Refined mapping of the human dentin sialophosphoprotein (DSPP) gene within the critical dentinogenesis imperfecta type II and dentin dysplasia type II loci

Dentinogenesis imperfecta type II and dentin dysplasia type II are diseases resulting in abnormal dentin formation, which have been mapped to overlapping regions of human chromosome 4q defined by markers D4S2691 and D4S2692 (6.6 cM) and D4S3291 and SPP1 (14.1 cM), respectively. Recently, two of the major non-collagenous proteins of dentin, dentin sialoprotein (DSP) and dentin phosphoprotein (DPP, phosphophoryn) have been shown to be encoded by a single gene, termed dentin sialophosphoprotein (DSPP), which has been mapped to human chromosome 4. The purpose of this study was to perform refined mapping of DSPP related to these disease loci by gene content mapping, as well as to place the DSPP gene oil the physical map of human chromosome 4 by sequence tagged site (STS) content mapping. Human genomic DSPP clones were isolated, and gene content mapping performed with specific primers for dentin matrix protein 1 (DMP1), bone sialoprotein (BSP) and osteopontin (secreted phosphoprotein 1, SPP1). STS content mapping was then performed with flanking STS markers to these dentin/bone gene loci. Our results demonstrate that the DSPP and DMP1 genes are within a maximum distance of 110 kb. Both DSPP and DMP-1 have been placed on the physical map of human chromosome 4 within the interval defined by markers D4S564 and D4S1291. DSPP is thereby strengthened as a candidate gene for both DGI-II and DD-II.