Capulet and Slingshot share overlapping functions during Drosophila eye morphogenesis

Abstract

BackgroundCAP/Capulet (Capt), Slingshot (Ssh) and Cofilin/Twinstar (Tsr) are actin-binding proteins that restrict actin polymerization. Previously, it was shown that low resolution analyses of loss-of-function mutations in capt, ssh and tsr all show ectopic F-actin accumulation in various Drosophila tissues. In contrast, RNAi depletion of capt, tsr and ssh in Drosophila S2 cells all affect actin-based lamella formation differently. Whether loss of these three related genes might cause the same effect in the same tissue remains unclear.MethodsLoss-of-function mutant clones were generated using the MARCM or EGUF system whereas overexpression clones were generated using the Flip-out system. Immunostaining were then performed in eye imaginal discs with clones. FRAP was performed in cultured eye discs.ResultsHere, we compared their loss-of-function phenotype at single-cell resolution, using a sheet of epithelial cells in the Drosophila eye imaginal disc as a model system. Surprisingly, we found that capt and ssh, but not tsr, mutant cells within and posterior to the morphogenetic furrow (MF) shared similar phenotypes. The capt/ssh mutant cells possessed: (1) hexagonal cell packing with discontinuous adherens junctions; and (2) largely complementary accumulation of excessive phosphorylated myosin light chain (p-MLC) and F-actin rings at the apical cortex. We further showed that the capt/ssh mutant phenotypes depended on the inactivation of protein kinase A (PKA) and activation of Rho.ConclusionsAlthough Capt, Ssh and Tsr were reported to negatively regulate actin polymerization, we found that Capt and Ssh, but not Tsr, share overlapping functions during eye morphogenesis.

E‐cadherin is downregulated in benign prostatic hyperplasia and required for tight junction formation and permeability barrier in the prostatic epithelial cell monolayer

“…Besides decreased expression, it is also notable that E‐cadherin displayed a discontinuous pattern in BPH, indicating alterations in prostatic epithelial cell‐cell contacts and perhaps deficits in its membrane protein trafficking. Discontinuous and weaker E‐cadherin staining patterns have been reported by others in epithelial choroid plexus cell lines used to study the blood‐cerebrospinal fluid barrier; and discontinuous adherens junctions have been associated with cell border retraction in endothelial cells . Our in vitro studies revealed that E‐cadherin knockdown increased monolayer permeability and disrupted tight‐junction formation without affecting cell density.…”

“…Discontinuous and weaker E-cadherin staining patterns have been reported by others in epithelial choroid plexus cell lines used to study the blood-cerebrospinal fluid barrier 35 ; and discontinuous adherens junctions have been associated with cell border retraction in endothelial cells. [36][37][38] Our in vitro studies revealed that E-cadherin knockdown and differentiation of the prostatic bud epithelium. 42 In murine urogenital sinus, blocking of E-cadherin function increases the number of prostatic buds undergoing morphogenesis and accelerates prostate lumen formation.…”

The role of cyclase-associated protein in regulating actin filament dynamics – more than a monomer-sequestration factor

“…It has been shown that rat CAP1 is enriched in the neuronal growth cones (Lu et al, 2011;Nozumi et al, 2009), suggesting that CAP is a conserved regulator of neuronal growth. Mutations in Drosophila CAP also disturb oocyte polarity (Baum et al, 2000), epithelial cell polarity (Baum and Perrimon, 2001), Hedgehog signaling (Benlali et al, 2000), Hippo signaling (Fernández et al, 2011) and eye development (Benlali et al, 2000;Lin et al, 2012). However, it is not clear whether these phenotypic changes are owing to the direct role of CAP in certain signaling pathways or because of secondary effects of disorganized actin filaments.…”

A Drosophila‐centric view of protein tyrosine phosphatases

“…Ssh is a cofilin phosphatase of the Slingshot family, with an important role in eye morphogenesis during the assembly of ommatidia (the basic units of the compound insect eye), where it works to inhibit actin polymerization by activating cofilin [168]. In addition to its catalytic domain, Ssh , like its human orthologs (SSH1, SSH2 and SSH3), also contains a DEK domain N‐terminal to the phosphatase catalytic domain, and C‐terminal serine‐ and glutamine‐rich regions.…”