Functional analysis of patient-derived mutations in the Fanconi anemia gene, FANCG/XRCC9

Objective. Fanconi anemia (FA) is an autosomal-recessive cancer susceptibil ity syndrome with seven complementation groups. Six of the FA genes have be en cloned (corresponding to subtypes A, C, D2, E, F, and G) and the encoded proteins interact in a common pathway. Patient-derived mutations in FA gen es have been helpful in delineating functional domains of FA proteins, The purpose of this work was to subtype FA patient-derived cell lines in our re pository and to identify FA gene mutations. Methods. We subtyped 62 FA patients as type A, G, C, or non-ACG by using a combination of retroviral gene transfer and immunoblot analysis. Among thes e FA patients, we identified six FA-G patients for further analysis, We use d a strategy involving amplification of FANCG/XRCC9 exons and direct sequen cing to identify novel FANCG mutations in cell lines derived from these FA- G patients, We functionally analyzed FANCG mutant alleles by transducing th e corresponding cDNAs into a known FA-G indicator cell line and scoring cor rection of MMC sensitivity, Results. Our results demonstrate a wide range of mutations in the FANCG gen e (splice, nonsense, and missense mutations), Based on this mutational scre en, a carboxy terminal functional domain of the FANCG protein appears to be required for complementation of FA-G cells and for normal assembly of the FANCA/FANCG/FANCC protein complex. Conclusion. The identification of patient-derived mutant alleles of FA gene s can provide important insights to the function of FA proteins. FA subtypi ng is also a necessary precondition for gene therapy. (C) 2001 Internationa l Society for Experimental Hematology. Published by Elsevier Science Inc.