Chromosome jumping from flanking markers defines the minimal region for alf/hsdr-1 within the albino-deletion complex

The locus alf/hsdr-1, defined by the albino-deletion complex on mouse chromosome 7, is essential for neonatal survival. Animals homozygous for a subset of the deletions die shortly after birth due to impaired gene expression in liver parenchymal cells and kidney proximal tubular cells. Here, we describe a detailed analysis of the region containing alf/hsdr-1 by means of chromosome jumping from flanking markers. Three chromosome jumping libraries based on the restriction enzymes XmaI and SalI were constructed. Isolation of eight jumping clones distributed over 450 kb allowed more than 240 kb to be cloned in genomic λ and cosmid libraries. Five of the probes map within the minimal genetic interval for alf/hsdr-1, which is defined by the proximal borders of the deletions c 10R75M and c 11DSD . The breakpoints of these deletions were precisely mapped, which allowed alf/hsdr-1 to be localized to a 310-kb interval.