Abstract
Abstract: :
Molecular analysis of Xcat mice, a mouse model of human XLCD. K.M. Huang, S. Geunes-Boyer, Y. Ai, D. Stambolian. Purpose: The human X-linked cataract dental (XLCD) syndrome (also called Nance Horan) is characterized by X-linked cataracts, microcornea and dental anomalies. Xcat is the mouse model for human XLCD. The Xcat mutation has been positionally mapped through an interspecific backcross and two markers have been identified (DXWas31 and DXPas18) that show no recombination with Xcat. The purpose of this study is to refine the Xcat critical region in order to facilitate identification of the Xcat gene. Methods: We screened a mouse BAC library with DXWas31 and DXPas18 and identified several overlapping BAC's that hybridized to these markers. BAC's, covering a 1 cM region, were sequenced and examined for potential Xcat candidate genes. BAC complementation to rescue the cataract phenotype in Xcat mice was performed to help identify a single BAC for further study. FISH with the BAC's was used to detect any gross chromosomal anomalies within the Xcat X chromosome. Results: We defined an Xcat critical region, composed of 6 BAC's and spanning ∼1Mb. Sequence analysis of all the BAC's has revealed one known gene (REPS2) and five potential genes within the Xcat critical region. We are evaluating REPS2 as well as the potential genes for conservation across species (homology to non-mouse EST's within the database) and expression in neonate eyes from normal and mutant Xcat mice. We successfully generated BAC transgenic animals from three of the six BAC's, but have not yet identified a complementing BAC. Conclusions: We have narrowed the Xcat critical region down to 1 Mb. Sequence analysis of this region and the subsequent identification of the Xcat gene should provide critical insight into the causative gene in human XLCD.
Keywords: 338 cataract • 418 gene mapping • 420 genetics