Biology subjects

Yien, Y. Y.

Publications and source records attributed to Yien, Y. Y..

4 recordsLinked to original sources

bioRxiv2023

FAM210B is dispensable for erythroid differentiation in adult mice

Iron is required for redox homeostasis but poses toxicity risks due to its redox activity. Erythropoiesis hence requires tight regulation of iron utilization for hemoglobin synthesis. The requirement for iron in erythropoiesis has necessitated the evolution of mechanisms to handle the iron required for hemoglobinization. FAM210B was identified as a regulator of mitochondrial iron import and heme synthesis in erythroid cell culture and zebrafish models. Here, we demonstrate that while FAM210B is required for erythroid differentiation and heme synthesis under standard cell culture conditions, holotransferrin supplementation was sufficient to chemically complement the iron-deficient phenotype. To investigate the role of FAM210B in erythropoiesis, we used knockout mice. While Fam210b-/- mice were viable and did not exhibit overt erythropoietic defects in the bone marrow, the male mice exhibited an increase in serum transferrin suggesting sex-specific alterations in systemic iron sensing. Upon phlebotomy-induced stress erythropoiesis, Fam210b-/- mice exhibited differences in serum transferrin levels, and more starkly, had markedly smaller spleens indicating defects in stress response. Fam210b-/- males had defects in neutrophil and monocyte numbers, as well as decreased erythroid progenitor numbers during erythropoietic stress. Together, our findings show that Fam210b plays a key role in splenic response to erythropoietic stress Our findings reveal a critical role for FAM210B in mediating splenic stress erythropoiesis and suggest it may act as a sex-specific regulator potentially linked to androgen signaling.

developmental biology↗

bioRxiv2022

Regulation of iron transport is required for terminal erythroid differentiation even under iron-replete conditions that are sufficient for hemoglobinization

Iron metabolism drives key erythropoietic processes, including hemoglobinization, survival, and proliferation. Here, we developed in vivo methods to interrogate how iron regulates erythropoiesis and report that mitochondrial iron transport via MFRN1 is essential for erythroid cell cycle progression. mfrn1 embryos had severely decreased erythroid cell number caused by cell cycle arrest at G2/M. They had enlarged nuclei, suggesting a mitotic defect. Iron supplementation rescued the cell cycle defect, implicating mitochondrial iron deficiency as its cause. In contrast, fpn1 mutants, anemic from systemic iron deficiency, had less severe decreases in erythroid mitochondrial iron than mfrn1 mutants and no proliferative defects. scRNAseq and FACS analyses for cd41 (thrombocytic) and gata1 reporters indicated that developmental defects in mfrn1 mutants were largely erythroid restricted. mfrn1 mutant gata1+ erythroid progenitors were severely decreased at 3 dpf, and a further decrease in globin- expressing terminally differentiating erythroid cells. While wild-type erythroid cells mostly lost expression of the gata1 progenitor marker by 3 dpf, mfrn1 mutant erythroid cells retained gata1 expression. These data are consistent with a model where mitochondrial iron transport facilitates development of gata1+ erythroid progenitors and is required for the completion of erythropoiesis by facilitating mitosis in the terminal cell cycles. Key pointsO_LIMitochondrial iron import through MFRN1 is required for progress through the G2/M checkpoint in the terminal cell cycles leading to terminal erythroid differentiation. C_LIO_LIMitochondrial iron supply through MFRN1 is required for maintenance/proliferation of erythroid progenitors and terminal maturation into globin expressing erythroid cells. C_LI

biochemistry↗

bioRxiv2021

Adaptation of peristaltic pumps for laminar flow experiments

Endothelial cells (ECs) are the primary cellular constituent of blood vessels that are in direct contact with hemodynamic forces over the course of a lifetime. Throughout the body, vessels experience different types of blood flow patterns and rates that alter vascular architecture and cellular behavior. Because of the complexities of studying blood flow in an intact organism, particularly during development, modeling of blood flow in vitro has become a powerful technique for studying hemodynamic dependent signaling mechanisms in ECs. While commercial flow systems that recirculate fluids exist, many commercially available pumps are peristaltic and best model pulsatile flow conditions. However, there are many important in vivo situations in which ECs experience laminar flow conditions, such as along long, straight stretches of the vasculature. To understand EC function under these situations, it is important to be able to consistently model laminar flow conditions in vitro. Here, we outline a method to reliably adapt commercially available peristaltic pumps to reproducibly study laminar flow conditions. Our proof of concept study focuses on 2-dimensional (2D) models but could be further adapted to 3-dimensional (3D) environments to better model in vivo scenarios such as organ development. Our studies make significant inroads into solving technical challenges associated with flow modeling, and allow us to conduct functional studies towards understanding the mechanistic role of flow forces on vascular architecture, cellular behavior, and remodeling during a variety of physiological contexts.

cell biology↗

bioRxiv2020

CLPX regulates erythroid heme synthesis by control of mitochondrial heme synthesis enzymes and iron utilization

Heme is a prosthetic group that plays a critical role in catalyzing life-essential redox reactions in all cells, including critical metabolic processes. Heme synthesis must be tightly co-regulated with cellular requirements in order to maximize utilization and minimize toxicity. Terminally differentiating erythroid cells have an extremely high demand for heme for hemoglobin synthesis. While the enzymatic reactions of heme synthesis are extremely well studied, the mechanisms by which the mitochondrial homeostatic machinery interacts with and regulates heme synthesis are poorly understood. Knowledge of these regulatory mechanisms are key to understanding how red cells couple heme production with heme demand. Heme synthesis is tightly regulated by the mitochondrial AAA+ unfoldase CLPX, which has been reported to promote heme synthesis by activation of yeast {delta}-aminolevulinate synthase (ALAS/Hem1). CLPX was also reported to mediate heme-induced turnover of ALAS1 in human cells. However, a mutation in the ATP binding domain of CLPX that abrogated ATP binding caused an increase in ALAS activity, contrary to previous predictions that CLPX activated ALAS. Using loss-of-function assays in murine cells and zebrafish, we interrogated the mechanisms by which CLPX regulates erythroid heme synthesis. We found that consistent with previous studies, CLPX is required for erythroid heme synthesis. We show that ALAS2 stability and activity were both increased in the absence of CLPX, suggesting that CLPX primarily regulates ALAS2 by control of its turnover. However, we also showed that CLPX is required for PPOX activity and maintenance of FECH levels, likely accounting for the heme deficiency in the absence of CLPX. Lastly, CLPX is required for iron metabolism during erythroid terminal differentiation. Our results show that the role of CLPX in heme synthesis is not conserved across eukaryotes. Our studies reveal a potential mechanism for the role of CLPX in anemia and porphyria, and reveal multiple nodes at which heme synthesis is regulated by the mitochondrial housekeeping machinery.

biochemistry↗