Heterogeneity in Fanconi anemia: evidence for 2 new genetic subtypes

Abstract

Fanconi anemia (FA) is an autosomal recessive syndrome featuring diverse symptoms including progressive bone marrow failure and early occurrence of acute myeloid leukemia. Nine genetic subtypes have been described for FA (A, B, C, D1, D2, E, F, G, and L), all of which have been connected to distinct disease genes, except B. Here we report on 8 unrelated FA patients who were excluded from the known subtypes on the basis of phenotypic correction or genetic data. Four of these cell lines failed to complement each other in somatic cell hybrids and therefore represent a new group, termed FA-I. The remaining cell lines complemented group FA-I but did not complement each other, thus representing a second new group, FA-J. Both FA-I and -J cell lines were capable of forming an FA multiprotein core complex. This complex is required for activation of the FANCD2 protein by mono-ubiquitination, a key downstream event in the FA pathway. In FA-I cells FANCD2 was not mono-ubiquitinated, indicating a defect upstream in the FA pathway, whereas in FA-J cells FANCD2 was mono-ubiquitinated, indicating a downstream defect. Our results suggest that the FA pathway of genome stabilization may be controlled by at least 11 different genes, including FANCI and FANCJ.

X-linked inheritance of Fanconi anemia complementation group B

“…The other cell lines were derived from individuals with Fanconi anemia who had been referred to the EUFAR cell repository for genetic subtyping. Individual EUFA178 was assigned to complementation group B on the basis of cell fusion studies 4,23 . We grew cell lines as described 4 .…”

“…Individual EUFA178 was assigned to complementation group B on the basis of cell fusion studies 4,23 . We grew cell lines as described 4 . The research was carried out after approval by the Institutional Review Board (VU University Medical Center, Amsterdam) and the Research Ethics Board (The Hospital for Sick Children, Toronto), and written consent was obtained from the subjects involved.…”

“…Individual cell lines HSC230, EUFA178 and EUFA1386 were transfected with pCEP4 vector containing FANCB cDNA and selected on medium containing hygromycin at 0.1 mg ml -1 . Crosslinker sensitivity was determined in a MMC-induced growth inhibition assay, as described 4 . For determination of FANCD2 monoubiquitination, we treated the cells with hydroxyurea (1 mM) for 24 h before collection.…”

Chemosensitizing tumor cells by targeting the Fanconi anemia pathway with an adenovirus overexpressing dominant-negative FANCA

“…27 Whether this assumption is correct remains to be demonstrated and the Ad.FANCA600DN virus could be a helpful tool in such studies. However, several other cellular factors can be hypothesized to interfere with FANCA600DN-dependent sensitization, including factors that might act at the same level or downstream FANCD2 (such as the gene product defective in the newly discovered FANCJ complementation group 8 ) and the BRCA1 and BRCA2 proteins. [28][29][30][31][32] Alternatively, other drug resistance mechanisms may compensate for virusinduced disruption of the FA pathway such as increased nucleotide excision repair (NER) or mismatch repair.…”

“…6,7 So far, 11 distinct FA complementation groups have been identified (A-C, D1, D2, E-G, I-J, L) and currently eight FA genes have been cloned. [8][9][10] These genes encode proteins whose precise molecular functions remain unclear. [10][11][12][13][14][15] The FA proteins are known to interact with each other in a complex network, designated the FA pathway, which plays an important role in the normal cellular response to crosslinking agent-induced damage and in maintaining genome stability (for recent reviews, see D'Andrea and Grompe 9 and Bogliolo et al 16 ).…”