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On the role of FAN1 in Fanconi anemia
Juan P Trujillo1, Leonardo B Mina, Roser Pujol
1Genome Instability and DNA Repair Group, Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, Barcelona, Spain.
Abstract:
Fanconi anemia (FA) is a rare bone marrow failure disorder with defective DNA interstrand crosslink repair. Still, there are FA patients without mutations in any of the 15 genes individually underlying the disease. A candidate protein for those patients, FA nuclease 1 (FAN1), whose gene is located at chromosome 15q13.3, is recruited to stalled replication forks by binding to monoubiquitinated FANCD2 and is required for interstrand crosslink repair, suggesting that mutation of FAN1 may cause FA. Here we studied clinical, cellular, and genetic features in 4 patients carrying a homozygous 15q13.3 micro-deletion, including FAN1 and 6 additional genes. Biallelic deletion of the entire FAN1 gene was confirmed by failure of 3'- and 5'-PCR amplification. Western blot analysis failed to show FAN1 protein in the patients' cell lines. Chromosome fragility was normal in all 4 FAN1-deficient patients, although their cells showed mild sensitivity to mitomycin C in terms of cell survival and G(2) phase arrest, dissimilar in degree to FA cells. Clinically, there were no symptoms pointing the way to FA. Our results suggest that FAN1 has a minor role in interstrand crosslink repair compared with true FA genes and exclude FAN1 as a novel FA gene.
Insights
Fanconi anemia (FA) is a rare disorder. Researchers investigated FAN1 gene deletions in patients, finding no evidence that FAN1 mutations cause FA, suggesting a minor role in DNA repair.
Area of Science:
- Genetics
- Molecular Biology
- Oncology
Background:
- Fanconi anemia (FA) is a rare genetic disorder characterized by bone marrow failure and defective DNA interstrand crosslink repair.
- While 15 genes are known to cause FA, some patients lack mutations in these genes, suggesting other genetic factors may be involved.
- FAN1 (FA nuclease 1) has been proposed as a candidate gene due to its role in DNA repair and its association with stalled replication forks.
Purpose of the Study:
- To investigate the clinical, cellular, and genetic features of four patients with a homozygous 15q13.3 micro-deletion encompassing the FAN1 gene.
- To determine if FAN1 deficiency, caused by this micro-deletion, leads to a Fanconi anemia-like phenotype.
- To evaluate the role of FAN1 in DNA interstrand crosslink repair and chromosome stability.
Main Methods:
- Genetic analysis of four patients with 15q13.3 micro-deletions using PCR to confirm biallelic deletion of the FAN1 gene.
- Western blot analysis to assess FAN1 protein expression in patient-derived cell lines.
- Cellular assays to evaluate chromosome fragility, sensitivity to mitomycin C, and G2 phase arrest.
Main Results:
- Biallelic deletion of the entire FAN1 gene was confirmed in all four patients.
- FAN1 protein was undetectable in the cell lines of these FAN1-deficient patients.
- Patients exhibited normal chromosome fragility but mild sensitivity to mitomycin C, differing from typical FA cells. No FA-like clinical symptoms were observed.
Conclusions:
- The study excludes FAN1 as a novel FA gene.
- FAN1 appears to play a minor role in DNA interstrand crosslink repair compared to established FA genes.
- FAN1 deficiency due to micro-deletion does not cause Fanconi anemia.
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