Establishment of Mouse Consomic Lines

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From the definition, two strains of mouse are referred to as consomic when they differ by one complete chromosome pair. Given that mouse has a karyotype with 21 different chromosomes (19 autosomes + X,Y chromosomes), 21 consomic mouse strains are required for full coverage of mouse chromosomes by donor strains, from which one complate chromosome is introduced into the common genetic background referred to as recipient. Chromosome substitution is achieved by six to seven times backcrossing of individuals identified as heterozygous for the selected chromosome to the recipient strain.It has been well established that many pathological conditions and diseases like cancer and diabetes are under multigenic control. They are generally difficult to analyze when a great number of genes are involved and epistatic interactions are present among the genes. In these cases, if a phenotype of interest appears to deviate in a consomic strain from what is known in the genetic background strain, its genetic control must be related to chromosomal substitution to be concerned. Further genetic analysis will then be considerably simplified.We started to establish consomic strains, using. MSM strain, which is derived from Japanese wild mouse, Mus musculus molossinus, as donor strain and a C57BL/6J laboratory strain as recipient. These two strains are genetically very remote from each other so that they differ in a number of genetic traits. This genetic defference faclitates in chromosomal assignment of any phenotype to be examined and is of great use in linkage analysis based on polymorphism of DNA markers. We used microsatellite DNA markers, at least five markers per chromosome, for selection of individuals in each step of backcrossing. As a result, we have obtained 15 consomic strains which carry MSM derived chromosomes in the genetic background of C57BL/6J strain.