IMMUNOLOCALIZATION OF CONNEXIN-43 IN THE TOOTH GERM OF THE NEONATAL RAT

Rabbit polyclonal antibodies to amino acids 346-360 of connexin 43, th e 'heart' gap junction protein, were employed to immunolocalize connex in 43 gap junctions in the neonatal rat molar tooth germ. Connexin 43 appears early in the differentiation of both ectodermally derived and ectomesenchymally derived cells of the developing tooth. Connexin 43 i mmunoreactivity is present in the epithelial components of the enamel organ, including the area of the proximal and distal junctional comple xes of the ameloblast layer, and the stratum intermedium, stellate ret iculum and outer enamel epithelium. Secretory odontoblasts and develop ing alveolar bone also display a pattern of connexin 43 immunostaining . Both the epithelial and ectomesenchymally-derived components of the developing tooth acquire connexin 43 channels in a manner that correla tes with cell differentiation. In addition, three regions can be defin ed by connexin 43 immunostaining: the epithelia of the enamel organ th at are derived from the oral epithelium, the odontoblast layer derived from the ectomesenchyme, and the alveolar bone. The results suggest t hat connexin 43 may provide the mechanism for functional compartmental ization of the tissues associated with tooth formation. Compartmentali zation suggested by connexin 43 expression could play important roles in the development and functions of these tissues.