Lamb, M. C. | Search bioRxiv

bioRxiv2019

Fascin regulates protrusions and delamination to promote invasive, collective cell migration in vivo.

Fascin is an actin bundling protein that is essential for developmental cell migrations and promotes cancer metastasis. In addition to bundling actin, Fascin has several actin-independent roles. Border cell migration during Drosophila oogenesis provides an excellent model to study Fascins various roles during invasive, collective cell migration. Border cell migration requires Fascin. Fascin functions not only within the migrating border cells, but also within the nurse cells, the substrate for this migration. Loss of Fascin results in increased, shorter and mislocalized protrusions during migration. Data supports the model that Fascin promotes the activity of Enabled, an actin elongating factor, to regulate migration. Additionally, loss of Fascin inhibits border cell delamination. These defects are partially due to altered E-cadherin localization in the border cells; this is predicted to be an actin-independent role of Fascin. Overall, Fascin is essential for multiple aspects of this invasive, collective cell migration, and functions in both actin-dependent and -independent manners. These findings have implications beyond Drosophila, as border cell migration has emerged as a model to study mechanisms mediating cancer metastasis.

cell biology↗

bioRxiv2019

Pharmaco-genetic screen to uncover actin regulators targeted by prostaglandins during Drosophila oogenesis

Prostaglandins (PGs) are lipid signaling molecules with numerous physiologic functions, including pain/inflammation, fertility, and cancer. PGs are produced downstream of cyclooxygenase (COX) enzymes, the targets of non-steroidal anti-inflammatory drugs (NSAIDs). In numerous systems, PGs regulate actin cytoskeletal remodeling, however, their mechanisms of action remain largely unknown. To address this deficiency, we undertook a pharmaco-genetic interaction screen during late-stage Drosophila oogenesis. Drosophila oogenesis is as an established model for studying both actin dynamics and PGs. Indeed, during Stage 10B, cage-like arrays of actin bundles surround each nurse cell nucleus, and during Stage 11, the cortical actin contracts, squeezing the cytoplasmic contents into the oocyte. Both of these cytoskeletal properties are required for follicle development and fertility, and are regulated by PGs. Here we describe a pharmaco-genetic interaction screen that takes advantage of the facts that Stage 10B follicles will mature in culture and COX inhibitors, such as aspirin, block this in vitro follicle maturation. In the screen, aspirin was used at a concentration that blocks 50% of the wild-type follicles from maturing in culture. By combining this aspirin treatment with heterozygosity for mutations in actin regulators, we quantitatively identified enhancers and suppressors of COX inhibition. Here we present the screen results and initial follow-up studies on three strong enhancers - Enabled, Capping protein, and non-muscle Myosin II Regulatory Light Chain. Overall, these studies provide new insight into how PGs regulate both actin bundle formation and cellular contraction, properties that are not only essential for development, but are misregulated in diseases.

cell biology↗