Have gene knockouts caused evolutionary reversals in the mammalian first arch?

Journal Article (Review;Journal Article)

Many recent gene knockout experiments cause anatomical changes to the jaw region of mice that several investigators claim are evolutionary reversals. Here we evaluate these mutant phenotypes and the assertions of atavism. We argue that following the knockout of Hoxa-2, Dlx-2, MHox, Otx2, and RAR genes, ectopic cartilages arise as secondary consequences of disruptions in normal processes of cell specification, migration, or differentiation. These disruptions cause an excess of mesenchyme to accumulate in a region through which skeletal progenitor cells usually migrate, and at a site of condensation that is normally present in mammals but that is too small to chondrify. We find little evidence that these genes, when disrupted, cause a reversion to any primitive condition and although changes in their expression may have played a role in the evolution of the mammalian jaw, their function during morphogenesis is not sufficiently understood to confirm such hypotheses.

Full Text

Duke Authors

Cited Authors

  • Smith, KK; Schneider, RA

Published Date

  • March 1, 1998

Published In

Volume / Issue

  • 20 / 3

Start / End Page

  • 245 - 255

PubMed ID

  • 9631652

Electronic International Standard Serial Number (EISSN)

  • 1521-1878

International Standard Serial Number (ISSN)

  • 0265-9247

Digital Object Identifier (DOI)

  • 10.1002/(sici)1521-1878(199803)20:3<245::aid-bies8>3.0.co;2-q


  • eng