Comparison of the Differing Impacts of Lowered N-Acetylglucosaminyltransferase-Ia/b Activity on Motor and Sensory Function in Zebrafish

Background/Objectives: Perturbation in terminal N-glycan processing is a feature of congenital disorders of glycosylation and neurological disorders. Since treatment options are limited, N-glycans are plausible therapeutic targets. Here, we investigated the consequences of substituting complex/hybrid with oligomannose types of N-glycans on nervous and musculature systems, employing mgat1a and mgat1b mutant zebrafish models. Methods: CRISPR Cas9 technology was employed to engineer the mgat1a zebrafish model. The N-glycan populations in Wt AB, mgat1a−/− and mgat1b−/− zebrafish were characterized via lectin blotting. Motor and sensory functions were measured by tail-coiling and touch-evoked response assays in embryos and larvae. Swimming locomotion and anxiety-like behavior were characterized in adult Wt AB, and mutant zebrafish using motility and novel tank dive assays. Results: The mgat1a−/− model had increased oligomannosylated proteins compared to Wt AB in embryos and dissected brain, spinal cord, skeletal muscle, heart, swim bladder, and skin from adults, supporting a global knockdown of GnT-I activity. Higher levels were also observed in mgat1a−/− relative to mgat1b−/−, except in the brain. Band patterns for oligomannosylated proteins were different between all three zebrafish lines. The mgat1−/− embryos and larvae had deficient motor and sensory functions which persisted into adulthood, with a higher deficiency in mgat1b−/−. Anxiety-like behavior was decreased and increased in adult mgat1a−/− and mgat1b−/−, respectively, compared to Wt AB. Conclusions: Taken together, this study revealed that aberrant terminal N-glycan processing impacts brain, spinal and muscle control, and hence will enhance our understanding of the vital role of complex/hybrid N-glycans in nervous system health.