Shining light on the dark matter of the genome
These studies make strides in better understanding retroelement L1 expression and regulation at the locus-specific level using a combination of sequencing technologies. A picture is painted demonstrating tissue specific patterns of L1 expression when identified stringently and confidently with our developed EL-Seq approach. As it was also determined that expressed L1s significantly correlate with regions of open chromatin, these tissue-specific patterns of L1 expression are then most likely explained by tissue-specific chromatin architecture. Evidence is also presented here that L1s in tissues respond differently with genomic stresses and perturbations as is seen in the case of aging indicating that the risk associated with L1 damage and mutagenesis is related to cell type and tissue. This is particularly notable when considering the genesis and promotion of age-related somatic diseases like epithelial cancers. L1s are commonly referred to as the dark matter of the genome, but here we illuminate its biology and regulation to better understand L1-associated damage and risk to human health.