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Loss of Sbds in zebrafish leads to neutropenia and pancreas and liver atrophy
Usua Oyarbide, … , Jacek Topczewski, Seth J. Corey
Usua Oyarbide, … , Jacek Topczewski, Seth J. Corey
Published August 6, 2020
Citation Information: JCI Insight. 2020;5(17):e134309. https://doi.org/10.1172/jci.insight.134309.
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Research Article Gastroenterology Hematology

Loss of Sbds in zebrafish leads to neutropenia and pancreas and liver atrophy

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Abstract

Shwachman-Diamond syndrome (SDS) is characterized by exocrine pancreatic insufficiency, neutropenia, and skeletal abnormalities. Biallelic mutations in SBDS, which encodes a ribosome maturation factor, are found in 90% of SDS cases. Sbds–/– mice are embryonic lethal. Using CRISPR/Cas9 editing, we created sbds-deficient zebrafish strains. Sbds protein levels progressively decreased and became undetectable at 10 days postfertilization (dpf). Polysome analysis revealed decreased 80S ribosomes. Homozygous mutant fish developed normally until 15 dpf. Mutant fish subsequently had stunted growth and showed signs of atrophy in pancreas, liver, and intestine. In addition, neutropenia occurred by 5 dpf. Upregulation of tp53 mRNA did not occur until 10 dpf, and inhibition of proliferation correlated with death by 21 dpf. Transcriptome analysis showed tp53 activation through upregulation of genes involved in cell cycle arrest, cdkn1a and ccng1, and apoptosis, puma and mdm2. However, elimination of Tp53 function did not prevent lethality. Because of growth retardation and atrophy of intestinal epithelia, we studied the effects of starvation on WT fish. Starved WT fish showed intestinal atrophy, zymogen granule loss, and tp53 upregulation — similar to the mutant phenotype. In addition, there was reduction in neutral lipid storage and ribosomal protein amount, similar to the mutant phenotype. Thus, loss of Sbds in zebrafish phenocopies much of the human disease and is associated with growth arrest and tissue atrophy, particularly of the gastrointestinal system, at the larval stage. A variety of stress responses, some associated with Tp53, contribute to pathophysiology of SDS.

Authors

Usua Oyarbide, Arish N. Shah, Wilmer Amaya-Mejia, Matthew Snyderman, Margaret J. Kell, Daniela S. Allende, Eliezer Calo, Jacek Topczewski, Seth J. Corey

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Figure 5

Transcriptional analysis identifies the upregulation of Tp53-associated genes, whereas Western blotting demonstrates a decrease in ribosomal proteins.

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Transcriptional analysis identifies the upregulation of Tp53-associated ...
RNA-Seq results. (A) Bioinformatic analysis of differentially expressed genes. (B) Gene enrichment analysis. (C) Heatmap of selected genes in Tp53 and pentose phosphate pathways. Relative expression based on fragments per kilobase of transcript per million mapped reads (FPKM) values significantly different between sbds mutants and WT. The color scale at the bottom represents the expression level, where red, blue, and white colors indicate upregulation, downregulation, and unaltered expression, respectively, on FPKM values. RT-qPCR analysis (D) mRNA levels at different time points of genes related to Tp53 pathway. (E) Western blotting at 10 dpf, 3 biological replicates for sbds+/+ and sbdsnu132/nu132. Two independent experiments with N = 3 each. (F) Quantification of Western blots using ImageJ (NIH). Statistical analysis was performed using the t test. *P < 0.05, **P < 0.001, ***P < 0.0001.

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