Zebrafish mutants provide insights into Apolipoprotein B functions during embryonic development and pathological conditions
Hanoch Templehof, Noga Moshe, Inbal Avraham-Davidi, Karina Yaniv
Hanoch Templehof, Noga Moshe, Inbal Avraham-Davidi, Karina Yaniv
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Research Article Development Vascular biology

Zebrafish mutants provide insights into Apolipoprotein B functions during embryonic development and pathological conditions

Abstract

Apolipoprotein B (ApoB) is the primary protein of chylomicrons, VLDLs, and LDLs and is essential for their production. Defects in ApoB synthesis and secretion result in several human diseases, including abetalipoproteinemia and familial hypobetalipoproteinemia (FHBL1). In addition, ApoB-related dyslipidemia is linked to nonalcoholic fatty liver disease (NAFLD), a silent pandemic affecting billions globally. Due to the crucial role of APOB in supplying nutrients to the developing embryo, ApoB deletion in mammals is embryonic lethal. Thus, a clear understanding of the roles of this protein during development is lacking. Here, we established zebrafish mutants for 2 apoB genes: apoBa and apoBb.1. Double-mutant embryos displayed hepatic steatosis, a common hallmark of FHBL1 and NAFLD, as well as abnormal liver laterality, decreased numbers of goblet cells in the gut, and impaired angiogenesis. We further used these mutants to identify the domains within ApoB responsible for its functions. By assessing the ability of different truncated forms of human APOB to rescue the mutant phenotypes, we demonstrate the benefits of this model for prospective therapeutic screens. Overall, these zebrafish models uncover what are likely previously undescribed functions of ApoB in organ development and morphogenesis and shed light on the mechanisms underlying hypolipidemia-related diseases.

Authors

Hanoch Templehof, Noga Moshe, Inbal Avraham-Davidi, Karina Yaniv

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Figure 3

Gut development is impaired in apoB mutants.

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Gut development is impaired in apoB mutants. (A and B) WISH showing the ...
(A and B) WISH showing the spatial expression of fabp2 at 2 (A) and 4 (B) dpf. (C–E) Confocal images at 4 dpf of WT (C), apoBa–/– apoBb.1MO (D), and mtpMO (E) embryos in the TgBAC(cldn15la-GFP)pd1034 reporter background, stained with phalloidin (red). Enlarged lumen caliber (arrow) is detected in apoBa–/– apoBb.1MO and mtpMO embryos, as quantified (F) (n = 2, nWT = 17, napoBa–/– apoBb.1MO = 15, nmtpMO = 16). The data are shown as the mean ± SEM, calculated using ANOVA followed by Tukey’s multiple-comparison test. *P < 0.05. (G and H) Confocal images of the guts of 4 dpf apoBa–/– and apoBa–/– apoBb.1MO embryos stained with Nile red, show no lipid accumulation. (I and J) Bright-field images of 5 dpf embryos stained with Alcian blue showing reduced number of goblet cells in apoBa–/– apoBb.1–/– double mutants (J) as compared with WT embryos (I), as quantified (K) (n = 3, nWT = 30, napoBa–/– apoBb.1–/– = 27, napoBa–/– apoBb.1MO = 27). The data are shown as the mean ± SEM, calculated using ANOVA followed by Tukey’s multiple-comparison test. ****P < 0.0001. (L) Confocal images at 5 dpf of WT and apoBa–/– apoBb.1MO embryos in the Tg(12xNRE:Egfp) reporter background. (M) Quantification of number of cells displaying active Notch signaling in the guts of WT and apoBa–/– apoBb.1MO embryos. The data are shown as the mean ± SEM, calculated using 2-tailed Student’s t test. Scale bar: (A–E, G, and H) 50 μm, (I, J, and L) 100 μm. **P < 0.01. P < 0.05 (considered significant versus control group).