Frequency of ApoB and ApoE gene mutations as causes of hypobetalipoproteinemia in the framingham offspring population |
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Authors: | FK Welty C Lahoz KL Tucker JM Ordovas PW Wilson EJ Schaefer |
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Affiliation: | Laboratory of Molecular Genetics, National Institute on Aging, National Institutes of Health, Baltimore, Maryland 21224, USA. |
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Abstract: | Rearranged immunoglobulin variable genes are extensively mutated after stimulation of B lymphocytes by antigen. Mutations are likely generated by an error-prone DNA polymerase, and the mismatch repair pathway may process the mispairs. To examine the role of the MSH2 mismatch repair protein in hypermutation, Msh2-/- mice were immunized with oxazolone, and B cells were analyzed for mutation in their VkappaOx1 light chain genes. The frequency of mutation in the repair-deficient mice was similar to that in Msh2+/+ mice, showing that MSH2-dependent mismatch repair does not cause hypermutation. However, there was a striking bias for mutations to occur at germline G and C nucleotides. The results suggest that the hypermutation pathway frequently mutates G.C pairs, and a MSH2-dependent pathway preferentially corrects mismatches at G and C. |
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