THE USE OF RESTRICTION LANDMARK GENOMIC SCANNING TO SCAN THE MOUSE GENOME FOR ENDOGENOUS LOCI WITH IMPRINTED PATTERNS OF METHYLATION

Restriction landmark genomic scanning (RLGS) has been used to screen e ndogenous loci for imprinted patterns of methylation, The screening me thod is based upon the identification of genetic variation in RLGS pro files between different strains and determining whether specific varia nt landmarks are transmitted equally to the progeny of reciprocal F1 m atings. The RLGS profiles of C57BL/6 (B6) and DBA/2 (D2) and their rec iprocal hybrids were produced with two enzyme combinations that used N otI as the landmark enzyme and two combinations that used BssHII. An e stimated 13% of the spots are either B5- or D2-specific in these tests , giving a total of nearly 1000 variant loci that were examined for im printed methylation. Three candidate loci for imprinted regulation wer e identified in these analyses, We also used crosses of more genetical ly diverse parents to increase the number of variant loci screened, In terspecific crosses of B6 with the M. musculus strain PWK and intrasub specific crosses between B6 and the M. molossinus strain MSM expanded the levels of variation between the parental strains in the cross to a n estimated 31% and 26%, respectively. The RLGS patterns for one NotI combination and one BssHII profile were examined for each of these cro sses, giving approximately 2000 additional loci that were screened for imprinted patterns of methylation. Eight loci with imprinted patterns of transmission were observed out of 3040 loci tested. The chromosoma l locations for the three B6 and D2 specific loci, Irlgs 1-3, were ide ntified using BXD recombinant inbred strain analysis. Irlgs 1 and 3 ar e B6- and D2-specific loci that had the same strain distribution patte rn which mapped to the central region of chromosome 9. Irlgs 2 (U2afbp -rs) was mapped to the proximal region of chromosome 11: which was rep orted as an imprinted region identified with uniparental disomy mice. An imprinted gene, U2 auxiliary factor binding protein-related sequenc e (U2afbp-rs), was identified for Irlgs2 locus, which encoded 51 kDa p rotein that had significant homology to the human U2af 35 kDa small su bunit.