Physical mapping of mouse collagen genes on Chromosome 10 by high-resolution FISH

Fluorescence in situ hybridization (FISH) on mechanically stretched chromos omes (MSCs) and extended DNA fibers enables construction of high-resolution physical maps by accurate ordering and orienting genomic clones as well as by measuring physical lengths of gaps and overlaps between them. These hig h-resolution FISH targets have hitherto been used mainly in the study of th e human genome. Here we have applied both MSCs and extended DNA fibers to t he physical mapping of the mouse genome. At first, five mouse collagen gene s were localized by metaphase-FISH: Coll0a1 to chromosomal bands 10B1-B3; C oll3a1 to 10B4; and Col6a1, Col6a2, and Col18a1 to 10B5-C1. The mutual orde r of the genes, centromere-Col10a1-Col13a1-Col6a2-Col6a1-Col18a1-telomere, was determined by FISH on metaphase chromosomes, MSCs, and extended DNA fib ers. To our knowledge, this is the first time mouse metaphase chromosomes h ave been stretched and used as targets for FISH. We also used MSCs to deter mine the transcriptional orientations, telomere-5 ' -3 ' -centromere, of bo th Col13a1 and Col18a1. With fiber-FISH, Col18a1, Col6a1, and Col6a2 were s hown to be in a head-to-tail configuration with respective intergenic dista nces of about 350 kb and 90 kb. Comparison of our physical mapping results with the homologous human data reveals both similarities and differences co ncerning the chromosomal distribution, order, transcriptional orientations, and intergenic distances of the collagen genes studied.