Expression of the boc gene during murine embryogenesis

BOC is a receptor-like protein that, with the related factor CDO, belongs to a newly recognized subfamily within the immunoglobulin superfamily of cell-surface molecules. BOC and CDO form complexes that positively regulate myogenesis in vitro. To gain a better understanding of the role of boc during vertebrate embryogenesis and whether it could cooperate with cdo in vivo, we carried out an extensive in situ hybridization analysis of boc expression in mouse embryos from E7.0 to E17.5. Our results show that boc is widely expressed during murine embryogenesis, in a spatially and temporally restricted pattern. Overall, the highest levels of boc expression are detected between E10.5 and E15.5, with the strongest signals observed in the developing musculoskeletal and central nervous systems. At late stages of development, boc expression becomes more restricted and is limited primarily to regions harboring proliferating cells, undifferentiated cells, or both. This expression pattern is strikingly similar to that described for cdo (Mulieri et al., 2000). The overlapping expression patterns of cdo and boc in vivo, combined with the promotion of myogenesis by CDO/BOC complexes in cultured cells, strongly suggests that these proteins play a role together in the determination, differentiation, or both, of numerous cell types during vertebrate embryogenesis.