Graduation Date

Spring 5-4-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Molecular Genetics & Cell Biology

First Advisor

Kyle J. Hewitt

MeSH Headings

Hematology, Anemia, Genetics, Cell Biology, Genomics

Abstract

Produced by steady state erythropoiesis, erythrocytes serve as vital regulators of metabolism and life by delivering oxygen to all the cells and tissues. Under acute anemia, steady state erythropoiesis is not sufficient to produce enough erythrocytes, leading to distinct mechanisms needed to regenerate large numbers of mature erythrocytes rapidly. Erythroid regeneration occurs in four stages: activation, expansion and differentiation, resolution, and post-resolution, according to the dynamics of erythrocyte numbers and progenitor activity. Erythroid regeneration throughout this timeline requires some critical extracellular cues, but the intrinsic molecular mechanisms needed to accelerate and decelerate the activity of erythroid progenitors in anemia and recovery are poorly understood. Unraveling the key transcription factors (TFs) and transcriptional mechanisms can reveal important fundamental principles of regenerative processes and relate it to disease states like chronic anemia and leukemia.

During erythroid regeneration, broad transcriptional changes are found in erythroid progenitors and precursors. Prior work revealed that an erythropoiesis-promoting cis-regulatory element (CRE) controlled by erythroid TFs GATA1/2 and TAL1 increases transcription of the Samd14 gene during erythroid regeneration, thereby accelerating erythropoiesis in anemia. My dissertation research identified a cohort of anemia-specific CREs with similar molecular features to Samd14 at the expansion and differentiation stage of erythroid regeneration. In addition, we discovered that stage-specific CREs in early activation stages have distinct features associated with AP-1 activity. To comprehensively analyze changes to chromatin accessibility, we generated ATAC-seq data over a 35-day time course post-anemia, encompassing all stages of erythroid regeneration. We found that ETS motifs are enriched, and GATA family motifs are depleted at the post-resolution stage. These findings revealed distinct chromatin accessibility dynamics before, during, and after acute anemia resolution. Remarkably, many of these dynamic changes to chromatin accessibility are at genomic regions containing naturally occurring genetic variants associated with human blood phenotypes.

Overall, these studies build a transcriptional and chromatin accessibility map through the stages of erythroid regeneration, revealing stage-specific CRE and TF activation during erythroid regeneration. Given the recent development of CREs editing-based gene therapy strategies in treating sickle cell disease and beta-thalassemia, investigating cis-regulatory mechanisms through different stages of erythroid regeneration will not only elucidate the stress erythropoiesis regulation but also shed light on new therapeutic targets of treating anemia.

Comments

2024 Copyright, the authors

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Available for download on Thursday, April 23, 2026

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