Speaker: Nir Yakoby, Rutgers University Camden


Title: Patterning the Drosophila eggshell: mechanisms in cis and trans regulation


Abstract: Regulated by signals in a spatiotemporal manner, morphology is a highly-diverse trait in nature. Different mechanisms have been proposed to control tissues’ morphogenesis, including gene regulation and changes in protein sequences. We use Drosophila oogenesis as a model system to study how cell-to-cell signaling pathways transform a naïve tissue into a highly-patterned 2D follicular epithelium, which consequently folds and secretes the intricate 3D structures of the Drosophila eggshell. Over the past 40 years, many gene expression patterns were found in the follicular epithelium, but the cis regulatory modules (CRMs) controlling these patterns remain mostly unidentified. We took advantage of the FlyLight collection intergenic and intronic DNA fragments that, if containing CRM, can drive the expression of a reporter GFP. Cross listing the known 81 genes expressed during oogenesis with the ~1,200 genes included in the FlyLight yielded 22 common genes represented by 281 lines. Of these lines, 19% expressed GFP and ~30% of the GFP positive lines recapitulated the full or partial pattern of the endogenous gene. I will discuss some of the analyses done on these patterns. In addition, I will discuss the formation of a morphological novelty that is generated by changes in the distribution of the TGF alpha-like Gurken (GRK) among Drosophila species. In particular, the formation of the dorsal ridge, a lumen-like structure along the dorsal side of the eggshell of several Drosophila species, is regulated by dramatic changes in the spatial distribution of GRK and activation of the epidermal growth factor receptor. D. melanogaster does not have a dorsal ridge. We showed that GRK is necessary and sufficient to regulate the formation of morphological novelty. The diversity of eggshell structures across species is a powerful platform to study cis and trans regulation of morphological processes.