Erythroid differenfiafion is controlled at the transcripfional level by the cell-specific DNA-binding proteins SCL and GATA1. Using zebrafish genefics, we found a new differentiation checkpoint in erythroid cells that likely ensures successful maturafion. We undertook the flrst recessive suppressor screen in vertebrates to find a novel mutant that can recover erythropoiesis in the background ofthe anemic zebrafish mutant moonshine. Moonshine encodes the zebrafish ortholog of transcripfional intermediary factor 1 gamma (TIFly), and the first suppressor of moonshine encoded cdc73, a chromatin factor involved in transcripfion elongafion. Moonshine mutants have paused blood-specific RNA transcripts, and cdc73 deficiency allows elongafion to occur and rescues erythroid gene expression. TIFly binds to the SCL transcription factor complex and PTEFb, the kinase that phosphorylates pol II and regulates the elongation of RNA transcripts. We have examined the hematopoiefic phenotype of a condifional mouse knockout for TIFly. Bone marrow erythropoiesis is defective, myelopoiesis is increased, and there is a severe deficiency of B cells. We plan to evaluate transcripfion elongation in erythroid and myeloid progenitors of this mouse mutant. Transplantafion experiments are planned to evaluate a putative stem cell funcfional defect and the autonomy ofthe red cell defect. We will establish if the differenfiafion checkpoint is acfivated in diseases such as hypochromic anemias or membrane assembly defects. HEXIM 1 was originally identified as a gene induced during MEL differenfiation, and it complexes with other proteins and 7SK RNA to regulate P-TEFb activity. We hypothesize that HEXIM complexes could serve as a sensor of erythroid differenfiafion. We plan to define the binding partners of HEXIM in erythroid cells, and to evaluate the funcfion ofthe HEXIM complex subunits during erythropoiesis in fish and mice. The function ofthe 7SK RNA component of HEXIM will be invesfigated. A new sequencing technology will determine if other small RNAs are bound to the HEXIM complex. The regulation of transcription elongation in the differentiation checkpoint of erythroid cells wili be relevant to diseases such as thalassemia, sickle cell anemia, iron deflciency, and membrane defects.
Differentiation is an important process for many cells, and is regulated by nuclear factors that establish a specific cell fate. We discovered a new mechanism by which differentiation is monitored in erythroid cells. We will examine if this checkpoint is activated in common blood disorders. These studies will have impact on our treatment of blood diseases such as thalassemia, sickle cell anemia, and membrane defects.
|Pishesha, Novalia; Thiru, Prathapan; Shi, Jiahai et al. (2014) Transcriptional divergence and conservation of human and mouse erythropoiesis. Proc Natl Acad Sci U S A 111:4103-8|
|Alvarez-Dominguez, Juan R; Hu, Wenqian; Gromatzky, Austin A et al. (2014) Long noncoding RNAs during normal and malignant hematopoiesis. Int J Hematol 99:531-41|
|Ludwig, Leif S; Gazda, Hanna T; Eng, Jennifer C et al. (2014) Altered translation of GATA1 in Diamond-Blackfan anemia. Nat Med 20:748-53|
|Chen, Cynthia; Lodish, Harvey F (2014) Global analysis of induced transcription factors and cofactors identifies Tfdp2 as an essential coregulator during terminal erythropoiesis. Exp Hematol 42:464-76.e5|
|Hagedorn, Elliott J; Durand, Ellen M; Fast, Eva M et al. (2014) Getting more for your marrow: boosting hematopoietic stem cell numbers with PGE2. Exp Cell Res 329:220-6|
|Yien, Yvette Y; Robledo, Raymond F; Schultz, Iman J et al. (2014) TMEM14C is required for erythroid mitochondrial heme metabolism. J Clin Invest 124:4294-304|
|Cheng, Albert W; Shi, Jiahai; Wong, Piu et al. (2014) Muscleblind-like 1 (Mbnl1) regulates pre-mRNA alternative splicing during terminal erythropoiesis. Blood 124:598-610|
|Shmukler, Boris E; Reimold, Fabian R; Heneghan, John F et al. (2014) Molecular cloning and functional characterization of zebrafish Slc4a3/Ae3 anion exchanger. Pflugers Arch 466:1605-18|
|Hu, Wenqian; Yuan, Bingbing; Lodish, Harvey F (2014) Cpeb4-mediated translational regulatory circuitry controls terminal erythroid differentiation. Dev Cell 30:660-72|
|Chung, Jacky; Anderson, Sheila A; Gwynn, Babette et al. (2014) Iron regulatory protein-1 protects against mitoferrin-1-deficient porphyria. J Biol Chem 289:7835-43|
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