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The Spring Festival of the Year of Rabbit is coming to an end. I believe you have seen many rabbits, but have you seen upside down rabbits?

？Bunny New Year?| Youtube / science news In 2015, an inverted rabbit with unique skills appeared in a zoo in Guangxi. It looks the same as a normal rabbit, but when it walks, it needs to support itself with its front legs.

？Also known as the strong rabbit.| It seems difficult to stand upside down like this. In fact, this is actually a disabled rabbit: they are not jumping and running like normal rabbits from birth, but can only stand upside down. This kind of rabbit is also called sauteur d'Alfort rabbit.

In 2021, a group of researchers focused on the rabbits who could not jump and began to explore why they were unusual. In addition to not jumping, sauteur rabbits have a defect: they are born with retinal dysplasia and develop cataracts less than a year after birth.

Rabbits who appear to be performing acrobatics are actually disabled.| For rabbits, not being able to run or jump is simply fatal, and their forelegs move uncoordinated and slowly. The European hare can reach an average speed of 40 km/h, and its reflexes are quick to escape danger, but the sauteur rabbit will never be able to run, let alone pursue speed.

To study the sauteur rabbit's genes, the researchers crossed male sauteur rabbits with normal female rabbits and then compared the genes of the offspring produced by the female rabbits. Genetic mapping revealed a mutation in a gene called RORB, specifically a small change in the first nucleotide of exon 9.

However, how did this mutation stop the rabbit from jumping?

The RORB gene is expressed as the corresponding RORB protein, which constitutes the RORB neurons of the rabbit. Sure enough, after fluorescent staining, the researchers found very few neurons in the sauteur rabbit spine and almost no RORB neurons. And that's why rabbits lose their ability to jump.

Sauteur rabbits (sam / sam) have far fewer neurons in their spine.| Jumping looks simple, but it requires complex abilities, requiring the spinal central neural network to regulate limb coordination and muscle relaxation and contraction. Therefore, the loss of RORB neurons in the spine seriously affects the motor ability of rabbits 'hind limbs, which is also necessary for rabbits to jump.

In addition to rabbits, mice with RORB gene deletions have also been studied. Scientists found that mice with RORB gene deletion, although not "upside down," walked like ducks, raising their hind legs exaggeratedly and appearing to move uncoordinated. Again, these mice showed signs of retinal degeneration.

A disabled mouse that walks like a duck.| Reference 2 It has also been found that RORB gene can be expressed in the cerebral cortex in addition to the spine, and is related to hearing, movement and other senses. Rabbits 'inability to jump may also have something to do with brain defects.

A gene mutation could make a cute rabbit look completely different. In 2012, a rabbit without ears "fire," it is called Til, born without ears, it was difficult to survive, but under the care of people to survive for three weeks.

Because it was too special, people decided to hold a press conference for the online celebrity rabbit Til, but in the chaotic scene, Til was accidentally trampled to death by photographers.

... what a sad Til| There is also a rabbit that is born without hair due to a genetic defect. This rare mutant rabbit doesn't live long, but an Australian hairless rabbit was an accident. Under the care of its owner, the hairless rabbit survived and grew healthily. In order to protect his skin, the owner also put on a sweater provided by many netizens.

In addition, those "cup rabbits" that are used as gimmicks by merchants are also a genetic defect. Although such "small rabbits" look cute, they often cannot survive without special care. They have many phenotypes of genetic defects, such as bone problems and abnormalities in digestion and endocrine ability.

Rabbits of normal size are very big.| Giphy normal size of small and medium-sized rabbits can often reach 3~5kg weight, some large rabbits can even reach 8kg~16kg. Therefore, there is no cup rabbit that does not grow up, rabbits that can grow up well are the healthiest and normal, and pets are not toys bought for "cuteness."

Giphy... I hope every rabbit can be healthy and healthy.

References:

[1] Carneiro, Miguel, et al. "A loss-of-function mutation in RORB disrupts saltatorial locomotion in rabbits. " PLoS genetics 17.3 (2021): e1009429.

[2] Koch, Stephanie C., et al. "RORβ spinal interneurons gate sensory transmission during locomotion to secure a fluid walking gait. "Neuron 96.6 (2017): 1419-1431.

[3] André, Elisabeth, et al. "Disruption of retinoid-related orphan receptor β changes circadian behavior, causes retinal degeneration and leads to vacillans phenotype in mice. "The EMBO journal 17.14 (1998): 3867-3877.

This article comes from Weixin Official Accounts: Bring Science Home (ID: steamforkids), Author: Everything

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