The Mexican Axolotl, Ambystoma mexicanum: Its Biology and Developmental Genetics, and Its Autonomous Cell-lethal Genes

SYNOPSIS. The Mexican axolotl, a neotonous salamander, has foundwidespread use as an experimental animal for studies in embryologyand physiology. The convenience with which the axolotl can bemaintained as a laboratory animal and the high quality of theeggs it produces contribute to its popularity in laboratoryresearch. A large array of mutant genes has been recognizedin the axolotl. These genes affect one or another process duringdevelopment of the organism, and have provided a basis for carryingout research in developmental genetics. Approximately threedozen mutant genes in the axolotl are known. These genes havebeen grouped into 5 different categories which reflect, forthe most part, the developmental stage at which the mutant phenotypecan first be recognized. One group of mutant genes, the autonomous cell-lethals, is discussedin detail. These genes share the common feature that homozygousembryos cannot be rescued by parabiosis with normal embryos.In addition, grafts of mutant tissue (e.g., gill or limb primorida)do not survive on normal hosts. These genes probably are responsiblefor metabolic or regulatory defects which affect all cells andtissues in the organism. The mutant phenotypes and potentialusefulness of these genes are discussed in detail.