Discipline: Biological Sciences
Subcategory: Cell and Molecular Biology
Briana Davis - North Carolina Central University
Co-Author(s): Lara J. Duffney and Yong-Hui Jiang, Duke University, Durham, NC
Autistic spectrum disorders (ASDs) represent a wide range of developmental disorders that are primarily characterized by impairments in social communication and restricted or repetitive behaviors. Although the neurobiological causes of ASD remain unclear, previous studies have implicated SHANK gene mutations as one of the missing pieces in its pathogenesis. Shank proteins form a scaffold in the postsynaptic ending of excitatory neurons that stabilizes receptors that are crucial for proper transmission of chemical and electrical signals in the brain. Additionally, Shank proteins anchored to the cytoskeleton of dendrites contribute to the maturation and formation of dendritic spines, which influences synaptic plasticity or changes in synaptic activity that are believed to shape memory and learning. Repetitive behaviors such as hand flapping observed in ASD patients are analogous to repetitive, self-injurious grooming behavior observed in mouse models. The first objective of this study was to use behavioral testing in order to compare grooming behavior of double knockout (dKO) mice (SHANK 2-/- and SHANK3-/-) to SHANK2-/- and SHANK3-/- mutant mice highlighted in ASD. There are previous studies that indicate SHANK3-/- mice exhibit repetitive self-grooming, but there is no data implicating this behavior in SHANK2-/-mice. This current study sought to investigate these differences by comparing dKO mice to SHANK2-/- and SHANK3-/- mutant mice and wild-type (WT) mice. It was hypothesized that the dKO mice would exhibit intermediate grooming behavior that resembled a midpoint between SHANK3-/- and SHANK2-/- mutant mice. Behavioral analysis involved observing the mice in an unfamiliar cage over a ten-minute period with the total time spent grooming recorded via stopwatch. This study also utilized a cellular approach to identify if significant morphological differences exist between the dendritic spines of neurons found in WT and dKO mice. Previous literature points to abnormalities that are seen in SHANK3-/- mice compared to wild-type, where the longer, thinner spines of the mutant mice are indicative of less mature spines. Despite these reports, there is very little data regarding dKOs. It was hypothesized that the dKO mice would have fewer and less mature spines than the wild-type mice. An FD Rapid GolgiStain Kit was utilized in order to prepare mouse brain tissue for staining and Golgi imaging. At the conclusion of this study, no significant difference between the mouse genotypes for average grooming time was found. A repeated experiment with increased sample size may yield more significant results. Further analysis of Golgi images is needed to draw conclusions regarding morphological changes relevant to dendritic spine formation and maturity. If there is evidence to support abnormalities in the dendritic spines of dKO mice, additional experiments will be conducted to associate these abnormalities with brain regions implicated in behavioral deficits.
Funder Acknowledgement(s): Duke Summer Research Opportunity Program
Faculty Advisor: Tonya Gerald Goins, email@example.com
Role: I completed the analysis of the mouse grooming behavior. While being blinded to the genotype, I recorded via stopwatch the amount of time that the mouse spent grooming during a ten-minute period after being placed in an unfamiliar cage. Additionally, I collaborated with an undergraduate student to stain slides containing sliced brain tissue while using the FD Rapid GolgiStain Kit. I was responsible for using the prepared slides to take images of the dendritic spines for both the WT and dKO mice utilizing a Lecia compound light microscope and companion software.