Transcription factor Sp3 is essential for post-natal survival and late tooth development

Sp3 is a ubiquitously expressed transcription factor closely related to Sp1 (specificity protein 1). We have disrupted the mouse Sp3 gene by homologou s recombination, Sp3-deficient embryos are growth retarded and invariably d ie at birth of respiratory failure. The cause for the observed breathing de fect remains obscure since only minor morphological alterations were observ ed in the lung, and surfactant protein expression is indistinguishable from that in wild-type mice. Histological examinations of individual organs in Sp3(-/-) mice show a pronounced defect in late tooth formation. In Sp3 null mice, the dentin/enamel layer of the developing teeth is impaired due to t he lack of ameloblast-specific gene products, Comparison of the Sp1 and Sp3 knockout phenotype shows that Sp1 and Sp3 have distinct functions in vivo, but also suggests a degree of functional redundancy.