM on the centrosome is a centriole-dependent function. Com-pared to the considerable number of PCM proteins known, the molecular characterization of centrioles is still very limited. Only a few centriolar proteins have been identified so far in Drosophila, most related to centriole duplication.

Results: We have cloned asterless (asl) and found that it encodes a 120 kD highly coiled-coil protein that is a constitutive pancentriolar and basal body component. Loss of asl function impedes the stabilization/maintenance of PCM at the centrosome. In embryos deficient for Asl, development is arrested right after fertilization. Asl shares significant homology with Cep152, a protein described as a component of the human centrosome for which no functional data is yet available.

Conclusions: The cloning of asl offers new insight into the molecular composition of Drosophila centrioles and a possible model for the role of its human homolog. In addition, the phenotype of asl-deficient flies reveals that a functional centrosome is required for Drosophila embryo development.