Mutations in the mouse Brachyury (T) gene are characterized by a dominant reduction of tail length and recessive lethality. Two quantitative trait loci, Brachyury-modifier 1 and 2 (Brm1 and Brm2) are defined by alleles that enhance the short-tail Brachyury phenotype. Here we report on a genetic analysis of a visible dominant mutation Abnormal feet and tail (Aft) located in the vicinity of Brm1. Affected animals display kinky tails and syndactyly in the hindlimbs, both likely resulting from a defect in apoptosis. We observed an unusual genetic incompatibility between Aft and certain genetic backgrounds. We show that Aft and T are likely to interact genetically, since some double heterozygotes are tailless. In addition to the tail and hindlimb phenotypes, Aft-bearing mutants display characteristic late-onset skin lesions. We therefore tested for allelism between Aft and a closely linked recessive mutation rough coat (rc) and found that these two mutations are likely nonallelic. Our results provide a valuable resource for the study of mammalian skin development and contribute to the genetic analysis of Brachyury function.
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