THE MURINE EXT1 GENE SHOWS A HIGH-LEVEL OF SEQUENCE SIMILARITY WITH ITS HUMAN HOMOLOG AND IS PART OF A CONSERVED LINKAGE GROUP ON CHROMOSOME-15

We have cloned and sequenced the murine homologue of the human EXT1 ge ne. At the protein level, these genes show almost complete identity as divergence is limited to only 5 amino acid positions that are scatter ed about the whole sequence. In addition, similarity searches identifi ed a protein from chromosome III of C. elegans that shows significant similarity to the human and murine EXT/Ext genes. Using high resolutio n backcross mapping, the murine Ext1 was mapped at 26.55 cM between D1 5Mit143 and D15Mit153 on mouse chromosome 15. Therefore, Ext1 is part of an evolutionarily conserved linkage group including SDC2/Hspg1, TRH R/Trhr, EXT1/Ext2, MYC/Myc, and TG/Tgn.