Quantitative Genexpressionsanalyse im respiratorischen Netzwerk an Mausmodellen für das Rett-Syndrom

Abstract

Rett syndrome is a severe neurodevelopmental disease that affects especially girls. The clinical characteristics are autistic behaviour, seizures, stereotypical movements like washing hands, mentale retardation, loss of already acquired skills and respiratory dysfunctions. Rett syndrome is caused by mutations in the gene MECP2. MECP2 loss as well as the duplication of the gene causes a Rett symptomatology or rather a Rett-like symptomatology. MECP2 is located on the X chromosome and encodes the transcription factor MeCP2 (methyl-CpG-binding protein-2) that binds methylated DNA. MeCP2 acts as a transcriptional repressor as well as a transcriptional activator. Bdnf and Dlx5 are already known as targets of MeCP2. The purpose of this dissertation is to show potential new targets and their regulation by MeCP2. The respiratory phenotype (apnoea, prolongated postinspiration, breathing irregulations) of Mecp2 knockout mice P40 (postnatal 40 days old) is related to respiratory dysfunctions of Rett patients. The early developmental stage of P7 (postnatal 7 days old) shows a dysbalance of excitation and inhibition in Mecp2 knockout mice which should be responsible for the Rett symptomatology such as respiratory dysfunctions. Rhythm-generating respiratory neurons are localised in the Pre-Boetzinger complex (preBotC) of the brainstem. Therefore RNA extractions of preBotC were analysed from Mecp2 knockout mice and transgenic mice with the age of P7 and P40. The transgenic model was generated with an additional copy of the gene Mecp2, because it is already known that a gene duplication causes a symptomatology similar to the Rett syndrome. Relative RNA expressions of potential targets of MeCP2 were analysed by quantitative polymerase chain reaction in case of missing (knockout mice) and overexpressing MeCP2 (transgenic mice). These results suggest that MeCP2 could act as a repressor of Grin1 (P7), Grin2a (P7), Gabrb1 (P7), Tph2 (P7), Ddc (P40), Slc6a4 (P7), Htr4 (P7) and as an activator of Grin2d (P7), Drd4 (P7), Oprm1 (P40). S trong evidences suggest that Htr5b and Foxp2 could also be targets of MeCP2 and that this results in a repressing expression of RNA. To fully understand the correlation of MeCP2 and its targets, especially the pathogenesis of Rett syndrome, other researches must be done.