HSCI Retreat 2020 Abstract 11

Transcriptional Regulation of Mitochondrial Metabolism by TIF1γ Drives Erythroid Progenitor Differentiation

Marlies P. Rossmann,*1,2 Karen Hoi,1,2 Victoria Chan,1,2 Julie R. Perlin,2 Elliott J. Hagedorn,2 Brian J. Abraham,#3 Song Yang,2 Sejal Vyas,4 Partha P. Nag,5 Lucas B. Sullivan,6 Curtis R. Warren,7 Bilguujin Dorjsuren,1,2 Eugenia Custo Greig,1,2 Isaac Adatto,1,2 Chad A. Cowan,7 Stuart L. Schreiber,5 Richard A. Young,3,8 Marcia Haigis,4 and Leonard I. Zon1,2
1 Department of Stem Cell and Regenerative Biology, Harvard University, Cambridge, MA, USA 
2 Stem Cell Program and Division of Hematology/Oncology, Boston Children's Hospital and Dana-Farber Cancer Institute, Howard Hughes Medical Institute, Harvard Stem Cell Institute, Harvard Medical School, Boston, MA, USA 
3 Whitehead Institute for Biomedical Research, Cambridge, MA, USA
4 Department of Cell Biology, Harvard Medical School, Boston, MA, USA 
5 Broad Institute of MIT and Harvard, Cambridge, MA, USA 
6 Fred Hutchinson Cancer Research Center, Seattle, WA, USA 
7 Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA
8 Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA

* Presenting and corresponding author: rossmann@fas.harvard.edu  

# Current address: Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN, USA

Submitted: Jun 11, 2020; Published online: Jul 27, 2020



Understanding in-vivo mechanisms of hematopoiesis is critical for developing directed blood differentiation approaches. Zebrafish moonshine (mon) mutant embryos defective for the conserved transcriptional intermediary factor 1 gamma (tif1γ) do not specify enough erythroid progenitors. To elucidate the TIF1γ-mediated mechanisms in erythroid differentiation, we performed a chemical suppressor screen and identified inhibitors of the essential mitochondrial pyrimidine synthesis enzyme dihydroorotate dehydrogenase (DHODH). Leflunomide as well as the structurally unrelated DHODH inhibitor brequinar rescue the formation of erythroid progenitors in 61% (38/62) and 68% (50/74) of mon embryos, respectively. In-vivo metabolomics analyses identified nucleotide metabolism as the most significantly altered process in mon mutants, with elevated levels of uridine monophosphate. This increase is functionally linked to a reduced oxygen consumption rate. DHODH is the only enzyme of the pyrimidine de novo synthesis pathway located on the inner mitochondrial membrane and its activity is coupled to that of the electron transport chain (ETC) via coenzyme Q (CoQ). Rotenone, a potent ETC complex I inhibitor reverses the rescue of the erythroid progenitor defect by DHODH inhibition in mon embryos. Through parallel genome-wide transcriptome and chromatin immunoprecipitation analyses, we found that genes encoding CoQ metabolic enzymes are direct TIF1γ targets. Treatment with the CoQ analog decylubiquinone results in rescue of erythroid progenitors in 26% (33/126) of mon embryos. Our work highlights the importance of transcription regulatory processes for tuning metabolism to drive cell fate decisions during lineage differentiation and could have therapeutic implications for blood diseases.