A function for dystroglycan in pronephros development in Xenopus laevis

Abstract

Dystroglycan (Dg) is a laminin receptor that is expressed at the interface between the basement membrane and the cell membrane. Dg has been reported to play a role in skeletal muscle cell stability, morphogenesis of neuroepithelial tissues, and in regulating cytoskeletal organization, cell polarization, and cell signalling. In this study, we have focused our analysis on the expression of Dg-mRNA and protein at different developmental stages in the pronephros of Xenopus laevis. In order to study its role, we performed loss-of-function experiments mediated by Dg antisense morpholinos and dominant negative mutant. We show that Dg expression is first detectable when epithelialization begins in the pronephric anlage and persists later during tubulogenesis. Loss-of-function experiments induced a disorganization of the basement membrane, a drastic reduction of pronephric tubules and duct that can lead to a renal agenesis. A diminished proliferation of pronephric cell progenitors was also observed in Dg depleted embryos. Together, these data indicate that Dg plays a key role for laminin-1 assembly and pronephric cell anchoring to the basement membrane during early development of the pronephros. They also indicate that Dg may induce a signal transduction pathway controlling cell proliferation needed for the formation of tubules and their growth.

In vivo analyzes of dystroglycan function during somitogenesis in Xenopus laevis

“…Of interest, in cell cultures, Dg has been shown to modulate the cell cycle by affecting extracellular signal-regulated kinase levels (Higginson et al, 2008). Although further studies are required, our results are consistent with those describing the role of Dg in Xenopus kidney development (Bello et al, 2008) and with the hypothesis that Dg is a component of the signaling cascade regulating cell proliferation during early development.…”

“…To address this question, we carried out loss-of-function experiments with Dg morpholino antisense oligonucleotides and overexpression of a Dg construct that lacks the cytoplasmic domain. Two oligonucleotides known for targeting the translation of Dg were used (Bello et al, 2008). We tested their specificity in MO-injected embryos by Western blotting of proteins extracted from somites and by indirect immunofluorescence.…”

“…Therefore, we have used two Dg antisense morpholinos (Dg-MO) to examine the Dg function in Xenopus laevis somitogenesis. Their efficiency has been demonstrated previously (Bello et al, 2008 To determine the requirement of Dg protein during somitogenesis, unilateral injections of Dg-MO were performed at the two-cell stage. Injected embryos developed normally through cleavage, gastrulation, and early neurulation.…”

“…Xenopus laevis embryos were obtained as previously described (Bello et al, 2008). At stage 9 (Nieuwkoop and Faber, 1967), the presumptive ectoderm explants (animal cap) were isolated in 1ϫ MBS (Modified Barth's Saline) and induction of muscle was obtained by incubation for 1 hr in 10 ng/ml of activin (A4941 Sigma).…”

“…Dg has been implicated in branching morphogenesis of lung and salivary glands (Durbeej et al, 2001). In vivo, depletion of Dg affects kidney morphogenesis and can lead to renal agenesis (Bello et al, 2008). In Drosophila, Dg has been reported to play a fundamental role for polarizing the epithelial cells and the oocytes in the ovaries (Deng et al, 2003).…”