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Loss of Dnajc21 leads to cytopenia and altered nucleotide metabolism in zebrafish

ABSTRACT: Mutations in the DNAJC21 gene were recently described in Shwachman-Diamond syndrome (SDS), a bone marrow failure syndrome with high predisposition for myeloid malignancies. To study the underlying biology in hematopoiesis regulation and disease, we generated the first in vivo model of Dnajc21 deficiency using zebrafish. Zebrafish dnajc21 mutants phenocopy key SDS patient phenotypes such as cytopenia, reduced growth and defective ribosome biogenesis. We show that cytopenia results from impaired hematopoietic differentiation and cell proliferation, and is accompanied by an expansion of hematopoietic stem and progenitor cells during both embryonic and adult hematopoiesis. The introduction of a tp53 point mutation in the dnajc21 mutants results in myelodysplastic syndrome with erythroid dysplasia as early as four months of age. Using transcriptomic and metabolomic analyses, we show that Dnajc21 regulates various metabolic pathways including nucleotide biosynthesis. Chemical modulation of the pyrimidine biosynthesis pathway in dnajc21 mutants reveals an association with neutrophil differentiation, suggesting a novel mechanism in dnajc21-mutant SDS biology.

ORGANISM(S): Danio rerio

PROVIDER: GSE225613 | GEO | 2023/03/01

REPOSITORIES: GEO

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Project description:Oncogenic signaling of the niche can have a severe effect on the hematopoietic compartment and could contribute or play an active role during the development of human leukemia predisposition syndromes. To provide insights into the mechanisms that underlie this concept, as well as their relevance to disease, this study uses the leukemia predisposition syndrome Shwachman-Diamond syndrome (SDS) as a model. This leukemia predisposition syndrome is established by constitutive homozygous or compound heterozygous loss-of-function mutations in the gene SBDS. SDS is characterized by skeletal defects and a striking predisposition for the development of myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML). Loss of Sbds in the hematopoietic compartment does not results in the induction of MDS or AML, however, could have an indirect effect on the hematopoietic system through the disruption of niche cells.<br>This submission concerns itself with gene expression profiling of transgenic mice. Osterix1 (Osx) is a zinc-finger transcriptional factor essential for osteoblast differentiation in mice and is expressed in cells of the mesenchymal lineage. A bacterial artificial chromosome (BAC) was modified such that it expressed the green fluorescent protein (GFP)::Cre recombinase (GFP::Cre) fusion protein. The artificial construct was inserted into the Osterix gene (Osx1, Sp7), enabling fusion gene GFP::Cre to be expressed from the Osx promotor (Osx1-GFP::Cre) and thereby creating transgenic mice. Cells isolated from these mice are therefore termed Osx::GFP cells. The Osx-GFP-Cre mice were crossed with Sbds f/f (flox/flox, loxp sites are inserted into the gene Sbds enabling the deletion of the region located between these loxp sites) mice to generate the transgenic Osx-GFP-Cre Sbds f/f (OCS) mice. Hence cells expressing the Osx/Sp7 gene therefore express the GFP::Cre fusion protein which enables the prospective isolation of GFP+ cells and it enables the deletion of the Sbds gene through the Cre-mediated recombination of the loxp sites.</br><br> OCS mice have skeletal defects similar to those observed in the human leukemia predisposition syndrome SDS. To obtain a detailed understanding of the underlying mechanisms Osx::GFP+ cells were prospectively isolated from bone cells suspensions, through fluorescence activated cell sorting (FACS), derived from OCS mice. Mutant OCS mice have a homozygous deletion of the Sbds gene in mesenchymal cells (e.g., osteoblasts), while wildtype mice have normal Sbds alleles. The gene expression profiles (GEPs) of both groups of mice were directly compared to determine major transcriptional changes.</br>

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Loss of Dnajc21 leads to cytopenia and altered nucleotide metabolism in zebrafish

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