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The role of Niemann-Pick type C2 in zebrafish embryonic development

ABSTRACT: Niemann-Pick disease type C (NPC) is a rare fatal neurodegenerative lysosomal storage disease caused by mutations of either NPC1 or NPC2. NPC2 is a soluble lysosomal protein that in coordination with NPC1 is responsible for the efflux of unesterified cholesterol from the lysosome. Mutations of both genes cause a similar cellular pathology, that includes the accumulation of unesterified cholesterol and other lipids in the late endosome/lysosome, while reducing cholesterol bioavailability. Here we describe a npc2 null zebrafish model generated by CRISPR/Cas9 gene targeting. Zygotic npc2m/m zebrafish from the intercross of npc2+/m individuals showed significant unesterified cholesterol accumulation at larval stages, and a reduction in body size in adulthood. Additionally, zygotic npc2m/m adults exhibited motor and balance defects shortly before a premature death. These findings mimic defects found in human and mice, however the phenotype at embryonic stages were milder than expected. To address the possible dose protection effects of npc2 mRNA present in the oocyte at the time of fertilization we intercrossed npc2m/m zebrafish to generate Maternal-zygotic (MZ) npc2m/m embryos. MZnpc2m/m zebrafish exhibited significant developmental defects including absent otolith, abnormal head/brain development, curved/twisted body axis, no circulating blood cells, and died by 72 hpf. These developmental defects have not previously been reported in connection with either NPC2 or NPC1. RNA-seq analysis conducted on 30 hpf npc2+/m and MZnpc2m/m embryos revealed a significant reduction in notch3 expression as well as reduction in other downstream genes in the signally pathway such as hey1 and her12 that could be partially rescued by microinjection of a plasmid containing the constitutively active notch3 ICD at the 1-cell stage, suggesting that impaired Notch3 signaling likely underlies some aspects of the developmental defects observed in MZnpc2m/m zebrafish.

ORGANISM(S): Danio rerio

PROVIDER: GSE161867 | GEO | 2021/03/20

REPOSITORIES: GEO

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Project description:In zebrafish, vitellogenic oocytes can incorporate significant amounts of 17β-estradiol released from nearby granulosa cells according to a first-order kinetics, since the steroid low polarity ensures high permeability and affinity for yolk lipids. Estrogen bioactivity is likely, because the maternal mRNA for the estrogen receptor-β2 (ers2a) is highly expressed in ovulated oocytes. This transcript is available for translation in the embryo until its sharp decline from 4 to 8 hours post-fertilization (hpf), being replaced by low levels of zygotic ers2a mRNA from 24 hpf to hatching at 48 hpf, as determined by qRT-PCR. Estrogen receptors-α and -β1 are only expressed zygotically at low levels from 24 hpf onwards. To test the functional role of maternal ers2a mRNA, 1- or 2-cell embryos were injected with 10.3 ng each of morpholino to knockdown translation (MO2-ers2a) of both maternal and zygotic ers2a transcripts, missplicing morpholino (MO3-ers2a) to block post-transcriptionally the zygotic transcript alone, and a nonspecific morpholino (MO-control) as a control. Treatment with MO2-ers2a caused severe malformations in 63% of 1-5 dpf larvae, as compared to 10-11% in those treated with MO3-ers2a and MO2-control. Defects included body growth delay and curved shape, abnormal brain and splanchnocranium development, enlarged and hemorrhagic pericardial cavity, uninflated swim bladder and rudimentary caudal fin with aberrant circular motion. Affected larvae could survive for only 12-14 days. Co-injection of an anti-p53 MO failed to rescue the MO2-ers2a-phenotypes, eliminating the possibility of off-target effects. Pangenomic microarray analysis revealed that 240 and 219 significantly expressed transcripts were up- and down-regulated, respectively, by maternal Ers2a protein deficiency in 8-hpf MO2-ers2a-embryos. Also at 48 hpf, 162 and 120 presumably zygotic transcripts were up- and down-regulated, respectively, but only 18 were in common with each of the 8-hpf sets. Whole-mount in situ hybridization revealed an intensified expression of the genes six3.1 and emx1 in MO2-ers2a-embryos at 24-48 hpf, as compared to controls. These findings suggest the involvement of maternal ers2a mRNA in the epigenetic programming of zebrafish development. MO2-ers2a morphants were compared with MO-control at 8 hpf and 48 hpf. MO2-ers2a is a morpholinos selected to knockdown translation of ers2a mRNA

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The role of Niemann-Pick type C2 in zebrafish embryonic development

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