PROGRAMMED CELL-DEATH IS AFFECTED IN THE NOVEL MOUSE MUTANT FUSED TOES (FT)

We have identified a novel dominant mouse mutant that is characterised by fused toes on the fore limbs and a thymic hyperplasia, in heterozy gous animals. Homozygosity of the mutation leads to malformation of th e developing brain, lost of the genetic control of left-right asymmetr y and to death around day 10 of development. Analysis of both limb dev elopment and induction of apoptosis in immature thymocytes in vitro su ggest that programmed cell death is affected by the mutation. Since th e mutation was caused via a transgene insertion we were able to map it to the D region on mouse chromosome 8. So far, no mutation that affec ts programmed cell death has been mapped to this chromosome. Thus, thi s mutation will allow the identification of a novel gene involved in p rogrammed cell death during mammalian development.