Systems properties of proteins encoded by imprinted genes.

Genomically imprinted genes show parentally fixed mono-allelic expression and are important for the mammalian development. Dysregulation of genomic imprinting leads to several complex pathological conditions. Though the genetic and epigenetic regulation of imprinted genes has been well studied, their protein aspects are largely ignored. Here, we systematically studied a sub-network centered on proteins encoded by imprinted genes within human interactome. Using concepts of network biology, we uncover a highly connected, transitive and central network module of imprinted gene-products and their interacting partners (IGPN). The network is enriched in development, metabolism and cell cycle related functions and its malfunctioning ascribes error intolerance to human interactome network. Further, detailed analysis revealed that its higher centrality is determined by 'date' interactions among the proteins belonging to different functional classes than the 'party' interactions within the same functional class. Interestingly, a significant proportion of this network genetically associates with disease phenotypes. Moreover, the network comprises of gene-sets that are upregulated in leukemia, psychosis, obesity/diabetes and downregulated in autism. We conclude that imprinted gene-products are part of a functionally and topologically important module of human interactome and errors in this sub-network are intolerant to, otherwise robust, human interactome. The findings might also shed light on how imprinted genes, which are rather very few, coordinate at protein level to pleiotropically regulate growth and metabolism during embryonic and post-natal development.