Expression of 18‐wheeler in the follicle cell epithelium affects cell migration and egg morphology in Drosophila

Abstract

The Drosophila ovary is a model system for examining the genetic control of epithelial morphogenesis. The somatic follicle cells form a polarized epithelium surrounding the 16-cell germ line cyst. The integrity of this epithelium is essential for the successful completion of oogenesis. Reciprocal signaling between germ line and somatic cells establishes embryonic and eggshell polarity. The follicle cells are responsible for shaping the egg and secreting the eggshell. Follicle cells at the boundary between the nurse cells and the oocyte migrate centripetally to cover the anterior end of the oocyte and secrete the operculum. Dorsal anterior main body follicle cells undergo elaborate patterning to produce the dorsal appendages. We have examined the expression of the Toll-like receptor, 18-wheeler (18w), in the ovary and find it to be restricted to subpopulations of follicle cells. Females carrying loss-of-function 18w mutant clones in their ovaries show delayed follicle cell migrations. The eggs laid by such females also show morphological defects in egg shape and dorsal appendage morphology. We propose that the 18W protein plays an adhesive or signaling role in regions of the epithelium engaged in cell migration.

Toll-like receptors — taking an evolutionary approach

“…Forced expression of Toll2 promotes the rapid and robust aggregation of cells in culture, suggesting that it can function as a cell-adhesion molecule and that it can facilitate cell movements 3 . Accordingly, Toll2 mutant embryos present salivary gland invagination defects similar to the embryos that lack components of the Rho pathway 57 and Toll2 mutant ovarian follicular cells show delayed migrations 58 . Therefore, Toll2 has an adhesive and a signalling role in epithelia that are engaged in cell migration that does not involve the canonical Toll cascade but possibly the RhoGTPase pathway.…”

Three-Dimensional Epithelial Morphogenesis in the Developing Drosophila Egg

“…Included among the genes with patterned expression in the late follicular epithelium are several that encode proteins involved in cytoskeleton regulation or cell-cell adhesion (Dinkins et al, 2008; James et al, 2002; Jordan et al, 2005; Wahlström et al, 2006; Ward and Berg, 2005a; Yakoby et al, 2008; Zartman et al, 2009). Mutations in some of these genes result in dorsal appendage defects (Kleve et al, 2006; Laplante and Nilson, 2006; Zartman et al, 2008), but whether these genes work through regulating tension or through some other process has been largely unexplored.…”

The involvement of the Toll-like receptor family in ovulation

“…Recently the expression of the Toll-like receptor, 18-wheeler (18 w), was found to affect cell migration and egg morphology in Drosophila [29]. Although none of the single TLR knockout mice are infertile, there is increasing evidence indicating that TLRs are functional in the ovary and they could affect fertility.…”