Bone morphogenetic proteins (BMPs) signal through a receptor complex c
omprising two distinct transmembrane serine/threonine kinases referred
to as type I and type II receptors. The identification of at least th
ree classes of type I receptors (ALK-2, -3, -6) and three classes of t
ype II receptors for the BMPs raises the possibility of multiple recep
tor complexes which may have distinct functions. An RNAse protection a
ssay has been established which allows simultaneous analyses of the mR
NAs for ALK-2, -3, and -6. As a test system, cultures of pluripotent C
3H10T1/2 cell line were incubated in the presence or absence of BMP-7,
and the relative levels of the receptor mRNAs were determined. Change
s in receptor mRNA levels for ALK-2 and -3 were detected during the pr
oliferation phase and adipogenic differentiation of the pluripotent C3
H10T1/2 cell line.