1. Making sense of the senseless: Evaluating sex differences of ASO
gene therapy in mice with Usher syndrome
Adam M. McNeela1, Kelsey T. Jennings1, Lucia A. Cherep1, Tia N. Donaldson1, Frederic F. Depreux2,
Dr. Michelle L. Hastings2, Dr. Douglas G. Wallace1
Northern Illinois University1
Department of Cell Biology and Anatomy, The Chicago Medical School, Rosalind Franklin2
Introduction
Results .
Figure 8 – Sample progressions are plotted from Figures 2 and 3. These plots demonstrate that females (left panel) mice follow direct progressions and male (right panel) mice follow indirect progressions.
Figure 2 – Exploratory behavior topography is plotted for a representative female mouse.
Figure 3 – Exploratory behavior topography is plotted for a representative male mouse.
Usher syndrome is an autosomal recessive disorder which is caused by mutations in the USH1C gene, which encodes the protein harmonin (Lentz et al., 2013). Harmonin is responsible for the development and maintenance of steriocilia in hair and photoreceptor cells. Consequently, improper splicing of harmonin results in an array of sensory impairments. Although Usher syndrome accounts for approximately 50% of deaf-blindness cases, it also causes vestibular impairments (Ouyang et al., 2004). An antisense oligonucleotide (ASO) gene therapy has been shown to correct the improper splicing of harmonin, thereby rescuing vestibular function (Lentz et al., 2013).
The relationship between spatial navigation and the vestibular system can be studied using an exploratory task in rodents. Throughout exploration where environmental cues are restricted, self-movement cue processing is critical to maintain spatial orientation (Wallace et al., 2008). Furthermore, the vestibular system has been shown to play an important role in self-movement cue processing in rodents (Wallace et al., 2002).
The current study examines self-movement cue processing in Usher mice, as well as gender differences in the effectiveness of an ASO gene therapy. Limited work has been done regarding the role of gender in gene therapies and the results have the potential to provide new insights into effective gene therapies for treating the vestibular impairments of Usher syndrome in human patients.
Figure 9 - Distance ratio was plotted for both groups across the 5 samples. Females exhibited a significantly greater distance ratio than males, indicating more direct paths taken throughout exploration.
Figure 4 – Average change in heading was plotted for both groups across the 5 samples. No significant group differences were observed.
Figure 5 - Average peak speed was plotted for both groups across the 5 samples. No significant group differences were observed.
Methods
Conclusions
Under dark conditions, mice organize their exploratory behavior into stops and progressions..
Females exhibited more direct progressions than males, suggesting that the ASO treatment was more effective in rescuing vestibular function in females.
Males traveled a greater distance than females, which is consistent with the circuitous paths taken by the male mouse (Figure 8).
Future research is needed to examine the persistence of the ASO therapy at 6 months of age as well as the effects under light conditions. Furthermore, work is needed to characterize sex differences in harmonin production as mechanism for the current pattern of results.
Female (n=7) and male (n=7) Usher mice were administered an ASO gene therapy at post-natal day 5. At 2 months of age, open field exploratory behaviors were recorded for 50 minutes under dark conditions. Five (5 minute) samples were analyzed for each mouse and motion capture software was used to quantify kinematic and topographic aspects of exploratory behavior. The data obtained represent total distance traveled, peak speed, distance ratio, movement scaling, and changes in heading across the five samples.
Figure 6 - Total distance was plotted for both groups across the 5 samples. Males traveled a significantly greater distance throughout exploration than females.
Figure 7 – Movement scaling was plotted for both groups across the 5 samples. No significant group differences were observed.
Figure 1- Photograph of exploratory table (122 cm diameter)
References
Lentz, J. J., Jodelka, F. M., Hinrich, A. J., McCaffrey, K. E., Farris, H. E., Spalitta, M. J., … Hastings, M. L. (2013). Rescue of hearing and vestibular function by antisense oligonucleotides in a mouse model of human deafness. Nature Medicine, 1-8.
Ouyang, X. M., Yan, D., Du, L. L., Hejtmancik, J. F., Jacobson, S. G., Nance, W. E., …Liu, X. Z. (2005). Characterization of Usher syndrome type I gene mutations in an Usher syndrome patient population. Human Genetics, 116,
Wallace, D. G., Hines, D. J., Pellis, S. M., Whishaw, I. Q., (2002). Vestibular information is required for dead reckoning in the rat. Journal of Neuroscience. 22(22):
Wallace, D. G., Martin, M. M., & Winter, S. S. (2008). Fractionating dead reckoning: role of the compass, odometer, logbook, and home base establishment in spatial orientation. Naturwissenschaften, 95(11),