These mice carry the spontaneous Aft (abnormal feet and tail) mutation and are characterized by syndactyly of the hind feet and tail kinks in heterozygotes. Homozygotes exhibit embryonic or perinatal lethality and postnatal lethality is seen in heterozygotes.Read More +
Aft is a dominant mutation that causes increased postnatal lethality in heterozygotes and nearly 100% embryonic or perinatal lethality in homozygotes. Aft/+ mice can be identified by tail kinks near the tail tip and syndactyly of the third and fourth digits of the hind feet, a trait which is often unilateral. This syndactyly does not result from bone fusion, but rather from the persistence of the skin web that normally is removed via apoptosis during development. The tail kinks appear to result from cartilage overgrowth and fusion. Alopecia is found at six to eight months of age and can progress into bleeding ulcerations. Histology of Aft/+ skin shows fewer follicles, fibrosis, and an increase in the number of mast cells. The penetrance of this mutation is only approximately 65% on the 129/Sv and C57BL/6J backgrounds and the expressivity is variable. The most prevalent trait in Aft/+ mice is tail kinks, followed by syndactyly then skin lesions. The Aft mutation interacts with T such that double heterozygosity for Aft and T together increases the likelihood of having no tail relative to heterozygosity for T alone. Aft maps within the vicinity of brachyury modifier 1 on chromosome 9. (Lane, 1987; Ruvinsky et al., 2002.)
Aft arose spontaneously in 1984 on the 129/Sv-p+ Tyrc-ch-KitW-54J background in the laboratory of Dr. Jane Barker at The Jackson Laboratory. KitW-54J was bred away from Aft and in 1988 N14F2 heterozygotes of either gender were bred with 129/Sv mates to generate embryos for cryopreservation.