Overlapping deletions define novel embryonic lethal loci in the mouse t complex

The t complex region of mouse chromosome 17 contains genetic information critical for embryonic development. To Identify and map loci required for normal embryogenesis, a set of overlapping deletions (D17Aus9^df10J, D17Aus9^df12J, and D17Aus9^df13J) surrounding the D17Aus9 locus and one encompassing the T locus, Del(17)^7J, were bred in various combinations and the consequences of nullizygosity in overlapping regions were examined. The results indicated that there are at least two functional units within 1 cM of D17Ausg. /17J1 is a peri-implantation lethal mutation within the region deleted in D17Aus9^df13J, whereas /17J2 is a lateracting lethal defined by the region of overlap between Del(17)T^7J and D17Aus9^df12J. Del(17)T^7J/D17Aus9^df12J embryos die around 10.5 dpc. The development of the mutant embryos is characterized by lack of axial rotation, an abnormal notochord structure, and a ballooning pericardium. These studies demonstrate the value of overlapping deletion complexes, as opposed to individual deletion complexes, for the identification, mapping, and analysis of genes required for embryonic development.