Parental imprinting: from tug of war to solidarity between the generations

While equally to the corresponding gene product, genes that undergo genomic imprinting are monoallelically expressed, either from the paternal allele or from the maternal allele. Until recently, the studies of the effects of departure from this monoallelic expression have been restricted to the impa ct of this imbalance on fetal growth and development supporting the theory of the parental much less than tug of war much greater than. Now several re ports, either in man or in mice, on new genes expressed also in adult brain shed a new light on the possible roles of genomic imprinting in adult soci al and cognitive behavior with unexpected marked differences between males and females. Moreover, epigenetic alterations such as those responsible for genomic imprinting could represent a buffering system capable to endorse a daption to environmental factors by silencing or enhancing expression of mo noallelically expressed genes. Failure to erase these epimutations in the g ermline would lead to stable transgenerational effects. This may revive the long debate on the inheritance of acquired characters as a tool for adapti on/evolution proposed almost a century ago by J.B. Lamarck. It is therefore probably time to think more about the a;advantages that genomic imprinting could confer to the survival of a species through solidarity between the g enerations.