The solution to some human diseases may be stuck in a handful of caves and rivers in eastern Mexico. The Astyanax mexicanus –better known as blind sardine–, a small whitish fish that is the subject of millenary rituals in the State of Tabasco (southeast of the country), has also been a privileged platform for studying biological evolution for years. Now a group of scientists from several prestigious British universities has identified one of the genes that allows you to regenerate the heart. A discovery that opens new avenues of study on cardiac pathologies in humans, one of the main causes of mortality in the world.
The history of these fish –and the reason for its usefulness for science –It begins more than a million years ago, when two groups of the same family take divergent paths: some continue to live in rivers, while others are trapped in caves, where over time they become albinos and blind –in the dark, the view becomes unnecessary. The former maintain the ability to regenerate the heart after suffering a heart attack, while the latter lose it and, instead, they develop a scar on the affected muscle part, which stops functioning, as happens in humans and other mammals.
Having two groups with these characteristics within the same species has allowed a team of scientists from the University of Oxford and University College London, with funding from the British Heart Foundation, to compare them genetically. "We have found a gene that is different and fundamental for the regeneration of the heart," explains Dr. Mathilda Mommersteeg, of Oxford, one of the team's researchers.
The Astyanax mexicanus he is not the only vertebrate with that talent. The zebrafish, from Southeast Asia, has so far dominated research in this field. But, as the report says, "it is difficult to identify new genes regulating the regeneration of the heart (…) if you compare species with different physiologies." There lies one of the main novelties of the study; This is the first time that this process has been compared within the same species, which makes it easier to isolate the key mechanisms.
The identified gene, the other novelty, is just one of the many that potentially participate in the process. The next step of the research, which has been underway for six years and whose first results have been published in Cell Reports in November, it's discovering what Mommersteeg calls "the gene that controls the other genes." "When we find it, we can know what allows a fish to regenerate the heart and bring that to the patient." The ultimate goal is to find a solution to the hardening of the cardiac tissue that occurs after suffering a heart attack and that leads to a variety of diseases.
Despite the evident biological distance between humans and fish, the research team and members of the scientific community are hopeful about the future applicability of these discoveries. "The genetic mechanisms behind the adaptation of these fish to extreme conditions are very similar to those behind certain human diseases," says biologist Craig Albertson, a professor at the University of Massachusetts-Amherst. "It's the tip of the iceberg and there's still a lot to learn, but the study gives us a deep understanding of these processes."
Beyond the research in the cardiac field, the blind sardine has become a famous fish within the scientific community specialized for its many curious facets. Their blindness and lack of pigmentation, a product of biological adaptation to the extreme conditions of the caves, have been studied by specialists in evolution for years, but a recent batch of studies points to new lines of research.
Diabetes and autism are two of them. On the first, scientists from Harvard University recently published a study in the prestigious magazine Nature, where they maintain that this fish can regulate the level of sugar in the blood to survive the lack of food in the caves. Other researchers from the universities of Minnesota and Hawaii have focused on the somewhat autistic nature of these fish. "They are asocial, hyperactive, have attention deficit (…). Interestingly, they are similar to the symptoms of human autistic spectrum disorder, "reads the report, published in June by the specialized journal BMC Evolutionary Biology.
"This fish is a supermodel for human diseases," sums up Dr. Albertson. In fact, the city of Querétaro (central Mexico) hosts a conference dedicated to animals every year. In March, experts from around the world will meet again to discuss the latest discoveries about this blind and albino fish, but scientifically virtuous.