EXPRESSION OF ACTIVIN RECEPTORS TYPE-I AND TYPE-II ONLY PARTIALLY OVERLAPS IN THE NERVOUS-SYSTEM

IN situ hybridization was used to localize mRNA encoding two cooperati ve serine/threonine kinase receptors. Activin receptor IIA mRNA in the adult rat brain is highly expressed in the dentate gyrus, in the pyra midal neurones of CA3 and CA1, in the entorhinal cortex, in the cortic al amygdaloid nucleus and in the amygdalo-hippocampal area. In the E16 rat embryo, labelling was found in the dorsal root ganglion neurones and in the spinal cord. Activin type I receptor (ALK-2/R-1) labelling was also localized to the hippocampal formation but with an even distr ibution over the granular cells of the dentate gyrus, the CA3 and CA1 pyramidal neurones, while no labelling was found in the entorhinal or amygdaloid areas. In the E16 rat no neuronal labelling was found. The incomplete overlap of these two expression patterns suggests that thes e receptors may locally have other partners for forming signalling rec eptor complexes.