Mice Lacking Zfhx1b, the Gene That Codes for Smad-Interacting Protein-1, Reveal a Role for Multiple Neural Crest Cell Defects in the Etiology of Hirschsprung Disease–Mental Retardation Syndrome

Abstract

Recently, mutations in ZFHX1B, the gene that encodes Smad-interacting protein-1 (SIP1), were found to be implicated in the etiology of a dominant form of Hirschsprung disease-mental retardation syndrome in humans. To clarify the molecular mechanisms underlying the clinical features of SIP1 deficiency, we generated mice that bear a mutation comparable to those found in several human patients. Here, we show that Zfhx1b-knockout mice do not develop postotic vagal neural crest cells, the precursors of the enteric nervous system that is affected in patients with Hirschsprung disease, and they display a delamination arrest of cranial neural crest cells, which form the skeletomuscular elements of the vertebrate head. This suggests that Sip1 is essential for the development of vagal neural crest precursors and the migratory behavior of cranial neural crest in the mouse. Furthermore, we show that Sip1 is involved in the specification of neuroepithelium.

Complementary expression pattern of Zfhx1 genes Sip1 and δEF1 in the mouse embryo and their genetic interaction revealed by compound mutants

“…In previous studies, the tissue distribution of the embryonic expression of Sip1 and ␦EF1 was studied focusing on the tissues and stages where knockout mouse embryos displayed the major phenotype, i.e., Sip1 expression around E8.5 in the neural plate/ crest ( Van de Putte et al, 2003) and in the paraxial mesoderm (Maruhashi et al, 2005), and ␦EF1 expression in the paraxial and limb skeletal elements of the stages up to E12 (Takagi et al, 1998). However, the expression of Sip1 and ␦EF1 has not been investigated in a systematic fashion.…”

“…The neural tube fails to close, short somites are produced, somite cleavage stops at somite 7 while embryo elongation continues, and then the entire embryonic development is arrested without the occurrence of turning (Fig. 4Dc,e) ( Van de Putte et al, 2003;Maruhashi et al, 2005). The defect of somitogenesis is caused by aberrant positioning of somite cleavage with normal production of presomitic mesoderm (Fig.…”

“…As Sip1Ϫ/Ϫ;␦EF1Ϫ/Ϫ double homozygous embryos did not survive after E8.5, as was the case with Sip1Ϫ/Ϫ single homozygotes ( Van de Putte et al, 2003;Maruhashi et al, 2005), genetic interaction between the deficiency of Sip1 and ␦EF1 at later developmental stages was further investigated using a Sip1ϩ/Ϫ heterozygous condition superimposed on a ␦EF1Ϫ/Ϫ homozygous condition. Sip1ϩ/Ϫ heterozygotes are healthy, except for the frequent occurrence of vaginal orifice closure in females (see Experimental Procedures section) and ␦EF1Ϫ/Ϫ homozygotes develop fully until birth but die perinatally (Takagi et al, 1998).…”

“…In vertebrates, Zfhx1 proteins are classified as either ␦EF1 or Sip1. Functional analyses of ␦EF1 and Sip1 proteins from mouse and chicken have demonstrated their similarities: binding to an identical consensus sequence CACCT and acting as transcriptional repressors when bound (Sekido et al, 1994Remacle et al, 1999), by a mechanism involving the binding of co-repressor CtBP (Furusawa et al, 1999;van Grunsven et al, 2003). These proteins also participate in gene activation in other contexts (Lazarova et al, 2001;Dillner and Sanders, 2004;Yoshimoto et al, 2005).…”

Sip1 regulates sequential fate decisions by feedback signaling from postmitotic neurons to progenitors

“…Sip1 knockout mice die at E9.5, fail to close the neural tube, lack vagal neural crest cells and show defective migration of cranial neural crest cells 14 . To investigate the function(s) of Sip1 in the developing neocortex (beginning at E11.5), we analyzed loxP/Cre-based conditional knockout mice.…”