RECOMBINANT INBRED AND CONGENIC STRAINS OF THE RAT FOR GENETIC-ANALYSIS OF LIMB MORPHOGENESIS

Recombinant inbred (RI) and congenic strains carrying the polydactyly- luxate syndrome (PLS) provide an experimental model for the analysis o f polygenic control of limb development, PLS is determined by a major gene Lx whose phenotypic expression is strongly influenced by the gene tic background upon which it operates. The morphometric analysis of th e skeleton of front and hind legs has been carried out. The morphotype s of PLS in RI strains exhibit a continuous variability and transgress ive variation compared to BN.Lx and SHR.Lx morphotypes, which strongly indicates the polygenic effects on PLS manifestation. Quantitative tr ait loci (QTL) were searched for through correlation of genetic marker s and morphometric traits. The association analysis revealed statistic ally significant correlations (P < 0.0003) of morphometric traits with two markers on chromosome 4 (Il6 and A2m) associated with the number of front feet and hind feet phalanges, respectively, one marker on chr omosome 7 (D7Mit17) associated with the tibia length, and the somatost atin gene on chromosome 11 associated with the number of front feet ph alanges. In addition, suggestive associations of morphometric traits w ith markers on further nine chromosomes have been found (correlation c oefficients ranging from 0.5 to 0.6). The verification of all these fi ndings is in progress by means of double congenic strains which, in ad dition to the Lx gene, carry differential chromosome segments with put ative modifiers.