Investigation of inter-individual epigenetic variability in bovine clones: a high throughput study

Adresse Présente de Daniel Le Bourhis: Physiologie de la Reproduction et des Comportements, INRA ToursAdresse Présente de Daniel Le Bourhis: Physiologie de la Reproduction et des Comportements, INRA ToursReprogramming the somalie cel! to totipotency can be obtained following the transfert ofits nucleus into an enucleated oocyte (cloning). We are using cattle clones as a mode!to assess the interindividual epigenetic variability and its consequences on phenotypes, including agronomical relevant traits and developmental pathologies. Indeed, the developmental defects frequently associated with cloning could be related to the insufficient extent of reprogramming, leading to long tenu consequences on phenotypes. To identifY epigenomic pattems affected by incomplete reprogramming, we used immunoprecipitation of methylated DNA followed by hybridization on a new bovine promoter microarray (MeDIP-chip). The microarray targets the upstream region (-2,000 to +1,360 bp) of21,416 genes (UMD3.1 assembly). We first focused on liver, because overgrowth of this organ is often observed in clones. The microarray has been hybridized with MeDIP sampies from livers of normal Holstein animais (4 perinatal controis and 8 adults, obtained by artificial insemination and all healthy) and livers of Holstein clones (7 perinatal clones, either stillborn or suffering from severe pathologies, and 7 adult clones, with normal to pathological phenotypes). After normalization of the data, enriched probes were identified using ChiPmix. Results of exploratory analysis, including correlation clustering, Principal ComponentAnalysis (PCA) and Independent ComponentAnalysis (ICA), will be presented. A statistical test based on differences in the spatial distribution of the enriched probes revealed that most of the promoters exhibit a clustered distribution of the enriched probes. This local enriclnnent shows interindividual variability for sorne of the promoters, which are currently being identified and validated