Biomedical subjects

Jean-Philippe Hugnot

Publications and source records attributed to Jean-Philippe Hugnot.

3 recordsLinked to original sources

PubMed2007

A meta-analysis of human embryonic stem cells transcriptome integrated into a web-based expression atlas.

Microarray technology provides a unique opportunity to examine gene expression patterns in human embryonic stem cells (hESCs). We performed a meta-analysis of 38 original studies reporting on the transcriptome of hESCs. We determined that 1,076 genes were found to be overexpressed in hESCs by at least three studies when compared to differentiated cell types, thus composing a "consensus hESC gene list." Only one gene was reported by all studies: the homeodomain transcription factor POU5F1/OCT3/4. The list comprised other genes critical for pluripotency such as the transcription factors NANOG and SOX2, and the growth factors TDGF1/CRIPTO and Galanin. We show that CD24 and SEMA6A, two cell surface protein-coding genes from the top of the consensus hESC gene list, display a strong and specific membrane protein expression on hESCs. Moreover, CD24 labeling permits the purification by flow cytometry of hESCs cocultured on human fibroblasts. The consensus hESC gene list also included the FZD7 WNT receptor, the G protein-coupled receptor GPR19, and the HELLS helicase, which could play an important role in hESCs biology. Conversely, we identified 783 genes downregulated in hESCs and reported in at least three studies. This "consensus differentiation gene list" included the IL6ST/GP130 LIF receptor. We created an online hESC expression atlas, http://amazonia.montp.inserm.fr, to provide an easy access to this public transcriptome dataset. Expression histograms comparing hESCs to a broad collection of fetal and adult tissues can be retrieved with this web tool for more than 15,000 genes.

Cell Differentiation↗

PubMed2006

NG2 and Olig2 expression provides evidence for phenotypic deregulation of cultured central nervous system and peripheral nervous system neural precursor cells.

Neural stem cells cultured with fibroblast growth factor 2 (FGF2)/epidermal growth factor (EGF) generate clonal expansions called neurospheres (NS), which are widely used for therapy in animal models. However, their cellular composition is still poorly defined. Here, we report that NS derived from several embryonic and adult central nervous system (CNS) regions are composed mainly of remarkable cells coexpressing radial glia markers (BLBP, RC2, GLAST), oligodendrogenic/neurogenic factors (Mash1, Olig2, Nkx2.2), and markers that in vivo are typical of the oligodendrocyte lineage (NG2, A2B5, PDGFR-alpha). On NS differentiation, the latter remain mostly expressed in neurons, together with Olig2 and Mash1. Using cytometry, we show that in growing NS the small population of multipotential self-renewing NS-forming cells are A2B5(+) and NG2(+). Additionally, we demonstrate that these NS-forming cells in the embryonic spinal cord were initially NG2(-) and rapidly acquired NG2 in vitro. NG2 and Olig2 were found to be rapidly induced by cell culture conditions in spinal cord neural precursor cells. Olig2 expression was also induced in astrocytes and embryonic peripheral nervous system (PNS) cells in culture after EGF/FGF treatment. These data provide new evidence for profound phenotypic modifications in CNS and PNS neural precursor cells induced by culture conditions.

Animals↗

PubMed2005

Exogenous and fibroblast growth factor 2/epidermal growth factor-regulated endogenous cytokines regulate neural precursor cell growth and differentiation.

Neurospheres (NSs) are clonal cellular aggregates composed of neural stem cells and progenitors. A comprehensive description of their proliferation and differentiation regulation is an essential prerequisite for their use in biotherapies. Cytokines are essential molecules regulating cell precursor fate. Using a gene-array strategy, we conducted a descriptive and functional analysis of endogenous cytokines and receptors expressed by spinal cord-derived NSs during their growth or their differentiation into neuronal and glial cells. NSs were found to express approximately 100 receptor subunits and cytokine/secreted developmental factors. Several angiogenic factors and receptors that could mediate neural precursor cell-endothelial cell relationships were detected. Among them, receptor B for endothelins was highly expressed, and endothelins were found to increase NS growth. In contrast, NSs express receptors for ciliary neurotrophic factor (CNTF), bone morphogenetic protein (BMP), interferon (IFN)-gamma, or tumor necrosis factor (TNF)-alpha, which, when added in the growth phase, led to a dramatic growth reduction followed by a reduction or a loss of oligodendrocyte formation on differentiation. In addition, NSs synthesize fibroblast growth factor 2/epidermal growth factor (FGF2/EGF)-regulated endogenous cytokines that participate in their growth and differentiation. Notably, BMP-7 and CNTF were expressed during expansion, but upon differentiation there was a remarkable switch from BMP-7 to BMP-4 and -6 and a sharp increase of CNTF. Reintroduction of growth factors reverses the BMP expression profile, indicating growth factor-BMP cross-regulations. The role of endogenous CNTF was investigated by deriving NSs from CNTF knockout mice. These NSs have an increased growth rate associated with reduction of apoptosis and generate astrocytes with a reduced glial fibulary acidic protein (GFAP) content. These results demonstrate the combined role of endogenous and exogenous cytokines in neural precursor cell growth and differentiation.

Animals↗