Identification and developmental expression of two activin receptors in baboon lung

Activins are members of the transforming growth factor-beta (TGF-beta) superfamily that exert their effects through interacting with specific cell surface TGF-beta superfamily receptors (TSRs). To determine whether activins are involved in lung development, we used a reverse transcription polymerase chain reaction (RT-PCR)-based approach to identify members of the activin receptors from baboon fetal lung mRNAs. Two partial cDNA sequences encoding serine/threonine kinase domains of baboon TSR type I (bTSR1) and type II (bTSR2) were identified by sequencing analysis. bTSR1 displays 96% identity to human activin type I receptor TSR1, whereas bTSR2 shows 80% identity to human activin type II receptor ActRIIB over the kinase domain region. Northern analysis revealed the expression of a 2.1 kb bTSR1 transcript and a 5.0 kb bTSR2 transcript in baboon lung tissues. Both bTSR1 and bTSR2 were expressed throughout embryonic lung development and in adult lung. The expressions of bTSR1 and bTSR2 were developmentally regulated and each had a distinct expression pattern. Furthermore, the expressions of bTSR1 and bTSR2 in fetal baboon lung were altered by oxygen exposure. This study for the first time identifies the presence of the activin receptors in the baboon lung and provides evidence that both bTSR1 and bTSR2 are regulated during lung development, suggesting that activins might play an important role during lung development.