Ingrid Laurendeau

Molecular profiling of malignant peripheral nerve sheath tumors associated with neurofibromatosis type 1, based on large-scale real-time RT-PCR

BackgroundNeurofibromatosis type 1 (NF1) is an autosomal dominant disorder with a complex range of clinical symptoms. The hallmark of NF1 is the onset of heterogeneous (dermal or plexiform) benign neurofibromas. Plexiform neurofibromas can give rise to malignant peripheral nerve sheath tumors (MPNSTs), and the underlying molecular mechanisms are largely unknown.ResultsTo obtain further insight into the molecular pathogenesis of MPNSTs, we used real-time quantitative RT-PCR to quantify the mRNA expression of 489 selected genes in MPNSTs, in comparison with plexiform neurofibromas.The expression of 28 (5.7%) of the 489 genes was significantly different between MPNSTs and plexiform neurofibromas; 16 genes were upregulated and 12 were downregulated in MPNSTs.The altered genes were mainly involved in cell proliferation (MKI67, TOP2A, CCNE2), senescence (TERT, TERC), apoptosis (BIRC5/Survivin, TP73) and extracellular matrix remodeling (MMP13, MMP9, TIMP4, ITGB4). More interestingly, other genes were involved in the Ras signaling pathway (RASSF2, HMMR/RHAMM) and the Hedgehog-Gli signaling pathway (DHH, PTCH2). Several of the down-regulated genes were Schwann cell-specific (L1CAM, MPZ, S100B, SOX10, ERBB3) or mast cell-specific (CMA1, TPSB), pointing to a depletion and/or dedifferentiation of Schwann cells and mast cells during malignant transformation of plexiform neurofibromas.ConclusionThese data suggest that a limited number of signaling pathways, and particularly the Hedgehog-Gli signaling pathway, may be involved in malignant transformation of plexiform neurofibromas. Some of the relevant genes or their products warrant further investigation as potential therapeutic targets in NF1.

Prion protein and neuronal differentiation: quantitative analysis of prnp gene expression in a murine inducible neuroectodermal progenitor

The biological function of the cellular prion protein, PrP(c), is currently unknown. The presence of PrP(c) transcripts in the developing neural tube from embryonic day 13.5 and the predominant expression of PrP(c) in the adult brain is suggestive of a role in the onset and/or modulation of neuronal functions. We took advantage of the bipotential neuroectodermal 1C11 cell line to monitor PrP(c) expression during its bioaminergic differentiations. The F9-derived 1C11 precursor cell line displays a stable and immature phenotype in the absence of extracellular signal and, upon induction, has the capacity to acquire a complete serotonergic or noradrenergic phenotype, the two pathways being mutually exclusive. A real-time quantitative PCR assay was developed to assess PrP(c) gene expression at definite times of the two programs that correspond to sequential acquisition of neurotransmitter-specific functions. 1C11 cells and their differentiated progenies express significant amounts of PrP transcripts and of the corresponding protein. A unique decrease in prnp gene expression is observed upon entry into the serotonergic pathway, correlating with a downregulation at the protein level. Moreover, nerve growth factor (NGF) is shown to induce a decrease in the level of prnp gene expression along the serotonergic - but not the noradrenergic - pathway. Our study accurately establishes that prnp gene expression (i) is strongly upregulated concomitantly with cell fate restriction of multipotential cells towards the neural lineage; (ii) is differentially regulated along the serotonergic versus noradrenergic differentiation program of a unique neuroectodermal progenitor. The 1C11 cell line may provide a new tool for studying prion infectivity in a well-defined neuronal context.

CGA Gene (Coding for the α Subunit of Glycoprotein Hormones) Overexpression in ERα-Positive Prostate Tumors

Abstract Objective: The precise role of estrogen, estrogen receptor (ER) and ER -responsive genes in prostate carcinogenesis is unclear. Paradoxically, estrogens and antiestrogens are used in the treatment of advanced metastatic prostate cancers. Recently, we identified CGA gene coding for the α subunit of glycoprotein hormones as a new ERα -responsive gene in human breast cancer cells. The aim of this study was to explore the role of CGA in the second major hormone-related cancer, i.e. prostate cancer. Patients and Methods: We quantified CGA mRNA in nine cases of benign prostatic hyperplasia (BPH) and 23 sporadic prostate tumors (TP) by using a real-time quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Results: CGA overexpression (>10 S.D. above the mean in normal prostate tissues (NP)) was observed in 39% of the TP (ranging from 4.4 to 174.5 times the level in NP) and in none of the BPH samples. CGA overexpression was not accompanied by overexpression of the CGB , LHB , TSHB or FSHB genes to produce ectopic glycoprotein hormones. CGA gene overexpression correlated with ERα normal expression ( P =0.016), but not with ERβ or androgen receptor ( AR ) expression status. Conclusion: These results point to CGA gene as a member of a novel dysregulated pathway in prostate cancer. CGA should therefore be considered for investigation as possible novel molecular marker in clinical applications and as possible new potential therapeutic target.

Identification of the first intragenic deletion of the PITX2 gene causing an Axenfeld-Rieger Syndrome: case report

BackgroundAxenfeld-Rieger syndrome (ARS) is characterized by bilateral congenital abnormalities of the anterior segment of the eye associated with abnormalities of the teeth, midface, and umbilicus. Most cases of ARS are caused by mutations in the genes encoding PITX2 or FOXC1. Here we describe a family affected by a severe form of ARS.Case presentationTwo members of this family (father and daughter) presented with typical ARS and developed severe glaucoma. The ocular phenotype was much more severe in the daughter than in the father. Magnetic resonance imaging (MRI) detected an aggressive form of meningioma in the father. There was no mutation in the PITX2 gene, determined by exon screening. We identified an intragenic deletion by quantitative genomic PCR analysis and characterized this deletion in detail.ConclusionOur findings implicate the first intragenic deletion of the PITX2 gene in the pathogenesis of a severe form of ARS in an affected family. This study stresses the importance of a systematic search for intragenic deletions in families affected by ARS and in sporadic cases for which no mutations in the exons or introns of PITX2 have been found. The molecular genetics of some ARS pedigrees should be re-examined with enzymes that can amplify medium and large genomic fragments.