The Planarian Flatworm: A Gateway to Human Immortality?

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A planarian is a species one of many non-parasitic flatworms. Planaria are common to many parts of the world, living in both salt-water and in freshwater ponds and rivers.  They are remarkable creatures. Some planarians exhibit an extraordinary ability to regenerate lost body parts. For example, a planarian split either lengthwise or crosswise will regenerate into two separate individuals.

Recently, one particular species of planarian,  S. mediterranea has emerged as the species of choice for modern molecular biological and genomic research due to its diploid chromosomes and the existence of both asexual and sexual strains. Recent genetic screens utilizing double-stranded RNA technology have uncovered 240 genes that affect regeneration in S. mediterranea. Many of these genes have “Orthologs” in the human genome. Orthologs are genes in different species that evolved from a common ancestral gene by speciation. Normally, orthologs retain the same function in the course of evolution. Identification of orthologs is critical for reliable prediction of gene function in newly sequenced genomes.

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The life cycle and  traits of planarians make them a model system for investigating a number of biological processes, many of which may well have implications for human health and disease. Even immortality. However, the flatworm’s regeneration ability has attracted a lot of attention. It may pave the way for humans to gain the ability to regenerate lost limbs and perhaps even organs. More recently Planarians are being examined in reserach into ageing.  That is because these animals have an apparently limitless regenerative capacity, and the asexual animals seem to maintain their “telomerase” levels throughout their lifetime, making them effectively immortal.

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Telomerase is an enzyme, active chiefly in tumours and reproductive cells, that  facilitates cell division and may account for the immortality of some cancer cells.

As we humans share a number of genes with Planaria, in theory it may be possible to use the planaria genes in bio-engineering the human body, so that we too can regenerate and have infinite longevity.

 

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