Browsing by Subject "craniofacial abnormalities"

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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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    MOLECULAR BASIS AND MODIFICATION OF A NEURAL CREST DEFICIT IN A DOWN SYNDROME MOUSE MODEL
    (Office of the Vice Chancellor for Research, 2012-04-13) Deitz, Samantha L.; Day, Melanie; Roper, Randall J.
    Trisomy 21 occurs in 1/700 live births and leads to phenotypes associat-ed with Down syndrome (DS), including craniofacial dysmorphology and a small mandible. Ts65Dn mice are trisomic for approximately half the genes on human chromosome 21 and display DS-like craniofacial anomalies. Cells cultured from Ts65Dn and euploid 1st pharyngeal arch (PA1) and neural tube (NT) tissues were used to analyze the effects of genetic dysregulation on cell proliferation and migration. In vitro studies revealed a proliferation deficit in trisomic PA1 and migration deficits from trisomic NT originating at embryonic day 9.5 (E9.5). DYRK1A is a gene thought to be involved in DS craniofacial development and we hypothesized that dysregulation of Dyrk1a contributes to altered craniofacial development in Ts65Dn mice. We also hypothesized that Dyrk1a agonists could be used to ameliorate this phenotype. To test our hypotheses, we quantified expression of Dyrk1a using qPCR. At E9.5, Dyrk1a is upregulated in Ts65Dn as relative to euploid PA1. We also showed that cell proliferation and migration could be returned to near euploid levels with the green tea polyphenol epigallocatechin gallate (EGCG) and harmine (known Dyrk1a inhibitors) in vitro. To further test our hypothesis, pregnant Ts65Dn and euploid mothers were treated with EGCG on E7 and E8 and E9.5 trisomic and euploid embryos were assessed for embryonic volume, PA1 vol-ume, and NCC number. Preliminary evidence suggests in vivo treatment leads to an increase in embryonic volume, PA1 volume, and NCC number in both euploid and trisomic embryos. Trisomic EGCG-treated embryos had similar PA1 volumes and NCC numbers to euploid embryos treated with PBS. Gene expression analysis of EGCG-treated NCCs is currently underway to better understand the effects of EGCG in these studies. Our results provide information about the molecular basis of DS craniofacial abnormalities and may lead to evidenced-based therapeutic options.
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    Treatment with a Green Tea Polyphenol Corrects Craniofacial Deficits Associated with Down Syndrome
    (Office of the Vice Chancellor for Research, 2013-04-05) Tumbleson, Danika M.; Deitz, Samantha L.; Chom, Alexis N.; Bose, Gracelyn C.; Novack, Rachel A.; Roper, Randall J.
    Down syndrome (DS) is caused by trisomy of human chromosome 21 (HSA21). Individuals with DS present craniofacial abnormalities including an undersized, dismorphic mandible leading 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) size at embryonic day 9.5. At E9.5, Dyrk1A, a triplicated DS candidate gene, is overexpressed and may cause the NCC and PA1 deficits. We hypothesize that treatment of pregnant Ts65Dn mothers with Epigallocatechin 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 from either E7-E8 or E0-E9.5. Our preliminary study found an increase in PA1 volume and NCC number in trisomic E9.5 embryos after treatment, but observed differences between treatment regimens. Differential gene expression was also quantified in trisomic treated embryos. This preliminary data suggests EGCG treatment has the potential to rescue the mandibular phenotype caused by trisomy. These findings provide preclinical testing for a potential therapy for craniofacial disorders linked to DS.