Abnormal Wnt and PI3Kinase Signaling in the Malformed Intestine of lama5 Deficient Mice

Léa Ritié,Michèle Kedinger,Caroline Spenlé,Anne-Laure Bolcato-Bellemin,Patricia Simon-Assmann,Dominique Bagnard,Christine Bole-Feysot,Bernard Jost,Annick Klein,Joël Lacroute,Gertraud Orend,Olivier Lefebvre,Christiane Arnold,Cara Gottardi

doi:10.1371/journal.pone.0037710

Abstract

Laminins are major constituents of basement membranes and are essential for tissue homeostasis. Laminin-511 is highly expressed in the intestine and its absence causes severe malformation of the intestine and embryonic lethality. To understand the mechanistic role of laminin-511 in tissue homeostasis, we used RNA profiling of embryonic intestinal tissue of lama5 knockout mice and identified a lama5 specific gene expression signature. By combining cell culture experiments with mediated knockdown approaches, we provide a mechanistic link between laminin α5 gene deficiency and the physiological phenotype. We show that laminin α5 plays a crucial role in both epithelial and mesenchymal cell behavior by inhibiting Wnt and activating PI3K signaling. We conclude that conflicting signals are elicited in the absence of lama5, which alter cell adhesion, migration as well as epithelial and muscle differentiation. Conversely, adhesion to laminin-511 may serve as a potent regulator of known interconnected PI3K/Akt and Wnt signaling pathways. Thus deregulated adhesion to laminin-511 may be instrumental in diseases such as human pathologies of the gut where laminin-511 is abnormally expressed as it is shown here.

Highlights

Development and homeostasis of the mammalian intestine is a complex morphogenetic process that requires sequential interactions between cells and the extracellular matrix (ECM)
The prominent expression of laminin-511 in tissues including the intestine suggests that this laminin isoform plays an important role in tissue homeostasis
To tackle the role of laminin-511 in intestinal homeostasis and cell behavior, we used RNA profiling of embryonic intestinal tissue of lama5 knockout mice combined with cell culture experiments

Summary

Introduction

Development and homeostasis of the mammalian intestine is a complex morphogenetic process that requires sequential interactions between cells and the extracellular matrix (ECM). ECM molecules and in particular BM components shape the sequential and reciprocal interaction between the epithelium and the mesenchyme. The laminin family of glycoproteins represents a major component of the BM found in the interface between endoderm and mesenchyme in the embryo and between epithelial cells and the underlying connective tissue in the adult tissue [5,6]. Laminin-511 (a5b1c1) is the prominent a5-containing laminin isoform (Figure S1) in the epithelial BM of developing and adult organs including intestine and is found around individual smooth muscle cells [9,10,11]. The effects of laminins on cellular behavior depend on the receptors that participate in intracellular signaling, namely b1- and b4-integrins, the dystroglycan complex and the Lutheran-glycoprotein [8]

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