Our world hosts some incredible organisms, some of which might teach humans more about our own biology or how we can develop therapeutics to treat our diseases. One such animal is the Mexican cavefish (Astyanax Mexicanus). About 1.5 million years ago, these fish were living in the rivers of Northern Mexico, washing into caves with seasonal rains that eventually stopped. That separated the fish into cave-dwelling and river-dwelling populations, which eventually took on different features - the Astyanax Mexicanus fish that still live on the river surface can regenerate their hearts after an injury, while one cave-dwelling type cannot.
A research team led by Dr. Mathilda Mommersteeg at the University of Oxford decided to compare the genomes of these two different types of similar fish to find the genetic reasons why one can still regenerate its heart tissue. The genes that are involved with heart repair would probably be missing from the cavefish. The findings from their study have been published in Cell Reports
and are outlined in the video.
"Millions of years ago, some surface fish living in rivers flooded into caves, became trapped when river levels retreated and lost their eyes and pigment to adapt to cave life," explained co-senior author Mathilda Mommersteeg, a developmental scientist at the University of Oxford. "We have discovered that, like zebrafish, the river surface fish regenerate their heart, while some cavefish cannot and form a permanent scar. We introduce the Mexican cavefish as a new model for heart regeneration research."
Indeed, the researchers were able to find three regions in the fish that they suspected were part of heart regeneration. There were two genes in particular: lrrc10 and caveolin, which were far more active in the river fish.
"Quantitative trait locus analysis (described in the video below) is a method that has allowed us to find out what part of all the surface fish DNA is most crucial for heart regeneration," said co-senior author Yoshiyuki Yamamoto, a developmental biologist at University College London. "We have identified three regions in the DNA that contain genes that make the difference between regeneration or scarring after heart injury."
For this work, the researchers deactivated lrrc10 in zebrafish and found that the fish lost its ability to repair heart damage completely.
"The next step is to find out what the reason is that surface fish can regenerate their hearts, but cavefish cannot," said Mommersteeg. "What is it that happened during their adaptation to cave life that stopped them from regenerating their hearts?"