The giraffe is big…
Biologists have discovered a unique variant of a gene in a giraffe that protects against hypertension
Scientists from China and Denmark deciphered the giraffe genome and, comparing it with the genomes of other ruminants, identified gene mutations specific to the giraffe that allowed it to adapt to high blood pressure and extreme growth. The results of the study are published in the journal Science Advances (Liu et al., A towering genome: Experimentally validated adaptations to high blood pressure and extreme status in the giraffe).
A giraffe is an animal with unique biological features, many of which are associated with evolutionary adaptation to unusual growth. For example, the blood pressure of a giraffe is twice as high as that of humans and most other mammals. This is due to the need to ensure a stable blood supply to the high-placed head. He also grows very fast, but at the same time his bones are formed very dense and strong.
Researchers from Northwestern Polytechnic University in China and The University of Copenhagen analyzed the giraffe genome at the chromosomal level to understand how the giraffe manages to avoid the side effects of high blood pressure, such as serious damage to the cardiovascular system or strokes.
The authors found out that the FGFRL1 gene (Fibroblast Growth Factor Receptor Like 1) in the giraffe genome has undergone many changes compared to all other animals.
Using sophisticated gene editing techniques, they injected this altered gene into laboratory mice. Observations showed that mice with the giraffe gene, compared with normal mice, suffered less cardiovascular and internal injuries when taking a drug that increases blood pressure, and their bones became more compact and dense.
"Both of these changes are directly related to the unique physiological characteristics of the giraffe: it copes with high blood pressure and maintains compact and strong bones, despite the fact that they grow faster than any other mammal to form an elongated neck and legs," the words of one of the the authors of the study of biologist Rasmus Heller (Rasmus Heller).
Another physiological feature of the giraffe is that it spends much less time sleeping than most other mammals. It is believed that this provides him with additional security when approaching predators, since getting up from the ground in giraffes is a long and inconvenient procedure.
The authors of the study found that the key genes regulating circadian rhythm and sleep in the giraffe were subjected to strong selection, which, perhaps, allows it to have a more intermittent sleep and wake cycle.
And giraffes, on the contrary, have a much worse sense of smell than other mammals.
"Giraffes in general are very careful and use their height advantage to scan the horizon, using their excellent eyesight for this. Conversely, they lost a lot of genes related to the sense of smell, which is probably due to the radical dilution of odors at a height of five meters compared to ground level," explains Heller.
According to the authors, their discovery not only gives an idea of the main ways of giraffe evolution, but also shows how the same gene, in this case FGFRL1, can influence several different aspects of the phenotype. In biology, this effect is called evolutionary pleiotropy. As a rule, pleiotropy alone can explain multiple major phenotypic changes that have occurred over a short evolutionary time, as is the case with the giraffe.
Scientists hope that further study of the FGFRL1 gene will be the key to creating a new method of treating hypertension in humans.
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