Gene expression and cell behavior study in cells from individuals with syndromic craniosynostosis

Author(s)

Roberto Dalto Fanganiello

• Document type: Doctoral Thesis
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2010-02-04

Examining board members

Maria Rita dos Santos e Passos Bueno; Sergio Verjovski de Almeida; Hugo Aguirre Armelin; Luciana Amaral Haddad; Oswaldo Keith Okamoto

• Advisor: Maria Rita dos Santos e Passos Bueno

Abstract

Craniosynostosis is one of the most important group of diseases linked to the development of the human skull and is characterized by the premature fusion of one or more cranial sutures. Dominant mutations in FGFR2 are frequent molecular causes amongst the mendelian inherited forms of the syndromic craniosynostosis and are associated to Apert, Crouzon and Pfeiffer syndromes. The intracellular signaling pathways following the activation of wild type or mutant FGFR2 are very complex due to several possible bifurcations. The initial portions of these pathways, immediately following the receptor activation, are relatively well delineated. However the great majority of the events related to the control of these pathways is still not well understood, mainly concerning its transcriptional regulation and its association to other cell behavior anomalies. Therefore the key scopes of this work were: 1) to study the differentiation potential and the differential gene expression profile of primary fibroblastoid cell cultures isolated from the periosteum of the coronal sutures of Apert Syndrome patients (heterozygous for the mutation p.Ser252Trp in FGFR2, the most common cause of the Apert Syndrome condition) and 2) to study the osteogenic differentiation potential and the transcriptional profile of mesenchymal cells and tissue isolated from the coronal sutures of a mouse model for the Crouzon and Pfeiffer Syndromes (heterozygous for the p.Cys342Tyr mutation in Fgfr2, the mutation most commonly associated to these syndromes). We assured the FGFR2 /FGFR2 gene and the protein expression in human fibroblastoid cells and Fgfr2 /Fgfr2 expression in the mesenchymal murine cells. We tested the (in vitro and in vivo ) osteogenic and the (in vitro ) adipogenic potentials of the Apert Syndrome patients cells compared to cells from the same tissue but from subjects without this mutation and the (in vitro ) osteogenic potential of mesenchymal cells from mice bearing the p.Cys342Tyr mutation in Fgfr2 compared to coronal suture cells but from wild type mice. On both experiments the differentiation potential of the mutant cells were very increased when compared to the potential of the wild type cells. We conducted gene expression microarray experiments (CodeLink system) using 7 samples from primary cultures of cells from Apert Syndrome patients compared to 7 samples from primary control cultures. We identified 263 genes with significantly different expression (SNR ≥ |0.4|, P ≤ 0,05) associated to the Apert Syndrome profile (118 upregulated, 145 downregulated). Enriched functional cathegories were regulation of cell proliferation, nucleotide metabolism, gene expression regulation, cell adhesion, extracellular matrix organization and PI3K MAPK cascades. In order to validate this gene expression signature we confirmed through Real-Time PCR the upregulation of genes identified as upregulated in the Apert cell profile in samples from the microarray experiment and in control cells treated with exogenous overactivate the receptor. The gene expression experiments with the coronal suture tissues from the mouse model were performed with 15 samples of mutant animal tissue in 3 groups of 5 and compared to samples from the same tissue of wild type animals, with identical grouping. We identified three sets of differentially expressed genes: the first set containing 188 transcripts (P ≤0,05, FC ≥ 1,5, 91 upregulated e 97 downregulated), and the other two filtered for coeficient of variation < 50% in each group, containing 488 transcripts (P ≤0,05, FC ≥ 1,2, sendo 183 upregulated and 305downregulated) e 31 transcripts (P ≤0,05, FC ≥ 1,5, 11 upregulated and 20 downregulated). The most enriched functional categories were growth, proliferation and cell cycle, cell differentiation, cell-to-cell signaling, cell mediated immune response and Wnt receptor signaling. These results allowed us: a) to demonstrate that fibroblastoid cells from coronal periosteum PF Apert Syndrome patients (p.Ser252Trp mutation in FGFR2) and mesenchymal cells from the coronal tissue of the mouse model for Crouzon and Pfeiffer syndromes (bearing the p.Cys342Tyr in Fgfr2) have enhanced osteogenic potential, summoning evidences suggesting that this cell behavior alteration have a fundamental role to the craniosynostotic process in these syndromes; b) to unravel gene expression signatures linked to these mutations in the studied conditions, that could orchestrate this abnormal cell behavior; c) to identify a ser of genes associated to the pathophysiology of Apert Syndrome and to the phenotypic characteristics of the animal model investigated, which might be candidate genes to other craniosynostosis of unknown cause. (AU)