Mouse t haplotypes.

A Y-linked gene(s) is undoubtedly a prerequisite for testicular development in mammals. However, exceptional cases suggest that the mere presence of the Y chromosome or the Y-linked testis-determining gene does not totally control the fate of the bipotential gonad. For example, in the mouse, a major as yet unmapped autosomal locus is necessary for normal testicular development and at least one additional autosomal locus is implicated. We present here a third autosomal sex-determining locus. This dominantly inherited trait, tentatively named T-associated sex reversal (gene symbol Tas), is closely linked to or a part of the T/t complex on chromosome 17 of the mouse. Gonads of chromosomally XY individuals who inherit Tas on the C57BL/6J inbred strain background differentiate as ovaries or ovotestes.

Sex reversal in XY mice caused by dominant mutation on chromosome 17

Two triglyceride lipases, lipoprotein lipase and hepatic triglyceride lipase, participate in the metabolism of plasma lipoproteins. A single recessive mutation, cld, on mouse chromosome 17 causes an apparent deficiency of both lipoprotein lipase and hepatic triglyceride lipase activities. Mice homozygous for this defect develop lethal hyperchylomicronemia within 2 days postpartum as a consequence of nursing. Plasma triglyceride values in affected mice often reach 20,000 milligrams per deciliter (100 times higher than that in normal littermates), and total lipase activity in plasma or tissues is 5 to 20 percent of that in controls.

https://science.sciencemag.org/content/sci/221/4606/167.full.pdf

Combined Lipase Deficiency (cld): A Lethal Mutation on Chromosome 17 of the Mouse

The T/t–H-2 region on mouse chromosome 17 is known from complex natural variants (‘t-haplotypes’) to contain numerous genes, including some affecting the immune system and the development of the embryo. Rapid progress in the isolation of recombinant DNA clones for this 50 megabasepair region is generating the material for its complete molecular anatomy. A crucial step in revealing the biological functions controlled by the region is to obtain mutants in which genes are inactivated individually. We have used a pair of inbred mouse strains and a series of classical breeding schemes that permit the detection of recessive lethal and detrimental mutations in the T/t–H-2 region.In this initial phase of our study, 280 gametes mutagenized in the male germ line by ethylnitrosourea (ENU) have yielded eleven independent pre-natal recessive lethal mutations. Four have been mapped against T mutations and have been shown to complement one another in all pairwise combinations.

G J Garrisi

Papers

Genetic analysis of the tw73 haplotype of the mouse using deletion mutations: evidence for a parasitic lethal mutation.