TORONTO -- In a far cry from the bunny hop, an unusual breed of domesticated rabbit uses it front paws to walk in a handstand position 鈥� and researchers have finally figured out why.
In a recent study, , academics from Uppsala University in Sweden and the University of Porto in Portugal, discovered that a single gene may explain why the sauteur d'Alfort, or 鈥淎lfort jumping rabbit,鈥� walks on their front legs instead of hopping.
According to the paper, this particular rabbit is unable to perform the characteristic jumping of other breeds and has therefore compensated for their discoordination by adopting an abnormal style of movement.
鈥淚ndividuals from this strain adapt their locomotion behaviour for longer and/or faster movements by lifting the hindlimbs off the ground and move supported solely by their forelimbs, similarly to a human acrobat when walking on hands,鈥� the authors wrote in the study.
The reason why these rabbits can鈥檛 move as efficiently as other rabbits comes down to a genetic mutation, according to the study.
鈥淲e have now characterized a recessive mutation present in a specific strain of domestic rabbits (sauteur d鈥橝lfort) that disrupts the jumping gait,鈥� the research stated.
That recessive mutation was found in the code of the RAR related orphan receptor B (RORB) gene, which affects the rabbits鈥� spinal cord and prevents them from performing a characteristic hop like other breeds.
In order to identify the gene in question, the research team bred a sauteur d鈥橝lfort rabbit with a New Zealand white rabbit, which can successfully hop. They then conducted a genetic analysis of the 52 offspring in order to identify possible mutations in the ones that couldn鈥檛 hop in comparison to the ones that could
鈥淭he classical way to study this is to cross this [rabbit breed] line with a line that has normal gait and then study the inheritance of the traits in families,鈥� the study鈥檚 co-author, Leif Andersson, a professor at Uppsala University, told CTVNews.ca in a telephone interview on Wednesday. 鈥淎nd then we use genetic markers to trace the different chromosome segments and by mapping data to very high resolution, you're able to identify a single gene that is underlying this.鈥�
They discovered the mutation in the RORB gene was to blame and that sauteur d鈥橝lfort rabbits have two copies of this mutation, unlike other wild rabbit breeds.
The RORB gene is expressed in many regions of the nervous system, including in the spinal cord, where it assists in the production of certain proteins.
鈥淭he spinal cord we have is full of these neurons that is connecting the brain with the musculature that drives our limbs and coordinate this perfect coordination of four legs,鈥� Andersson explained.
With this particular mutation, however, the researchers noticed these particular neurons weren鈥檛 present in the spinal cords of the rabbits that couldn鈥檛 hop.
Without those proteins, which help to coordinate the left and right side of the body, the rabbits were unable to properly coordinate their hind legs.
鈥淥ur results show that expression of RORB is drastically reduced in the spinal cord of affected rabbits which results in a developmental defect,鈥� the authors explained.
The researchers concluded that RORB function is 鈥渞equired鈥� for rabbits, and potentially other animals, to be able to leap.
鈥淚t contributes to understanding how the spinal cord functions, which genes it depends on, which neurons are critical for how muscle contractions are coordinated during locomotion,鈥� Andersson said. 鈥淩ORB is not like a gene for hopping, it's a gene for coordinating limb mobility during locomotion. So RORB is most likely important for humans as well in our locomotion.鈥�
