EXPRESSION OF ALK-1, A TYPE-1 SERINE THREONINE KINASE RECEPTOR, COINCIDES WITH SITES OF VASCULOGENESIS AND ANGIOGENESIS IN EARLY MOUSE DEVELOPMENT/

ALK-1 is a type I serine/threonine kinase receptor for members of the TGF-beta superfamily of growth factors; its endogenous ligand is not k nown. In this study, we have analyzed the temporal and spatial express ion pattern of ALK-1 mRNA in mouse embryos from the one-cell zygote un til 12.5 dpc using RT-PCR and in situ hybridization, ALK-1 mRNA was fi rst detected in the embryo at 6.5 dpc, From 7.5-8.5 dpc expression was highest at sites of vasculogenesis in both the embryonic and extraemb ryonic part of the conceptus, in trophoblast giant cells, and in the e ndothelial lining of the blood vessels in the decidua, From 9.5-12.5 d pc, ALK-1 was found to be expressed in several different tissues and o rgans, but was highest in blood vessels, mesenchyme of the lung, submu cosal layer of the stomach and intestines, and at specific sites of ep ithelial-mesenchymal interactions. Its expression pattern suggests tha t ALK-1 is a type I receptor for TGF-beta 1 in the developing mouse. ( C) 1997 Wiley-Liss, Inc.