The ALX4 homeobox gene is mutated in patients with ossification defects of the skull (foramina parietalia permagna, OMIM 168500)

Foramina parietalia permagna (FPP) (OMIM 168500) is caused by ossification defects in the parietal bones. Recently, it was shown that loss of function mutations in the MSX2 homeobox gene on chromosome 5 are responsible for the presence of these lesions in some FPP patients. However, the absence of MSX2 mutations in some of the FPP patients analysed and the presence of FPP associated with chromosome 11p deletions in DEFECT 11 (OMIM 601224) patients or associated with Saethre-Chotzen syndrome suggests genetic heterogeneity for this disorder. Starting from a BAC/P1/cosmid contig of the DEFECT 11 region on chromosome 11, we have now isolated the ALX4 gene, a previously unidentified member of the ALX homeobox gene family in humans. Mutation analysis of the ALX4 gene in three unrelated FPP families without the MSX2 mutation identified mutations in two families, indicating that mutations in ALX4 could be responsible for these skull defects and suggesting further genetic heterogeneity of FPP.


Keywords: ALX4; FPP; DEFECT 1

Cloning a new human gene from chromosome 21q22.3 encoding a glutamic acid-rich protein expressed in heart and skeletal muscle.

International audienceThe identification and functional characterization of genes on chromosome 21 is a necessary step to understand the pathogenesis of the various phenotypic anomalies that affect Down syndrome patients. Using direct cDNA selection we have identified a new gene, SH3BGR, that maps to 21q22.3, proximal to HMG14, and is differentially expressed in heart and skeletal muscle. SH3BGR encodes a novel protein that is characterized by the presence of a proline-rich region containing the consensus sequence for a SH3-binding domain and by an acidic carboxyl-terminal region containing a glutamic acid-rich domain predicted to assume a coiled coil. The presence of two functional domains involved in protein-protein interactions suggests that SH3BGR could be part of a multimeric complex. Its overexpression might alter specific functions of muscular tissue and therefore take part in the pathophysiology of muscular hypotonia in Down syndrome

Identification and characterization of a new human gene encoding a small protein with high homology to the proline-rich region of the SH3BGR gene

As part of an effort to identify genes potentially involved in the Down Syndrome pathogenesis, in this paper we report the identification and characterization of a new human gene (named SH3BGRL), which shows a high homology to the SH3BGR gene, previously mapped to the Down Syndrome region of chromosome 21. The SH3BGRL gene encodes for a small protein of 114 amino acids, sharing 60% identity and 84% conservation on the amino acid level with themiddle, proline-rich region of the SH3BGR gene and containing a similar SH3 (Scr homology 3) binding motif. The SH3BGRL and the proline-rich region of SH3BGR proteins appear to be highly conserved, sharing 95 and 98% identity, respectively, with the mouse homologues. A 1.9 kb transcript of the SH3BGRL gene has been found in all the tissues examined, in contrast with the expression pattern of the SH3BGR gene which is transcribed only in heart and skeletalmuscle. The SH3BGR gene and its homologue, SH3BGRL, could be members of a new family of genes containing a highly conserved proline-rich functional domain. The SH3BGRL gene has been mapped by fluorescent in situ hybridization to Chromosome Xq13.3