Paternal or Maternal Uniparental Disomy of Chromosome 16 Resulting in Homozygosity of a Mutant Allele Causes Fanconi Anemia.

Fanconi anemia (FA) is a rare inherited disorder caused by pathogenic variants in one of 19 FANC genes. FA patients display congenital abnormalities, and develop bone marrow failure, and cancer susceptibility. We identified homozygous mutations in four FA patients and, in each case, only one parent carried the obligate mutant allele. FANCA and FANCP/SLX4 genes, both located on chromosome 16, were the affected recessive FA genes in three and one family respectively. Genotyping with short tandem repeat markers and SNP arrays revealed uniparental disomy (UPD) of the entire mutation-carrying chromosome 16 in all four patients. One FANCA patient had paternal UPD, whereas FA in the other three patients resulted from maternal UPD. These are the first reported cases of UPD as a cause of FA. UPD indicates a reduced risk of having another child with FA in the family and has implications in prenatal diagnosis.

Natural history and management of Fanconi anemia patients with head and neck cancer: A 10-year follow-up.

OBJECTIVES/HYPOTHESIS: To describe the management and outcomes of Fanconi anemia (FA) patients with head and neck squamous cell carcinoma. STUDY DESIGN: Cohort study. METHODS: Demographic information, prognostic factors, therapeutic management, and survival outcomes for FA patients enrolled in the International Fanconi Anemia Registry who developed head and neck squamous cell carcinoma (HNSCC) were analyzed. RESULTS: Thirty-five FA patients were diagnosed with HNSCC at a mean age of 32 years. The most common site of primary cancer was the oral cavity (26 of 35, 74%). Thirty patients underwent surgical resection of the cancer. Sixteen patients received radiation therapy with an average radiation dose of 5,050 cGy. The most common toxicities were high-grade mucositis (9 of 16, 56%), hematologic abnormalities (8 of 16, 50%), and dysphagia (8 of 16, 50%). Three patients received conventional chemotherapy and had significant complications, whereas three patients who received targeted chemotherapy with cetuximab had fewer toxicities. The 5-year overall survival rate was 39%, with a cause-specific survival rate of 47%. CONCLUSIONS: Fanconi anemia patients have a high risk of developing aggressive HNSCC at an early age. Fanconi anemia patients can tolerate complex ablative and reconstructive surgeries, but careful postoperative care is required to reduce morbidity. The treatment of FA-associated HNSCC is difficult secondary to the poor tolerance of radiation and chemotherapy. However, radiation should be used for high-risk cancers due to the poor survival in these patients. LEVEL OF EVIDENCE: 4.

A Dominant Mutation in Human RAD51 Reveals Its Function in DNA Interstrand Crosslink Repair Independent of Homologous Recombination.

Repair of DNA interstrand crosslinks requires action of multiple DNA repair pathways, including homologous recombination. Here, we report a de novo heterozygous T131P mutation in RAD51/FANCR, the key recombinase essential for homologous recombination, in a patient with Fanconi anemia-like phenotype. In vitro, RAD51-T131P displays DNA-independent ATPase activity, no DNA pairing capacity, and a co-dominant-negative effect on RAD51 recombinase function. However, the patient cells are homologous recombination proficient due to the low ratio of mutant to wild-type RAD51 in cells. Instead, patient cells are sensitive to crosslinking agents and display hyperphosphorylation of Replication Protein A due to increased activity of DNA2 and WRN at the DNA interstrand crosslinks. Thus, proper RAD51 function is important during DNA interstrand crosslink repair outside of homologous recombination. Our study provides a molecular basis for how RAD51 and its associated factors may operate in a homologous recombination-independent manner to maintain genomic integrity.

Deficiency of UBE2T, the E2 Ubiquitin Ligase Necessary for FANCD2 and FANCI Ubiquitination, Causes FA-T Subtype of Fanconi Anemia.

Fanconi anemia (FA) is a rare bone marrow failure and cancer predisposition syndrome resulting from pathogenic mutations in genes encoding proteins participating in the repair of DNA interstrand crosslinks (ICLs). Mutations in 17 genes (FANCA-FANCS) have been identified in FA patients, defining 17 complementation groups. Here, we describe an individual presenting with typical FA features who is deficient for the ubiquitin-conjugating enzyme (E2), UBE2T. UBE2T is known to interact with FANCL, the E3 ubiquitin-ligase component of the multiprotein FA core complex, and is necessary for the monoubiquitination of FANCD2 and FANCI. Proband fibroblasts do not display FANCD2 and FANCI monoubiquitination, do not form FANCD2 foci following treatment with mitomycin C, and are hypersensitive to crosslinking agents. These cellular defects are complemented by expression of wild-type UBE2T, demonstrating that deficiency of the protein UBE2T can lead to Fanconi anemia. UBE2T gene gains an alias of FANCT.

Genetic counseling for Fanconi anemia: crosslinking disciplines.

Fanconi anemia (FA) is the most common of the inherited bone marrow failure syndromes with an incidence of approximately 1/100,000 to 1/200,000 live births. FA is a genetically complex and phenotypically heterogeneous condition involving birth defects, bone marrow failure, and cancer predisposition. This rare disease became well known in the genetic counseling community in 2002, when it was identified that biallelic mutations in BRCA2 can cause FA. Knowledge gained from the growing association between FA and breast cancer pathways has brought even more light to the complex genetic issues that arise when counseling families affected by this disease. Genetic counseling issues surrounding a diagnosis of FA affect many different disciplines. This review will serve as a way to cross-link the various topics important to genetic counselors that arise throughout the life of a patient with FA. Issues covered will include: an overview of FA, phenotypic presentation, management and treatment, the genetics and inheritance of FA, cytogenetic and molecular testing options, and the risks to family members of an individual with FA.

Comprehensive analysis of pathogenic deletion variants in Fanconi anemia genes.

Fanconi anemia (FA) is a rare recessive disease resulting from mutations in one of at least 16 different genes. Mutation types and phenotypic manifestations of FA are highly heterogeneous and influence the clinical management of the disease. We analyzed 202 FA families for large deletions, using high-resolution comparative genome hybridization arrays, single-nucleotide polymorphism arrays, and DNA sequencing. We found pathogenic deletions in 88 FANCA, seven FANCC, two FANCD2, and one FANCB families. We find 35% of FA families carry large deletions, accounting for 18% of all FA pathogenic variants. Cloning and sequencing across the deletion breakpoints revealed that 52 FANCA deletion ends, and one FANCC deletion end extended beyond the gene boundaries, potentially affecting neighboring genes with phenotypic consequences. Seventy-five percent of the FANCA deletions are Alu-Alu mediated, predominantly by AluY elements, and appear to be caused by nonallelic homologous recombination. Individual Alu hotspots were identified. Defining the haplotypes of four FANCA deletions shared by multiple families revealed that three share a common ancestry. Knowing the exact molecular changes that lead to the disease may be critical for a better understanding of the FA phenotype, and to gain insight into the mechanisms driving these pathogenic deletion variants.

Disability training in the genetic counseling curricula: bridging the gap between genetic counselors and the disability community.

Over the past two decades, disability activists, ethicists, and genetic counselors have examined the moral complexities inherent in prenatal genetic counseling and considered whether and in what ways genetic counseling may negatively affect individuals in the disability community. Many have expressed concerns about defining disability in the context of prenatal decision-making, as the definition presented may influence prenatal choices. In the past few years, publications have begun to explore the responsibility of counselors in presenting a balanced view of disability and have questioned the preparedness of counselors for this duty. Currently, the Accreditation Council for Genetic Counseling (ACGC) only minimally includes disability training in their competencies for genetic counselors, and in their accreditation requirements for training programs. In an attempt to describe current practice, this article details two studies that assess disability training in ABGC-accredited genetic counseling programs. Results from these studies demonstrate that experience with disability is not required by the majority of programs prior to matriculation. Though most program directors agree on the importance of including disability training in the curriculum, there is wide variability in the amount and types of training students receive. Hours dedicated to disability exposure among programs ranged from 10 to 600 hours. Eighty-five percent of program directors surveyed agree that skills for addressing disability should be added to the core competencies. Establishing a set of disability competencies would help to ensure that all graduates have the skills necessary to provide patients with an accurate understanding of disability that facilitates informed decision-making.

Massively parallel sequencing, aCGH, and RNA-Seq technologies provide a comprehensive molecular diagnosis of Fanconi anemia.

Current methods for detecting mutations in Fanconi anemia (FA)-suspected patients are inefficient and often miss mutations. We have applied recent advances in DNA sequencing and genomic capture to the diagnosis of FA. Specifically, we used custom molecular inversion probes or TruSeq-enrichment oligos to capture and sequence FA and related genes, including introns, from 27 samples from the International Fanconi Anemia Registry at The Rockefeller University. DNA sequencing was complemented with custom array comparative genomic hybridization (aCGH) and RNA sequencing (RNA-seq) analysis. aCGH identified deletions/duplications in 4 different FA genes. RNA-seq analysis revealed lack of allele specific expression associated with a deletion and splicing defects caused by missense, synonymous, and deep-in-intron variants. The combination of TruSeq-targeted capture, aCGH, and RNA-seq enabled us to identify the complementation group and biallelic germline mutations in all 27 families: FANCA (7), FANCB (3), FANCC (3), FANCD1 (1), FANCD2 (3), FANCF (2), FANCG (2), FANCI (1), FANCJ (2), and FANCL (3). FANCC mutations are often the cause of FA in patients of Ashkenazi Jewish (AJ) ancestry, and we identified 2 novel FANCC mutations in 2 patients of AJ ancestry. We describe here a strategy for efficient molecular diagnosis of FA.

Postoperative clinical radiosensitivity in patients with fanconi anemia and head and neck squamous cell carcinoma.

OBJECTIVE: To describe the complications and adverse effects of postoperative radiotherapy in patients with Fanconi anemia (FA). DESIGN: Cohort study. SETTING: Patients with FA treated at community and tertiary care hospitals throughout the United States. PATIENTS: The study included patients with FA who were enrolled in the International FA Registry (IFAR) and who developed head and neck squamous cell carcinoma and received postoperative radiotherapy. MAIN OUTCOME MEASURES: Demographics of patients with FA and adverse effects and dosages of radiotherapy. RESULTS: Twelve patients with FA (7 men and 5 women) were identified. They developed cancers at a mean age of 35.5 years (age range, 20-48 years). The sites of primary cancer were the oral cavity (n = 8), larynx (n = 2), pharynx (n = 1), and unknown (n = 1). The median radiation dose was 5590 cGy (range, 2500-7020 cGy). The most common adverse effects were mucositis (n = 9), dysphagia (n = 8), and pancytopenia (n = 6). Other complications included esophageal stenosis, laryngeal edema, and wound breakdown. Radiotherapy could not be completed in 5 cases. Overall, 8 patients died, 4 during the course of radiotherapy. The postoperative disease-free survival time ranged from 0 to 55 months. CONCLUSIONS: Patients with FA have a high rate of complications from radiotherapy. Common adverse effects, particularly mucositis, are especially prevalent and difficult to manage in this population. Pancytopenia is common and may lead to further complications, particularly bleeding and infection. Overall survival is poor. Further study of the response to radiotherapy in patients with FA should be attempted to establish appropriate dosages to balance treating disease while limiting adverse effects.

Double-blind therapeutic trial in Angelman syndrome using betaine and folic acid.

Angelman syndrome (AS) is caused by reduced or absent expression of the maternally inherited ubiquitin protein ligase 3A gene (UBE3A), which maps to chromosome 15q11-q13. UBE3A is subject to genomic imprinting in neurons in most regions of the brain. Expression of UBE3A from the maternal chromosome is essential to prevent AS, because the paternally inherited gene is not expressed, probably mediated by antisense UBE3A RNA. We hypothesized that increasing methylation might reduce expression of the antisense UBE3A RNA, thereby increasing UBE3A expression from the paternal gene and ameliorating the clinical phenotype. We conducted a trial using two dietary supplements, betaine and folic acid to promote global levels of methylation and attempt to activate the paternally inherited UBE3A gene. We performed a number of investigations at regular intervals including general clinical and developmental evaluations, biochemical determinations on blood and urine, and electroencephalographic studies. We report herein the data on 48 children with AS who were enrolled in a double-blind placebo-controlled protocol using betaine and folic acid for 1 year. There were no statistically significant changes between treated and untreated children; however, in a small subset of patients we observed some positive trends.

An expanded version of the Hammersmith Functional Motor Scale for SMA II and III patients.

PURPOSE: To develop and evaluate an expanded version of the Hammersmith Functional Motor Scale allowing for evaluation of ambulatory SMA patients. PROCEDURES: Thirty-eight patients with SMA type II or III were evaluated using the Gross Motor Function Measure and the Hammersmith Functional Motor Scale. Based on statistical and clinical criteria, we selected 13 Gross Motor Function Measure items to develop an expanded HFMS. The expanded Hammersmith Functional Motor Scale was validated by comparison with the Gross Motor Function Measure minus the 13 items (GMFM-75) and an assessment of clinical function. The reliability of the expanded Hammersmith Functional Motor Scale in 36 patients was established. FINDINGS: The expanded Hammersmith Functional Motor Scale was highly correlated with the GMFM-75 and the clinical function assessment (p=0.97, and p=0.90). The expanded Hammersmith Functional Motor Scale showed excellent test-retest reliability (International Coordinating Committee = 0.99). CONCLUSIONS: The expanded Hammersmith Functional Motor Scale allows assessment of high functioning SMA type II and III patients. Ease of administration and correlation with established motor function measures justify use in future SMA clinical trials.