Redneck, a new mutant of the axolotl (Ambystoma mexicanum) likely affects the development of cranial neural crest

A novel developmental mutant in the Mexican axolotl is described. Designate d redneck (rn), the mutant gene is inherited as a simple Mendelian recessiv e. In homozygotes, rn causes massive haemorrhage in the posterior head, ros trocaudal compression of the craniovisceral skeleton, abnormal differentiat ion of vertebral cartilage, micrognathia, aglossia, microphthalmia and abno rmal hepatic development. Affected larvae become evident at the onset of fe eding, and eventually die of starvation. Based on the tissues affected, we propose that rn affects later developmental events in the differentiation a nd morphogenesis of a subset of cranial neural crest cells. Thus, rn may pr ove a valuable model system for examining the role of neural crest cells in the development of cranial and endodermal derivatives.