Additional RFLPs at D10S94 and the development of PCR-based variant detection systems: implications for disease genotype prediction in MEN 2A, MEN 2B, and MTC1 families.
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Biomedical subjects
Publications and source records attributed to A R Brooks-Wilson.
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We report the characterization of a dense cluster of CpG islands at D10S94 in proximal 10q11.2. D10S94 is tightly linked to the gene responsible for multiple endocrine neoplasia type 2A (MEN 2A), a dominantly inherited tumor syndrome characterized by medullary thyroid carcinoma (MTC), pheochromocytoma, and/or parathyroid adenoma. To date, no recombinants between D10S94 and MEN2A have been identified. The gene(s) responsible for two additional dominantly inherited disorders involving cancer of the medullary thyroid, MEN 2B (MEN2B), and dominantly inherited MTC without additional clinical features (MTC1), also map to this region. The gene or genes responsible for these disorders may be located at or near the D10S94 locus. A 570-kb long-range restriction map has been generated by pulsed-field gel electrophoresis using probes developed during a 160-kb bidirectional cosmid walk at D10S94. Six CpG islands are clustered within a 180-kb region; five fall within a 145-kb NotI restriction fragment that is contained in its entirety in our cosmid contig. The SacII, SfiI, and NotI restriction maps for lymphoblast and cloned DNA are concordant. These CpG islands may represent the 5' ends of candidate genes for MEN2A, MEN2B, and/or MTC1. One gene designated mcs94-1, which is associated with one of the CpG islands in this cluster, has been isolated and characterized in detail.
Repeat element-mediated PCR can facilitate rapid cloning and mapping of human chromosomal region-specific DNA markers from somatic cell hybrid DNA. PCR primers directed to human repeat elements result in human-specific DNA synthesis; template DNA derived from a somatic cell hybrid containing the human chromosomal region of interest provides region specificity. We have generated a series of repeat element-mediated PCR clones from a reduced complexity somatic cell hybrid containing a portion of human chromosome 10. The cloning source retains the centromere and tightly linked flanking markers, plus additional chromosome 10 sequences. Twelve new inter-Alu, two inter-L1, and four inter-Alu/L1 repeat element-mediated PCR clones were mapped by hybridization to Southern blots of repeat element-mediated PCR products amplified from somatic cell hybrid DNA templates. Two inter-Alu clones mapped to the pericentromeric region. We propose that a scarcity of Alu elements in the pericentromeric region of chromosome 10 contributed to the low number of clones obtained from this region. One inter-Alu clone, pC11/A1S-6-c23, defines the D10S94 locus, which is tightly linked to MEN2A and D10Z1.
The recent advent of Alu element-mediated PCR (Alu PCR) allows the rapid isolation of human-specific fragments from mixed DNA sources. This technique greatly facilitates the isolation of DNA fragments from specific regions of the human genome. We report a novel technique utilizing Alu PCR products as differential hybridization probes to isolate human DNA fragments from a chromosomal subregion. We used the Alu PCR products from a pair of somatic cell hybrids in which the human DNA content differs only in the 5q11.2-q13.3 region as differential hybridization probes. One hybrid (GM10114) retains an intact chromosome 5, while the other (HHW1064) contains a chromosome 5 deleted for the q11.2-q13.3 region. Phage from a flow-sorted chromosome 5 library were hybridized with the Alu PCR synthesis product from the chromosome 5 hybrid. Positively hybridizing phage were then screened with the Alu PCR product from the deletion 5 hybrid. Phage that hybridized to the Alu PCR product of the chromosome 5 hybrid but did not hybridize to the Alu PCR product of the deletion 5 hybrid were further characterized. We isolated five phage from 5q11.2-q13.3 using this differential hybridization procedure. Only one of these phage corresponded to a detectable difference between the ethidium bromide-stained Alu PCR products of the two somatic cell hybrids. This technique should be applicable to any somatic cell hybrid-deletion hybrid pair.
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Alu element-mediated polymerase chain reaction is a strategy for rapidly cloning and mapping human DNA markers from mixed DNA sources. A novel primer homologous to the 3' end of the human Alu repeat element provides the basis for preferential synthesis of human DNA fragments from human/rodent somatic cell hybrid DNA template. This approach has been used to isolate a series of new markers from chromosome 10. The Alu element-mediated PCR probes were regionally assigned on chromosome 10 by hybridization to Southern blots of Alu PCR-synthesized DNA derived from somatic cell hybrid template DNA. Alu element-mediated PCR is generally applicable and makes possible the analysis of complex genomes with a speed and sensitivity that has not been previously possible.
Combined somatic cell hybrid and linkage studies between D10S94 and five pericentromeric loci (FNRB, D10Z1, MEN2A, RBP3, and D10S15) have localized the new DNA sequence pcl1/A1S-6-c23 at D10S94 to 10q11.2. No recombinants were observed between D10S94 and D10Z1 or MEN2A. D10S94 maps in proximal 10q11.2 very near to MEN2A. There are three possible orders for the six loci that we investigated from the centromeric region of chromosome 10. At present the genetic data do not allow us to order MEN2A with respect to D10Z1 and D10S94. The three possible orders are FNRB-D10Z1-D10S94-MEN2A-RBP3-D10S15, FNRB-D10Z1-MEN2A-D10S94-RBP3-D10S15, and FNRB-MEN2A-D10Z1-D10S94-RBP3-D10S15. In view of the fact that no recombinants between D10S94 and MEN2A or between D10S94 and D10Z1 were observed, the combined haplotypes formed from RFLPs and D10Z1 and D10S94 will increase the informativeness and accuracy of genotype prediction for at-risk members of the families having the MEN 2A syndrome, particularly when the affected parent is female. The localization of D10S94 with respect to MEN2A will prove valuable in experiments directed toward cloning the MEN2A locus.
The P130gag-fps protein-tyrosine kinase of Fujinami sarcoma virus contains an N-terminal fps-specific domain (Nfps) that is important for oncogenicity. The N-terminal 14 amino acids of p60v-src, which direct myristylation and membrane association, can replace the gag-Nfps sequences of P130gag-fps (residues 1 to 635), producing a highly transforming src-fps polypeptide. Conversely, gag-Nfps can restore modest transforming activity to a nonmyristylated v-src polypeptide. These results emphasize the modular construction of protein-tyrosine kinases and indicate that Nfps, possibly in conjunction with gag, functions in the subcellular localization of P130gag-fps.