Physical and genetic analysis of the human chromosome 14 long arm subtelomeric region at 14q32.33 going to 14qter

grantor: University of TorontoThe human immunoglobulin heavy chain gene cluster (IGH) is located at 14q32.33, near the long arm telomere of chromosome 14. Physical maps suggested that 14qter might be some distance from IGH. Human subtelomeric regions are the sites of increased recombination and have a male to female recombination ratio that is higher than elsewhere in the genome. My goal was to complete the map of distal 14q, to develop genetic markers for 14qter, and to examine recombination in this subtelomeric region. Initially, 13 DNA markers were used to characterize naturally occurring terminal deletions, to refine the physical map and determine if deletion breakpoints were near 14qter. Two markers, previously mapped distal to IGH, were mapped proximal to IGH. The breakpoint of a ring chromosome was mapped to a 350 kb interval within IGH, representing the smallest region of distal monosomy 14q reported to date. Somatic cell hybrid lines were next used to map IGH variable region (VH) segments that previously were not placed within IGH. Four NotI DNA fragments, representing eleven VH segments, mapped to chromosomes 15 and 16. Two yeast artificial chromosomes (YAC) containing functional human telomeres were mapped to the telomeric end of IGH. A VH segment at the distal ends of the YACs was sensitive to nuclease Bal31 digestion of human DNA, demonstrating that these represent the 14q telomere. The physical map of IGH was completed and extends to within 25 kb of the telomere. Polymorphic markers were cloned from the distal part of IGH, approximately 90 and 200 kb from the telomere. Haplotypes of these markers were constructed for use as a highly polymorphic genetic marker which will be useful for anchoring genetic maps. Linkage analysis using the 40 pedigree CEPH reference panel revealed increased recombination within this region. Recombination was not significantly higher in males than in females, indicating that this region differs from other human subtelomeric regions.Ph.D