Mapping a syntenic modifier on mouse chromosome 1 influencing the expressivity of the compact phenotype in the myostatin mutant (MstnCmpt-dl1Abc) compact mouse.

A novel method for mapping a modifier gene that is syntenic to its major gene was used to map a male-sex-limited modifier of the expressivity of the Compact phenotype in the myostatin mutant (Mstn(Cmpt-dl1Abc)) Compact mouse. The modifier was mapped to the general region of D1Mit262, 40 cM distal to Mstn on chromosome 1. Myogenin, a postulated downstream target of myostatin, maps to the same region.

Mapping modifiers affecting muscularity of the myostatin mutant (Mstn(Cmpt-dl1Abc)) compact mouse.

The hypermuscular Compact phenotype was first noted in a line of mice selected for high body weight and protein content. A new line, based on mice showing the Compact phenotype, was formed and selected for maximum expression of the Compact phenotype. Previously we mapped and identified a 12-bp deletion in the myostatin gene, denoted Mstn(Cmpt-dl1Abc), which can be considered as a major gene responsible for the hypermuscular phenotype.