BMPs are necessary for stomach gland formation in the chicken embryo: a study using virally induced BMP-2 and Noggin expression

Epithelial-mesenchymal interactions are necessary for the normal developmen t of various digestive organs, In chicken proventriculus (glandular stomach ), morphogenesis and differentiation of the epithelium depend upon the indu ctive signals coming from underlying mesenchyme. However, the nature of suc h signals is still unclear despite extensive analyses carried out using exp erimental tissue recombinations. In this study we have examined the possibl e involvement of bone morphogenetic proteins (BMPs) in the formation of sto mach glands in the chicken embryo. Analysis of the expression patterns of B MP-2, -4 and -7 showed that these BMPs were present in the proventricular m esenchyme prior to the initiation of the proventricular gland formation. BM P-2 expression, in particular, was restricted to the proventriculus among a nterior digestive organs. Virus-mediated BMP-2 overexpression resulted in a n increase in the number of glands formed. Moreover, ectopic expression of Noggin, which antagonizes the effect of BMPs, in the proventricular mesench yme or epithelium, led to the complete inhibition of gland formation, indic ating that BMP signals are necessary for the proventricular gland formation . These findings suggest that BMPs are of prime importance as mesenchymal s ignals for inducing proventricular glands.