Mammalian sialidase Neu1 is involved in various physiological functions, including cell adhesion, differentiation, cancer metastasis, and diabetes through lysosomal catabolism and desialylation of glycoproteins at the plasma membrane. Various animal models have been established to further explore the functions of vertebrate Neu1. The present study focused on zebrafish (Danio rerio) belonging to Cypriniformes as an experimental animal model with neu1 gene deficiency. The results revealed that the zebrafish Neu1 desialyzed both α2-3 and α2-6 sialic acid linkages from oligosaccharides and glycoproteins at pH 4.5, and it is highly conserved with other fish species and mammalian Neu1. Furthermore, Neu1-knockout zebrafish (Neu1-KO) was established through CRISPR/Cas9 genome editing. Neu1-KO fish exhibited slight abnormal embryogenesis with the accumulation of pleural effusion; however, no embryonic lethality was observed. Although Neu1-KO fish were able to be maintained as homozygous, they showed smaller body length and weight than the wild-type (WT) fish, and muscle atrophy and curvature of the vertebra were observed in adult Neu1-KO fish (8 months). The expression patterns of myod and myog transcription factors regulating muscle differentiation varied between Neu1-KO and WT fish embryo. Expression of lysosomal-related genes, including ctsa, lamp1a, and tfeb were up-regulated in adult Neu1-KO muscle as compared with WT. Furthermore, the expression pattern of genes involved in bone remodeling (runx2a, runx2b, and mmp9) was decreased in Neu1-KO fish. These phenotypes were quite similar to those of Neu1-KO mice and human sialidosis patients, indicating the effectiveness of the established Neu1-KO zebrafish for the study of vertebrate Neu1 sialidase.

中文翻译：

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Neu1基因敲除斑马鱼的建立和表征及其异常的临床表型。

哺乳动物唾液酸酶Neu1通过溶酶体分解代谢和质膜糖蛋白的去唾液酸化作用参与各种生理功能，包括细胞粘附，分化，癌症转移和糖尿病。已经建立了各种动物模型以进一步探索脊椎动物Neu1的功能。本研究集中于斑马鱼（Danio rerio）属于Cyniniformes作为具有neu1基因缺陷的实验动物模型。结果表明，斑马鱼Neu1在pH为4.5时会从寡糖和糖蛋白中脱唾液酸化α2-3和α2-6唾液酸键，与其他鱼类和哺乳动物Neu1高度保守。此外，通过CRISPR / Cas9基因组编辑建立了Neu1-knockout斑马鱼（Neu1-KO）。Neu1-KO鱼表现出轻微的异常胚胎发生，并伴有胸腔积液。但是，没有观察到胚胎致死性。尽管Neu1-KO鱼能够保持纯合，但它们的体长和体重比野生型（WT）鱼小，成年Neu1-KO鱼（8个月）观察到肌肉萎缩和椎骨弯曲。Neu1-KO和野生型鱼胚胎之间调节肌肉分化的myod和myog转录因子的表达模式有所不同。与野生型相比，成年Neu1-KO肌肉中溶酶体相关基因（包括ctsa，lamp1a和tfeb）的表达上调。此外，在Neu1-KO鱼中，参与骨骼重构的基因（runx2a，runx2b和mmp9）的表达模式降低了。