Giraffe genome sequence reveals clues to its unique morphology and physiology

Giraffe gene changes protected mice from high blood pressure. A giraffe needs high pressure to send blood about two metres upwards from its heart to its brain. Earlier mouse experiments showed that deleting a gene called FGFRL1 disrupted both bone and heart development, suggesting a possible connection between the two systems. In 2016, researchers investigated whether changes in genes with such shared roles could help explain giraffes' height and circulation.

Morris Agaba and his team compared genetic sequences from two Masai giraffes and one okapi with those of cattle and other mammals. The okapi, the giraffe's closest living relative, has a much shorter neck, making it a useful comparison. The team searched for distinctive giraffe changes in genes, looking especially for changes predicted to affect how the proteins they encode work.

FGFRL1, which helps regulate growth signals, stood out: the giraffe version encoded seven distinctive changes in the protein. These made it a candidate for connecting skeletal and cardiovascular adaptations, although sequences alone could not establish their effects. Five years later, Liu and colleagues put seven giraffe-type changes into mice. Those mice resisted the rise in blood pressure induced by angiotensin II, a substance used to trigger hypertension; this did not establish the same protection in giraffes or people. The 2016 comparison had identified a gene through which giraffe evolution could link growth and circulation, and the later experiment demonstrated an effect on blood pressure in mice.