Browsing by Author "Deitz, Samantha L."

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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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    Mandibular and Neural Crest Cell Deficits Seen in TsDn65 Down Syndrome Mouse Model Rescued By Green Tea Polyphenol, EGCG
    (Office of the Vice Chancellor for Research, 2013-04-05) Bose, Gracelyn C.; Novack, Rachel A.; Tumbleson, Danika M.; Chom, Alexis N.; Deitz, Samantha L.
    Down Syndrome (DS) is caused by trisomy of the human chromosome 21 (Hsa21) and occurs in ~1 of every 700 births. DS is distinguished by over 80 phenotypic abnormalities including skeletal deficits and craniofacial phenotypes characterized by a flattened skull, slanted eyes, and a smaller mandible. To study these abnormalities, we utilize the Ts65Dn DS mouse model containing a triplication of approximately half of the gene homologues found on Hsa21 and mirrors the skeletal and mandibular phenotypes observed in DS. In Ts65Dn mice, the origin of the mandibular deficits were traced to a reduction in size of the 1st branchial arch (BA1), the developmental precursor to the mandible, occurring at embryonic day 9.5 (E9.5). At E9.5, we observe a lack of proliferation and migration of neural crest cells (NCC) from the neural tube (NT) into the BA1, causing a reduced BA1. We hypothesize that an overexpression of Dyrk1a, a Hsa21 homologue, contributes to the mandibular deficit seen in E9.5 Ts65Dn embryos. We propose that EGCG, a green tea polyphenol, will inhibit DYRK1a activity, rescuing the BA1 deficit. To test our hypothesis, Ts65Dn mothers were treated with EGCG from E0-E9.5 and sacrificed to retrieve the E9.5 embryos. Our results from unbiased stereological assessments show that E0-E9.5 EGCG in vivo treatment has the potential to increase NCC number, BA1 volume, and embryo volume of trisomic embryos. This data provide preclinical testing for a potential therapy of DS craniofacial disorders, which may extend to treating bone deficits in DS and osteoporosis.
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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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    Molecular Basis and Modification of a Neural Crest Deficit in a Down Syndrome Mouse Model
    (2013-07-12) Deitz, Samantha L.; Roper, Randall J.; Chang, Hua-Chen; Chernoff, Ellen; Atkinson, Simon
    Down syndrome (DS) is the result of trisomy of human chromosome 21 (Hsa 21) and occurs in approximately 1/700 live births. Mouse models of DS have been crucial in understanding the gene-phenotype relationships that underlie many DS anomalies. The Ts65Dn mouse model, trisomic for half of the Hsa 21 orthologs replicates many DS phenotypes including craniofacial alterations such as a small, dysmorphic mandible, midface, and maxilla. Other mouse models, such as the Ts1Rhr which contains a triplication of 33 Hsa 21 orthologs, have been used to better understand the genes responsible for craniofacial alterations. Our laboratory has demonstrated that the postnatal mandibular phenotype found in Ts65Dn mice can be traced back to an original neural crest cell (NCc) deficit in the developing first pharyngeal arch (PA1) at embryonic day 9.5 (E9.5). Furthermore, evidence suggested that both a proliferation deficit in the PA1 and a migration deficit in the NCC from the neural tube (NT) could be the mechanism behind this deficit. However, the molecular mechanisms behind these deficits remain to be elucidated. Due to the involvement of the Hsa 21 genes DYRK1A and RCAN1 in regulation of signaling pathways including NFATc (NFAT2), a transcription factor known to influence cellular proliferation and, later, bone development, we hypothesized that dysregulation of these genes could underlie the cellular deficit in the PA1. Furthermore, we hypothesized that targeting Dyrk1a by decreasing activity or available protein could ameliorate the established deficits. Through the use of RNA isolation techniques and cell culture systems of cell from the PA1 and NT of E9.5 Ts65Dn, Ts1Rhr, and control embryos, we established that trisomic genes Dyrk1a and Rcan1 ara dysregulated in both structures and that these two genes may interact. Furthermore, we established that a proliferation deficit in the Ts65Dn PA1 and a migration deficit in the Ts65Dn PA1 and NT exists at E9.5 and can be rescued to euploid levels in vitro with the addition of the Dyrk1a inhibitor, EGCG, a green tea polyphenol. We also confirmed that harmine, a more highly studied and specific Dyrk1a inhibitor, is capable of similar effects on proliferation of PA1 cell from E9.5 Ts65Dn embryos. Furthermore, when Ts65Dn pregnant mothers were treated with EGCG in vivo, the cellular deficit found in the developing E9.5 embryonic PA1 was rescued to near euploid volume and NCC number. Treatment with EGCG did not adversely impact litter size or embryonic development. Interestingly, euploid embryonic volume increased with EGCG treatment. Expression analysis of the E9.5 PA1 of EGCG treated Ts65Dn and control embryos revealed dysregulation of several genes involved in craniofacial and developmental pathways including Dyrk1a, Rcan1, Ets2 and members of the sonic hedgehog pathways. Our novel results provide a foundation for better understanding the molecular mechanisms of craniofacial development and may provide evidence-based therapeutic options to improve the quality of life for individuals with DS.
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    TREATMENT OF CRANIOFACIAL DEFICITS ASSOCIATED WITH DOWN SYN-DROME IN A MOUSE MODEL
    (Office of the Vice Chancellor for Research, 2012-04-13) Chom, Alexis N.; Deitz, Samantha L.; Roper, Randall J.
    Trisomy 21 is the genetic source of the group of phenotypes commonly known as Down syndrome (DS). These phenotypes include cognitive im-pairment, heart defects and craniofacial abnormalities, including a small mandible. The Ts65Dn mouse model contains three copies of approximately half the genes found on human chromosome 21 and exhibits similar pheno-types to individuals with DS including a small, dysmorphic mandible. Our lab has traced this deficit to a smaller first branchial arch (BA1) consisting of fewer neural crest cells (NCCs) at embryonic day 9.5 (E9.5). At E9.5, Dyrk1a, a gene known to affect craniofacial development, is upregulated in the BA1, likely contributing to its cell deficit. Using epigallocatechin gallate (EGCG), an extract from green tea and a known inhibitor of Dyrk1a, we are attempting to rescue this deficit. We hypothesize the consumption of EGCG by pregnant mothers at E7 and E8 will rescue the mandibular deficit in de-veloping embryos by reducing the expression or activity of Dyrk1a. From our data we conclude the treatment of pregnant mothers with EGCG results in increased embryo size of trisomic embryos. Further analysis will be done to determine embryo volume, the volume of the BA1, and number of NCCs within the BA1 to determine the effects of EGCG in vivo. This research will better our understanding of craniofacial development and could lead to po-tential genetic-based therapies in the future.
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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.