The small GTPase Ran and ß-importins Tnpo-SR and Cadmus promote ovarian cyst formation in Drosophila

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Allison N Beachum (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: Germ cells follow a precise and coordinated molecular timeline to produce a viable oocyte. While undergoing mitotic expansion via incomplete cytokinesis, cysts of undifferentiated cells form and remain interconnected prior to meiotic initiation, through mechanisms that are not well-defined. In somatic cells, Ras-related nuclear protein (Ran) spatiotemporally regulates mitotic spindle assembly, cleavage furrow formation and abscission. Here, we identify Ran and [beta]-importins as critical regulators of cyst development in the Drosophila ovary. Depletion of Ran or the [beta]-importins Tnpo-SR and Cadmus results in egg chambers with variable numbers of germ cells, suggesting abnormal cyst development and cyst fragmentation, and consequently disrupts oocyte selection. We demonstrate that Ran, Tnpo-SR, and Cadmus regulate key cellular processes during cyst formation, including cell cycle dynamics, fusome biogenesis, and ring canal stability, all independently of mitotic spindle assembly. Further, Tnpo-SR and Cadmus control cyclin accumulation and suppress cytokinesis, suggesting that [beta]-importins sequester protein cargos that normally promote the mitotic-to-meiotic transition. Our data demonstrates that Ran and [beta]-importins are critical for the cell fate decisions of germ cells, a role that is likely conserved in other organisms.

Additional Information

Publication

Thesis

Language: English

Date: 2023

Subjects

stem cells;oocyte;karyopherin

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