Endogenously imprinted genes in Drosophila melanogaster

Genomic imprinting is an epigenetic state that results from differential processing of chromosomes during gametogenesis and which can cause differential expression of genes depending on the sex of the parent transmitting that gene. In Drosophila, many examples of imprinted marker genes have been documented and imprinting of these genes involves highly conserved epigenetic regulators. However, no endogenously imprinted genes have yet been identified. Here we present a phenotypic and transcriptional analysis of parthenogenetic (gynogenetic) and genotypically identical but sexually produced adult female Drosophila. We find that while parthenogenetic females have a superficially normal phenotype and are viable and fertile, their lifespan is extended relative to their sexually-produced counterparts. Microarray/transcriptional analysis of parthenogenetic versus sexually-produced females reveals 76 genes with consistently altered patterns of expression, 36 upregulated and 40 downregulated, some with known effects on aging. Analysis of individuals with uniparental inheritance of only portions of their genome suggest that many of these genes may be indirectly imprinted, responding to either other imprinted genes or redistribution of chromatin components that are differentially allocated to sex and autosomal heterochromatin in a sex-dependent manner during gametogenesis. As gene expression dependent on the parental origin of the genome meets the definition of genomic imprinting, our study provides evidence that endogenous genes are imprinted in Drosophila.