Independent origin of genomic imprinting in placental fish.

Genomic imprinting is demonstrated in the placental poeciliid fish Poeciliopsis prolifica, with 84 protein-coding genes showing robust parent-of-origin biased expression in placenta.

• Why it matters: Imprinting may help balance maternal control of resource allocation with paternal control of resource acquisition during offspring provisioning, but it was unclear whether it evolves with placenta outside mammals.
• What they did: Using transcriptomes from reciprocal crosses between two inbred strains of Poeciliopsis prolifica, the study identified 84 protein-coding genes with robust imprinting evidence, including imprinted orthologs of grb10 and oppositely imprinted dpp4 and gcga.
• The result: Significantly elevated allelic DNA methylation on promoters of two focal imprinted genes and convergent recruitment of a nutrient-transport gene network suggest mammal-like epigenetic mechanisms and parental-conflict resolution in this fish placenta.

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