Knockout of the gene in zebrafish causes neurodevelopmental defects.

Congenital disorders of glycosylation (CDG) are a cluster of monogenic disorders resulting from defects in glycosylation. encodes fucokinase, an enzyme that catalyzes the phosphorylation of L-fucose to generate fucose-1-phosphate, an important step in fucosylation. Mutations in lead to CDG with an autosomal recessive inheritance pattern, primarily manifesting as developmental delay, hypotonia, and brain abnormalities. However, no mutant animal models have yet been established. This study constructed the first knockout ( ) zebrafish model using CRISPR/Cas9 technology. Notably, zebrafish exhibited impaired growth, characterized by delayed epiboly and DNA accumulation during early embryonic development, as well as brain atrophy in adulthood. Larval-stage zebrafish displayed locomotor deficits and increased susceptibility to pentylenetetrazole-induced seizures. In adulthood, zebrafish showed neurodevelopmental abnormalities, including increased anxiety, decreased aggression, reduced social preference, and impaired memory. Additionally, total protein fucosylation was markedly reduced in zebrafish, accompanied by decreased expression of , which encodes protein O-fucosyltransferase 2, an enzyme involved in the fucosylation salvage pathway. Apoptotic activity was elevated in the midbrain-hindbrain boundary (MHB) of zebrafish. Supplementation with GDP-L-fucose or the human gene restored developmental defects and total protein fucosylation in zebrafish. RNA sequencing revealed dysregulated gene expression associated with glycosylation, apoptosis, and neurodegenerative diseases. These findings suggest that zebrafish exhibit neurodevelopmental disorders, providing the first gene knockout animal model and offering a platform for investigating the molecular underpinnings of the disease and facilitating drug screening efforts.