Session : Genetic diversity and polymorphisms ; The question of evolution of imprinting in vertebrates and its existence in birds is evoked in the literature, but not yet definitely answered. Genomic imprinting is an epigenetic modification leading to parent-oforigin- specific expression of certain genes. It has been observed in eutherian mammals and marsupials, but not in birds. So far, the allelic expression of imprinted gene orthologs has been analyzed in the chicken, without any reliable evidence of imprinting. Several imprinted QTL have been found in poultry; as some of them may finally be considered as not relevant to genomic imprinting, others appeared to be consistent, when using appropriate animal design and methodology. Our main objectives are to detect genes for which variation in expression is observed according to the allele, either because of an allele-specific expression or a parent-of-origin dependent expression. We screened the entire genome for allele-specific differential expression on whole embryonic transcriptomes by using high-throughput sequencing. Two chicken lines were used, as inbred and as genetically distant as possible, to unquestionably identify the parental origin of each observed haplotype. Two families from 2 reciprocal crosses were produced and transcripts from 20 embryos (4.5 d) have been tagged and sequenced through 6 HiSeq2000 lanes. About 200 Gb have been generated and are under analysis.