Transcriptional Control of Hemoglobin Synthesis and Erythrocyte Development

PROJECT SUMMARY
Hemoglobin synthesis and erythrocyte development are often studied independently, yet their mechanisms are
inextricably linked. Differentiation defects yield immature precursors, and impaired hemoglobin synthesis causes
ineffective erythropoiesis. A common thread of these mechanisms is GATA transcription factor involvement.
Many questions remain regarding how GATA factor networks instruct progenitors to generate vast numbers of
erythrocytes, which broadly informs molecular/cellular biology and hematology. We discovered: 1) locus-specific
coregulator utilization by GATA1 to control differentiation; 2) GATA factor/regeneration-activated enhancer
confers expression of an unstudied sterile alpha motif domain protein that controls erythrocyte regeneration; 3)
GATA factor-regulated zinc transporter switch governs differentiation; 4) mechanism of heme targeting chromatin
genome-wide; 5) GATA factor-regulated solute carrier protein (SLC) cohort transports diverse small molecules
to control erythropoiesis. Our multi-omic work supports the aims to analyze how GATA factors establish small
molecule ensembles that target the genome and regulate the GATA factor to ensure differentiation. Aim 1 will
dissect a multi-component mechanism by which GATA1 and heme control genome function and
erythrocyte development. GATA1 activates genes mediating heme biosynthesis, heme facilitates or restricts
GATA1 function and heme downregulates GATA1. Heme regulates transcription by downregulating the
repressor Bach1, and we discovered a Bach1-independent heme-regulated mechanism. We hypothesize that
Bach1-dependent and -independent mechanisms establish critical erythroid functions, and these mechanisms
provide translational opportunities. Using all heme target genes and a gene-specific approach, we will establish
the mechanisms. Aim 2 will elucidate a GATA factor-dependent small molecule transporter axis that
regulates erythroid differentiation. We hypothesize that diverse small molecules function in GATA factor
mechanisms and discovering GATA factor-regulated solute carrier (Slc) transporters will unveil new dimensions
to these mechanisms. We defined a GATA1/2-regulated Slc cohort that transports diverse small molecules. We
prioritized a subset with GATA factor-occupied predicted enhancers and will elucidate mechanisms that link
GATA factors with small molecule ensembles and differentiation. Aim 3 will test models for how GATA1
instigates a sphingolipid-dependent regulatory network. GATA1-regulated Slcs included sphingolipid
transporters. Lipidomics revealed GATA1-induced sphingolipid remodeling. Ceramide synthase inhibition blocks
GATA1-mediated GATA2 downregulation, β-globin induction and erythroid maturation. Sphingolipid signaling
controls apoptosis, proliferation and migration, high S1P is deleterious in sickle cell disease, and human
ceramide deficiency involves disrupted erythropoiesis. We hypothesize that sphingolipidome regulation by
GATA1 is vital in biology and pathology. We will develop basic and translational insights into GATA factor
mechanisms governing small molecules that control GATA factors, globin synthesis and differentiation.

Grant Number: 5R01DK050107-29
NIH Institute/Center: NIH
Principal Investigator: Emery Bresnick