Madrid. A research published in Scientific Reports reveals the genes that likely allowed whales to grow to gigantic sizes compared to their ancestors.
The findings highlight the role of four genes (GHSR, IGFBP7, NCAPG, and PLAG1) and suggest that they promote large sizes while mitigating potentially negative effects, such as increased cancer risk.
Whales, dolphins and porpoises (known as cetaceans) evolved from small land ancestors around 50 million years ago, but some species are now among the largest animals that have ever lived. However, gigantism can bring biological downsides, such as reduced reproductive performance and increased chances of diseases such as cancer, and it remains unclear what role different genes have played in driving gigantism in whales.
Researcher Mariana Nery and her colleagues from the University of Campinas, in Brazil, carried out an evolutionary molecular analysis of nine candidate genes: five genes (GHSR, IGF2, IGFBP2, IGFBP7 and EGF) of the growth hormone/growth factor axis similar to insulin, and four genes (NCAPG, LCORL, PLAG1, and ZFAT) that are associated with increased body size in hoofed animals such as cattle and sheep, which are distantly related to whales.
They evaluated these genes in 19 species, including seven that have a body length of more than 10 meters and are considered giants: the sperm whale, bowhead whale, gray whale, humpback whale, North Pacific right whale, rorqual common and the blue whale.
The authors found positive evolutionary selection for the GHSR and IGFBP7 genes on the growth hormone/insulin-like growth factor axis, and for the NCAPG and PLAG1 genes.
According to the authors, this indicates that these four genes were probably involved in the increase in body size of giant whales. In addition, GHSR controls aspects of the cell cycle and IGFBP7 acts as a suppressor in several types of cancer, which together could counteract some of the biological disadvantages associated with large body size.
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