The Mov 34 mutation is a recessive embryonic lethal mutation caused by retroviral integration in the murine germline. This integration disrupts a transcription unit that appears to encode a novel protein. The Mov 34 proviral integration is located on mouse chromosome 8 and the human homolog of this gene has been mapped to chromosome region 16q23-q24. An evolutionarily conserved syntenic relationship exists between this region of human chromosome 16 and a region of mouse chromosome 8 that also contains oligosyndactyly (Os), another recessive lethal mutation. Genetic studies have ruled out Os as residing at the same locus as the Mov 34 integration. The Mov 34 transcript is conserved in evolution, and a Drosophila homolog appears to encode a protein with 62% amino acid identity to the murine protein. In situ hybridization to Drosophila polytene chromosomes localizes the Drosophila homolog to 60B,C on chromosome 2. Several Drosophila lethal mutations also map to this region.