Our fingers “started” about 380 million years ago, in the cloaches of a prehistoric fish and not in the fins, says new study.
A new study suggests that the reason why humans have fingers can go back to a surprising genetic heritage: Cloacas of the fish.
The investigation, in Nature on September 17, indicates that the DNA switch responsible for the formation of finger and fingertips 380 million yearsinitially regulating the development of these structures in the fish.
Second Denis DubouleGeneticist Development of the University of Geneva cited here, this is a clear example of how evolution reuse old mechanisms for new functions: instead of creating a fully new regulatory system for fingers, nature has adapted an existing, initially active in cloaca.
The origin of digits in tetrape – Animals with four members – has been a central question for science. Although the most common theory argues that fingers derive from fins, the new investigation points to a more complex process.
The team of researchers from the United States and Switzerland compared the genomes of rats and unlip fish, focusing on the HOXD genes and adjacent regions containing the DNA switches responsible for their activation. Although unlucky fish do not have digits and lack some of these genes, they maintain the associated regulatory scenario. The question was: What function would this system have in fish?
To answer this question, scientists marked some of these switches with fluorescent markers in mouse and unlucky embryos. In rats, the activity arose in the fingers; In the unlocked fish, in the cloaca. When they resorted to the Crispr-Cas9 technique to eliminate these regions, they found that the mouse embryos developed finger and defective feet, while in the fish it was the cloaca that did not form correctly-not the fins.
The results indicate that the original function of this genetic landscape would be to support the development of cloaca, the multifunctional orifice used in excretion and reproduction. As Tetrapods evolved from their aquatic ancestors, the same mechanism was reused to shape the ends of the limbs.
Although more investigations are needed, the discovery offers a new perspective on how biological tools recycle evolution: the origin of our fingers may be, after all, in the rear of a prehistoric fish.
