A genomic study may have revealed how Greenland sharks live for centuries and yet rarely get cancer.
These sharks (Somniosus microcephalus) are slow-moving dwellers of the deep that can reach more than 6 metres long and weigh over a tonne. We know little about their lives because they roam in dark, cold waters, but it is thought they don鈥檛 reach sexual maturity until they are 150 years old and their lifespan has been estimated at about , making them the longest-living vertebrates that we know of.
To shed some light on how they live so long without frequently developing tumours, at the University of Tokyo in Japan and his colleagues have sequenced a Greenland shark鈥檚 genome, uncovering the genes in each chromosome. They estimate that their sequenced genome is 86.5 per cent complete, with about 37,000 genes found so far.
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The researchers discovered a higher number of copies of genes involved in activating the so-called NF-魏B signalling pathway than are seen in other shark species, such as the whale shark (Rhincodon typus) or the whitespotted bamboo shark (Chiloscyllium plagiosum), which are thought to live to about 54 and 25 years, respectively.
This pathway is used when the body鈥檚 immune system responds to threats and is involved in processes such as inflammation and tumour growth. has been shown to lead to continuous tumour cell proliferation and to pathogens evading immune system attacks.
鈥淪ince immune responses, inflammation and tumour formation significantly affect ageing and lifespan, the increase in genes involved in NF-魏B signalling might be related to the Greenland shark鈥檚 longevity,鈥� says Kinoshita.
The work helps show why some sharks get much less cancer than might be expected given their large size, says at Dalhousie University in Nova Scotia, Canada. 快猫短视频s at University College London recently found that big animals have a higher cancer risk, but have also evolved better defences against the condition.
A high number of genes related to NF-魏B signalling was also reported recently in 听(Mesocentrotus franciscanus), which can live for more than 100 years.
bioRxiv
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