Hridayabhiranjan Shukla

Physical and genetic mapping of the telomeric major histocompatibility complex region in man and relevance to the primary hemochromatosis gene (HFE)

We performed pulsed-field gel electrophoresis (PFGE) on genomic DNA from a radiation hybrid (RH) cell line and constructed a high-resolution physical map of the major histocompatibility complex class I region in 6p21.3, where the gene for primary hemochromatosis (HFE) is believed to be located. Due to the intact microsegment of hemizygous human genomic DNA preserved in the RH cell line, simplified and distinct restriction fragment banding patterns were generated. Using the RH cell line, we were able to extend the physical map of the HLA class I region to about 3000 kb, order the known HLA class I genes from centromere to telomere: HLA-B, -C, -E, (-A, -H, -G), and -F, and orient the HLA-F gene along the chromosome. The proximity of HLA-F to HLA-A was confirmed by linkage and linkage disequilibrium analysis. This study shows that RH cell lines can be useful for constructing long-range physical maps in specific regions of the human genome with PFGE. Physical and genetic mapping studies of this region are consistent with a localization of the HFE gene proximal or distal to HLA-A.

A class I jumping clone places the HLA-G gene approximately 100 kilobases from HLA-H within the HLA-A subregion of the human MHC

By the combination of cosmid cloning, chromosomal jumping, and pulsed-field gel electrophoresis (PFGE), we have fine-mapped the HLA-A subregion of the human major histocompatibility complex (MHC). Through the isolation of a class I jumping clone, the Q alpha-like HLA-G class I gene has been placed within 100 kb of HLA-H. The tight physical linkage of these class I genes has been further supported by hybridizing PFGE blots with locus-specific probes. It has been found that both of the above class I genes are linked to HLA-A, with HLA-H residing no more than 200 kb from the HLA-A gene. These data support the possible existence of a Q alpha-like subregion composed of nonclassical HLA class I genes within the human MHC linked telomerically to the HLA-A locus.