Centrosomin: A Complex Mix of Long and Short Isoforms Is Required for Centrosome Function During Early Development in Drosophila melanogaster

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Centrosomin (Cnn) is a required core component in mitotic centrosomes during syncytial development and the presence of Cnn at centrosomes has become synonymous with fully functional centrosomes in Drosophila melanogaster. Previous studies of Cnn have attributed this embryonic function to a single isoform or splice variant. In this study, we present new evidence that significantly increases the complexity of cnn. Rather than a single isoform, Cnn function can be attributed to two unique classes of proteins that comprise a total of at least 10 encoded protein isoforms. We present the initial characterization of a new class of Cnn short isoforms required for centrosome function during gametogenesis and embryogenesis. We also introduce new evidence for a complex mix of Cnn isoforms present during early embryogenesis. Finally, we reexamine cnn mutations, in light of the short isoforms, and find previously overlooked differences attributable to allele-specific mutant phenotypes. This study addresses several questions surrounding Cnn function at the centrosome during embryogenesis and shows that cnn function cannot be ascribed to a single protein.