How giraffes overcome high blood pressure caused by long necks

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Giraffa is a mammal of the giraffe family that lives in Africa, and it is known that there are four species. It is characterized by long legs and long neck. In particular, the two-metre long neck is made up of seven bones, like other mammals, and evolutionists such as Darwin and Lamarck have come up with several theories about how the giraffe's neck became so long. Either to reach prey from high places, to watch out for predators or competitors while looking away from high places, it has evolved in a way that is beneficial to survival.

Whatever the cause of evolution, for scientists, the engineering problem with this long neck was a particularly unsolvable mystery. This is because the giraffe's heart must pump blood at 2.5 times higher pressure than humans in order to send oxygen to the brain through its long neck. This caused the giraffe's cardiovascular wall to thicken and the circulatory system to adapt to prevent sudden changes in blood pressure when the giraffe raises or lowers his neck. The ligaments at the nape of the neck have also expanded to support the long, heavy neck. So, the lengthening of the giraffe's neck is the result of the evolution of several biological and physiological features together.

Recently published in Science Advance magazine, the genome of the Rothschild giraffe (Giraffa camelopardalis rothschildi) was completed and analyzed as a chromosomal assembly. It was possible to specify what'red mutation' was, and in an experiment in which this mutation was introduced into transgenic mice, it was reported that these mice did not develop hypertension even if they induced hypertension.

First, after obtaining the genomic sequence information of the giraffe, the researchers compared and analyzed it with the coding region that specifies the protein sequence in other mammals. 359 visible genes were detected. These were genes involved in functional growth and development, neurological and optic nervous system, circadian rhythm, and blood pressure regulation.

Among them, the research team has previously suggested that it is naturally selected from giraffes, and in this analysis, they paid attention to the gene FGFRL1, which was identified as a giraffe-specific mutation compared to other genes. This gene is known to affect the cardiovascular system and skeleton in humans and mice. Compared to other ungulates and mammals, this gene has seven bases that cause amino acid mutations unique to giraffes. Therefore, the researchers hypothesized that this gene mutation may be related to the specific cardiovascular hemodynamic characteristics of giraffes, in which the symptoms seen in hypertensive conditions in other animals are not observed even though the blood pressure is very high due to the long neck. Giraffe-type mutations were cut into the mouse's FGFRL1 gene using a genetic scissors technique. In addition, high blood pressure was induced in wild-type rats and rats with giraffe-type genetic mutations, respectively, whereas wild-type rats developed hypertension for 28 days afterwards, whereas in rats with giraffe-type genetic mutations, changes in heart rate, blood pressure, and other heart diseases were not observed. This is a discovery that can contribute to the treatment of hypertension in humans, as well as confirming through experiments on the genetic characteristics of giraffes, the researchers stressed.

The researchers also reported that mice with a giraffe-type genetic mutation in FGFRL1 had stunted symptoms as soon as they were born. They were smaller than wild-type rats, had slower skull and facial development, and shorter vertebrae. However, when they became adults, they did not show any difference from wild-type mice. The researchers interpreted this to mean that FGFRL1 not only helps fight hypertensive conditions in giraffes, but is also involved in bone formation. However, as adults did not show any difference from the wild type, he added that FGFRL1 alone does not cause giraffe-specific bone formation, but because other genes are linked together.

On the other hand, compared to other ruminants, the researchers reported that giraffes showed differences in functions related to tissues affected by hypertension, such as blood vessels, heart, and kidneys. The interpretation is that, as many scholars have thought, the evolution of the giraffe's long neck implies that genetic mutations related to several functions were involved.

The research team emphasizes that it provides insight into human diseases through the study of genetic mutations related to the evolution of giraffes.