Comparative mapping for positional cloning and defining homology regions between the mouse and human genomes

The goal of this dissertation project was to utilize genetic and physical mapping methods as a means to define genomic homology between human and mouse genomes, as well as to use this information to define functional relationships between the two species. The Comparative mapping studies were designed to expand upon the current knowledge of comparative mapping and homology regions between mouse and man, and to begin to study the homology region borders. Positional cloning research was initiated to localize the translocation breakpoints in a mutant mouse associated with a neurological defect as a first step toward isolation of genes that could be involved in the phenotype of this animal.Comparative mapping of human chromosome 19 and related regions of the mouse genome represents one major focus of this research. Human chromosome 19 was a good target for comparative studies due to the extensive physical mapping of the chromosome,and availability of conserved, mapped gene markers to use for these studies. Comparative Studies involved both the 19q- and 19p-arms of the chromosome, and helped lay the foundation of a chromosome-wide comparative map. One region, 19pl3.1, was investigated in detail. This region is shown to be prone to rearrangements during evolution, as indicated by the homology groups associated within both the mouse and human genomes. These studies revealed the need for more fine mapping of the genome for both species, demonstrating that examination of specific homology groups at a higher resolution reveals that both similarities and surprising differences between related mouse and human regions. These studies provided data suggesting that repeated sequences are associated with at least some homology region borders, a concept that may serve as a guide for future comparative mapping between human, mouse, and other species.One application of comparative mapping is its ability to link functional information derived from mouse mutations to specific genes and disease within the human genome. As part of this effort, research focused upon localizing and physical mapping a region surrounding the breakpoint in IGso, a mouse mutation associated with a reciprocal translocation. Homozygosity for the translocation causes developmental lethality. Animals That are heterozygous display neurological defects including the inability to swim and abnormal startle responses. A genetic map of the region surrounding one of the translocation breakpoints was established on mouse chromosome 2. Fluorescence in situ hybridization (FISH) techniques were used to localize translocation breakpoints to a small interval less than IcM in length. This region shows remarkable linkage conservation with a well-characterized region of human chromosome lip 13, which harbors genes responsible for the WAGR syndrome (Wilms tumor, aniridia, genitourinary malformations, and mental retardation). Comparative mapping information was used to narrow down the translocation interval, and establish a contig consisting of yeast artificial chromosomes (YACs), bacterial artificial chromosomes (BACs), and Pl-derived artificial chromosomes (PACs), which covered approximately 600 kb throughout the breakpoint region. This allowed the breakpoint to be isolated within a single PAC clone of 150 kb in length.Together these studies have set the stage for future investigations of genes located on chromosome 19, and for the cloning of gene(s) associated with the IGso phenotype in mice.