By Judy Gelman Myers
If someone said a worm gene could illuminate a cause or cure for Alzheimer’s disease, you might doubt their good sense.
But Randy Blakely, Ph.D., believes this is possible, and worth spending several years to find out. He plans to further this research through a $350,000 grant from the Florida Department of Health, opening new opportunities to treat a disease that currently affects more than six million Americans.
Blakely, Stiles-Nicholson Distinguished Professor in Neuroscience and professor of biomedical sciences in the Charles E. Schmidt College of Medicine, said his work is all about evolution — of our species, technology and of an idea he began pursuing 25 years ago.
IN THE BEGINNING
Neurotransmitter transporters, which are complex molecules that enable neurons to communicate with each other, have always piqued Blakely’s interest, he said. While he wanted to study how they contribute to brain disease, he first needed to understand their structure.
In 1993, he and postdoctoral fellow Sammanda Ramamoorthy, cloned the human transporter gene," but the technology for solving the structure of the protein it encoded would not be achieved for another 23 years. “We had the gene. We knew the amino acids that made up the protein. But we didn’t know how these amino acids, connected to each other like beads on a string, folded to make the transporter protein in the shape needed to whisk away neurotransmitters like dopamine and serotonin from the synapse,” Blakely said.
A few years later, he made a choice that defined a significant part of his research for the next 25 years: he turned to evolution — specifically, its bias to protect structures that are important to survival, a feature revealed by sequence conservation. “What I needed was a genome from a distant organism that was making a form of the same protein that I had discovered in humans,” he said.
He chose Caenorhabditis elegans for his research, a tiny worm with 302 neurons that multiplies rapidly and prolifically. The last common ancestor it shared with humans lived 500 to 600 million years ago.
Blakely said his next goal was to identify amino acids in the worm that were conserved in the human protein predicted by the gene he had cloned, in order to determine which ones were critical for how the protein worked.
The genome of the worm, published in 1998, helped him identify the worm’s dopamine transporter gene two years later. Next, “I wanted to see where the transporter was expressed in a living nervous system,” Blakely said.
LIGHTING UP A BRAIN
Blakely and postdoctoral fellow Richard Nass., Ph.D., applied the Nobel Prize-winning technique of putting a green fluorescent protein from algae in cells of another organism, and making them glow green, to worms in an attempt to light up the dopamine neurons of worms. “For the first time, the dopamine neurons of a living nervous system could be seen in all their glory,” said Blakely, adding if he could see the presence of dopamine neurons, he could identify when they were missing.
Since dopamine neurons selectively die in Parkinson’s disease, he said, he wondered if he had stumbled on ways to protect dopamine neurons from this disease.
In 2002, Blakely and his team verified that genetic elimination of dopamine transporters keeps dopamine neurons alive, even when the worms are bathed in toxins. “However, If I stayed with this line
of research, I’d be orienting my work to the study of dying cells. I was more interested in the function of normal synapses and wanted to understand how transporters work in a living synapse,” he said. “So I encouraged my postdoc to use the toxin approach to start his own lab.”
SINK OR SWIM
Blakely resumed research on living worms, searching for a way to identify worms whose dopamine transporters were not working.
A few years later, another postdoctoral fellow, Shannon Hardie, Ph.D., discovered that when worms lack dopamine transporters, they crawl on solid surfaces relatively normally but rapidly paralyze when placed in water, due to a buildup of dopamine that deactivates neurons needed for swimming. His lab coined the phenotype Swip.
In 2015, Andrew Hardaway, Ph.D, a graduate student working with Blakely, used the paralysis phenotype to identify a novel gene they named swip-10, a molecule whose loss caused an extremely rapid form of paralysis when the worms were placed in water. Hardaway’s research showed that paralysis was due to the dopamine neurons being excessively excited by other neurons, which was triggering the release of too much dopamine. Just as striking, another graduate student working with Blakely Chelsea Gibson, Ph.D, discovered that the dopamine neurons were not just excessively excited – they were dying as if they were the dopamine neurons of a Parkinson’s patient. “I saw that there might be a two-for-one prize here — a gene that regulates both the signaling and the health of dopamine neurons,” Blakely said.
A deeper examination of the swip-10 structure revealed that the protein encoded by swip-10 shared a piece of its sequence with a human protein called MBLAC1. The element shared by MBLAC1 with its worm cousin, called an MBD, is ancient, having appeared first in bacteria millions of years earlier to allow these cells to inactivate lethal toxins made
by fungi.
In 2018, a third graduate student working with Blakely Cassie Retzlaff, Ph.D,, established that the antibiotic ceftriaxone binds directly to MBLAC1 and appears to be the primary, if not sole, brain target for the neuroprotective drug.
A CLUE TO ALZHEIMER'S DISEASE RISK
The next step in this research is studying how swip-10 and MBLAC1 keep neurons alive. Blakely’s current lab members are researching mice whose MBLAC1 protein has been genetically eliminated, a project funded by the Florida Department of Health. (Critical initial funding for the project was provided by a Mangurian Alzheimer’s Disease and Related Disorders pilot grant.)
That should be the final credit. The film should be done. But like a modern adventure movie, there’s always something waiting at the back end.
In 2019, a team of scientists reported that MBLAC1 is a risk factor for late-onset Alzheimer’s in people with cardiovascular disease. Blakely and his current team (Maureen Hahn, Ph.D., Peter Rodriguez, Jacob LaMar, Matt Gross, Zayna Gichi), suspect that in humans, MBLAC1 protects not only the brain, but also the heart and its blood vessels, leading to both brain and heart disease arising together.
“If we can understand why the loss of swip-10 causes neurons to die in the worm, we should be able to understand why MBLAC1, its human version, is a risk factor in Alzheimer’s disease, and maybe then we can use what we have learned to develop medications to treat the disorder,” Blakely said. “That’s a dream of course, that’s why we come to work every day.”
