Browsing by Author "Diallo, Mariyamou"

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    Correction of Craniofacial Deficits using Epigallocatechin-3’-gallate Treatment in a Down Syndrome Mouse Model
    (Office of the Vice Chancellor for Research, 2014-04-11) Tumbleson, Danika M.; Haley, Emily M.; Diallo, Mariyamou; Deitz, Samantha L.; Roper, Randall J.
    Down syndrome (DS) is caused by trisomy of human chromosome (HSA21). Individuals with DS display distinct craniofacial abnormalities including an undersized, dismorphic mandible which leads to difficulty with eating, breathing, and swallowing. Using the Ts65Dn DS mouse model (three copies of ~50% HSA21 homologs), we have traced the mandibular deficit to a neural crest cell (NCC) deficiency and reduction in first pharyngeal arch (PA1 or mandibular precursor) at embryonic day 9.5. Previous studies have shown that this deficit is caused when NCC fail to migrate from the neural tube to populate the PA1 and fail to proliferate in the PA1. At E9.5, Dyrk1A, a triplicated DS candidate gene, is overexpressed in the PA1 and may cause the NCC and PA1 deficits. We hypothesize that treatment of pregnant Ts65Dn mothers with Epigallocatechin-3’-gallate (EGCG), a known Dyrk1A inhibitor, will correct NCC deficits and rescue the undersized PA1 in trisomic E9.5 embryos. To test our hypothesis, we treated pregnant Ts65Dn mothers with EGCG, where embryos received treatment from either E7-E8 or E0-E9.5. Our preliminary study found variable increases in PA1 volume and NCC number between treatment regimens, with several treatment groups indicating EGCG treatment has the potential to rescue the NCC deficit in the mandibular precursor. We found an increase in NCC number and PA1 volume with E7-E8 EGCG treatment in 21-24 somite embryos from trisomic mothers and in euploid embryos from euploid mothers treated from E0-E9.5. With EGCG treatment, we also observed a decrease in the average somite number of embryos from trisomic mothers, but an increase in those mothers’ average litter size. This study is important because it helps define the specific dosage and timing of ECGC and how it may affect specific DS phenotypes. These findings provide preclinical testing for a potential therapy for craniofacial disorders linked to DS.
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    Effects of Trisomic Dyrk1a and EGCG Treatment on Craniofacial Development in Ts65Dn Down Syndrome Mice
    (Office of the Vice Chancellor for Research, 2015-04-17) Diallo, Mariyamou; Haley, Emily; Tumbleson, Danika; Roper, Randall J.
    Down syndrome (DS), also known as Trisomy 21, is a genetic disorder caused by an extra copy of human chromosome 21. Individuals with DS exhibit various phenotypes such as cognitive, skeletal and craniofacial abnormalities. The Ts65Dn mouse model displays similar craniofacial abnormalities as observed in humans with DS including a small, undersized mandible. To gain a better understanding of craniofacial abnormalities, we study the molecular and cellular mechanisms underlying these abnormalities. Previous studies conducted in our lab identified a deficit in neural crest (NC) cells in the first pharyngeal arch (PA1) or mandibular precursor by embryonic day 9.5 (E9.5). We hypothesize that the inherent molecular mechanism responsible for the small, undersized mandible is overexpression of dual-specificity tyrosine (Y) phosphorylation regulated kinase 1A (Dyrk1a), a gene that is found in three copies in individuals with DS and Ts65Dn mice. To test our hypothesis, we bred Ts65Dn mice with Dyrk1a knockout mice, thus reducing Dyrk1a copy number to normal levels. This study provides the foundation for understanding the function of Dyrk1a. We also treated embryos with Epigallocatechin gallate (EGCG), a green tea polyphenol that is known to inhibit Dyrk1a activity. We will examine the molecular and cellular effects of Dyrk1a and EGCG on the developing PA1 on E9.5 embryos. In both the genetic and pharmacological manipulations, we expect to find a larger overall embryonic size, a larger PA1 size and increased number of NC cells.
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    The Effects of Trisomic Dyrk1a on Ts65Dn Embryonic Craniofacial Development
    (Office of the Vice Chancellor for Research, 2015-04-17) Haley, Emily; Diallo, Mariyamou; Roper, Randall J.
    Down syndrome (DS) is caused by Trisomy 21 in humans and leads to distinctive craniofacial features in all affected individuals. The Ts65Dn mouse model of DS has orthologs of about half of the genes found on chromosome 21 and mirrors craniofacial phenotypes seen in DS including a small dysmorphic mandible. Previous studies have shown that the small mandible is due to deficits in proliferation and migration from the neural tube of neural crest cell (NCC) craniofacial precursors. Dyrk1a is a trisomic gene found in humans with DS and Ts65Dn mice, and it is overexpressed in the 1st pharyngeal arch (PA1) of our mouse model. We hypothesize that Ts65Dn, Dyrk1a+/- embryos (otherwise trisomic with the normal 2 copies of Dyrk1a) will show similar PA1 and overall embryo size as well as NCC number when compared to euploid littermates. To test our hypothesis we bred Ts65Dn, Dyrk1a+/- mothers to generate the following genotypes; Ts65Dn, Eu, Ts65Dn, Dyrk1a+/- and Eu, Dyrk1a+/-. At E9.5 embryos were removed from mothers. Using unbiased stereology on sectioned E9.5 embryos, we measured PA1 NCC number and total embryonic volume. We propose that if Ts65Dn, Dyrk1a+/- embryos show a normalized PA1, future work should be concentrated in viable therapies to target overexpression of Dyrk1a in the Ts65Dn mouse model.