Browsing by Author "East, Audrey"

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    Can Epigallocatechin gallate (EGCG) Treatment Rescue Hippocampal-Dependent Cognitive Function in a Down Syndrome Mouse Model?
    (Office of the Vice Chancellor for Research, 2016-04-08) East, Audrey; Stringer, Megan; Abeysekera, Irushi; Goodlett, Charles R.; Roper, Randall J.
    Down Syndrome (DS) is caused by the trisomy of human chromosome 21 (Hsa21). Trisomy 21 can cause various behavioral, cognitive, learning and memory deficits. Deficits in hippocampal structure and function have been identified in mouse models of DS and are implicated in cognitive and learning impairments. Mouse models have suggested that deficits in cognitive function are associated with overexpression of Dyrk1a, a gene on Hsa21 found in three copies of individuals with DS. Dyrk1a is a gene that is involved in brain development and function. Ts65Dn DS model mice exhibit trisomy for approximately half of the genes on Hsa21 including Dyrk1a and exhibit cognitive and learning impairments. We are using Ts65Dn mice to test the effects of Epigallocatechin gallate (EGCG), a Dyrk1a inhibitor, on Dyrk1a activity and cognitive function. We hypothesize that EGCG will reduce Dyrk1a activity in the hippocampus and improve hippocampal-dependent spatial learning and memory in the Morris water maze place learning task in Ts65Dn mice. The mice were given daily EGCG treatment (200 mg/kg per day) by means of oral gavage beginning on postnatal day 54 and continuing throughout water maze testing (postnatal days 67-74). Measures of spatial learning included latency and path length to find a submerged platform during acquisition trials (postnatal days 67-73). Memory for the previously learned location of the platform was assessed on a probe trial (postnatal day 74) in which the platform was removed and the amount of time spent swimming in the area of the tank previously containing the platform was measured. These measures allowed us to analyze the mice’s ability to learn and remember the position of the platform and to spatially orient themselves. Preliminary data indicates that EGCG treatment may not be an effective treatment for the spatial learning and memory deficits evident in this mouse model of DS.
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    Deficits in a Radial-Arm Maze Spatial Pattern Separation Task and Cell Proliferation in a Mouse Model for Down Syndrome
    (Office of the Vice Chancellor for Research, 2016-04-08) Stringer, Megan; Podila, Himabindu; Dalman, Noriel; East, Audrey; Roper, Randall J.; Goodlett, Charles R.
    Down syndrome (DS) is caused by three copies of human chromosome 21 (Hsa21) and results in an array of phenotypes including intellectual disability. Ts65Dn mice have three copies of ~50% of the genes on Hsa21 and display many phenotypes associated with DS, including cognitive deficits. DYRK1A is found in three copies in humans with Trisomy 21 and in Ts65Dn mice, and is involved in a number of critical pathways including CNS development. Epigallocatechin-3-gallate (EGCG), the main polyphenol in green tea, inhibits Dyrk1a activity. We have shown that a three-week EGCG treatment normalizes skeletal abnormalities in Ts65Dn mice, yet did not rescue deficits in the Morris water maze spatial learning task or novel object recognition. The current study investigated deficits in a radial arm maze pattern separation task in Ts65Dn mice. Pattern separation requires differentiation between similar memories acquired during learning; distinguishing between these similar memories is thought to depend on distinctive encoding in the hippocampus. Pattern separation has been linked to functional activity of newly generated granule cells in the dentate gyrus. Recent studies in Ts65Dn mice have reported significant reductions in adult hippocampal neurogenesis, and after EGCG treatment, enhanced hippocampal neurogenesis. Thus, it was hypothesized that Ts65Dn mice would be impaired in the pattern separation task, and that EGCG would alleviate the pattern separation deficits seen in trisomic mice, in association with increased adult hippocampal neurogenesis. Beginning on postnatal day 75, mice were trained on a radial arm maze-delayed non-matching-to-place pattern separation task. Euploid mice performed significantly better over training than Ts65Dn mice, including better performance at each of the three separations. EGCG did not significantly alleviate the pattern separation deficits in Ts65Dn mice. The euploid controls had significantly more BrdU labeled cells than Ts65Dn mice, however, EGCG does not appear to increase proliferation of the hippocampal neuroprogenitor cells.
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    The Effect of 200mg/kg EGCG Oral Gavage Treatment on the Cerebellar-Dependent Behavior in a Down Syndrome Mouse Model
    (Office of the Vice Chancellor for Research, 2016-04-08) Dalman, Noriel; Stringer, Megan; Abeysekera, Irushi; East, Audrey; Patel, Roshni; Roper, Randall J.; Goodlett, Charles R.
    Trisomy 21 (Ts21) causes deficits in motor and cognitive ability that are hallmark phenotypes in Down syndrome (DS). The Ts65Dn mouse model of DS has about 50% of the orthologous genes that are triplicated from human chromosome 21, including the Dual specificity tyrosinephosphorylation-regulated kinase 1A (Dyrk1A) gene. Three copies of Dyrk1A have been implicated in the motor and cognitive deficits and altered cerebellar structure and function may contribute these impairments in Ts65Dn mice. Epigallocatechin 3-gallate (EGCG) is a catechin found in green tea and an inhibitor of Dyrk1A activity. We hypothesize that a 200mg/kg EGCG treatment given by oral gavage will inhibit Dyrk1A activity in the cerebellum of Ts65Dn mice and rescue deficits in motor coordination while performing the balance beam task. Evidence of improvement in this task would be observed as a reduction of paw slips as the animal traverses across beams of varying widths. In previous studies, EGCG treatment was placed in the animal’s water to be consumed but EGCG rapidly degrades in solution and it is difficult to control treatment doses via treatment in drinking water, due to each animal’s consumption behavior. This study utilized a daily oral gavage treatment of EGCG to control the dose and limits loss due to degradation. Results to date indicate that the Ts65Dn mice show deficits on the balance beam task relative to the euploid mice, particularly at the narrowest beam width used. The EGCG treatment does not appear to improve the performance of the Ts65Dn mice, though the lack of observed effects of EGCG may be due to the relatively low numbers of Ts65Dn-EGCG treated mice that have completed testing so far. One notable trend is that we will continue to test additional mice to gain sufficient power to determine conclusively whether EGCG improves motor coordination performance in Ts65Dn mice.