Iron is required to produce haem and iron-sulphur (Fe-S) clusters, processes thought to occur independently. Here we show that the hypochromic anaemia in shiraz (sir) zebrafish mutants is caused by deficiency of glutaredoxin 5 (grx5), a gene required in yeast for Fe-S cluster assembly. We found that grx5 was expressed in erythroid cells of zebrafish and mice. Zebrafish grx5 rescued the assembly of grx5 yeast Fe-S, showing that the biochemical function of grx5 is evolutionarily conserved. In contrast to yeast, vertebrates use iron regulatory protein 1 (IRP1) to sense intracellular iron and regulate mRNA stability or the translation of iron metabolism genes. We found that loss of Fe-S cluster assembly in sir animals activated IRP1 and blocked haem biosynthesis catalysed by aminolaevulinate synthase 2 (ALAS2). Overexpression of ALAS2 RNA without the 5' iron response element that binds IRP1 rescued sir embryos, whereas overexpression of ALAS2 including the iron response element did not. Further, antisense knockdown of IRP1 restored sir embryo haemoglobin synthesis. These findings uncover a connection between haem biosynthesis and Fe-S clusters, indicating that haemoglobin production in the differentiating red cell is regulated through Fe-S cluster assembly.
The van gogh (vgo) mutant in zebrafish is characterized by defects in the ear, pharyngeal arches and associated structures such as the thymus. We show that vgo is caused by a mutation in tbx1, a member of the large family of Tbox genes. tbx1 has been recently suggested to be a major contributor to the cardiovascular defects in DiGeorge deletion syndrome (DGS) in humans, a syndrome in which several neural crest derivatives are affected in the pharyngeal arches. Using cell transplantation studies, we demonstrate that vgo/tbx1 acts cell autonomously in the pharyngeal mesendoderm and influences the development of neural crest-derived cartilages secondarily. Furthermore, we provide evidence for regulatory interactions between vgo/tbx1 and edn1 and hand2, genes that are implicated in the control of pharyngeal arch development and in the etiology of DGS.
Vertebrate hematopoiesis is regulated by distinct cell-specific transcription factors such as GATA-1 and SCL. Mammalian p45-NFE2 was characterized for its ability to bind the hypersensitive sites of the globin locus control region. NFE2 is a member of a cap'n'collar (CNC) and basic zipper (BZIP) superfamily that regulates gene transcription. It has been implicated in diverse processes such as globin gene expression, oxidative stress, and platelet lineage differentiation. Here, we have isolated the zebrafish ortholog of NFE2. The gene is highly homologous, particularly in the DNA-binding domain. Mapping the zebrafish NFE2 to linkage group 23 establishes a region of chromosomal synteny with human chromosome 12, further suggesting evolutionary conservation. During embryogenesis, the zebrafish gene is expressed specifically in erythroid cells and also in the developing ear. NFE2 expression is lacking in zebrafish mutants that have no hematopoietic cells. An analysis of the sauternes mutant, which carries a mutation in the ALAS-2 gene and thus has defective heme synthesis, demonstrates higher levels of NFE2 expression than normal. This further establishes the block to erythroid differentiation in the sauternes mutant. Our studies demonstrate conservation of the vertebrate genetic program for the erythroid lineage.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.