Centrosomes are the major and best-understood microtubule-organizing centers (MTOCs) in animal cells. Mutations in genes that encode key centrosomal proteins impact developmental processes leading to syndromic microcephaly, primordial dwarfisms, and other inherited disorders. A major regulator of microtubules at centrosomes and other MTOCs is ?-tubulin, a highly conserved and tubulin variant that is specialized in catalyzing the initiation of microtubule polymer assembly. ?-tubulin associates with gamma tubulin complex proteins (GCPs) to form a ring complex (?-TuRC). We found two distinct types of ?-TuRCs in Drosophila testis: the conventional one that is essential throughout the organism, and a second uncharacterized one whose unique GCP subunits are expressed in late stage testis and are required for sperm motility. This is the first known case of diversity of ?-TuRC core complexes in one organism. We propose to determine the subunit composition of the new testis-specific ?-TuRC and determine if it can assemble hybrid ?-TuRCs with the conventional GCP proteins. We will ascertain the MT nucleation properties of both ?-TuRCs and determine the role for the novel testis-specific variant in sperm motility. The outcomes of this project will be a new understanding of the functions of this essential MT nucleator complex biochemically and in vivo.
Microtubules comprise a major cytoskeletal network required for many diverse and critical cellular functions such as structural support, molecular and vesicle trafficking, etc, that is coordinated from specific organizing centers that vary according to cell type and function. The goals of this proposal are to determine the mechanisms by which a new type of a highly conserved microtubule assembly catalyst functions biochemically to assemble microtubules, and in vivo to support sperm flagellar motility.
