Hunt, Paul Nicholas; (1992) Expression of vertebrate hox genes during craniofacial morphogenesis. Doctoral thesis (Ph.D), UCL (University College London).

Text out.pdf Download (8MB)

Abstract

Previous work has implicated Hox genes in the development of the branchial region. At 8 1/2 days I have shown Hox 2 expression in neural crest emerging from the neural plate, while at 9 days of mouse development, after neural crest migration is complete, each branchial arch has a distinct code of Hox 2 expression. Arch 1 has no expression, arch 2 expresses Hox 2.8 alone, and arch 3 expresses Hox 2.8 and Hox 2.7. Given the role of the homologous genes in insects, and the suggestion that neural crest is specified before migration, it is possible that a step in the development of this level of the body is a specification of the hindbrain and branchial arches by a code of Hox expression. Retinoic acid is known to affect craniofacial development, and is able to alter the expression of Hox genes in vitro in a coordinated way. I have analysed gene expression in rat embryos treated with a drug unrelated to retinoic acid that nevertheless causes similar fusion of first and second branchial arches, and show that in addition rhombomere compression and fusion of cranial ganglia occur. The implications of this on the signalling events occuring during development of the branchial region are discussed. There are three other Hox clusters in vertebrates as well as Hox 2, thought to be derived from a single ancestral cluster of genes present in the common ancestor of vertebrates and insects. I have shown that equivalent genes in other clusters show identical expression domains in hindbrain and neural crest to their Hox 2 equivalents at 9 1/2 d.p.c. In contrast, the expression limits of subfamily members are offset from one another in the trunk somites. The implications of this on head versus trunk development are discussed.

Download activity - last month

Export as XMLJSONCSV

Download activity - last 12 months

Export as CSVXMLJSON

Downloads by country - last 12 months

Export as JSONXMLCSV

Archive Staff Only

View Item