REGULATION OF AMELOGENIN GENE-EXPRESSION DURING TOOTH DEVELOPMENT

The amelogenins are the predominant matrix proteins in developing enam el and are crucial for proper enamel mineralization. Transgenic mice w ere constructed in order to identify the segment of the amelogenin gen e required for specific expression in enamel organ cells. A 3.5 kb fra gment of the bovine X-chromosomal amelogenin gene that includes a TATA box, the transcription initiation site, and 32 bp of exon 1 was linke d to the betagalactosidase gene and injected into fertilized mouse egg s. Newborn transgene positive mice expressed betagalactosidase activit y in developing teeth treated with the chromogenic substrate Xgal. Foc i of ameloblasts were positive in newborn mice; stain intensity and nu mber of positive ameloblasts increased in 1-day and 2-day postnatal mi ce. Some of the adjacent stratum intermedium cells also were positive in the tater stages. Targeting of the transgene to the enamel organ wa s specific; the only other cells observed to be positive were macropha ges, which have endogenous betagalactosidase activity. (C) 1994 Wiley- Liss, Inc.