Browsing by Author "Sheikh, Zahir"

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    Effect of EGCG on granule cell proliferation in the adult dentate gyrus of the Ts65Dn mouse
    (Office of the Vice Chancellor for Research, 2015-04-17) Sheikh, Zahir; Goodlett, Charles R.
    Down syndrome (DS) is the most common genetic disorder that results in cognitive abnormalities and occurs in approximately 1 in 700 live births. This disorder is caused by an extra copy of human chromosome 21 (Hsa21) which increases the dosage of the genes on that chromosome. Ts65Dn mice, which are the most studied mouse model for DS, are trisomic for segments of mouse chromosome 16 (Mmu16) which contain approximately half the genes found on Hsa21. These mice express some of the physical and behavioral abnormalities associated with DS. Previous research has shown impaired performance of Ts65Dn mice in hippocampaldependent tasks, such as in the radial arm maze task, compared to euploid control mice. Success in such tasks is thought to depend on the ability of the hippocampus to generate granule cells within the dentate gyrus. Young granule cells are highly active after integration and are required for memory formation. Previous research shows that Ts65Dn have a reduction in the formation of granule cells which leads us to hypothesize that Ts65Dn mice will perform worse in the radial arm maze compared to euploid controls. This leads us to conclude that Ts65Dn mice have reduced granule cell proliferation relative to controls. We are investigating the effects of EGCG, a polyphenolic component of green tea, on granule cell proliferation in adult mice. Different pathways are suggested to be effected by EGCG, such as by inhibiting Dyrk1a that is overproduced in DS mice or by up-regulation of the sonic hedgehog receptor Patched. Using BrdU peroxidase immunohistochemistry to label newly generated granule cells in the adult mouse dentate gyrus, we hypothesize that EGCG will increase cell proliferation in the granule cell layer of the dentate gyrus.
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    Effects of EGCG treatment on deficits in a radial-arm maze spatial pattern separation task in a Down syndrome mouse model
    (Office of the Vice Chancellor for Research, 2015-04-17) Stringer, Megan; Stancombe, Kailey; Gainey, Sean; Sheikh, Zahir; Abeysekera, Irushi; Goodlett, Charles R.; Roper, Randall J.
    Down syndrome (DS) is caused by three copies of human chromosome 21 (Hsa 21) and results in a constellation of phenotypes that include intellectual disability. Ts65Dn mice, the most extensively studied model of DS, have three copies of approximately half the genes on Hsa 21 and display many of the phenotypes associated with DS, including cognitive deficits. DYRK1A is found in three copies in humans with Trisomy 21 and has increased expression in a number of tissues. Dyrk1a is also found in three copies in Ts65Dn mice, and has been shown to be involved in a number of critical pathways including CNS development and osteoclastogenesis. Epigallocatechin-3-gallate (EGCG), the main polyphenol found in green tea, is an inhibitor of Dyrk1a activity. We have previously shown that a three week treatment with EGCG normalizes skeletal abnormalities in Ts65Dn mice. Previous work has found that Ts65Dn mice are significantly impaired in several hippocampal-dependent tasks, including the Morris water maze and novel object recognition. Another hippocampal-dependent process, pattern separation, is the ability to differentiate between similar memories acquired during learning. Distinctive encoding of these similar memories in hippocampal formation is thought to be necessary to distinguish between them. Experimental reductions in adult neurogenesis have produced impairments in pattern separation performance. Given that recent studies in Ts65Dn mice have reported significant reductions in adult hippocampal neurogenesis, we hypothesize that Ts65Dn mice will be impaired in the pattern separation task. Furthermore, we hypothesize that treating Ts65Dn mice with EGCG throughout task learning would improve performance to control levels. A radial arm maze-delayed non-matching-toplace pattern separation task with three different degrees of spatial separation is used. Preliminary data suggests that, in contrast to control mice, Ts65Dn mice do not improve their performance over training.
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    ETS1 induction by the microenvironment promotes ovarian cancer metastasis through focal adhesion kinase
    (Elsevier, 2018-02-01) Tomar, Sunil; Plotnik, Joshua P.; Haley, James; Scantland, Joshua; Dasari, Subramanyam; Sheikh, Zahir; Emerson, Robert; Lenz, Dean; Hollenhorst, Peter C.; Mitra, Anirban K.; Pathology and Laboratory Medicine, School of Medicine
    Metastatic colonization involves paracrine/juxtacrine interactions with the microenvironment inducing an adaptive response through transcriptional regulation. However, the identities of transcription factors (TFs) induced by the metastatic microenvironment in ovarian cancer (OC) and their mechanism of action is poorly understood. Using an organotypic 3D culture model recapitulating the early events of metastasis, we identified ETS1 as the most upregulated member of the ETS family of TFs in metastasizing OC cells as they interacted with the microenvironment. ETS1 was regulated by p44/42 MAP kinase signaling activated in the OC cells interacting with mesothelial cells at the metastatic site. Human OC tumors had increased expression of ETS1, which predicted poor prognosis. ETS1 regulated OC metastasis both in vitro and in mouse xenografts. A combination of ChIP-seq and RNA-seq analysis and functional rescue experiments revealed FAK as the key transcriptional target and downstream effector of ETS1. Taken together, our results indicate that ETS1 is an essential transcription factor induced in OC cells by the microenvironment, which promotes metastatic colonization though the transcriptional upregulation of its target FAK.
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    Phase II – Biomechanics of Smooth Muscle Cell Differentiation: Experimental Study Using an Innovative In Vitro Mechanical System
    (Office of the Vice Chancellor for Research, 2014-04-11) Collins, Jessica; Sheikh, Zahir; Vipra, Niraj; Yeoh, Joseph
    Smooth muscle cells (SMCs) controls involuntary contractions and express different genotypic and phenotypic traits on specific organs such as blood vessels, bladder and stomach. However, studies have shown different SMC lineages tend to gradually lose specific characteristics due to a static milieu without exerting forces that they would experience naturally when cultured in vitro. The research provided in vivo conditions are mimicked effectively in vitro by applying controlled mechanical loading, SMCs should express their differentiated characteristics. We have validated an innovative mechanical device that simulates the pulsatile stretching SMCs undergo in their in vivo environment. Using the new system and cell and molecular biology techniques, we are evaluating cell differentiation and strain induced alignment when phenotypically modulated SMCs undergo cyclic mechanical loading at 10 and 20 percent strains, for 4, 6, or 8 hours at physiological frequency. We collected proteins after stretch experiments and analyzed via western blot, α-actin, γ-actin, transgelin, and calponin protein expression changes in: coronary SMCs strained 10% and 20% at 4, 6, and 8 hours, bladder SMCs strained 10% at 4, 6, and 8 hours, and BAECs for varying intensities and durations. In order to improvise the machine capability, LabVIEW code is been developed as the user interface providing advantageous of Graphical Approach instead of Cool Muscle Language code. Developed coding provide a complete coverage of acquisition, analysis, reporting, and display features to create modern applications that can scale as system requirements change over time. The next phase of this experiment enable analysis of gene expression using quantitative RT-PCR (qRT-PCR). This facet of research may prove valuable in the analysis of the effect of mechanical stress on maintaining SMC lineage as well as the study of how pathological stretch conditions affect SMC and endothelial cell gene and protein expressions.