The jumping rabbits of Alfort, of jumping, only have the name. When they want to move around slowly, these animals march on all fours – just like any other rabbit. But, to run, the French rodents support themselves on both front legs and project the rest of the body upwards, planting a banana tree.
This peculiarity was first observed by French veterinarians in 1935. Until then, nobody knew how to explain what led rabbits to adopt this curious walk, but it seems that the mystery has finally been solved. A study published in the scientific journal Plos Genetics showed that the trait is linked to a genetic mutation that disrupts communication between nerve cells and the animal’s muscles, causing a motor problem.
In 2014, geneticists at the University of Uppsala, Sweden, and the University of Porto, in Portugal, sequenced the genome of the species. Then, the researchers crossed a jumping male from Alfort with a female without motor deficits, reaching an offspring of 52 offspring (they lived up to their reproductive fame). All new animals also had their genomes sequenced, and the researchers found the mutant gene, like the father’s, in 23% of them.The mutation in question is in a gene called RORB. It interferes with the production of a protein of the same name in a specific group of interneurons – nerve cells that transmit sensory information to the motor neurons that control muscles.
This RORB protein is responsible for neutralizing the activity of other nerve cells present in the spinal cord. Without their action, rabbits end up flexing certain muscles too much and their motor coordination is impaired, which causes the animal to raise its hind legs more than necessary.
The study of this gene does not help to understand only the gait of the jumping rabbits of Alfort, but of all mammals. In previous research, scientists observed mice that also walked in this acrobatic way and had a mutation in the RORB gene. In addition, theStudies involving rats have shown that these animals are more likely to have vision problems – which was also observed in rabbits, which are usually born blind or develop cataracts in the first year of life.
The authors explain that “in addition to its importance in the spinal cord, RORB is also expressed in many regions of the brain, such as the primary, auditory, visual and motor somatosensory cortices, in some nuclei of the thalamus and hypothalamus, in the pituitary gland and in the superior coliculus”.
The researchers see the discovery as a possibility to better understand some motor deficits in humans, such as Charcot-Marie-Tooth disease, which causes the weakening of muscle tone. In this condition, the patient’s RORB gene is also atypical, and future research may show how it is influencing the spinal cord communication centers of affected people.
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