422A Poster - 05. Reproduction and gametogenesis
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
Swagota Roy; Mohammed Shah Jalal; Sabarish Nagarajan; Atanu Duttaroy

Affiliation: The Howard University, Washington DC

Keywords:
b. oogenesis; aa. tissue growth

The transcriptional coactivators Peroxisome Proliferator Activated Receptor-1 (PGC-1) play a key role in wide range of physiological processes in mammals including mitochondrial biogenesis, oxidative metabolism, and adaptive thermogenesis. There are three mammalian PGC-1 paralogs: PGC-1α, PGC-1β, and PRC-1. Spargel/dPGC-1 is an ancestral PGC-1 homolog in Drosophila that is predominantly expressed in the ovaries during adult life. Ovary-specific knockdown of srl induces complete sterility indicating that Spargel plays an essential role in oogenesis and ovarian growth. Spargel shares many structural features with PGC-1 proteins including the Serine-Arginine rich repeats (RS), RNA recognition motif (RRM) and a nuclear localization signal (NLS). Due to their functional redundancy, attempts to make domain specific deletions in PGC-1 failed to demonstrate the role of RRM in mammalian system. We generated two srl mutant lines using CRISPR/CAS9 system: (1) A 3336 bp deletion was created within the srl beginning from Exon 2 (srl^del), and (2) RRM domain specific deletion (∆RRM). Homozygous srl^del embryos complete the embryonic development but can’t proceed beyond 1^st instar larval stage as these larvae failed to emerge out of the chorion. This suggests that Spargel function is not limited to oogenesis, but it is also essential for postzygotic development. Mitotic clones of srl^delestablished it as an amorphic allele which may be the reason why most srl^del/del egg chambers don’t survive beyond previtellogenic stages. Incidentally, germ line homozygous knockouts of PGC-1α or PGC-β are viable and fertile with no global changes in mitochondrial number or morphology, however a germ line knock-out of the PPRC1 gene in mice results in neonatal lethality. Phylogenetic analysis supports that Spargel is actually a closer ancestor to mammalian PRC-1 as compared to PGC-1α or PGC-β. Homozygous srl∆RRM females are viable but carries very few mature eggs in their ovaries. Further analysis shows the infertility of srl∆RRMfemales stems from disrupted actin cable and cortical actin loss in nurse cells resulting in dumpless phenotype. Together, this collection of spargel mutants is helping us to address (1) the role of Spargel on ovarian growth and development, and (2) to determine the role of Spargel in postzygotic development.