Telomere Diseases and Other Constitutional and Acquired Genetic Disorders of Hematopoiesis

National Heart, Lung, And Blood Institute

Investigators

Linked publications, trials & patents

Abstract

In the Hematology Branch’s bone marrow failure clinic, a large proportion of patients have genetic diseases: constitutional syndromes, most frequently telomere biology disorders but also other etiologies and difficult diagnoses; clonal hematopoiesis of indeterminate potential (CHIP) and clonal cytopenia of unknown significance (CCUS); and acquired genetic diseases, PNH and VEXAS. Research protocols range from interventional (drugs and stem cell transplant) to natural history. Our approach is collaborative, as with NCI experts in telomere disease and GATA2 deficiency, NHGRI experts in RUNX1 disease, and NIAMS rheumatologists for VEXAS. We continue to accrue patients to our current protocol of low doses of danazol, which includes ancillary testing by flow-FISH for telomere length, and both extended observation and wash-out periods. We have established protocols for hematopoietic stem cell transplantation in VEXAS, and natural history studies of CHIP and marrow failure syndromes in general. Associated research laboratory experiments are based on advanced and sophisticated single cell DNA and RNA sequencing methodologies. Our clinic is a major referral center for VEXAS. In collaborative investigations, we have characterized the disease in general, aiming for a scoring system of severity and corticosteroid exposure; frequent infectious complications, the major cause of mortality; and diverse cutaneous manifestations, which often are presenting manifestations and, when persistent, require continuous steroid. Patients continue to accrue to our prospective clinical trial of hematopoietic stem cell transplantation; the aim is cure by marrow replacement but morbidity and mortality are impacted by age, comorbidities, and especially hyperinflammation that can exacerbate later graft-versus-host disease. An important observation has been the remarkable effect of hypomethylating agents, routinely employed in myelodysplastic syndromes, which in VEXAS not only can lead to clinical improvement but reduce and even appear to eradicate the mutated clone. A prospective clinical trial of azacitidine with correlative laboratory studies is underdevelopment to trial this mode of therapy. VEXAS has a peculiar demography: it appears in mainly Caucasian men, with a possible higher prevalence in Ashkenazi Jewish males, and it has not been observed in individuals of African ethnicity. We have obtained funding from the Womens’ Health Initiative and Center for Autoimmunity for germline sequencing, with the goal of identifying constitutional genetic differences that create either predilection or intolerance to a block in ubiquinylation from mutated UBA1. Single cell RNA sequencing has been successful in VEXAS studies, and we have added to our published study of bone marrow detailed investigation of peripheral blood. These data reveal an unexpectedly complex immune landscape, involving not only aberrant myeloid cells but abnormalities of B and T cells, natural killer and regulatory cell numbers, phenotype, and transcriptomes, and surprisingly suppressed monocyte and macrophage inflammatory responses and function. Our current laboratory focus is the link between upregulation of specific misfolded protein degradation pathways in hematopoietic cells and in cell lines is significant and the cellular inflammatory response. scRNAseq has also been revealing of PNH pathophysiology. An advantage of PNH in the laboratory is the ability to sort mutated and wild type cells by flow cytometry based on GPI-anchored proteins. In an extension of earlier work with less sophisticated methods, we discovered marked differences in transcriptomes between patients with large and small PNH clones, confirming our earlier claim that the major shifts in gene expression occur in the normal population of hematopoietic cells, PNH cells appearing more resistant to immune effects. Remarkably, in single cell DNA genomic testing, we find multiple distinctly mutated PNH clones in patients with aplastic anemia and patterns of clonal dominance and recession over time, powerful evidence of fitness and selection in the immune marrow failure environment. In the telomeropathies, we have characterized immune abnormalities in a large cohort of patients, indicating immunodeficiency and consequent infections as a complication of these syndromes. In the research laboratory, we have more fully defined, using single cell DNA genomics and lineage tracing, patterns of mutation acquisition that are strongly predictive of evolution to malignancy and also of clonal rescue that confers an improved prognosis. Our low dose danazol trial has closed for analysis, but we continue as a referral center for patients in our marrow failure clinic.