Development of specific growth charts for children with Fanconi anemia.

Patients with Fanconi anemia (FA) are often perceived to have poor growth when general population growth curves are utilized. We hypothesize that FA patients have unique growth and aimed to create FA-specific growth charts. Height and weight data from ages 0 to 20 years were extracted from medical records of patients treated at the Fanconi Anemia Comprehensive Care Clinic at the University of Minnesota. Height, weight, and BMI growth curves were generated and fitted to reference percentiles using the Lambda-Mu-Sigma method. FA-specific percentiles were compared to WHO standards for ages 0-2 and CDC references for ages 2-20. In FA males, the 50th height- and weight-for-age percentiles overlap with the 3rd reference percentile. In FA females, only the 50th height-for-age percentile overlaps with the 3rd reference percentile. For weight, FA females show progressive growth failure between 6 and 24 months followed by stabilization around the 50th percentile. The FA BMI-for-age percentiles show similar patterns to the weight-for-age percentiles but have different timing of onset of adiposity rebound and broader variability in females. Growth in FA patients follows a different trajectory than available normative curves. FA-specific growth charts may be useful to better guide accurate growth expectations, evaluations, and treatment.

Inhibition of TGFß1 and TGFß3 promotes hematopoiesis in Fanconi anemia.

Fanconi anemia (FA) is a chromosome instability syndrome with congenital abnormalities, cancer predisposition and bone marrow failure (BMF). Although hematopoietic stem and progenitor cell (HSPC) transplantation is the recommended therapy, new therapies are needed for FA patients without suitable donors. BMF in FA is caused, at least in part, by a hyperactive growth-suppressive transforming growth factor ß (TGFß) pathway, regulated by the TGFß1, TGFß2, and TGFß3 ligands. Accordingly, the TGFß pathway is an attractive therapeutic target for FA. While inhibition of TGFß1 and TGFß3 promotes blood cell expansion, inhibition of TGFß2 is known to suppress hematopoiesis. Here, we report the effects of AVID200, a potent TGFß1- and TGFß3-specific inhibitor, on FA hematopoiesis. AVID200 promoted the survival of murine FA HSPCs in vitro. AVID200 also promoted in vitro the survival of human HSPCs from patients with FA, with the strongest effect in patients progressing to severe aplastic anemia or myelodysplastic syndrome (MDS). Previous studies have indicated that the toxic upregulation of the nonhomologous end-joining (NHEJ) pathway accounts, at least in part, for the poor growth of FA HSPCs. AVID200 downregulated the expression of NHEJ-related genes and reduced DNA damage in primary FA HSPC in vitro and in in vivo models. Collectively, AVID200 exhibits activity in FA mouse and human preclinical models. AVID200 may therefore provide a therapeutic approach to improving BMF in FA.

Compromised repair of radiation-induced DNA double-strand breaks in Fanconi anemia fibroblasts in G2.

Fanconi anemia (FA) is a rare chromosomal instability syndrome with various clinical features and high cancer incidence. Despite being a DNA repair disorder syndrome and a frequently observed clinical hypersensitivity of FA patients towards ionizing radiation, the experimental evidence regarding the efficiency of radiation-induced DNA double-strand break (DSB) repair in FA is very controversial. Here, we performed a thorough analysis of the repair of radiation-induced DSBs in G1 and G2 in FA fibroblasts of complementation groups A, C, D1 (BRCA2), D2, E, F, G and P (SLX4) in comparison to normal human lung and skin fibroblasts. γH2AX, 53BP1, or RPA foci quantification after X-irradiation was combined with cell cycle markers. Cytogenetic analyses were performed on first metaphases after irradiation in G1 and by premature chromosome condensation after exposure in G2. Furthermore, the role of canonical-NHEJ and alternative-NHEJ for the fidelity of the repair of radiation-induced DSBs was examined. In FA fibroblasts, DSB repair was normal in G1 but compromised and more error-prone in the slow repair component of G2 as suggested by higher yields of radiation-induced γH2AX and 53BP1 foci as well as chromatid exchanges. However, RPA foci quantification in G2 indicated proficiency for homology-directed repair of DSBs in FA except for FA D1 (BRCA2). In lung fibroblasts, DSB repair in G1 was conducted with normal kinetics but elevated chromosome exchanges compared to skin fibroblasts. The overall repair of radiation-induced DSBs and the formation of chromosome exchanges in normal and FA fibroblasts in G1 and G2 were governed by canonical-NHEJ with no contribution of alternative-NHEJ. Together, we show impaired repair of radiation-induced DSBs in various FA complementation groups in the slow repair component of G2 that might promote the formation of potentially oncogenic aberrations and clinical radiation hypersensitivity.

Distinct roles of BRCA2 in replication fork protection in response to hydroxyurea and DNA interstrand cross-links.

DNA interstrand cross-links (ICLs) are a form of DNA damage that requires the interplay of a number of repair proteins including those of the Fanconi anemia (FA) and the homologous recombination (HR) pathways. Pathogenic variants in the essential gene BRCA2/FANCD1, when monoallelic, predispose to breast and ovarian cancer, and when biallelic, result in a severe subtype of Fanconi anemia. BRCA2 function in the FA pathway is attributed to its role as a mediator of the RAD51 recombinase in HR repair of programmed DNA double-strand breaks (DSB). BRCA2 and RAD51 functions are also required to protect stalled replication forks from nucleolytic degradation during response to hydroxyurea (HU). While RAD51 has been shown to be necessary in the early steps of ICL repair to prevent aberrant nuclease resection, the role of BRCA2 in this process has not been described. Here, based on the analysis of BRCA2 DNA-binding domain (DBD) mutants (c.8488-1G>A and c.8524C>T) discovered in FA patients presenting with atypical FA-like phenotypes, we establish that BRCA2 is necessary for the protection of DNA at ICLs. Cells carrying BRCA2 DBD mutations are sensitive to ICL-inducing agents but resistant to HU treatment consistent with relatively high HR repair in these cells. BRCA2 function at an ICL protects against DNA2-WRN nuclease-helicase complex and not the MRE11 nuclease that is implicated in the resection of HU-induced stalled replication forks. Our results also indicate that unlike the processing at HU-induced stalled forks, the function of the SNF2 translocases (SMARCAL1, ZRANB3, or HLTF), implicated in fork reversal, are not an integral component of the ICL repair, pointing to a different mechanism of fork protection at different DNA lesions.

Chromosome instability syndromes.

Fanconi anaemia (FA), ataxia telangiectasia (A-T), Nijmegen breakage syndrome (NBS) and Bloom syndrome (BS) are clinically distinct, chromosome instability (or breakage) disorders. Each disorder has its own pattern of chromosomal damage, with cells from these patients being hypersensitive to particular genotoxic drugs, indicating that the underlying defect in each case is likely to be different. In addition, each syndrome shows a predisposition to cancer. Study of the molecular and genetic basis of these disorders has revealed mechanisms of recognition and repair of DNA double-strand breaks, DNA interstrand crosslinks and DNA damage during DNA replication. Specialist clinics for each disorder have provided the concentration of expertise needed to tackle their characteristic clinical problems and improve outcomes. Although some treatments of the consequences of a disorder may be possible, for example, haematopoietic stem cell transplantation in FA and NBS, future early intervention to prevent complications of disease will depend on a greater understanding of the roles of the affected DNA repair pathways in development. An important realization has been the predisposition to cancer in carriers of some of these gene mutations.

Fancd2-deficient hematopoietic stem and progenitor cells depend on augmented mitochondrial translation for survival and proliferation.

Members of the Fanconi anemia (FA) protein family are involved in multiple cellular processes including response to DNA damage and oxidative stress. Here we show that a major FA protein, Fancd2, plays a role in mitochondrial biosynthesis through regulation of mitochondrial translation. Fancd2 interacts with Atad3 and Tufm, which are among the most frequently identified components of the mitochondrial nucleoid complex essential for mitochondrion biosynthesis. Deletion of Fancd2 in mouse hematopoietic stem and progenitor cells (HSPCs) leads to increase in mitochondrial number, and enzyme activity of mitochondrion-encoded respiratory complexes. Fancd2 deficiency increases mitochondrial protein synthesis and induces mitonuclear protein imbalance. Furthermore, Fancd2-deficient HSPCs show increased mitochondrial respiration and mitochondrial reactive oxygen species. By using a cell-free assay with mitochondria isolated from WT and Fancd2-KO HSPCs, we demonstrate that the increased mitochondrial protein synthesis observed in Fancd2-KO HSPCs was directly linked to augmented mitochondrial translation. Finally, Fancd2-deficient HSPCs are selectively sensitive to mitochondrial translation inhibition and depend on augmented mitochondrial translation for survival and proliferation. Collectively, these results suggest that Fancd2 restricts mitochondrial activity through regulation of mitochondrial translation, and that augmented mitochondrial translation and mitochondrial respiration may contribute to HSC defect and bone marrow failure in FA.

Successful engraftment of gene-corrected hematopoietic stem cells in non-conditioned patients with Fanconi anemia.

Fanconi anemia (FA) is a DNA repair syndrome generated by mutations in any of the 22 FA genes discovered to date1,2. Mutations in FANCA account for more than 60% of FA cases worldwide3,4. Clinically, FA is associated with congenital abnormalities and cancer predisposition. However, bone marrow failure is the primary pathological feature of FA that becomes evident in 70-80% of patients with FA during the first decade of life5,6. In this clinical study (ClinicalTrials.gov, NCT03157804 ; European Clinical Trials Database, 2011-006100-12), we demonstrate that lentiviral-mediated hematopoietic gene therapy reproducibly confers engraftment and proliferation advantages of gene-corrected hematopoietic stem cells (HSCs) in non-conditioned patients with FA subtype A. Insertion-site analyses revealed the multipotent nature of corrected HSCs and showed that the repopulation advantage of these cells was not due to genotoxic integrations of the therapeutic provirus. Phenotypic correction of blood and bone marrow cells was shown by the acquired resistance of hematopoietic progenitors and T lymphocytes to DNA cross-linking agents. Additionally, an arrest of bone marrow failure progression was observed in patients with the highest levels of gene marking. The progressive engraftment of corrected HSCs in non-conditioned patients with FA supports that gene therapy should constitute an innovative low-toxicity therapeutic option for this life-threatening disorder.

A novel frame-shift deletion in FANCF gene causing autosomal recessive Fanconi anemia: a case report.

BACKGROUND: Fanconi anemia (FA) is a heterogeneous genetic disorder characterized by congenital anomalies, early-onset bone marrow failure, and a high predisposition to cancers. Up to know, different genes involved in the DNA repair pathway, mainly FANCA genes, have been identified to be affected in patients with FA. CASE PRESENTATION: Here, we report clinical, laboratory and genetic findings in a 3.5-year-old Iranian female patient, a product of a consanguineous marriage, who was suspicious of FA, observed with short stature, microcephaly, skin hyperpigmentation, anemia, thrombocytopenia and hypo cellular bone marrow. Therefore, Next Generation Sequencing was performed to identify the genetic cause of the disease in this patient. Results revealed a novel, private, homozygous frameshift mutation in the FANCF gene (NM_022725: c. 534delG, p. G178 fs) which was confirmed by Sanger sequencing in the proband. CONCLUSION: Such studies may help uncover the exact pathomechanisms of this disorder and establish the genotype-phenotype correlations by identification of more mutations in this gene. It is the first report of a mutation in the FANCF gene in Iranian patients with Fanconi anemia. This new mutation correlates with a hematological problem (pancytopenia), short stature, and microcephaly and skin hyperpigmentation. Until now, no evidence of malignancy was detected.

Fanconi anemia protein FANCI functions in ribosome biogenesis.

Fanconi anemia (FA) is a disease of DNA repair characterized by bone marrow failure and a reduced ability to remove DNA interstrand cross-links. Here, we provide evidence that the FA protein FANCI also functions in ribosome biogenesis, the process of making ribosomes that initiates in the nucleolus. We show that FANCI localizes to the nucleolus and is functionally and physically tied to the transcription of pre-ribosomal RNA (pre-rRNA) and to large ribosomal subunit (LSU) pre-rRNA processing independent of FANCD2. While FANCI is known to be monoubiquitinated when activated for DNA repair, we find that it is predominantly in the deubiquitinated state in the nucleolus, requiring the nucleoplasmic deubiquitinase (DUB) USP1 and the nucleolar DUB USP36. Our model suggests a possible dual pathophysiology for FA that includes defects in DNA repair and in ribosome biogenesis.

Endoscopic findings and esophageal cancer incidence among Fanconi Anemia patients participating in an endoscopic surveillance program.

BACKGROUND AND AIMS: The primary clinical characteristics of Fanconi Anemia (FA) include typical physical features, progressive bone marrow failure, and an increased incidence of neoplasms, including esophageal carcinoma. Currently, there are no data regarding endoscopic findings or the interval time to malignancy in these patients. Data about the contribution of Human Papilloma Virus (HPV) to esophageal carcinoma is conflicting. Our objective is to document the upper gastrointestinal (GI) findings at baseline, document cancer incidence, and evaluate the role of HPV among these cancers. METHODS: We reviewed endoscopic and clinical data of FA subjects who participated in active surveillance before cancer diagnosis. Incident esophageal cancers were stained for HPV p16 protein. RESULTS: Eight FA patients were included (men 62.5%; median age at first endoscopy 20 years, median endoscopies number: 5.5). At baseline, 8/8 had endoscopic evidence for reflux esophagitis. In 3/8 the reflux esophagitis was mild and in 5/8 it was moderate or severe. During the follow up time (median time 4.5 years 2/8 developed Barrett's esophagus and 2/8 patients had incident esophageal squamous cell carcinoma during follow up, at intervals of eight and eighteen months from the previous upper endoscopy. Both cancers stained negative for HPV P16. CONCLUSIONS: FA subjects have both an extremely high risk for esophageal cancer within short intervals and a very high prevalence of reflux esophagitis with various severities. Active surveillance programs in specialized centers including annual upper endoscopies should be considered in these patients.

Multiplexed CRISPR/Cas9-mediated knockout of 19 Fanconi anemia pathway genes in zebrafish revealed their roles in growth, sexual development and fertility.

Fanconi Anemia (FA) is a genomic instability syndrome resulting in aplastic anemia, developmental abnormalities, and predisposition to hematological and other solid organ malignancies. Mutations in genes that encode proteins of the FA pathway fail to orchestrate the repair of DNA damage caused by DNA interstrand crosslinks. Zebrafish harbor homologs for nearly all known FA genes. We used multiplexed CRISPR/Cas9-mediated mutagenesis to generate loss-of-function mutants for 17 FA genes: fanca, fancb, fancc, fancd1/brca2, fancd2, fance, fancf, fancg, fanci, fancj/brip1, fancl, fancm, fancn/palb2, fanco/rad51c, fancp/slx4, fancq/ercc4, fanct/ube2t, and two genes encoding FA-associated proteins: faap100 and faap24. We selected two indel mutations predicted to cause premature truncations for all but two of the genes, and a total of 36 mutant lines were generated for 19 genes. Generating two independent mutant lines for each gene was important to validate their phenotypic consequences. RT-PCR from homozygous mutant fish confirmed the presence of transcripts with indels in all genes. Interestingly, 4 of the indel mutations led to aberrant splicing, which may produce a different protein than predicted from the genomic sequence. Analysis of RNA is thus critical in proper evaluation of the consequences of the mutations introduced in zebrafish genome. We used fluorescent reporter assay, and western blots to confirm loss-of-function for several mutants. Additionally, we developed a DEB treatment assay by evaluating morphological changes in embryos and confirmed that homozygous mutants from all the FA genes that could be tested (11/17), displayed hypersensitivity and thus were indeed null alleles. Our multiplexing strategy helped us to evaluate 11 multiple gene knockout combinations without additional breeding. Homozygous zebrafish for all 19 single and 11 multi-gene knockouts were adult viable, indicating FA genes in zebrafish are generally not essential for early development. None of the mutant fish displayed gross developmental abnormalities except for fancp-/- fish, which were significantly smaller in length than their wildtype clutch mates. Complete female-to-male sex reversal was observed in knockouts for 12/17 FA genes, while partial sex reversal was seen for the other five gene knockouts. All adult females were fertile, and among the adult males, all were fertile except for the fancd1 mutants and one of the fancj mutants. We report here generation and characterization of zebrafish knockout mutants for 17 FA disease-causing genes, providing an integral resource for understanding the pathophysiology associated with the disrupted FA pathway.

Spectrin and its interacting partners in nuclear structure and function.

Nonerythroid αII-spectrin is a structural protein whose roles in the nucleus have just begun to be explored. αII-spectrin is an important component of the nucleoskelelton and has both structural and non-structural functions. Its best known role is in repair of DNA ICLs both in genomic and telomeric DNA. αII-spectrin aids in the recruitment of repair proteins to sites of damage and a proposed mechanism of action is presented. It interacts with a number of different groups of proteins in the nucleus, indicating it has roles in additional cellular functions. αII-spectrin, in its structural role, associates/co-purifies with proteins important in maintaining the architecture and mechanical properties of the nucleus such as lamin, emerin, actin, protein 4.1, nuclear myosin, and SUN proteins. It is important for the resilience and elasticity of the nucleus. Thus, αII-spectrin's role in cellular functions is complex due to its structural as well as non-structural roles and understanding the consequences of a loss or deficiency of αII-spectrin in the nucleus is a significant challenge. In the bone marrow failure disorder, Fanconi anemia, there is a deficiency in αII-spectrin and, among other characteristics, there is defective DNA repair, chromosome instability, and congenital abnormalities. One may speculate that a deficiency in αII-spectrin plays an important role not only in the DNA repair defect but also in the congenital anomalies observed in Fanconi anemia , particularly since αII-spectrin has been shown to be important in embryonic development in a mouse model. The dual roles of αII-spectrin in the nucleus in both structural and non-structural functions make this an extremely important protein which needs to be investigated further. Such investigations should help unravel the complexities of αII-spectrin's interactions with other nuclear proteins and enhance our understanding of the pathogenesis of disorders, such as Fanconi anemia , in which there is a deficiency in αII-spectrin. Impact statement The nucleoskeleton is critical for maintaining the architecture and functional integrity of the nucleus. Nonerythroid α-spectrin (αIISp) is an essential nucleoskeletal protein; however, its interactions with other structural and non-structural nuclear proteins and its functional importance in the nucleus have only begun to be explored. This review addresses these issues. It describes αIISp's association with DNA repair proteins and at least one proposed mechanism of action for its role in DNA repair. Specific interactions of αIISp with other nucleoskeletal proteins as well as its important role in the biomechanical properties of the nucleus are reviewed. The consequences of loss of αIISp, in disorders such as Fanconi anemia, are examined, providing insights into the profound impact of this loss on critical processes known to be abnormal in FA, such as development, carcinogenesis, cancer progression and cellular functions dependent upon αIISp's interactions with other nucleoskeletal proteins.

Clinical Report: Warsaw Breakage Syndrome with small radii and fibulae.

We present two new cases of Warsaw Breakage Syndrome (WABS), an autosomal recessive cohesinopathy, in sisters aged 13 and 11 years who both had compound heterozygous mutations in DDX11. After exclusion of Fanconi anemia, Bloom syndrome and Nijmegen breakage syndrome, whole exome sequencing revealed two novel variants-c.1523T>G, predicting (p.Leu508Arg) and c.1949-1G>A (IVS19-1G>A), that were confirmed with Sanger sequencing in both affected individuals. DDX11 encodes an iron-sulfur-containing DNA helicase, and mutations in this gene have been reported in the five WABS cases previously identified to date. The sisters reported here display the distinguishing clinical features of WABS: pre- and post-natal growth restriction, microcephaly, intellectual disability, sensorineural hearing loss with cochlear abnormalities, and facial dysmorphic features. In addition, our cases had early menarche at 8 and 10 years of age, bilateral small thumbs, and the younger, more severely affected sister had small fibulae. These findings broaden the WABS phenotype and the limb malformations demonstrate further clinical overlap with Fanconi anemia and other cohesinopathies, such as Roberts Syndrome.

Loss of the homologous recombination gene rad51 leads to Fanconi anemia-like symptoms in zebrafish.

RAD51 is an indispensable homologous recombination protein, necessary for strand invasion and crossing over. It has recently been designated as a Fanconi anemia (FA) gene, following the discovery of two patients carrying dominant-negative mutations. FA is a hereditary DNA-repair disorder characterized by various congenital abnormalities, progressive bone marrow failure, and cancer predisposition. In this report, we describe a viable vertebrate model of RAD51 loss. Zebrafish rad51 loss-of-function mutants developed key features of FA, including hypocellular kidney marrow, sensitivity to cross-linking agents, and decreased size. We show that some of these symptoms stem from both decreased proliferation and increased apoptosis of embryonic hematopoietic stem and progenitor cells. Comutation of p53 was able to rescue the hematopoietic defects seen in the single mutants, but led to tumor development. We further demonstrate that prolonged inflammatory stress can exacerbate the hematological impairment, leading to an additional decrease in kidney marrow cell numbers. These findings strengthen the assignment of RAD51 as a Fanconi gene and provide more evidence for the notion that aberrant p53 signaling during embryogenesis leads to the hematological defects seen later in life in FA. Further research on this zebrafish FA model will lead to a deeper understanding of the molecular basis of bone marrow failure in FA and the cellular role of RAD51.

An abnormal bone marrow microenvironment contributes to hematopoietic dysfunction in Fanconi anemia.

Fanconi anemia is a complex heterogeneous genetic disorder with a high incidence of bone marrow failure, clonal evolution to acute myeloid leukemia and mesenchymal-derived congenital anomalies. Increasing evidence in Fanconi anemia and other genetic disorders points towards an interdependence of skeletal and hematopoietic development, yet the impact of the marrow microenvironment in the pathogenesis of the bone marrow failure in Fanconi anemia remains unclear. Here we demonstrated that mice with double knockout of both Fancc and Fancg genes had decreased bone formation at least partially due to impaired osteoblast differentiation from mesenchymal stem/progenitor cells. Mesenchymal stem/progenitor cells from the double knockout mice showed impaired hematopoietic supportive activity. Mesenchymal stem/progenitor cells of patients with Fanconi anemia exhibited similar cellular deficits, including increased senescence, reduced proliferation, impaired osteoblast differentiation and defective hematopoietic stem/progenitor cell supportive activity. Collectively, these studies provide unique insights into the physiological significance of mesenchymal stem/progenitor cells in supporting the marrow microenvironment, which is potentially of broad relevance in hematopoietic stem cell transplantation.

Fanconi anaemia.

Fanconi anaemia is a rare inherited genetic condition that can lead to aplastic anaemia and bone marrow failure. People with the condition have a predisposition to some cancers. The condition is named after Swiss paediatrician Guido Fanconi.

Fanconi Anemia: A DNA repair disorder characterized by accelerated decline of the hematopoietic stem cell compartment and other features of aging.

Fanconi Anemia (FA) is a rare autosomal genetic disorder characterized by progressive bone marrow failure (BMF), endocrine dysfunction, cancer, and other clinical features commonly associated with normal aging. The anemia stems directly from an accelerated decline of the hematopoietic stem cell compartment. Although FA is a complex heterogeneous disease linked to mutations in 19 currently identified genes, there has been much progress in understanding the molecular pathology involved. FA is broadly considered a DNA repair disorder and the FA gene products, together with other DNA repair factors, have been implicated in interstrand cross-link (ICL) repair. However, in addition to the defective DNA damage response, altered epigenetic regulation, and telomere defects, FA is also marked by elevated levels of inflammatory mediators in circulation, a hallmark of faster decline in not only other hereditary aging disorders but also normal aging. In this review, we offer a perspective of FA as a monogenic accelerated aging disorder, citing the latest evidence for its multi-factorial deficiencies underlying its unique clinical and cellular features.

Impaired mitophagy in Fanconi anemia is dependent on mitochondrial fission.

Fanconi anemia (FA) is a rare genetic disorder associated with bone-marrow failure, genome instability and cancer predisposition. Recently, we and others have demonstrated dysfunctional mitochondria with morphological alterations in FA cells accompanied by high reactive oxygen species (ROS) levels. Mitochondrial morphology is regulated by continuous fusion and fission events and the misbalance between these two is often accompanied by autophagy. Here, we provide evidence of impaired autophagy in FA. We demonstrate that FA cells have increased number of autophagic (presumably mitophagic) events and accumulate dysfunctional mitochondria due to an impaired ability to degrade them. Moreover, mitochondrial fission accompanied by oxidative stress (OS) is a prerequisite condition for mitophagy in FA and blocking this pathway may release autophagic machinery to clear dysfunctional mitochondria.

Increased red cell distribution width in Fanconi anemia: a novel marker of stress erythropoiesis.

BACKGROUND: Red cell distribution width (RDW), a classical parameter used in the differential diagnosis of anemia, has recently been recognized as a marker of chronic inflammation and high levels of oxidative stress (OS). Fanconi anemia (FA) is a genetic disorder associated to redox imbalance and dysfunctional response to OS. Clinically, it is characterized by progressive bone marrow failure, which remains the primary cause of morbidity and mortality. Macrocytosis and increased fetal hemoglobin, two indicators of bone marrow stress erythropoiesis, are generally the first hematological manifestations to appear in FA. However, the significance of RDW and its possible relation to stress erythropoiesis have never been explored in FA. In the present study we analyzed routine complete blood counts from 34 FA patients and evaluated RDW, correlating with the hematological parameters most consistently associated with the FA phenotype. RESULTS: We showed, for the first time, that RDW is significantly increased in FA. We also showed that increased RDW is correlated with thrombocytopenia, neutropenia and, most importantly, highly correlated with anemia. Analyzing sequential hemograms from 3 FA patients with different clinical outcomes, during 10 years follow-up, we confirmed a consistent association between increased RDW and decreased hemoglobin, which supports the postulated importance of RDW in the evaluation of hematological disease progression. CONCLUSIONS: This study shows, for the first time, that RDW is significantly increased in FA, and this increment is correlated with neutropenia, thrombocytopenia, and highly correlated with anemia. According to the present results, it is suggested that increased RDW can be a novel marker of stress erythropoiesis in FA.

FANCJ suppresses microsatellite instability and lymphomagenesis independent of the Fanconi anemia pathway.

Microsatellites are short tandem repeat sequences that are highly prone to expansion/contraction due to their propensity to form non-B-form DNA structures, which hinder DNA polymerases and provoke template slippage. Although error correction by mismatch repair plays a key role in preventing microsatellite instability (MSI), which is a hallmark of Lynch syndrome, activities must also exist that unwind secondary structures to facilitate replication fidelity. Here, we report that Fancj helicase-deficient mice, while phenotypically resembling Fanconi anemia (FA), are also hypersensitive to replication inhibitors and predisposed to lymphoma. Whereas metabolism of G4-DNA structures is largely unaffected in Fancj(-/-) mice, high levels of spontaneous MSI occur, which is exacerbated by replication inhibition. In contrast, MSI is not observed in Fancd2(-/-) mice but is prevalent in human FA-J patients. Together, these data implicate FANCJ as a key factor required to counteract MSI, which is functionally distinct from its role in the FA pathway.