It is known that mouse strains differ in their susceptibility to corticosteroid-induced cleft palate. It has also been shown that this variation in corticosteroid (CORT) responsiveness is related to genetic variation in loci at or near the major histocompatibility complex (MHC, H-2 in mice). We have demonstrated that H-2 haplotype differences are sufficient to alter CORT-induced susceptibility to cleft palate and temporal changes in normal long maturation. Our new data indicates that the mechanism for these haplotype-specific differences in CORT responsiveness is likely related to factors modulating the expression of the glucocorticoid receptor (GR), which is encoded outside the H-2 genomic region. We have designed a series of Specific Aims using the well characterized H-2 congenic mouse model and immunochemical, biochemical and molecular methodologies to test the hypothesis that H-2 associated modulation of GR expression and/or function is a key molecular mechanism regulating CORT responsiveness and, hence, CORT- induced cleft palate.
Aim 1. GR translational and post-translational regulation: to analyze haplotype-specific qualitative and quantitative variation in GR characteristics and pattern of in situ spatial distribution with progressive development among H-2 congenic mice.
Aim 2. GR transcriptional regulation: to compare haplotype-specific differences in the steady state levels, developmental expression, and in situ spatiotemporal localization of GR mRNA among H-2 congenic strains with progressive development.
Aim 3. GR function analysis: to delineate the mechanism of H-2 associated differences in GR function among H-2 congenic mice by comparing haplotype-specific variation in (a) ligand-GR binding to a specific high affinity GRE DNA (GR-GRE binding), and (b) mRNA expression and spatial distribution of four developmentally expressed """"""""CORT-responsive"""""""" genes (EGF, TGF-beta1, TGF- beta2, TGF-beta3) in the presence of exogenous CORT. The demonstration of haplotype-specific variation in GR expression and CORT respons- iveness will support the hypothesis that the H-2 complex contains genetic information encoding trans-acting factors which regulate GR expression and/or function. We will then pursue gene mapping and cloning studies to identify the glucocorticoid responsiveness gene locus (GRG) at or near the H-2 complex on mouse chromosome 17, subsequently human homologs.
| Melnick, M; Chen, H; Buckley, S et al. (1998) Insulin-like growth factor II receptor, transforming growth factor-beta, and Cdk4 expression and the developmental epigenetics of mouse palate morphogenesis and dysmorphogenesis. Dev Dyn 211:11-25 |
| Jaskoll, T; Choy, H A; Chen, H et al. (1996) Developmental expression and CORT-regulation of TGF-beta and EGF receptor mRNA during mouse palatal morphogenesis: correlation between CORT-induced cleft palate and TGF-beta 2 mRNA expression. Teratology 54:34-44 |
| Jaskoll, T; Choy, H A; Chen, H et al. (1995) The CORT-GR signal transduction pathway and CORT-induced cleft palate in H-2 congenic mice. J Craniofac Genet Dev Biol 15:57-65 |
