The Secrets Of Life Underground

The genome of the Damaraland mole rat provides an insight into the adaptations required for life underground.

AsianScientist (Aug. 29, 2014) – Scientists from Harvard Medical School, Ewha Womans University, BGI and other institutes, present a high-quality Damaraland mole rat genome, revealing the genomic and transcriptomic events underlying longevity and adaptations to subterranean environment. This study was published in the journal Cell Reports.

African mole rats spend their lives in dark, unventilated environments that are low in oxygen and rich in carbon dioxide and ammonia. The genome of the naked mole rat (NMR) was sequenced in 2011. Now, scientists have sequenced the genome of another African mole rat, the Damaraland mole rat (DMR), and improved the genome assembly of NMR.

They found 6,133 single-copy orthologous genes by comparing the sequences of DMR, NMR, rat, mouse, Chinese hamster, guinea pig, rabbit, dog, rhesus macaque and human. An interesting finding is that the DMR and NMR diverged 26 million years ago, similar to the time that mice and rats or rhesus macaques and humans separated into distinct lineages.

This study revealed 212 and 378 additonal gene families in DMR and NMR lineages, respectively, which are enriched in olfaction (sense of smell) genes that likely play an important role in social interaction and locating food in complete darkness. Meanwhile, of the 59 and 29 gene families lost in DMR and NMR were tens of genes related to visual perception category.

When exploring the genetic mechanisms associated with the adaptations to subterranean environment, researchers found the arginase 1 (ARG1) was mutated in both the NMR and DMR, which may explain their enhanced ammonia removal efficiency. Transcriptomic analysis revealed several genes associated with DNA damage repair and responses to stress showed higher expression in subterranean rodents even during normoxia. This finding suggested that the improved DNA repair is an intrinsic mechanism of adaptation to an underground environment.

In contrast to shorter lived rodents such as mice, subterranean rodents can live for as long as 20 to 30 years. In the study, researchers found that two peroxiredoxins (PRDX2 and PRDX5) were expressed at lower levels in NMR and DMR livers. Lowever peroxiredoxins may result in increased levels of reactive oxygen species (ROS), suggesting that the long-lived NMR and DMR can thrive despite elevated oxidative stress.

Huang Zhiyong, project manager from BGI, said, “The subterranean rodents are specialized species. The genome sequencing and comparison analysis of two mole rats can help us to understand the molecular mechanisms of subterranean rodents characteristics like longevity, hypoxia adaptation and cancer resistance. These findings also would benefit other biology and biomedical research.”

The article can be found at: Fang et al. (2014) Adaptations to a Subterranean Environment and Longevity Revealed by the Analysis of Mole Rat Genomes.


Source: BGI; Photo: Benny Mazur/Flickr/CC.
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