Reyes, J. M. | bioRxiv Science

bioRxiv2021

Constitutive loss of DNMT3A causes morbid obesity through misregulation of adipogenesis

DNA Methyltransferase 3A (DNMT3A) is an important facilitator of differentiation of both embryonic and hematopoietic stem cells. Heterozygous germline mutations in DNMT3A lead to Tatton-Brown-Rahman Syndrome (TBRS), characterized by obesity and excessive height. While DNMT3A is known to impact feeding behavior via the hypothalamus, here we investigated a role in adipocyte progenitors utilizing heterozygous knockout mice that recapitulate cardinal TBRS phenotypes. These mice become morbidly obese due to adipocyte enlargement and tissue expansion. Adipose tissue in these mice exhibited defects in preadipocyte maturation and precocious activation of inflammatory gene networks, including interleukin-6 signaling. Adipocyte progenitor cell lines lacking DNMT3A exhibited aberrant differentiation. Furthermore, mice in which Dnmt3a was specifically ablated in adipocyte progenitors showed enlarged fat depots and increased progenitor numbers, partly recapitulating the TBRS obesity phenotypes. Loss of DNMT3A led to constitutive DNA hypomethylation, such that the DNA methylation landscape of young adipocyte progenitors resemble that of older wild-type mice. Together, our results demonstrate that DNMT3A coordinates both the central and local control of energy storage required to maintain normal weight and prevent inflammatory obesity.

cell biology↗

bioRxiv2020

Modeling IKZF1 lesions in B-ALL reveals distinct chemosensitivity patterns and potential therapeutic vulnerabilities

IKAROS family zinc finger 1 (IKZF1) alterations represent a diverse group of genetic lesions that are associated with an increased risk of relapse in B-lymphoblastic leukemia (B-ALL). Due to the heterogeneity of concomitant lesions it remains unclear how IKZF1 abnormalities directly affect cell function and therapy resistance and whether their consideration as a prognostic indicator is valuable in improving outcome. We used CRISPR/Cas9 to engineer multiple panels of isogeneic lymphoid leukemia cell lines with a spectrum of IKZF1 lesions in order to measure changes in chemosensitivity, gene expression, cell cycle, and in vivo engraftment dynamics that can be directly linked to loss of IKAROS protein. IKZF1 knockout and heterozygous null cells displayed relative resistance to a number of commonly employed therapies for B-ALL including dexamethasone, vincristine, asparaginase, and daunorubicin. Transcription profiling revealed a stem/myeloid cell-like phenotype and JAK/STAT upregulation after IKAROS loss. We also used a CRISPR homology-directed repair (HDR) strategy to knock-in the dominant-negative IK6 isoform tagged with GFP into the endogenous locus and observed a similar drug resistance profile with the exception of retained sensitivity to dexamethasone. Interestingly, IKZF1 knockout and IK6 knock-in cells both have significantly increased sensitivity to cytarabine, suggesting intensification of nucleoside analog therapy may be specifically effective for IKZF1-deleted B-ALL. Both types of IKZF1 lesions decreased survival time of xenograft mice, with higher numbers of circulating blasts and increased organ infiltration. Given these findings, exact specification of IKZF1 status in patients may be a beneficial addition to risk stratification and could inform therapy. Key pointsO_LIEngineered IKZF1 perturbations result in a stem-cell like expression signature, enhanced engraftment in vivo, and multi-drug resistance C_LIO_LILoss of IKAROS may result in new vulnerabilities due to increased sensitivity to cytarabine and upregulation of JAK/STAT and mAb targets C_LI

cancer biology↗