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Imprintome Definition Clarified

3 February 2017: Amber Dance published in TheScientist the paper, Characterizing the Imprintome: Three Techniques for Identifying the Collection of Maternal and Paternal Genes Silenced in Offspring.

Although it is important to inform people that scientists are attempting to define this subset of genes in a number of species, “imprintome” is not used in this paper as it was originally intended. The word “imprintome” needs to be used in the precise way we initially defined it so confusion is not introduced into a scientific subject that is already difficult to understand.

There are a number of genes in the human genome that are expressed from only one copy or allele of the gene. The parental origin of some of these monoallelically expressed autosomal genes is random, like DGCR6 and DGCR6L (R. Das, 2010); however, others are expressed in a parent-of-origin dependent manner (Jirtle and Weidman 2007). The latter are called genomic imprinted genes, and are known to play critical roles in normal development, particularly in the brain. Since a single genomic mutation or epigenetic event can alter the normal function of these genes, it is necessary to define the repertoire of imprinted genes and their regulatory elements, the “imprintome.”

“Imprintome” first appeared in the scientific literature when I wrote a 2009 editorial for the premier issue of Epigenomics (Jirtle 2009). I further clarified its meaning in the paper, The Human Imprintome: Regulatory Mechanisms, Methods of Ascertainment, and Roles in Disease Susceptibility (Skaar et al. 2012). The “imprintome” is simply the complete set of environmentally labile imprint regulatory elements in the genome.

In other words, “imprintome" refers only to the differentially methylated regulatory (DMR) elements that control the parent-of-origin, monoallelic expression of genomic imprinted genes. It is NOT the repertoire of genes that are monoallelically expressed in a parental dependent manner, as suggested in TheScientist report.

As discussed in this article, there have been attempts to define imprinted genes in a number of animal and plant species, but so far, neither the “imprintome” nor the imprinted genes these regulatory elements control have been completely defined in any species. Nevertheless, in order to fully understand the genesis of diseases and disorders like autism, cancer, diabetes, obesity, and schizophrenia, this information will have to be determined for humans.