Emerin preserves stem cell survival through maintenance of centrosome and nuclear lamina structure

Abstract

Drosophila female germline stem cells (GSCs) complete asymmetric mitosis in the presence of an intact, but permeable, nuclear envelope and nuclear lamina (NL). This asymmetric division requires a modified centrosome cycle, wherein mitotic centrosomes with mature pericentriolar material (PCM) embed in the NL and interphase centrosomes with reduced PCM leave the NL. This centrosome cycle requires emerin, a NL protein critical for GSC survival and germ cell differentiation. In emerin mutants, interphase GSCs centrosomes retain excess PCM, remain embedded in the NL and nucleate microtubule asters at positions of NL distortion. Here, we address contributions of abnormal interphase centrosomes to GSC loss. Remarkably, reducing interphase PCM in emerin mutants rescues GSC survival and partially restores germ cell differentiation. Direct tests of effects of abnormal centrosomes were achieved by expression of constitutively active Polo kinase that drove enlargement of interphase centrosomes in wild type GSCs. Notably, these conditions failed to alter NL structure or decrease GSC survival. However, coupling enlarged interphase centrosomes with nuclear distortion promoted GSC loss. These studies establish that emerin maintains centrosome structure to preserve stem cell survival.