Jellyfish have been swimming through Earth’s oceans since dinosaurs went extinct 66 million years ago, even managing to hit reset and go back into their larval stage following sexual reproduction.
One species known as the “immortal jellyfish” has managed to do this repeatedly, and now scientists have managed to unlock its genetic code to gain insight into why and how.
Life Cycle
As we age, our bodies begin to break down. Recently, scientists discovered an animal which can reverse this process and offer insights into immortality.
An incredible journey awaits a jellyfish as its life cycle unfolds. When fertilized by sperm, female jellyfish eggs grow into free-swimming larvae known as planulae that swim around until they find a solid surface to attach themselves to. Once there, planulae begin growing polyps which eventually transform into bell-shaped medusae as its polyps give jellyfish their signature shapes; an ephyra develops from within polyps as its polyps further develop and becomes increasingly complex with age.
At this stage, an ephyra can be seen emitting spores that will eventually develop into new medusae or polyps. This process leads to an outbreak of jellyfish blooms in a given area.
Ephyra will continue to expand until it can move on its own, when it starts resembling more mature jellyfish. At this stage, its colors may change to attract prey or warn predators away.
Typically, jellyfish only spend a few months in this medusa stage before beginning to die of old age and officially reaching the end of its lifecycle. But under certain conditions, this medusa can revert back into its polyp form and resume living another cycle.
Recent research has demonstrated that Turritopsis dohrnii jellyfish has the remarkable ability to reproduce multiple times postsexual reproduction, effectively making it what scientists refer to as biologically immortal jellyfish. Scientists at Oviedo University have mapped the genes behind their extraordinary ability and hope that understanding these might lead to anti-aging medications for humans as well.
Jellyfish may seem like an appealing answer in our search for eternal youth, but we should remember they’re only one species among many. Most species seen both in aquariums and nature displays only survive as long as their adult medusae can reproduce successfully – which may not always be easy!
Genetics
Genetics is the study of genes, the units of heredity passed from parent to offspring that contain instructions that determine characteristics such as eye color or susceptibility to certain diseases. Genetics also investigates how variations in genes affect an organism’s health and well-being.
Scientists have recently identified several genes that appear to protect against the aging process. The longevity genes, specifically, appear able to keep cells active for longer than would otherwise be the case – this may help cells better withstand stressors such as high temperatures or lack of food and water in various environments around the globe.
Other genes have also been shown to accelerate aging, often linked to age-related diseases that can have serious if not fatal consequences. One such gene involved with insulin production often exhibits such characteristics.
Researchers have recently discovered that changing specific genes can reverse their harmful effects. One way this was achieved was using a harmless virus to deliver rejuvenating Yamanaka factors directly to damaged retinal ganglion cells in mice’s eyes, producing results such as younger-looking eyes capable of sending new messages along their axons to the brain.
Altering how genes are folded within cells is another approach to combatting aging, and researchers used proteins that regulate DNA folding as tools in this process. Unfortunately, however, results weren’t always satisfying; sometimes changes made to proteins altered how certain genes were read by other proteins, leading to changes in cell activity that altered activity levels further still.
Researchers are working hard to make these protein changes permanent in order to create a drug that could effectively slow or reverse human aging. While this task will likely prove daunting due to our complex ecosystem consisting of trillions of cells and over 10,000 genes, even if this could only slow aging for some cells or genes it would still represent a great step forward.
Transdifferentiation
Transdifferentiation, as a relatively novel phenomenon, questions the idea that differentiated cells have reached an irreversible and permanent state. Transdifferentiation involves direct conversion from one cell type into another without restarting development; its main criteria being lineage relationship and molecular differences that distinguishes between these cell types on an intracellular level.
Chemical methods for inducing transdifferentiation allow scientists to precisely control the concentration, duration, and timing of small molecule treatments that induce reprogramming, which allows for the generation of specific cell types in an exact fashion. Furthermore, stepwise or sequential transdifferentiation mimicking natural development provides useful strategies in creating complex cell populations.
Chemical transdifferentiation’s reprogramming effects may be more robust and efficient than that of fibroblast-to-iPSC conversion, making it an attractive method of regenerating desired cell types for therapeutic applications. Furthermore, using chemicals for inducing transdifferentiation leads to greater differentiation which results in functional cells with desirable biophysical properties.
Researchers have devised numerous protocols for inducing neuronal transdifferentiation using different sources of somatic cells. These procedures provide a powerful means of creating alternative autologous cell therapies for neurodegenerative conditions as well as human mechanistic studies and new drug screening systems.
Furthermore, these methods offer an invaluable complement to reprogramming models that explore neurological disease modeling from iPSCs – particularly when producing cell types that retain age-related neurological disease phenotypes.
Recently, an example of direct conversion occurred with dermal fibroblasts to striatal neurons using miRNA-based direct reprogramming. The newly generated neurons displayed various neurodegenerative disease traits found in patients with Huntington’s disease such as nuclear huntingtin protein aggregates and spontaneous aggregation phenotypes that are characteristic of this degenerative condition.
Chemical transdifferentiation research offers promise; however, several obstacles and limitations prevent its clinical application. With further advancements and technological developments, its future looks bright.
Regeneration
Jellyfish are great examples of regeneration in nature, with new arms, tails and even bodies emerging through regeneration processes called epimorphic regeneration. Scientists are now trying to harness this power so as to produce replacement organs for those lost organs.
Regeneration can also help address environmental problems, like jellyfish swarming in an area to alter its chemical makeup. They remove nutrients by digesting dead fish and squid, competing against phytoplankton that deplete oxygen from waterbodies, and bind microplastics out of circulation through mucus production in their bodies.
As with other cnidarians, jellyfish are hermaphrodites that can self-fertilize. Reproducing asexually by releasing eggs and sperm into the water where they float until meeting other gametes; some species spawn all at once before female jellyfish fertilize their eggs by dipping their bell into sperm-containing pools; once fertilized, embryos may move onto new body forms such as medusas or tentacled forms of lion’s mane jellyfishes.
As fish populations decline, jellyfish blooms have become more widespread worldwide. Overfishing creates “dead zones” in which oxygen levels drop precipitously; competing jellyfish species vie with phytoplankton for the limited supply. With less competition for zooplankton consumed by other marine life, jellies are freer to expand their habitats and reproduce more quickly – this bodes well for mankind as jellies help clean up our oceans; but an expanding population may prove dangerous and it is essential that ways are found for keeping growth balanced against needs other marine life species.
