College of Arts and Sciences - Spring 2021 - University of Miami

One of the lesser-known dwellings on the
University of Miami campus is a place referred
to as the “Zebrafish Hilton” by facility
manager, Ricardo Cepeda, whimsically listed
in the directory as the “local fish whisperer.”
A former literature teacher in Colombia,
Cepeda keeps close watch on the nearly 6,000 zebrafish
living in the Zebrafish Core Facility, the site of cutting-edge
research used by faculty and students to model human
genetics and disease, from Parkinson’s and autism to
peripheral neuropathy.
Known scientifically as Danio rerio, zebrafish are a
striped species of fish native to Southeast Asia. They grow
to only about an inch and a half in length. But that small
size, which makes the entire fish easier to view with magnification,
is just one of its many advantages for research.
Zebrafish eggs and young are translucent, which makes
for easy observation of their internal organs. They mature
quickly, developing as much in a day as a human embryo
does in a month. And as vertebrates, they have physiology
similar to humans with comparable nervous system, muscle,
blood, kidney and eye structures.
“We keep thousands and thousands of adults and they
live for years in the Zebrafish Hilton,” says Julia Dallman,
Zebrafish Core Facility director and associate professor of
biology. In addition to overseeing operations at the facility,
Dallman also studies zebrafish. Her main area of research
is autism, using genome editing technologies to study some
of the hundreds of genes linked to the condition.
In terms of genetics, zebrafish have a structure remarkably
close to humans and share 70 percent of the same
genes (as well as more than 80 percent of the genes linked
to human diseases). They’re also cheaper to acquire and
use than mice, in part because you can get a whole bunch
of zebrafish very quickly thanks to their prolific reproductive
cycle and the ease of genetic manipulations.
“Zebrafish females produce up to 300 eggs at a time,
once a week,” says Dallman, who also started the
Department of Biology’s zebrafish colony with 40
“pioneers” she brought from New York after joining UM in
2007. “We’re using an animal model to get to the
underlying mechanisms of disruption of genes. It’s not
autism per se that we’re addressing so much as comorbidities
common to autism, like seizures or gastrointestinal
Photo: Alan Cressler
distress. A lot of other conditions are also associated with
gastrointestinal distress, like Parkinson’s. It can be an early
indicator of nervous-system trouble.”
Another Zebrafish Core Facility tenant is Associate
Professor Sandra Rieger, who primarily studies neuropathy
and appendage regeneration in the Department of Biology.
Zebrafish is one of the few vertebrates with robust
regenerative abilities. Rieger’s team is studying the
nervous system’s role in fin regeneration, cutting them off
and watching them grow back.
Using zebrafish, Rieger is studying the use of possible
inhibitors to prevent chemotherapy and diabetes-related
nerve degeneration. Initial results have been promising
with zebrafish as well as rodents, so much so that she has
been starting up a company to develop a molecule for
testing and eventual treatment in humans. That’s years off,
but it can’t happen soon enough.
“Chemotherapy-induced and diabetic neuropathy are
very relevant topics, affecting approximately 15.5 million
people in the US,” Rieger says. “Patients frequently email
me and have hope in my research as a new approach that
could potentially treat them. Right now, there is no treatment,
so people are desperate and living with pain as well
as numbness and loss of balance. Pain is the most common
and terrible symptom, and pain medicines can be
addictive. I hope to find treatments for them.”
As for neuropathy, it’s a degenerative nerve condition
that commonly manifests as pain or numbness in the
hands and feet. Neuropathy is associated with a wide range
of conditions and causes besides chemotherapy and
diabetes, including environmental toxins, alcohol,
trauma, and antibiotics. It’s also a common side effect
of the chemotherapy drugs used to treat cancer, which is
where Rieger’s research comes in.
“From an evolutionary standpoint, regeneration occurs
more frequently in invertebrates and lower vertebrates and
has been lost in the mammalian lineage throughout
evolution,” says Miguel A. Portales Guemes, one of
Rieger’s student collaborators. “We want to understand
why humans do not regenerate their tissues as well, and
if there is a way to supplement or reactivate that, since we
have the same genes as zebrafish. If we find the mystery
behind growing back tissues, maybe we can improve the
healing process in people.” n
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