Quick Summary The Hydra is a small freshwater invertebrate that possesses miraculous regenerative capabilities

Celina Juliano studies the molecular mechanisms that allow this creature to continuously renew its stem cells

A recent $1.5 million NSF grant will help Juliano and colleagues develop genomic tools to promote regenerative research

What comes to mind when you think of the animals scientists use for life sciences research? Worms? Flies? Mice?

While these popular model organisms are staples in research laboratories across the globe, understanding some of life’s mysteries, such as regeneration, require a different kind of creature.

Enter the Hydra, a small freshwater invertebrate that’s got a knack for biological immortality and regeneration. Despite its miraculous abilities, the Hydra remains understudied. But thanks to a roughly $1.5 million grant from the National Science Foundation’s Enabling Discovery through Genomic Tools (EDGE) program, Assistant Professor Celina Juliano, Department of Molecular and Cellular Biology, and her lab will help develop genomic tools that will promote regenerative research and hopefully increase the number of researchers using Hydra as a model system.

Stefan Siebert/Juliano Lab

Constantly-renewed stem cells

Hydra have been referred to as the “eternal embryo.” And the name is fitting. The embryo of any animal, including humans, has the ability to produce all cell types. This ability doesn’t usually continue into adulthood. But Hydra constantly renew all of their cells from stem cell populations throughout their entire lives, meaning these creatures have a bottomless well for replacing every single type of cell in their body.

“If you or I were injured, say our hands were cut off, there’s a specific genetic program that is activated and is required to heal the wound, but the hand wouldn’t grow back” said Juliano “That same genetic program is activated after injury throughout the animal kingdom, but in some cases, instead of triggering scarring, it triggers regeneration and thus the missing body part is replaced.”

Juliano and her lab are currently wrapping up a single-cell sequencing project on the Hydra. Over the course of the last year and half, they’ve sequenced every cell type in the Hydra body, defining the exact genes expressed in each cell type.

With that information, Juliano and her team now know the genes expressed in every cell type, which allows them to understand how all cell types are made in Hydra. This information also gives Juliano and her team greater control over the genes they’d like to study in the cells of their experimental organisms.

“You want to be able to modify gene function and then look at the resulting phenotype, or observable characteristics,” said Juliano. “So you can manipulate gene function and maybe something really drastic would happen. For example, in Drosophila changing the expression of just one gene leads to a leg growing out of the eye. That’s a very extreme example.”

But in order to better control genes, certain tools need to be developed. And that’s where the grant funding comes in.

Making Hydra a model for all

Hydra being immobilized in a microfluidic chamber designed to provide tight confinement for electrophysiological measurements. Krishna Badhiwala/Robinson Lab

Juliano is partnering with Jacob Robinson, a neuroengineer from Rice University, to develop methods that can be used to study gene function in Hydra. The team will use the grant to focus on improving methods to study the regeneration of Hydra, including the regeneration of neurons.

Juliano’s team will construct tools to turn genes on and off at specific times and places in a Hydra’s continuous development as an adult. Robinson, according to Juliano, will create tools that will help them study the Hydra’s nervous system including the first microfluidic technologies designed to probe neural activity and behavior in Hydra. Combined, the genetic tools and phenotyping technologies will help them understand how Hydra can regenerate all of its cells, including the nervous system and, potentially, why humans can’t.

But there’s also another tool Robinson is developing that Juliano knows members of her lab will appreciate. One tricky thing about keeping Hydra is they require a lot of maintenance. And you have to clean the Hydra by hand. With the thousands of animals Juliano and her lab manage, the work is time intensive. Using his engineering expertise, Robinson is developing a robot that will carry out maintenance of the Hydra and their enclosures.

“He’s designing what we’re calling the ‘Hydra robot,’” said Juliano.