Evolution of imprinting via lineage-specific insertion of retroviral promoters
Aaron B. Bogutz, Julie Brind’Amour, Hisato Kobayashi, Kristoffer N. Jensen, Kazuhiko Nakabayashi, Hiroo Imai, Matthew C. Lorincz, and Louis Lefebvre
Received Date: 31st July 19
Imprinted genes are expressed from a single parental allele. In mammals, this unusual mode of transcription generally depends on the epigenetic silencing of one allele by DNA methylation (DNAme) established in the germline. While many species-specific imprinted orthologues have been documented in eutherians, the molecular mechanisms underlying the evolutionary switch from biallelic to imprinted expression are currently unknown. During mouse oogenesis, gametic differentially methylated regions (gDMRs) acquire DNAme in a process guided by transcription. Here we show that transcription initiating in proximal lineage-specific endogenous retroviruses (ERVs) is likely responsible for DNAme established in oocytes at 4/6 mouse-specific and 17/110 human-specific maternal imprinted gDMRs (igDMRs). The latter can be further divided into Catarrhini (Old World monkeys and apes)- or Hominoidea (ape)-specific igDMRs, which are embedded within transcription units initiating in ERVs specific to these primate lineages. Using CRISPR-Cas9 mutagenesis, we deleted the relevant murine-specific ERVs upstream of the maternally methylated genes Impact and Slc38a4. Strikingly, imprinting at these genes was lost in the offspring of females harboring these deletions and biallelic expression was observed. Our work reveals a novel evolutionary mechanism whereby maternally silenced genes arise from biallelically expressed progenitors.
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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.