Expression of the nicotinic receptor α7 gene in tendon and periosteum during early development

Abstract: One of the most abundant nicotinic acetylcholine receptors expressed in the central and peripheral nervous systems is a species that contains the α7 gene product, binds α-bungarotoxin with high affinity, and has a high relative permeability to calcium. The α7 gene is also expressed at low levels in embryonic muscle tissue. We show here that the α7 gene is expressed in tendon fibroblasts and periosteal cells during development. In situ hybridizations identify α7 transcripts in tissue sections containing embryonic tendon and periosteum. RNase protection experiments demonstrate α7 mRNA in primary tendon cells grown in culture. Immunofluorescence with subunit-specific monoclonal antibodies reveals α7 protein in embryonic tendon. Immunoprecipitation assays with the antibodies indicate that the α7-containing species in tendon is capable of binding α-bungarotoxin and that a similar species can be identified at low levels on the surface of fibroblasts in culture. The results show that the α7 gene product is expressed in a range of tissues, including cells thought to be nonexcitable. The distribution of α7 expression early in development and the ability of α7-containing receptors to elevate intracellular calcium suggest that the gene may influence a variety of calcium-dependent events during embryogenesis.