EXPRESSION OF SERINE THREONINE KINASE RECEPTORS INCLUDING THE BONE MORPHOGENETIC FACTOR TYPE-II RECEPTOR IN THE DEVELOPING AND ADULT-RAT BRAIN/

The expression patterns of serine/threonine kinase receptors in the ce ntral nervous system of the developing and adult rat were studied by i n situ hybridization. The recently cloned bone morphogenetic factor re ceptor type II (BMPR-II) was compared with the ActR-II and several typ e I receptors including ActR-I, ActR-IB, BMPR-IA, BMPR-IB and T beta R -I. We found that these receptors are spatially and temporally regulat ed. As early as embryonic day 11 (E11), BMPR-II mRNA was expressed in the neuroepithelium in brain and spinal cord. At E15, the expression o f ActR-II mRNA was stronger than that of BMPR-II in the spinal cord, f ollowed in intensity by the expression of ActR-I, ActR-IB, BMPR-IA, BM PR-IB and T beta R-I mRNA. The BMP type I receptors were expressed onl y in the ependymal epithelium and in the sympathetic ganglia at E15. M any of the examined receptor mRNAs were expressed at peak levels in th e brain around birth. In the adult brain, mRNA for BMPR-II was express ed in different patterns together with ActR-II and ActR-I. Thus, BMPR- II mRNA was found in neurons of the cortex, dentate gyrus, hippocampus , habenula and substantia nigra. ActR-II, ActR-I, ActR-IB and, weakly, T beta R-I were all expressed in the dentate gyrus. In contrast mRNA for BMPR-IA and BMPR-IB was not found in the adult brain. It is sugges ted that the expressed receptors may mediate actions of members of the TGF beta superfamily, e.g. BMPs, controlling the development and plas ticity in the nervous system.