Perturbed hematopoiesis in individuals with germline DNMT3A overgrowth Tatton-Brown-Rahman syndrome

Abstract

Tatton-Brown-Rahman syndrome (TBRS) is an overgrowth disorder caused by germline heterozygous mutations in the DNA methyltransferase DNMT3A. DNMT3A is a critical regulator of hematopoietic stem cell (HSC) differentiation and somatic DNMT3A mutations are frequent in hematologic malignancies and clonal hematopoiesis. Yet, the impact of constitutive DNMT3A mutation on hematopoiesis in TBRS is undefined. To establish how constitutive mutation of DNMT3A impacts blood development in TBRS we gathered clinical data and analyzed blood parameters in 18 individuals with TBRS. We also determined the distribution of major peripheral blood cell lineages by flow cytometric analyses. Our analyses revealed non-anemic macrocytosis, a relative decrease in lymphocytes and increase in neutrophils in TBRS individuals compared to unaffected controls. We were able to recapitulate these hematologic phenotypes in multiple murine models of TBRS and identified rare hematological and nonhematological malignancies associated with constitutive Dnmt3a mutation. We further show that loss of DNMT3A in TBRS is associated with an altered DNA methylation landscape in hematopoietic cells affecting regions critical to stem cell function and tumorigenesis. Overall, our data identify key hematopoietic effects driven by DNMT3A mutation with clinical implications for individuals with TBRS and DNMT3A-associated clonal hematopoiesis or malignancies.

Constitutive loss of DNMT3A causes morbid obesity through misregulation of adipogenesis

“…TBRS patients harbor heterozygous frameshift or missense mutations in DNMT3A , predicted to be partial or complete loss-of-function, distributed throughout the gene’s main functional domains ( Tatton-Brown et al, 2018 ; Tovy et al, 2022 ). In order to study the role of DNMT3A in weight gain and adipose tissue biology, we utilized mice heterozygous for a Dnmt3a null allele (‘3A-HET’) along with their wild-type (WT) counterparts.…”

“…Germline heterozygous mutations in DNMT3A lead to Tatton-Brown-Rahman syndrome (TBRS; OMIM: 615879) ( Tatton-Brown et al, 2014 ), a dominant disorder characterized by excessive height (~80% of individuals), intellectual disability (~80% of individuals), and obesity (~70% of individuals) ( Tatton-Brown et al, 2014 ; Tatton-Brown et al, 2018 ). We and others have recently shown that Dnmt3a haploinsufficent mice can be used to study TBRS ( Christian et al, 2020 ; Tovy et al, 2022 ). These mice recapitulate key TBRS phenotypes, including enlarged body size and obesity ( Christian et al, 2020 ).…”

Murine Models of Acute Myeloid Leukemia

“…Our group recently used CRISPR/Cas9-mediated gene editing of murine embryonic stem cells to create constitutive models germline Dnmt3a lesions that have been previously described in patients with the rare overgrowth, intellectual disability syndrome, Tatton-Brown-Rahman syndrome. We found that each model recapitulated the distinct growth, behavioral and hematologic phenotypes observed in their human counterparts including increased risk of hematologic malignancy ( 135 ). Dr. Amanda Smith in the lab of Dr. Timothy Ley similarly found that a germline Dnmt3a R878 model also recapitulated the features of TBRS including risk of hematologic malignancy development ( 136 ).…”

DNMT3Aovergrowth syndrome is associated with the development of hematopoietic malignancies in children and young adults

“…1 Mutations were found in all three functional domains of DNMT3A, and likely caused loss-offunction of the mutant allele. [1][2][3][4] Affected individuals shared distinctive facial features, intellectual disability, obesity, and tall stature. Although somatic mutations in DNMT3A are among the most common initiating events for normal karyotype AML patients and clonal hematopoiesis, [5][6][7][8][9] mutations of DNMT3A are rarely found in pediatric AML patients.…”

“…A recent study evaluating the effects of germline DNMT3A pathogenic variants on hematopoiesis in DOS patients found similar total white cell counts and hemoglobins in DOS patients and controls, but noted some DOS patients had an increased fraction of circulating neutrophils, a decrease in B cells, and mild macrocytosis. 4 We recently described the DNA methylation landscape for 11 DOS patients (including one with a history of AML) compared to unaffected controls, which showed focal hypomethylation in nonleukemic peripheral blood cells that was more pronounced in patients with DNMT3A R882H than other DNMT3A mutations. 3 Although reports of AML have been described in two DOS patients, 2,11 and a single Tlymphoblastic lymphoma/leukemia, 12 the incidence of hematopoietic malignancies in DOS patients is not yet clear.…”