HOMEOBOX GENES AND CONNECTIVE-TISSUE PATTERNING

In vertebrates, limb tendons are derived from cells that migrate from the lateral plate mesoderm during early development. While some of the developmental steps leading to the formation of these tissues are kno wn, little is known about the molecular mechanisms controlling them, W e have identified two murine homeobox-containing genes, Six 1 and Six 2, which are expressed in a complementary fashion during the developme nt of limb tendons. Transcripts for both genes are found in different sets of phalangeal tendons. Six 1 and Six 2 also are expressed in skel etal and smooth muscle, respectively. These genes may participate in t he patterning of the distal tendons of the limb phalanges by setting p ositional values along the limb axes.