Genetic Analysis of Hedgehog Signaling in Ventral Body Wall Development and the Onset of Omphalocele Formation

Daisuke Matsumaru,Frits Meijlink,Shinichi Miyagawa,Ryuma Haraguchi,Gen Yamada,Naomi Nakagata,Mai Har Sham,Jun Motoyama

doi:10.1371/journal.pone.0016260

Abstract

BackgroundAn omphalocele is one of the major ventral body wall malformations and is characterized by abnormally herniated viscera from the body trunk. It has been frequently found to be associated with other structural malformations, such as genitourinary malformations and digit abnormalities. In spite of its clinical importance, the etiology of omphalocele formation is still controversial. Hedgehog (Hh) signaling is one of the essential growth factor signaling pathways involved in the formation of the limbs and urogenital system. However, the relationship between Hh signaling and ventral body wall formation remains unclear.Methodology/Principal FindingsTo gain insight into the roles of Hh signaling in ventral body wall formation and its malformation, we analyzed phenotypes of mouse mutants of Sonic hedgehog (Shh), GLI-Kruppel family member 3 (Gli3) and Aristaless-like homeobox 4 (Alx4). Introduction of additional Alx4Lst mutations into the Gli3Xt/Xt background resulted in various degrees of severe omphalocele and pubic diastasis. In addition, loss of a single Shh allele restored the omphalocele and pubic symphysis of Gli3Xt/+; Alx4Lst/Lst embryos. We also observed ectopic Hh activity in the ventral body wall region of Gli3Xt/Xt embryos. Moreover, tamoxifen-inducible gain-of-function experiments to induce ectopic Hh signaling revealed Hh signal dose-dependent formation of omphaloceles.Conclusions/SignificanceWe suggest that one of the possible causes of omphalocele and pubic diastasis is ectopically-induced Hh signaling. To our knowledge, this would be the first demonstration of the involvement of Hh signaling in ventral body wall malformation and the genetic rescue of omphalocele phenotypes.

Highlights

The embryonic visceral organs transiently protrude out of the body trunk during mid-gestation, where they are covered with the peritoneal membrane
The bilateral primordia of the pelvic girdle started to be perceptible from E11.5 (Fig. 1E) [76] and they were positioned in parallel along with the body trunk at E12.5 (Fig. 1F)
The development of the ventral body wall displays dynamic processes, such as that observed during the formation and recovery of the physiological umbilical hernia

Summary

Introduction

The embryonic visceral organs transiently protrude out of the body trunk during mid-gestation, where they are covered with the peritoneal membrane They return to the peritoneal cavity in both mouse and human embryos. Patients with omphalocele-exstrophy-imperforate anus-spinal defects complex (OEIS complex, OMIM: 25840) or bladder exstrophy (OMIM: %600057) exhibit defects in the body wall region and in urogenital organs and its adjacent tissues, including the pelvic girdle [15,16,17,18]. Our understanding of these malformations is hampered by the complexity of these syndromes. The relationship between Hh signaling and ventral body wall formation remains unclear

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Conclusion