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Natural gene-expression variation in Down syndrome modulates the outcome of gene-dosage imbalance

Deutsch, Samuel
Delorenzi, Mauro
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Published in American journal of human genetics. 2007, vol. 81, no. 2, p. 252-263
Abstract Down syndrome (DS) is characterized by extensive phenotypic variability, with most traits occurring in only a fraction of affected individuals. Substantial gene-expression variation is present among unaffected individuals, and this variation has a strong genetic component. Since DS is caused by genomic-dosage imbalance, we hypothesize that gene-expression variation of human chromosome 21 (HSA21) genes in individuals with DS has an impact on the phenotypic variability among affected individuals. We studied gene-expression variation in 14 lymphoblastoid and 17 fibroblast cell lines from individuals with DS and an equal number of controls. Gene expression was assayed using quantitative real-time polymerase chain reaction on 100 and 106 HSA21 genes and 23 and 26 non-HSA21 genes in lymphoblastoid and fibroblast cell lines, respectively. Surprisingly, only 39% and 62% of HSA21 genes in lymphoblastoid and fibroblast cells, respectively, showed a statistically significant difference between DS and normal samples, although the average up-regulation of HSA21 genes was close to the expected 1.5-fold in both cell types. Gene-expression variation in DS and normal samples was evaluated using the Kolmogorov-Smirnov test. According to the degree of overlap in expression levels, we classified all genes into 3 groups: (A) nonoverlapping, (B) partially overlapping, and (C) extensively overlapping expression distributions between normal and DS samples. We hypothesize that, in each cell type, group A genes are the most dosage sensitive and are most likely involved in the constant DS traits, group B genes might be involved in variable DS traits, and group C genes are not dosage sensitive and are least likely to participate in DS pathological phenotypes. This study provides the first extensive data set on HSA21 gene-expression variation in DS and underscores its role in modulating the outcome of gene-dosage imbalance.
Keywords AneuploidyCell LineCell Transformation, ViralChromosomes, Human, Pair 21Down Syndrome/ geneticsFibroblastsGene DosageGene ExpressionGene Expression ProfilingGenetic VariationHumansLymphocytesReverse Transcriptase Polymerase Chain Reaction
PMID: 17668376
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PRANDINI, Paola et al. Natural gene-expression variation in Down syndrome modulates the outcome of gene-dosage imbalance. In: American journal of human genetics, 2007, vol. 81, n° 2, p. 252-263. doi: 10.1086/519248 https://archive-ouverte.unige.ch/unige:8969

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Deposited on : 2010-07-12

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