TARGETED DISRUPTION OF DELTA14-STEROL REDUCTASE GENE AS A MOUSE MODEL FOR GREENBERG SKELETAL DYSPLASIA AND REGULATION OF GENE EXPRESSION

Greenberg skeletal dysplasia is a syndrome caused by a genetic defect of cholesterol biosynthesis, characterised by severe developmental abnormalities. The analysis of sterols extracted from foetuses of patients revealed the accumulation of sterol molecules characterised by unsaturation at carbon 14. This finding indicates a defect of delta14-sterol reductase, the enzyme responsible for the conversion of these intermediates to the corresponding carbon 14 saturated sterols, in the pathway for cholesterol biosynthesis. Recently TM7SF2, localised on chromosome 1, was identified as the gene encoding human delta14-sterol reductase. Until now, analysis of TM7SF2 gene of Greenberg patients failed to disclose mutations. However, a defect of the TM7SF2-encoded protein seems to be the most probable cause of the disease. The objective of the present project is the disruption of delta14-sterol reductase gene in mouse embryonic stem cells, in order to create a delta14-sterol reductase defective mouse model. This animal model will contribute to elucidate the molecular mechanisms underlying Greenberg skeletal dysplasia and to verify the importance of the gene on developmental processes. By considering the possibility that regulatory mechanisms fail in Greenberg skeletal dysplasia, we will investigate the regulation of delta14-sterol reductase gene expression, by functional analysis of the gene region that control gene transcription. This could be relevant to understand some of the mechanisms controlling the development/differentiation of organs such as adrenals and testis.