AmphiBMP2/4, an amphioxus bone morphogenetic protein closely related to Drosophila decapentaplegic and vertebrate BMP2 and BMP4: insights into evolution of dorsoventral axis specification.

Amphioxus AmphiBMP2/4 appears to be a single gene closely related to vertebrate BMP2 and BMP4. In amphioxus embryos, the expression patterns of AmphiBMP2/4 suggest patterning roles in the ectodermal dorsoventral axis (comparable to dorsoventral axis establishment in the ectoderm by Drosophila decapentaplegic and vertebrate BMP4). In addition AmphiBMP2/4 may be involved in somite evagination, tail bud growth, pharyngeal differentiation (resulting in club-shaped gland morphogenesis), hindgut regionalization, differentiation of olfactory epithelium, patterning of the anterior central nervous system, and establishment of the heart primordium. One difference between the developmental role of amphioxus AmphiBMP2/4 and vertebrate BMP4 is that the former does not appear to be involved in the initial establishment of the dorsoventral polarity of the mesoderm.