A Gja1 missense mutation in a mouse model of oculodentodigital dysplasia

Abstract

Oculodentodigital dysplasia (ODDD) is an autosomal dominant disorder characterized by pleiotropic developmental anomalies of the limbs, teeth, face and eyes that was shown recently to be caused by mutations in the gap junction protein alpha 1 gene (GJA1), encoding connexin 43 (Cx43). In the course of performing an Nethyl-N-nitrosourea mutagenesis screen, we identified a dominant mouse mutation that exhibits many classic symptoms of ODDD, including syndactyly, enamel hypoplasia, craniofacial anomalies and cardiac dysfunction. Positional cloning revealed that these mice carry a point mutation in Gja1 leading to the substitution of a highly conserved amino acid (G60S) in Cx43. In vivo and in vitro studies revealed that the mutant Cx43 protein acts in a dominant-negative fashion to disrupt gap junction assembly and function. In addition to the classic features of ODDD, these mutant mice also showed decreased bone mass and mechanical strength, as well as altered hematopoietic stem cell and progenitor populations. Thus, these mice represent an experimental model with which to explore the clinical manifestations of ODDD and to evaluate potential intervention strategies.

Connexin43 Potentiates Osteoblast Responsiveness to Fibroblast Growth Factor 2 via a Protein Kinase C-Delta/Runx2–dependent Mechanism

“…In the presence of Cx43 gap junctions, we see a more robust activation of Runx2 recruitment to the osteocalcin promoter and increased transcriptional activity after FGF2 treatment. The involvement of Cx43 in regulating the cellular responses to osteogenic cues provides insight into the molecular mechanisms underlying the skeletal phenotypes observed in mouse models of Cx43 genetic deficiency (Lecanda et al, 2000;Flenniken et al, 2005;Chung et al, 2006). Furthermore, these data suggest the intriguing possibility that increasing gap junction communication may augment the response of bone to anabolic therapies.…”

GJA1mutations, variants, and connexin 43 dysfunction as it relates to the oculodentodigital dysplasia phenotype

“…Motifs QPG and SHVR at residues 58-60 and 73-76 of EL1 and SRPTEK at residues 201-206 of EL2 have been shown by peptide competition assays to be involved in junction formation [Warner et al, 1995]. ODDD mutations occur within each of these motifs at residues 58, 59, 74, 76, 201, and 202, as well as residue 60 in the mouse model of ODDD [Flenniken et al, 2005].…”

“…They suggest that lack of mutant Cx43 effect in vitro may not reflect in vivo embryonic developmental bone abnormalities resulting in the ODDD phenotype. Flenniken et al [2005] studied their mutant mouse G60S and found that the protein localized at the cell surface and the Golgi apparatus. Gap junction plaques were greatly reduced in the myocardium and granulosa cells with total Cx43 levels well below 50% of control littermates.…”

“…Richardson et al [2004], using a developmental series of morphologically-staged mouse embryos and whole-mount in situ hybridization demonstrate the spatiotemporal expression pattern of Gja1 in the developing craniofacial complex and limbs. An ODDD mouse model heterozygous for a Gja1 mutation coding for Cx43 G60S is characterized by Flenniken et al [2005] and exhibits many classic symptoms of ODDD, including syndactyly, enamel hypoplasia, and craniofacial anomalies. The cardiac dysfunction observed in the ODDD mouse model, as well as female infertility, are features not commonly seen in human subjects affected by GJA1 mutations.…”

Multimodal imaging of mouse development: Tools for the postgenomic era

“…MRM has evolved as an important phenotyping tool and has been used to identify defects in embryos mutant for developmentally relevant genes such as Gja1/Connexin 43 (Huang et al, 1998;Flenniken et al, 2005), Cited2 (Schneider et al, 2003a,b;2004), phosphatidylserine receptor , and Tbx5 (Zhou et al, 2005). Abnormalities in embryonic and postnatal neural development can be facilitated by highly sensitive methods such as diffusion tensor imaging (DTI), which makes use of water diffusion to highlight ordered structures such as axonal tracts (Mori et al, 2001).…”