572A Poster - 08. Patterning, morphogenesis and organogenesis
Thursday April 07, 2:00 PM - 4:00 PM

Authors:
Mohammed Shah Jalal; Sabarish Nagarajan ; Atanu Duttaroy

Affiliation: Howard University, Washington, DC

Keywords:
a. axis specification; b. cell polarity

PGC-1 (Peroxisome proliferator-activated receptor-gamma coactivator-1) is a robust activator of mitochondrial biogenesis in the liver and skeletal muscles. On the other hand, Drosophila PGC-1, Spargel (Srl), is predominantly expressed in the Drosophila ovary, and germline-specific knockdown of srl arrests late-stage egg chamber development, resulting in arrested oogenesis and female sterility. Unlike srl RNAi, srl hypomorphic mutants (srl¹/srl¹) have a marked decrease in growth rate, body size, life span, and fecundity. A CRISPR-mediated srl deletion (srl^del) is an amorphic allele that is embryonic lethal. But a trans-heterozygous mutant mother (srl^del/srl¹) is fertile and used to investigate further the effects of low dosage of Spargel on oogenesis. We determined the maternal requirement of Spargel during embryogenesis because trans-heterozygous (srl^del/srl¹) females produced deformed embryos, most of which remained unhatched. A range of embryonic deformities was noticed in eggs produced by srl^del/srl¹ mother, which includes ventralized eggshells with phenotypes including single dorsal appendage (DA), 2 short DAs, or 2 DAs close together compared to the control. Broad (Br), a zinc-finger transcription factor that specifies the dorsal appendages forming cells, was not repatterned to clear the dorsal-anterior region in 10 of the 12 stages 10 egg-chambers investigated in srl^del/srl¹ ovaries. Roughly, a third of the post-vitellogenic oocytes are found with Gurken mislocalization. Interestingly, more than 90% of the srl^del/srl¹ egg chambers above stage 9 were found to have actin cytoskeletal defects, which might contribute towards dumping defects leading to small eggs. Follicle cell-specific knockdown of srl has minimum effect on dorsal appendage formation, implying that germ cell Spargel may regulate eggshell patterning via signaling interaction with follicle cells. We also found gaps in the distribution of the syncytial nuclei (nuclear fallout) in a majority of the embryos from srl^del/srl¹ mother, which also show cytoskeletal defects in pseudocleavage furrow formation. Together, our findings suggest that maternal spargel is required for eggshell patterning and cytoskeleton organization during oogenesis and early embryonic development.