Domain-specific early and late function of Dpatj inDrosophilaphotoreceptor cells

Abstract

The formation and maintenance of cell polarity is essential for epithelial morphogenesis. Dpatj (Drosophila homolog of mammalian Patj) is a multi-PDZ domain protein that localizes to the apical cell membrane and forms a protein complex with cell polarity proteins, Crumbs (Crb) and Stardust (Sdt). Whereas Crb and Sdt are known to be required for the organization of adherens junctions (AJs) and rhabdomeres in differentiating photoreceptors, the in vivo function of Dpatj as a member of the Crb complex in developing eye has been unclear due to the lack of loss-of-function mutations specifically affecting the dpatj gene.

Localization and Function of Pals1-associated Tight Junction Protein in Drosophila Is Regulated by Two Distinct Apical Complexes

“…Overexpression of the same construct using arm:: GAL4 resulted in increased rescue capacity, and the recued flies can be maintained as a stable stock. Therefore, only artificially increased levels of the protein consisting of the L27 domain and the first PDZ domain can accomplish the function of PATJ during development, which is in line with previous studies using overexpressed proteins (11,23).…”

“…Therefore, the follicular epithelium represents a phenotypic characteristic that differs from the epidermis (PATJ localization is only dependent on Baz-Sdt but not on Crb-Sdt) and resembles rather pupal photoreceptor cells in which PATJ localization depends on Crb (10,46). Notably, in photoreceptor cells, PATJ seems to be crucial for the stabilization of the CrbSdt complex (10,11,22), whereas this phenotype is much weaker in the follicular epithelium. In follicle epithelial cells, loss of PATJ results in decreased apical junctional accumulation of Crb/Sdt but without subsequent disassembly of the complex and polarity defects.…”

“…Because overexpression of a truncated version of PATJ has been reported to be capable of rescuing a PATJ mutant to some extent (10,11,23), we determined which minimal region of PATJ is sufficient for the function of the protein. As expected, ubiquitous expression of the isolated L27 domain (PATJ 1-151 ) shows a mostly apical localization (Fig.…”

Increased levels of the cytoplasmic domain of Crumbs repolarise developingDrosophilaphotoreceptors

“…2A,C,E,G,I and data not shown) (Bachmann et al, 2008;Hong et al, 2003;Izaddoost et al, 2002;Johnson et al, 2002;Nam and Choi, 2003;Nam and Choi, 2006;Pellikka et al, 2002;Richard et al, 2006). In PRCs overexpressing Crb FLAGintra under the control of elavGal4, localisation of Crb complex members was strongly affected.…”

Crumbs is required to achieve proper organ size control duringDrosophilahead development

“…The following fly strains where used: y,w;; FRT82B, crb 11A22 (Johnson et al, 2002), w;;FRT82B, crb 36 and w;;FRT82B, crb 4 (Pichaud and Desplan, 2001), crbRNAi 39178 (Vienna Drosophila RNAi Center), UAS-crbExtTM-GFP (Pellikka et al, 2002), UAS-crbExt (Wodarz et al, 1995), lin-7 54 and lin-7 66 (Bachmann et al, 2004), UAS-dpatjRNAi (Nam and Choi, 2006), sdt XP96 (Hong et al, 2001), N 264-39 and N 55e11 (Bloomington Stock Center), Dl revF10 (Fanto and Mlodzik, 1999), aph1 D35 (Hu and Fortini, 2003), E(spl) mlacZ (Nellesen et al, 1999), UAS-mam DN (Giraldez et al, 2002), Hrs…”