Misexpression of Hoxa-13 induces cartilage homeotic transformation and changes cell adhesiveness in chick limb buds.

Abstract

During chick limb development, the Abd-B subfamily of genes in the HoxA cluster are expressed in a region-specific manner along the proximodistal axis. To elucidate the function of Hoxa-13 that is expressed in the autopod during normal limb development, Hoxa-13 was misexpressed in the entire limb bud with a replication-competent retroviral system. Misexpression of Hoxa-13 resulted in a remarkable size reduction of the zeugopodal cartilages as a result of the arrest of cartilage cell growth and differentiation restricted in the zeugopod. This size reduction seems to be attributable to homeotic transformation of the cartilages in the zeugopod to the more distal cartilage, that of the carpus/tarsus. This transformation was specific to Hoxa-13 and was not observed by overexpression of other Hox genes. These results indicate that Hoxa-13 is responsible for switching the genetic code from long bone formation to short bone formation during normal development. When the limb mesenchymal cells were dissociated and cultured in vitro, Hoxa-13-expressing limb mesenchymal cells reassociated and were sorted out from nonexpressing cells. Forced expression of Hoxa-13 at the stage that endogenous Hoxa-13 was not expressed as of yet altered the homophilic cell adhesive property. These findings indicate the involvement of Hoxa-13 in determining homophilic cell-to-cell adhesiveness that is supposed to be crucial for the cartilage pattern formation.

Rethinking the proximodistal axis of the vertebrate limb in the molecular era

“…Test for cross-interactions between Meis1 and Hoxa11 have not been reported, but it seems likely that these genes also have a reciprocal negative regulatory relationship. Perhaps surprisingly, however, Hoxa11 and Hoxa13, which share a very sharp boundary in the late limb bud, do not appear to directly regulate one another, and Hoxa13 misexpression has no effect on Hoxa11 expression (Yokouchi et al 1995). This suggests that perhaps their adjacent, nonoverlapping expression domains are established by reciprocal response to a common signal.…”

Ossification of the mouse metatarsal: Differentiation and proliferation in the presence/absence of a defined growth plate

“…For instance, patterning mechanisms such as Hox genes have been shown to affect growth plate formation and behavior and chondrocyte proliferation (Yokouchi et al, 1995;Goff and Tabin, 1997;Papenbrock et al, 2000;Boulet and Capecchi, 2002). In addition, mice with ablated PTHrP or PTH/PTHrP receptor (PPR) genes have shortened, disorganized growth plates in the embryonic skele-ton as a consequence of accelerated differentiation of their columnar chondrocytes (Amizuka et al, 1994;Lanske et al, 1996).…”

Hox Proteins Functionally Cooperate with the GC Box-binding Protein System through Distinct Domains

“…Antibody Preparation and Immunohistochemical Staining of Transfected Cells-Preparation of anti-chick HoxA-13 antibody was as previously described (28). This antibody is cross-reactive with mouse HoxA-13 proteins.…”