A Dutch Fanconi Anemia FANCC Founder Mutation in Canadian Manitoba Mennonites.

Fanconi anemia (FA) is a recessive DNA instability disorder associated with developmental abnormalities, bone marrow failure, and a predisposition to cancer. Based on their sensitivity to DNA cross-linking agents, FA cells have been assigned to 15 complementation groups, and the associated genes have been identified. Founder mutations have been found in different FA genes in several populations. The majority of Dutch FA patients belongs to complementation group FA-C. Here, we report 15 patients of Dutch ancestry and a large Canadian Manitoba Mennonite kindred carrying the FANCC c.67delG mutation. Genealogical investigation into the ancestors of the Dutch patients shows that these ancestors lived in four distinct areas in The Netherlands. We also show that the Dutch and Manitoba Mennonite FANCC c.67delG patients share the same haplotype surrounding this mutation, indicating a common founder.

Test 1 analyser for determination of ESR. 2. Experimental evaluation and comparison with RBC aggregometry.

BACKGROUND: Test 1 is a recently introduced technique claiming to determine Erythrocyte Sedimentation Rate (ESR) in 20 s. In contrast to the original Westergren procedure this new technique uses undiluted blood and operates at 37 degrees C. It is hypothesized that Test 1 is in fact an erythrocyte aggregometer and does not measure any sedimentation. METHODS: Test 1 results were compared to those obtained with StaRRsed, an automated ESR analyser based on the Westergren technique, and the results of both were correlated to various indices of red blood cell (RBC) aggregation, obtained with an aggrego--meter (LORCA). Measurements were made on blood from 75 patients with various rheumatic disorders. Furthermore, blood that was experimentally manipulated in order to affect RBC aggregation, i.e. by changing the hematocrit, by diminishing plasma protein concentration, by inducing hyperaggregation or by RBC rigidification, was tested on all three instruments. RESULTS: Generally in patient blood, Test 1 results demonstrated a higher correlation with the various aggregation parameters than StaRRsed. Highest correlation (R = -0.8)) with both Test 1 and StaRRsed outcome were seen with I(20), a RBC aggregation parameter directly related to the backscatter intensity. All experimentally induced changes in RBC aggregation paralleled closely those obtained with Test 1 while StaRRsed results followed a different course. CONCLUSIONS: The results obtained in this study strongly support the hypothesis that Test 1 measures only the RBC aggregation process and does not cover any of the indices directly linked to the sedimentation process as determined by the Westergren method.

Test 1 analyser for determination of ESR. 1. Practical evaluation and comparison with the Westergren technique.

BACKGROUND: various modifications of the Erythrocyte Sedimentation Rate (ESR) determination have been suggested since the original Westergren procedure that has been adopted as the gold standard by the International Council for Standardization in Haematology (ICSH). Recently, an automated method, (Alifax Test 1), based on a technique completely different from Westergren, has been introduced. MATERIAL AND METHODS: In this comparative study, ESR of blood from 680 patients with various rheumatic diseases was determined on both Test 1 and the StaRRsed automated ESR analyser which performs measurements in accordance with ICSH specifications. Furthermore the robustness of the new technique was evaluated. RESULTS: Direct correlation of Test 1 and StaRRsed measurements confirmed the results of previous studies: an overall correlation coefficient of R = 0.90. However, further statistical analysis showed that, depending on the instrument that was used, in 78 samples (i.e. 11.5%) the results could lead to different treatment suggestions. Furthermore it appeared that several procedural factors could influence the final Test 1 outcome. CONCLUSIONS: Due to its sensitivity for procedural variations, Test 1 measurements should be carried out under strictly standardized conditions. Especially at the higher ESR levels the Test 1 technique is, however, not a reliable alternative for the ICSH approved 'Westergren' method.

Determination of fibroblast growth factor 23.

BACKGROUND: Fibroblast growth factor 23 (FGF-23) is a recently discovered hormone, which plays a key role in phosphate regulation. To investigate whether FGF-23 can be determined reliably, we validated the three available FGF-23 assays. METHODS: Currently, two intact FGF-23 assays (Kainos; Immutopics) and one C-terminal FGF-23 assay (Immutopics) are available. We determined intra- and inter-assay variation, linearity and matrix interference in these assays. Moreover, we compared assay results from healthy subjects with those of patient groups with expected high FGF-23 concentrations. RESULTS: Intra-assay variation was reasonably good in all three assays. Inter-assay variation and linearity were poor for the intact Immutopics assay but reasonable for both other assays. Immutopics assays gave best results in ethylenediaminetetraacetic acid (EDTA) plasma, while the Kainos assay showed comparable reproducibility in EDTA plasma and serum. Although the manual of the Kainos assay states that an automatic washing machine can be used, acceptable results were only found by manual washing. Patients with kidney disease and patients with hypophosphatemic osteomalacia had increased C-terminal FGF-23 concentrations compared with healthy controls. CONCLUSION: Two assays of reasonable quality are available for FGF-23, the intact FGF-23 assay (Kainos) provided proper attention is paid to the washing procedure, and the C-terminal assay (Immutopics).

Performance of free beta-human chorionic gonadotrophin (free beta-hCG) and pregnancy associated plasma protein-A (PAPP-A) analysis between Delfia Xpress and AutoDelfia systems in The Netherlands.

BACKGROUND: The VU University Medical Center (VUmc) was the first hospital in the Netherlands to introduce the Delfia Xpress for the analysis of free beta-human chorionic gonadotrophin (beta-hCG) and pregnancy associated plasma protein-A (PAPP-A) in the first trimester screening program for Down syndrome. Since then, others have implemented this system. In this study, we tested the equality of measurements for free beta-hCG and PAPP-A between Delfia Xpress systems and one AutoDelfia system. METHODS: A total of 40 serum samples were aliquoted and stored at -20 degrees C. Samples were analyzed by six Delfia Xpress systems and one AutoDelfia system over a time period of 2 years. RESULTS: The relationships between free beta-hCG and PAPP-A were excellent for the different Delfia Xpress systems (r>0.99, p<0.0001). For PAPP-A, the agreement between the main system at VUmc and five other systems was linear with slopes between 0.99 and 1.06. Similarly, agreement for free beta-hCG was linear with slopes between 0.99 and 1.09. Likewise, agreement for PAPP-A and free beta-hCG was excellent for the AutoDelfia vs. the main Delfia Xpress at the VUmc (r>0.99, p<0.0001). For both PAPP-A and free beta-hCG, the relationships were linear with slopes of 1.08 and 1.07. CONCLUSIONS: We demonstrate an excellent agreement for the analysis of PAPP-A and free beta-hCG between Delfia Xpress systems and one AutoDelfia system.

Identification of the Fanconi anemia complementation group I gene, FANCI.

To identify the gene underlying Fanconi anemia (FA) complementation group I we studied informative FA-I families by a genome-wide linkage analysis, which resulted in 4 candidate regions together encompassing 351 genes. Candidates were selected via bioinformatics and data mining on the basis of their resemblance to other FA genes/proteins acting in the FA pathway, such as: degree of evolutionary conservation, presence of nuclear localization signals and pattern of tissue-dependent expression. We found a candidate, KIAA1794 on chromosome 15q25-26, to be mutated in 8 affected individuals previously assigned to complementation group I. Western blots of endogenous FANCI indicated that functionally active KIAA1794 protein is lacking in FA-I individuals. Knock-down of KIAA1794 expression by siRNA in HeLa cells caused excessive chromosomal breakage induced by mitomycin C, a hallmark of FA cells. Furthermore, phenotypic reversion of a patient-derived cell line was associated with a secondary genetic alteration at the KIAA1794 locus. These data add up to two conclusions. First, KIAA1794 is a FA gene. Second, this gene is identical to FANCI, since the patient cell lines found mutated in this study included the reference cell line for group I, EUFA592.

The Fanconi anemia pathway of genomic maintenance.

Fanconi anemia (FA), a recessive syndrome with both autosomal and X-linked inheritance, features diverse clinical symptoms, such as progressive bone marrow failure, hypersensitivity to DNA cross-linking agents, chromosomal instability and susceptibility to cancer. At least 12 genetic subtypes have been described (FA-A, B, C, D1, D2, E, F, G, I, J, L, M) and all except FA-I have been linked to a distinct gene. Most FA proteins form a complex that activates the FANCD2 protein via monoubiquitination, while FANCJ and FANCD1/BRCA2 function downstream of this step. The FA proteins typically lack functional domains, except for FANCJ/BRIP1 and FANCM, which are DNA helicases, and FANCL, which is probably an E3 ubiquitin conjugating enzyme. Based on the hypersensitivity to cross-linking agents, the FA proteins are thought to function in the repair of DNA interstrand cross-links, which block the progression of DNA replication forks. Here we present a hypothetical model, which not only describes the assembly of the FA pathway, but also positions this pathway in the broader context of DNA cross-link repair. Finally, the possible role for the FA pathway, in particular FANCF and FANCB, in the origin of sporadic cancer is discussed.

The DNA helicase BRIP1 is defective in Fanconi anemia complementation group J.

The protein predicted to be defective in individuals with Fanconi anemia complementation group J (FA-J), FANCJ, is a missing component in the Fanconi anemia pathway of genome maintenance. Here we identify pathogenic mutations in eight individuals with FA-J in the gene encoding the DEAH-box DNA helicase BRIP1, also called FANCJ. This finding is compelling evidence that the Fanconi anemia pathway functions through a direct physical interaction with DNA.

X-linked inheritance of Fanconi anemia complementation group B.

Fanconi anemia is an autosomal recessive syndrome characterized by diverse clinical symptoms, hypersensitivity to DNA crosslinking agents, chromosomal instability and susceptibility to cancer. Fanconi anemia has at least 11 complementation groups (A, B, C, D1, D2, E, F, G, I, J, L); the genes mutated in 8 of these have been identified. The gene BRCA2 was suggested to underlie complementation group B, but the evidence is inconclusive. Here we show that the protein defective in individuals with Fanconi anemia belonging to complementation group B is an essential component of the nuclear protein 'core complex' responsible for monoubiquitination of FANCD2, a key event in the DNA-damage response pathway associated with Fanconi anemia and BRCA. Unexpectedly, the gene encoding this protein, FANCB, is localized at Xp22.31 and subject to X-chromosome inactivation. X-linked inheritance has important consequences for genetic counseling of families with Fanconi anemia belonging to complementation group B. Its presence as a single active copy and essentiality for a functional Fanconi anemia-BRCA pathway make FANCB a potentially vulnerable component of the cellular machinery that maintains genomic integrity.

Heterogeneity in Fanconi anemia: evidence for 2 new genetic subtypes.

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.