Xiaojie Xian - Academia.edu (original) (raw)

Papers by Xiaojie Xian

Background: In most measurements of gene expression, mRNA is first reverse-transcribed into cDNA.... more Background: In most measurements of gene expression, mRNA is first reverse-transcribed into cDNA. We studied the reverse transcription reaction and its consequences for quantitative measurements of gene expression. Methods: We used SYBR green I-based quantitative real-time PCR (QPCR) to measure the properties of reverse transcription reaction for the �-tubulin, glyceraldehyde-3-phosphate dehydrogenase, Glut2, CaV1D, and insulin II genes, using random hexamers, oligo(dT), and gene-specific reverse transcription primers. Results: Experimental variation in reverse transcription-QPCR (RT-QPCR) was mainly attributable to the reverse transcription step. Reverse transcription efficiency depended on priming strategy, and the dependence was different for the five genes studied. Reverse transcription yields also depended on total RNA concentration. Conclusions: RT-QPCR gene expression measurements are comparable only when the same priming strategy and reaction conditions are used in all exper...

Stem Cell Research & Therapy

Cell Tissue Research, 2010

The Journal of cell biology, Jan 28, 2015

Transmembrane heparan sulfate proteoglycans regulate multiple aspects of cell behavior, but the m... more Transmembrane heparan sulfate proteoglycans regulate multiple aspects of cell behavior, but the molecular basis of their signaling is unresolved. The major family of transmembrane proteoglycans is the syndecans, present in virtually all nucleated cells, but with mostly unknown functions. Here, we show that syndecans regulate transient receptor potential canonical (TRPCs) channels to control cytosolic calcium equilibria and consequent cell behavior. In fibroblasts, ligand interactions with heparan sulfate of syndecan-4 recruit cytoplasmic protein kinase C to target serine714 of TRPC7 with subsequent control of the cytoskeleton and the myofibroblast phenotype. In epidermal keratinocytes a syndecan-TRPC4 complex controls adhesion, adherens junction composition, and early differentiation in vivo and in vitro. In Caenorhabditis elegans, the TRPC orthologues TRP-1 and -2 genetically complement the loss of syndecan by suppressing neuronal guidance and locomotory defects related to increase...

Extracellular Matrix: Pathobiology and Signaling, 2012

Tumour biology : the journal of the International Society for Oncodevelopmental Biology and Medicine

To understand by which mechanism neural cell adhesion molecule (N-CAM) limits beta tumour cell di... more To understand by which mechanism neural cell adhesion molecule (N-CAM) limits beta tumour cell disaggregation and dissemination, we searched for potential downstream genes of N-CAM during beta tumour cell progression by gene expression profiling. Here, we show that N-CAM-deficient beta-cell tumorigenesis is associated with changes in the expression of genes involved in cell-matrix adhesion and cytoskeletal dynamics, biological processes known to affect the invasive and metastatic behaviour of tumour cells. The extracellular matrix (ECM) molecules emerged as the primary target, i.e. N-CAM deficiency resulted in down-regulated mRNA expression of a broad range of ECM molecules. Consistent with this result, deficient deposition of major ECM stromal components, such as fibronectin, laminin 1 and collagen IV, was observed. Moreover, N-CAM-deficient tumour cells displayed defective matrix adhesion. These results offer a potential mechanism for tumour cell disaggregation during N-CAM-defici...

Molecular Biology of the Cell, 2011

Syndecan-2 is a heparan sulfate proteoglycan that has a cell adhesion regulatory domain contained... more Syndecan-2 is a heparan sulfate proteoglycan that has a cell adhesion regulatory domain contained within its extracellular core protein. Cell adhesion to the syndecan-2 extracellular domain (S2ED) is β1 integrin dependent; however, syndecan-2 is not an integrin ligand. Here the protein tyrosine phosphatase receptor CD148 is shown to be a key intermediary in cell adhesion to S2ED, with downstream β1 integrin–mediated adhesion and cytoskeletal organization. We show that S2ED is a novel ligand for CD148 and identify the region proximal to the transmembrane domain of syndecan-2 as the site of interaction with CD148. A mechanism for the transduction of the signal from CD148 to β1 integrins is elucidated requiring Src kinase and potential implication of the C2β isoform of phosphatidylinositol 3 kinase. Our data uncover a novel pathway for β1 integrin–mediated adhesion of importance in cellular processes such as angiogenesis and inflammation.

Journal of Clinical Investigation, 2006

Cell and Tissue Research, 2010

Syndecans are type I transmembrane proteins having a core protein modified with glycosaminoglycan... more Syndecans are type I transmembrane proteins having a core protein modified with glycosaminoglycan chains, most commonly heparan sulphate. They are an ancient group of molecules, present in invertebrates and vertebrates. Among the plethora of molecules that can interact with heparan sulphate, the collagens and glycoproteins of the extracellular matrix are prominent. Frequently, they do so in conjunction with other receptors, most notably the integrins. For this reason, they are often referred to as “co-receptors”. However, just as with integrins, syndecans can interact with actin-associated proteins and signalling molecules, such as protein kinases. Some aspects of syndecan signalling are understood but much remains to be learned. The functions of syndecans in regulating cell adhesion and extracellular matrix assembly are described here. Evidence from null mice suggests that syndecans have roles in postnatal tissue repair, inflammation and tumour progression. Developmental deficits in lower vertebrates in which syndecans are eliminated are also informative and suggest that, in mammals, redundancy is a key issue.

PLOS One, 2010

Background: Pluripotency and self-renewal of human embryonic stem cells (hESCs) is mediated by a ... more Background: Pluripotency and self-renewal of human embryonic stem cells (hESCs) is mediated by a complex interplay between extra-and intracellular signaling pathways, which regulate the expression of pluripotency-specific transcription factors. The homeodomain transcription factor NANOG plays a central role in maintaining hESC pluripotency, but the precise role and regulation of NANOG are not well defined.

Endocrinology, 2009

The neural cell adhesion molecule (NCAM) is required for cell type segregation during pancreatic ... more The neural cell adhesion molecule (NCAM) is required for cell type segregation during pancreatic islet organogenesis. We have investigated the functional consequences of ablating NCAM on pancreatic beta-cell function. In vivo, NCAM(-/-) mice exhibit impaired glucose tolerance and basal hyperinsulinemia. Insulin secretion from isolated NCAM(-/-) islets is enhanced at glucose concentrations below 15 mM but inhibited at higher concentrations. Glucagon secretion from pancreatic alpha-cells evoked by low glucose was also severely impaired in NCAM(-/-) islets. The diminution of insulin secretion is not attributable to defective glucose metabolism or glucose sensing (documented as glucose-induced changes in intracellular Ca(2+) and K(ATP)-channel activity). Resting K(ATP) conductance was lower in NCAM(-/-) beta-cells than wild-type cells, and this difference was abolished when F-actin was disrupted by cytochalasin D (1 muM). In wild-type beta-cells, the submembrane actin network disassembles within 10 min during glucose stimulation (30 mM), an effect not seen in NCAM(-/-) beta-cells. Cytochalasin D eliminated this difference and normalized insulin and glucagon secretion in NCAM(-/-) islets. Capacitance measurements of exocytosis indicate that replenishment of the readily releasable granule pool is suppressed in NCAM(-/-) alpha- and beta-cells. Our data suggest that remodeling of the submembrane actin network is critical to normal glucose regulation of both insulin and glucagon secretion.

Tumor Biology, 2005

To understand by which mechanism neural cell adhesion molecule (N-CAM) limits ß tumour cell disag... more To understand by which mechanism neural cell adhesion molecule (N-CAM) limits ß tumour cell disaggregation and dissemination, we searched for potential downstream genes of N-CAM during ß tumour cell progression by gene expression profiling. Here, we show that N-CAM-deficient ß-cell tumorigenesis is associated with changes in the expression of genes involved in cellmatrix adhesion and cytoskeletal dynamics, biological processes known to affect the invasive and metastatic behaviour of tumour cells. The extracellular matrix (ECM) molecules emerged as the primary target, i.e. N-CAM deficiency resulted in down-regulated mRNA expression of a broad range of ECM molecules. Consistent with this result, deficient deposition of major ECM stromal components, such as fibronectin, laminin 1 and collagen IV, was observed. Moreover, N-CAM-deficient tumour cells displayed defective matrix adhesion. These results offer a potential mechanism for tumour cell disaggregation during N-CAM-deficient ß tumour cell progression. Prospective consequences of these findings for the role of N-CAM in ß tumour cell dissemination are discussed.