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Browsing by Author "Hardy, Tabitha"
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Item Dyrk1a Dynamics: The Influence of Gene Copy Number on Neurodevelopment in the Ts65dn Mouse Model of Down Syndrome(2024-05) Hawley, Laura E.; Roper, Randall; Belecky-Adams, Teri; Cummins, Theodore; Goodlett, Charles; Hardy, Tabitha; Marrs, KathleenDown syndrome (DS) arises from the triplication of human chromosome 21 (Hsa21), leading to a spectrum of phenotypes characterized by neurodevelopmental and cognitive abnormalities. The Ts65Dn mouse model emulates DS by harboring three copies of genes found on Hsa21 resulting in trisomy 21 (Ts21)- like traits, including disruptions in neuronal pathways, delays in sensorimotor and behavior milestones, and deficits in learning and memory tasks. There is no cure for DS and available therapies primarily address symptoms stemming from Ts21-associated phenotypes. DYRK1A, a gene triplicated in Ts21, has a pivotal role in pathways of neurodevelopment and has been a focus of inhibition treatment research aimed at preempting abnormal brain phenotypes. This study aimed to find a point of substantial Dyrk1a expression dysregulation during a period of critical neonatal neurodevelopment and employ targeted pharmacological and genetic knockdown methods to alleviate the presence or severity of characteristically abnormal brain and behavior phenotypes. The hypothesis of this study was that administering a targeted intervention prior to a point of known overexpression in trisomic pups would ameliorate molecular, sensorimotor, and neurobehavioral deficits, redirecting growth trajectories of Ts65Dn neonatal pups towards more neurotypical outcomes. To test this hypothesis, the spatiotemporal pattern of DYRK1A expression was quantified during the first three weeks of neonatal development across the hippocampus, cerebral cortex, and cerebellum of the Ts65Dn mouse model and found to fluctuate according to the genotype, age, sex, and brain region of the subject. Dyrk1a protein and mRNA expression levels were delineated in trisomic animals by age, exploring the correlation between expression and age, sex, genotype, and brain region. Next a constitutive Dyrk1a knockdown model was integrated with the Ts65Dn model to investigate the impact of gene copy number reduction on protein and mRNA expression levels during phases of known DYRK1A dysregulation. On postnatal day 6, protein expression was rescued in all three brain regions of male animals but was rescued only in the cerebellum of females. There were no significant differences in mRNA transcript levels in either sex at this age. Finally, genetic elements were introduced into the Ts65Dn model to facilitate a spatiotemporally controlled functional reduction of Dyrk1a and discern how the timing of gene copy number reduction affects molecular and neurobehavioral development in a trisomic system. Results from these studies suggest that only functionally reducing Dyrk1a gene copy number on the day of birth is not sufficient to rescue the majority of deficits and delays present in the Ts65Dn mouse model of DS. These findings significantly enhance the understanding of trisomic Dyrk1a expression dynamics during neonatal development and shed light on tailored therapeutic approaches to modulate intrinsic DS characteristics based on age, sex, and phenotypic considerations.Item Quantifying Dyrk1a During Perinatal Development in the Hippocampus, Cerebral Cortex and Cerebellum of the Ts65Dn(2020-05) Hawley, Laura Elizabeth; Roper, Randall J.; Goodlett, Charles R.; Belecky-Adams, Teri; Marrs, Kathleen; Hardy, TabithaThe relationship between gene copy number and protein expression levels has not thoroughly been examined in humans or mouse models of Down syndrome (DS) in relationship to developmental changes in the trisomic brain. Found on human chromosome 21 (Hsa21) and triplicated in DS, Dual-specificity tyrosine-phosphorylated regulated kinase 1A (DYRK1A) has been linked in DS to neurological deficits by restricting cell growth and proliferation. Little information exists regarding DYRK1A during perinatal development and how its expression may lead to cognitive deficits, and none exists that explores the gene-to-protein relationship during these critical time periods. This study aims to 1) Quantify variable DYRK1A expression across development as a function of age, sex, and brain region in trisomic Ts65Dn mice compared to euploid counterparts and 2) establish that the spatiotemporal pattern of developmental DYRK1A in the brain is not influenced solely by gene copy number, and that reduction of Dyrk1a in euploid and trisomic mice does not result in a corresponding global reduction of DYRK1A expression. DYRK1A was quantified in three areas of the postnatal brain at seven ages using the Ts65Dn mouse, the most studied model of DS, and found that trisomic expression is significantly increased on postnatal day ([P]6), declining by the third week to near euploid levels. We also uncovered a sexual dimorphic expression of DYRK1A when comparing animals of different sexes within the same genotype. Data from Dyrk1a knockdown mice indicated that reducing only Dyrk1a in euploid and in otherwise trisomic animals yields highly variable levels of DYRK1A, dependent on sex and tissue type, supporting the non-intuitive relationship between gene dosage and protein expression. These data emphasize the need to understand the age-dependent regulation of antecedent conditions that are causing changes in Dyrk1a expression in the brain.