Project description:Gene modified autologous hematopoietic stem cells (HSC) can provide significant clinical benefits to patients suffering from X-linked chronic granulomatous disease (X-CGD), a rare inherited immunodeficiency characterized by recurrent, often life threatening bacterial and fungal infections. Here we report on the molecular and cellular events observed in two patients treated by gene therapy in 2004. After the initial resolution of bacterial and fungal infections, both patients exhibited silencing of transgene expression due to methylation of the viral promoter, and myelodysplasia with monosomy 7 as a result of insertional activation of EVI1. One patient died from overwhelming sepsis 27 months after gene therapy, whereas a second patient underwent an allogeneic HSC transplantation. Our data shows that forced overexpression of MDS1/EVI1 or EVI1 in human cells disrupts normal centrosome duplication, linking MDS1/EVI1 activation to the development of genomic instability, monosomy 7 and clonal progression towards myelodysplasia. Genomic copy number alterations were detected by analyzing the fluorescence signal intensities of each SNP on the GeneChip Human Mapping 100K array st (Affymetrix, Santa Clara, Ca) with the Copy Number Analyzer for Affymetrix GeneChip 100K arrays (CNAT) version 2.0. The log2 ratio of each SNP, the local averaged log2 signal ratio (averaged for 10 SNPs) and the inferred chromosome copy number according to the Hidden Markov Model (HMM) were calculated. Copy number analysis of Affymetrix 100K SNP arrays was performed for one young adult with the X-linked chronic granulomatous disease (X-CGD)