Over the past year, the SciWhys column has explored a number of different topics, from our immune system to plants, from viruses to DNA. But why is an understanding of topics such as these so important? In short, using science to understand our world can help to improve our lives. In my last post and in this one, I want to illustrate this point with an example of how progress in science is providing hope for the future for one family, and many others like them.
By Jonathan Crowe
In my last post, I introduced you to Carys, a young girl living with the effects of Rett syndrome. Thanks to scientific research, we now understand quite a lot about why Rett syndrome occurs – what is happening among the molecules within our cells to mean that some cells don’t behave as they should. Simply knowing about something is one thing, though; making constructive use of this knowledge is another thing entirely. During this post I hope to show you how our understanding of what causes Rett syndrome is being translated into the potential for its treatment – a cure for Carys, and the other young girls like her.
In my previous post I mentioned how Rett syndrome is caused by a faulty gene called MECP2 that affects the proper function of brain cells. However, the syndrome doesn’t actually kill the cells (unlike neurodegenerative diseases that do cause cells to die). Instead, the cells affected by Rett syndrome just function improperly. This leads us to an intriguing question: if the faulty gene that causes the syndrome could be ‘fixed’ somehow, would the cells start to behave properly? In other words, could the debilitating symptoms associated with Rett syndrome be relieved?
Obviously, researchers can’t simply play around with humans and their genes to answer questions such as these. Instead, researchers have studied Rett syndrome by using “mouse models.” But what does this mean? In short, mice and humans have biological similarities that allow the mouse to act as a proxy – a model – for a human. How can this be? Well, even though the huge variety of creatures that populate the earth look very different to a casual observer, they’re not all that different when considered at the level of their genomes. In fact, around 85% of the human and mouse genomes are the same.
Now, if the biological information – the information stored in these genomes – is similar, the outcome of using this information will also be similar. If we start out with two similar recipes, the foods we prepare from them will also be very similar. Likewise, if two creatures have similar genes, their bodies will work in broadly similar ways, using similar proteins and other molecules. (It is the bits of the mouse and human genomes that aren’t the same that make mice and humans different.)
In essence, the mouse Mecp2 gene is to all intents and purposes the same as the human MECP2 gene, and has the same function in both mice and humans. Equally, if this gene malfunctions, the consequences are the same in both mouse and human: a mouse with a mutation in its Mecp2 gene exhibits symptoms that are very like a human with a mutation in the same gene – that is, someone with Rett syndrome. In short, mice with a Mecp2 gene mutation are a model for humans with the same mutation.
With all this in mind, if we can learn how to overcome the effects of the Mecp2 mutation in the mouse, we might gain valuable insights into how we can overcome the equivalent effects in humans.
And this is wh
Over the past year, the SciWhys column has explored a number of different topics, from our immune system to plants, from viruses to DNA. But why is an understanding of topics such as these so important? In short, using science to understand our world can help to improve our lives. In this post and the next, I want to illustrate this point with an example of how progress in science is providing hope for the future for one family, and many others like them.
By Jonathan Crowe
Carys is an angelic-looking two-year old, with a truly winning smile. At first sight, then, she seems no different from any other child her age. Yet Carys’ smile belies a heart-rending reality: Carys has Rett syndrome, a disorder of the nervous system that is as widespread in the population as cystic fibrosis, yet is recognised to only a fraction of the same extent. (I, for one, had never heard of it until just a few months ago.)
Rett syndrome is a delayed onset disorder — something whose effects only become apparent with time. When Carys was born, she appeared perfectly healthy, and developed in much the same way as any other healthy infant. Just as she began to master her first few words, however, she lost the power of speech, and soon lost the use of her hands too. The effects of Rett syndrome were beginning to be felt.
Over time, Rett syndrome robs young girls of their motor control: they lose the ability to walk, to hold or carry objects, and to speak. But there be other complications too: there may be digestive problems; difficulties eating, chewing, and swallowing; and seizures and tremors. It is a truly debilitating disorder.
So what causes Rett syndrome? What’s happened inside the body of young girls like Carys? We know that the syndrome is caused by as little as a single error (a mutation) in a single gene. (As I mention in a previous post, it’s quite unsettling to realise that just one error in the tens of millions of letters that spell out the sequence of our genomes is sufficient to cause certain diseases. Sometimes there’s very little room for error.) The normal, healthy gene (called MECP2) contains the instructions for the cell to manufacture a particular protein; the mutated gene produces a broken form of this protein, which no longer functions as it should.
But how can a single protein affect so many processes – from speech to the movement of limbs? The answer lies in the way the protein interacts with other genes, particularly in brain cells. Essentially, the protein acts like a cellular librarian by helping the cells in the brain to make use of the information stored in their genomes (their libraries of genes). If the protein is broken, the cells can no longer make use of all of the genetic information needed for them to work properly (a bit like trying to use an instruction manual with some of the pages blacked out), so normal processes begin to break down. The broken protein doesn’t just affect the ability of the brain cells to use one or two other genes, but a whole range of them – and that’s why the effects of Rett syndrome are so wide-ranging.
But the story of Rett syndrome runs deeper than this. The mutation that causes Rett syndrome occurs in sperm; it happens after the sp
By: Nicola,
on 2/4/2012
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On World Cancer Day 2012, we speak with Dr Lauren Pecorino, author of Why Millions Survive Cancer: the Successes of Science, to learn the latest in the field of cancer research. – Nicola
There are so many myths about cancer that it is sometimes difficult to understand exactly what it is. Can you briefly explain how cancer develops?
Cancer is a disease of the human genome. Many agents that cause cancer cause permanent changes to your genes. These permanent changes are called mutations. Cancer is usually caused by the accumulation of mutations over time. This is why cancer risk increases with age. The altered genes may produce faulty proteins that lead to abnormal cell growth and this appears as a tumour. Cancer is characterized by abnormal cell growth and the ability of tumour cells to spread throughout the body. It is this second characteristic, called metastasis that is the most difficult aspect to treat.
It is said that cancer now affects one in three people over a lifetime. What’s the latest progress in the field of cancer research?
There has been tremendous progress in the field of cancer management. The good news is that trends in death rates are decreasing for many cancers though that is not to say for all cancers. There are millions of cancer survivors who have had their diagnosis ten or more years ago. Many people are now living with cancer. Conventional treatments such as surgical procedures have been refined and new drugs that target tumour-specific molecules have proved efficient and promises less side effects.
In addition, we are learning to make lifestyle choices that science has shown reduces cancer risk — the most obvious being not smoking. We also have cancer screening programmes that can catch cancer early and even prevent cancer by treating pre-cancerous growths. The latest means for preventing a specific type of cancer is a cancer vaccine. Interestingly the vaccine designed to prevent cervical cancer vaccine also prevents several other cancers caused by the human papilloma virus such as some head and neck cancers.
What do you see as the priorities for future cancer research? Where will the next great advances be?
I see four main priorites for future cancer research.
1 – To develop better and less invasive diagnostics so that we can detect cancer earlier. It is well-known that catching cancer earlier gives a better outcome or prognosis.
2 – To expand our understanding of the individual molecular differences between tumors and to be able to fully practice personalized medicine which allows a better match between a patient and a drug. This understanding will need to be supported by technology that allows a patient’s tumour DNA to be sequenced (similar to the methods used for the Human Genome Project).
3 – To understand if we can turn a cancer cell back into a normal cell. This may sound strange but lessons from stem cells and cloning tell us that changing one cell type into another is possible.
4 – To better understand metastasis and how we can better treat it. The spreading of cancer cells throughout the body is the most difficult aspect of treating
By: Kirsty,
on 6/27/2011
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This is the latest post in our regular OUPblog column SciWhys. Every month OUP editor and author Jonathan Crowe will be answering your science questions. Got a burning question about science that you’d like answered? Just email it to us, and Jonathan will answer what he can. Today: how do organisms evolve?
By Jonathan Crowe
The world around us has been in a state of constant change for millions of years: mountains have been thrust skywards as the plates that make up the Earth’s surface crash against each other; huge glaciers have sculpted valleys into the landscape; arid deserts have replaced fertile grasslands as rain patterns have changed. But the living organisms that populate this world are just as dynamic: as environments have changed, so too has the plethora of creatures inhabiting them. But how do creatures change to keep step with the world in which they live? The answer lies in the process of evolution.
Many organisms are uniquely suited to their environment: polar bears have layers of fur and fat to insulate them from the bitter Arctic cold; camels have hooves with broad leathery pads to enable them to walk on desert sand. These so-called adaptations – characteristics that tailor a creature to its environment – do not develop overnight: a giraffe that is moved to a savannah with unusually tall trees won’t suddenly grow a longer neck to be able to reach the far-away leaves. Instead, adaptations develop over many generations. This process of gradual change to make you better suited to your environment is called what’s called evolution.
So how does this change actually happen? In previous posts I’ve explored how the information in our genomes acts as the recipe for the cells, tissues and organs from which we’re constructed. If we are somehow changing to suit our environment, then our genes must be changing too. But there isn’t some mysterious process through which our genes ‘know’ how to change: if an organism finds its environment turning cold, its genome won’t magically change so that it now includes a new recipe for the growth of extra fur to keep it warm. Instead, the raw ‘fuel’ for genetic change is an entirely random process: the process of gene mutation.
In my last post, I considered how gene mutation alters the DNA sequence of a gene, and so alters the information stored by that gene. If you change a recipe when cooking, the end product will be different. And so it is with our genome: if the information stored in our genome – the recipe for our existence – changes, then we must change in some way too.
I mentioned above how the process of mutation is random. A mutation may be introduced when an incorrect DNA ‘letter’ is inserted into a growing chain as a chromosome is being copied: instead of manufacturing a stretch of DNA with the sequence ATTGCCT, an error may occur at the second position, to give AATGCCT. But it’s just as likely that an error could have been introduced at the sixth position instead of the second, with ATTGCCT becoming ATTGCGT. Such mutations are entirely down to chance.
And this is where we encounter something of a paradox. Though the mutations that occur in our genes to fuel the process of evolution do so at random, evolution itself is anything but random. So how can we reconcile this seeming conflict?
To answer this question, let’s imagine a population of sheep, all of whom have a woolly coat of similar thickness. Quite by chance, a gene in one of the sheep in the population picks up a mutation so that offspring of that sheep develop a slightly thicker coat. However, the thick-coated sheep is in a minority: most of the population carry the normal, non-mutated gene, and so have coats of normal thickness. Now, the sheep population live in a fairly tempera
