Jun 4, 2017

How the Galápagos cormorant lost the ability to fly

Galapagas cormorant (l) Caroline Duffie Judy / Brandt's cormorant (r) Alan Schmierer/Flickr

Scientists report they have narrowed in on the genetic changes that made the iconic Galápagos cormorant unable to fly. The researchers found mutations that may have shortened the bones in the bird's wings, a finding they say may help to better understand the genetic factors play in some rare bone disorders in humans.

"We were quite surprised to discover that the Galápagos cormorant had accumulated a large number of mutations in a particular group of genes, which when mutated in humans lead to problems in bone development," Alejandro Burga, UCLA geneticist and lead author of study.

What they did: The team of UCLA scientists sequenced genomes from three cormorant species and compared them with that of the flightless Galápagos cormorant (out of roughly 40 species of the birds, only one can't fly). They identified variants in genes involved in the formation of cilia - the tiny hair-like processes that extend from the surface of a cell that help receive signals from other cells and are key to bone development in animals. The scientists then tested their findings by inserting the gene mutations into roundworms and mouse cartilage cells. They found it appeared to cause a partial loss in cilia function in the worm and an interference in the bone growth of the mouse.

What it tells us: "We found many physical and genetic similarities between the evolution of loss of flight in the Galápagos [c]ormorant and a particular group of human syndromes called skeletal ciliopathies. Although we generally understand the principle behind skeletal ciliopathies — mutations that effect the cilia lead to problems in bone development — there are still many mysteries... Thus, by better understanding how mutations in these genes work together, as it happens in evolution, we can gain insights into human disease," Burga says.

The limitations:

  • UCSD scientist Kimberly Cooper wrote it is not yet clear which mutations act together to replicate wing reduction in this flightless bird, or whether wing reduction and flightlessness are even necessarily advantageous to this species. Cooper added that questions also remain about how mutations in genes that participate in multiple developmental events — especially those related to disease in humans — are tolerated during evolution.
  • Leonardo Campagna, an evolutionary biologist at Cornell University, says the research is "pioneering" but further study is needed. "We don't really know what could be happening with non-coding sequences because these were not investigated in detail," he told Axios.
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