The mechanisms surrounding genomic imprinting has always been a bit of black-box, especially when it comes to the erasure of paternal methylation patterns. A recent study led by Yi Zhang at the Boston Children’s Hospital has made a breakthrough in our understanding of imprinting, showing that Tet1 is a major part of the clean-up crew that sanitizes DNA methylation imprints for the next generation.

The Children’s Hospital groups overcame some difficult challenges in their experiments; genomic imprinting is hypersensitive to the environment and very difficult to replicate in vitro. On top of that, maintaining a proper genomic imprinting pattern is an integral part of cellular differentiation and development, with even the slightest abnormality introduced via cultured differences frustrating many a stem cell researcher in the past.

As Zhang points out in their press release, “We’ve long known what proteins are responsible for establishing imprinting patterns, but how erasure occurs has been less clear.” So, guess which active demethylation pathway they looked into first? That’s right, it was Tet. Here’s what the Zhang team found: