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Seven Things in Common with a Worm |
Simple mutations in worms can double their normal lifespan, giving interesting models to study the molecular basis of aging.
Eat healthy and exercise – the key ingredients to a long life, right? New research from worms is suggesting that your genes play a big role in determining lifespan. Some mutant worms can live up to twice as long as normal and this provides researchers with a model organism to study the genetic factors that control aging.
The genetic pathways that are found to control worm aging are very similar to genes in humans and this has allowed researchers to make worms a model for human aging. Some long lived worm mutants have differences in their insulin pathway, the same molecules in humans responsible for regulating blood sugar levels. Other mutants have been found to affect the energy generating compartment of the cell. Aging is much more complex than just one gene but mutations in worms are giving clues to the process.
We may not have found the secret to a happy life but worms are becoming an important ingredient to understanding how to live a long life.
Nervous system.
Worms and humans share similar patterning and development of the nervous system and now researchers are using worms to model neurodegenerative diseases like Alzheimers.
The human brain contains an estimated 100 billion (that’s Billion!) neurons that allow for the basic senses and higher functions like creativity or thought. Studying all the possible connections of those billions of neurons is an almost impossible task. Instead, scientists have been using C. elegans (a type of worm) with only 300 neurons to help understand how neurons find their targets, the process of neurodegeneration and the basic function of neurons.
Worms can even get neurodegenerative diseases like Alzheimer’s and Parkinson’s making it easy for scientists to study the basic science of these conditions. Worms probably don’t think or understand the world they live in, but their nervous system is similar enough to ours at the level of basic biology that we can ask fundamental questions about the structure and function of our brain using worms.
We can think because of the types of connections that neurons make. The molecules that help neurons find each other are nearly identical between humans and worms, giving good models for neuron connections. Unlike in humans, neurons in worms make the same connections every time so a scientist can easily spot when that process doesn’t happen properly in different mutants. Plus, scientists can use fluorescent molecules to see the nervous system in the transparent worms. All of these things make worms a very convenient organism to study neural pathfinding.
Cell Fates.
The fate of human embryonic cells is decided in a complex way and this process can be studied in the simpler system of C. elegans. The worm provides a predictable system to study human development because every cell has the same fate in every worm. A much more predictable system than human development.
Our bodies are made up of lots of different tissues – bones, heart and lung to name a few. Each of these tissues has to develop from a bunch of identical cells during embryogenesis and this means that cells have to ‘decide’ a particular fate. The lineage of C. elegans allows researchers to study how cell and tissue fates are interpreted at the molecular level.
Mammalian embryos make similar fate decisions during development but the decisions each cell makes vary between animals making it difficult to study the molecules that control it. Because worms share many genes with mammals they are a good system to study how different tissues arise during development. Every cell in the worm divides in the same way in every organism and always has the same fate. For instance, the first cell division in the worm decides that one cell will develop into nervous system and other tissues while the other cell will become germline, muscle and intestine.
Using C. elegans, researchers have been able to answer questions like how a cell ‘knows’ that it will eventually form part of the intestinal tract, or heart or eye. All of these fate decisions are made during human development using a similar set of genes as the worm.
Small Interfering RNAs.
These tiny nucleic acid messages were first discovered in worms and are a potential therapeutic tool for gene therapy
Possible cures for cancer, Alzheimer’s and blindness – all from a discovery in the ‘lowly’ worm. Nobel prize-winning researchers have found that injecting small pieces of the genetic intermediate, RNA, can silence a particular genes activity. The discovery that RNAi interference (RNAi) can efficiently and specifically silence a gene has led to a completely new understanding of the biology of the cell.
RNAi-based strategies may be used to decrease the amount or function of genes. This could create therapies for several disorders including cancers where there is too much of one gene product. The promise of RNAi is that it provides an exceptionally specific mechanism to silence genes, a vast improvement to the carpet-bomb strategy of many cancer drugs on the market today. Alzheimer’s disease can also be caused by too much of one particular protein so RNAi may be a possible cure. These sound like unlikely promises from worm science but they are all too possible.
Not only has studying RNAi in worms allowed researchers to propose therapeutics for humans, the understanding of the basic biology of gene regulation has turned the scientific community on its head. Now, the field of microRNA research is growing by the minute and research on the mechanism of RNAi in worms is fuelling much of this understanding.
Space flight.
Worms have made several trips to space on NASA flights. Cool stuff!
We may see astronauts on Mars in our lifetime – a journey that will take them over 3 years – but we don’t know the effects of longer space travel. Space brings a considerable amount of exposure to radiation plus obvious weightlessness; scientists want to know the long-term consequences of this environment to humans.
Space-bound worms provide a model to study the effects of space radiation on the genome. Worms reproduce rapidly and their genome has been completely sequenced making it easy for scientists to observe if there are any hereditary defects after long times spent in space.
The effects of extended periods without gravity are also being studied using astronaut worms. Some studies have shown that worms in space undergo the same changes in their muscle structure as humans providing key insights to extended periods of time in space.
The impact is clear: results in worms will allow scientists and star-gazers alike to understand how long astronauts should live at the space station - or even if living in space is possible one day.
Gene Number.
Humans and C. elegans have almost the same amount of functional genes - a finding that surprised almost everyone!
Much to the delight of worm researchers around the world, human geneticists were humbled to find out that the tiny worm has almost as many genes as humans. It was first thought that humans would have at least 80,000 genes to account for the incredible complexity of the human body. Animals like the worm surely had far fewer genes and were much less genetically complex. However, after researchers completed analyzing the human genome they quickly realized that there were only approximately 25,000 genes in humans compared to 20,000 in worms. Maybe worms aren’t so ‘simple’ after all!
Even more shocking was when researchers compared the types of genes in worms and humans and found that we share 60 - 70% of our genes with worms. Some genes are so similar that worm genes can be substituted for human genes. This insight has told us that studying organisms like the worm or fly may be a lot more useful in understanding humans.
Nicotine.
Worms and mammals have similar responses to nicotine, including acute response, tolerance, withdrawal, and sensitization.
There is no mystery that smoking is addictive, at least in part to the effect of nicotine. The cellular effects of nicotine and the nuances surrounding the behavior of addicts are being studied by looking at C. elegans.
Worms exposed to nicotine in their food act like human smokers; they increase the speed of their movements, develop a tolerance over time and show signs of withdrawal when the nicotine is removed. Not only are the behaviors similar, the molecules responsible for sensing and responding to nicotine are shared between worms and humans. Therefore, worms provide a very simple behavior model while having cellular functions equally as complex and similar to the human cell.
The nicotine response in worms allows researchers to study the cellular effects of nicotine as well as have a rapid tool to search for drugs against nicotine addiction.
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