Abstract
Purpose :
Genetic Leukoencephalopathies (gLEs) are white matter disorders affecting the central nervous system, causing progressive abnormalities in visual and motor systems. A mutation in Vacuolar Protein Sorting 11 (VPS11) has been identified in humans as a causative allele of gLE. Functioning with VPS11, VPS16 forms membrane-tethering complexes that control crucial cellular processes in the endolysosomal pathway. However, the role of VPS16 in gLE is unknown. Here, we are characterizing the behavioral responses of a zebrafish vps16 mutant line as potential model for gLE.
Methods :
Immunohistochemistry and TUNEL were used to assess retinal and brain pathology and hypomyelination at 7 days post-fertilization (dpf). Behavioral assays were used at 5 and 7dpf to assess evoked visuomotor responses, short-term memory (habituation), and long-term memory (using various time periods between two habituation stimuli). Appropriate statistical analyses were used to determine differences between wild-type and mutant animals.
Results :
Immunohistochemical and TUNEL analysis indicated that vps16 mutant larva showed retinal and brain pathology, including hypomyelination and increased apoptosis. Behavioral analysis showed that mutants could visualize changes in light/dark backgrounds but showed a progressive loss of distance moved and velocity from 5-7dpf. Mutants showed signs of short-term memory (habituation to 10 consecutive tap stimuli) but habituated faster than wild-type siblings. Finally, in response to two sets of multiple taps with 2min, 5min or 30min rest periods in between, both wild-type and mutant larva “remembered” the first habituation response after a 2min rest. After 5min, wild-type animals still “remembered” the first response, but mutant animals did not. Finally, after 30min, neither group “remembered” the first habituation event and responded to the second set as a novel habituation stimulus. Together, these results suggest that loss of Vps16 function has a progressive adverse effect on larval zebrafish visual, motor, and cognitive systems, which is consistent with their hypomyelination phenotype.
Conclusions :
Our findings support the use of zebrafish to further characterize behavioral defects associated with gLE and provide the first insights into impaired Vps16 function.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.