RDLX, A NOVEL DISTAL-LESS-LIKE HOMEOPROTEIN IS EXPRESSED IN DEVELOPING CARTILAGES AND DISCRETE NEURONAL TISSUES

From a rat chondrosarcoma we isolated a cDNA that encodes a novel home oprotein rDlx. The homeodomain of rDlx shows a high degree of sequence identity with those of Drosophila Distal-less, mouse Dir, and Xenopus Xdll proteins. Northern hybridization of rDlx revealed a 1.4- to 1.6- kb RNA species in a rat chondrosarcoma and a cell line derived from th is tumor and in mouse C3H10T1/2 cells, but no rDlx RNA was detected in mouse NIH3T3 fibroblasts, rat skin fibroblasts, mouse C2 myoblasts, m ouse myeloma S194 cells, human B-cell lymphoma Daudi cells, or human a cute myelocytic leukemia cells. RNase protection assays showed that rD lx transcripts were present at high levels in 14-day-old rat embryos, 18-day-old rat embryo skeletal tissues, and adult rat brain. rDlx RNAs were present at lower levels in newborn rat rib cartilage, 18-day-old rat embryo soft tissues, newborn rat skin, and adult rat heart. rDlx transcripts were not detected in adult rat liver, spleen, lung, kidney , testis, or skeletal muscle. In situ hybridization of rat embryos at different stages revealed that rDlx transcripts were present in otic v esicle, branchial arches, apical ectodermal ridge of limb bud, develop ing cartilages, perichondria of mature cartilages, mesenchymal cells o f developing membranous bones, developing teeth, ganglionic eminence o f the telencephalon, diencephalon, olfactory epithelia, and epidermis of the skin. rDlx RNAs were also detected in the developing parasympat hetic mesenteric ganglia of the gastrointestinal tract. Hence, rDlx RN As are mainly expressed in several neuronal tissues and developing ske letal tissues. (C) 1994 Academic Press, Inc.