"Deubiquitinase USP8 targets ESCRT-III to promote incomplete cell division"
Juliette Mathieu is research scientist who was recruited in 2010 at CNRS and integrated Jean-René Huynh’s team. The team is interested in evolution and development of germ cells. Juliette focuses more particularly on the regulation of abscission process in female germline in Drosophila.
ABSTRACT
In many vertebrate and invertebrate organisms, gametes develop within groups of interconnected cells called germline cysts. Cysts form by several rounds of incomplete divisions, whose underlying molecular mechanisms remain unknown. Here, we found that loss of a single gene, encoding the deubiquitinase USP8, can transform incomplete divisions of germline cells into complete divisions. Conversely, overexpression of USP8 in germline stem cells (GSCs) is sufficient for the reverse transformation from complete to incomplete cytokinesis. We further demonstrate that two ESCRT proteins, are targets of the deubiquitinating activity of USP8. In Usp8 mutant sister cells, ectopic recruitment of ESCRT proteins at intercellular bridges causes cysts to break apart and reducing ESCRT levels is sufficient to suppress these abscissions. Finally, we show that an ESCRT variant that cannot be ubiquitinated, does not localize at abscission bridges and cannot substitute for endogenous ESCRT during complete abscission of the GSCs. Taken together, our results uncover ubiquitination of ESCRT-III as a major switch between two types of cell division.