A study from UC Berkeley researchers suggests that transposons, previously referred to as ‘junk DNA,’ are not only involved in but also required for the development of mice.

‘Junk DNA,’ or transposons, were previously understudied due to their perceived nonimportance in development. The study, led by Lin He, senior author and campus professor of molecular and cell biology, and first author and Andrew Modzelewski, assistant project manager of He’s lab, began around four to five years ago and was published Oct. 12.

“In the beginning, we were just really shocked at first of all, how many transposable elements are expressed in mammalian preimplantation embryos, not just for mice, but also for eight different mammalian species we’re looking at, including human,” He said.

The study also included 13 co-authors who worked with He and Modzelewski.

On a larger scale, this study may have an impact on the field of reproductive assistance and in-vitro fertilization, or IVF, said Mackenzie Noon, co-author and post-graduate research associate at Yale University.

“The main clinical relevance is probably to IVF and assisted reproductive technologies, understanding that the transcriptomic environment in very early development is very important, especially with respect to endogenous retroviruses,” Noon said.

The researchers used a number of methodologies to study mice and seven other species, including CRISPR technology and research in the fields of genetics, molecular biology, biochemistry and bioinformatics, Modzelewski said.

Modzelewski added that this study, in addition to others, opens up the study of transposons beyond being “filler DNA.”

“Scientists have long suspected that more of the genome actually does something, and it is exciting to see so many publications coming out to support that and describe the unexpected and wonderful things the rest of the genome is up to,” Modzelewski said in an email.

In terms of future research, He and Modzelewski said they both plan to continue in this line of research.

Modzelewski said he will be moving to work at the University of Pennsylvania where he plans to open a lab of his own.

“We’ll see how hosts can utilize those species-specific elements to achieve species-specific gene regulation and typical regulation,” He said.