THE GENE DEFECTIVE IN ANHIDROTIC ECTODERMAL DYSPLASIA IS EXPRESSED INTHE DEVELOPING EPITHELIUM, NEUROECTODERM, THYMUS, AND BONE

Anhidrotic ectodermal dysplasia (EDA) is characterized by defects in t he development of teeth, hair, and sweat glands. To study the expressi on of the human gene defective in EDA in human fetal development (Week s 6-23 of gestational age) and in adult tissues, in situ hybridization and immunohistochemistry were used. First signs of expression were de tected at Week 8 in epidermis and in neuroectodermal cells. Starting a t Week 12, osteoblasts and thymus were positive for EDA mRNA. Hair fol licles expressed EDA mRNA from 18 weeks. The presence of the EDA prote in coincided with mRNA expression in the tissues examined. The express ion pattern of the EDA gene is consistent with typical involvement of the skin in the syndrome. However, the expression is not limited to th e ectodermal tissues and many sites of expression are not obviously re flected in the clinical features of the syndrome.