CLMP Is Essential for Intestinal Development, but Does Not Play a Key Role in Cellular Processes Involved in Intestinal Epithelial Development

Christine S Van Der Werf,Sven C D Van Ijzendoorn,Joana Paredes,Helga Westers,Ana S Ribeiro,Yunia Sribudiani,Nai-Hua Hsiao,Raquel Seruca,Siobhan Conroy,Robert M W Hofstra

doi:10.1371/journal.pone.0054649

Abstract

Loss-of-function mutations in CLMP have been found in patients with Congenital Short Bowel Syndrome (CSBS), suggesting that its encoded protein plays a major role in intestinal development. CLMP is a membrane protein that co-localizes with tight junction proteins, but its function is largely unknown. We expressed wild-type (WT)-CLMP and a mutant-CLMP (associated with CSBS) in human intestinal epithelial T84 cells that, as we show here, do not produce endogenous CLMP. We investigated the effects of WT-CLMP and mutant-CLMP proteins on key cellular processes that are important for intestinal epithelial development, including migration, proliferation, viability and transepithelial resistance. Our data showed that expression of WT-CLMP or mutant-CLMP does not affect any of these processes. Moreover, our aggregation assays in CHO cells show that CLMP does not act as a strong adhesion molecule. Thus, our data suggest that, in the in vitro model systems we used, the key processes involved in intestinal epithelial development appear to be unaffected by WT-CLMP or mutant-CLMP. Further research is needed to determine the role of CLMP in the development of the intestine.

Highlights

CLMP is a membrane protein that belongs to the CTX family of proteins [1]
We found that T84 cells do not endogenously express CLMP (Figure 1), which makes this cell line a suitable model system to explore the effect of CLMP and Congenital Short Bowel Syndrome (CSBS)-related CLMP mutants on epithelial functions related to the tight junction
Since the goblet cells were absent in the morphant zebrafish, knock down of the orthologue of CLMP in zebrafish would probably result in the absence of the small intestine

Summary

Introduction

CLMP (coxsackie- and adenovirus receptor-like membrane protein) is a membrane protein that belongs to the CTX (cortical thymocyte marker in Xenopus) family of proteins [1]. It has been suggested that CLMP plays a role in immunological processes [1,2] This is based on the fact that there is a high homology between CLMP and Junctional adhesion molecules (JAMs), both belonging to the CTX family of proteins. It has been suggested that CLMP plays a role in cell-cell adhesion, based on the finding that it co-localizes with the tight junction proteins zonula occludens 1 (ZO-1) [1,4,5] and occluding [1]. Transfection of human CLMP into Madin-Darby canine kidney (MDCK) epithelial cells induces transepithelial electrical resistance (TER), suggesting a role for CLMP in the junction-barrier function of intestinal epithelial cells [1]

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