Journal Club – A mutation in mice to study ALS

Amyotrophic Lateral Sclerosis (ALS) is a debilitating neurodegenerative disease that affects neurons in the brain, brain stem, and spinal cord. When these neurons die, it affects the connections that they have to muscles throughout the body resulting in muscle weakness that affects speaking, swallowing and breathing leading to paralysis and eventual dead.  The cause of ALS isn’t known in 90-95% of cases.  However, recently scientists have identified a mutation in a gene nondescriptly called “chromosome 9 open reading frame 72,” which is abbreviated to C9ORF72.  This mutation results in six nucleotides, GGGGCC, being repeating up to 1000 times within this gene in ALS patients.  Even though this is the most common mutation found in ALS patients, it’s still unclear exactly how these repeats affect neurons or the progression of the disease. The two hypotheses that are most studied are that the mutated C9ORF72 makes mutated RNA transcripts (RNA is the molecule that usually helps DNA be translated into proteins) or makes unusual proteins called dipeptide repeat proteins (DRPs), each of which can aggregate (clump) together and disrupt the normal activity of the neurons leading to neurodegeneration.

neuron_als_c9ORF72

The pink dots show clumped up RNA from the many many repeats in the C9ORF72 gene. Each panel shows these clumps in different areas of the mouse brain. Taken from the article Peters et al. 2015 Neuron

In two recent publications in the journal Neuron, researchers have used mice as a model system to look at how these large GGGGCC repeats in C9ORF72 affect the mouse nervous system.  Why use a mouse? First, scientists know how to experimentally change the mouse genome in order to add hundreds or thousands of repeats to a single gene, like C9ORF72.  Second, mouse and human genes are about 85% identical, so if scientists can understand how a gene like the mutated C9ORF72 affects neurons in mice, it may also help scientists understand how it works in humans. Third, by creating a mouse “model” of ALS, scientists can use this model to better understand ALS and to test potential future therapies (it’s worth noting that only one drug currently exists for ALS and it typically extends life only by a few months).

In each article, the mouse model was slightly different – one had a mutated C9ORF72 with 500 GGGGCC repeats and the other varied between 100-1000 repeats. However, both sets of researchers found the same results.  The mice had aggregated RNA transcripts and DRPs in their neurons just like what are found in human patients with ALS, but none of the mice had behavioral changes or neurodegeneration that are seen in human ALS patients.  So why didn’t the clumped up RNA and proteins cause neurodegeneration in mice like they do in humans?  There are lots of potential reasons – including the fact that even though mice and humans are similar, there are still lots of differences and mice may respond to these aggregated RNA and proteins differently than humans.  However, the authors of these papers suggest that other environmental and/or genetic factors along with the aggregates caused by the C9ORF72 mutation must be involved in developing the neurodegeneration.  It may also mean that getting rid of these aggregates before neurodegeneration occurs may prevent development of ALS.  Now that these mice are available to study, they should help in identifying the other factors involved in ALS development along with developing possible treatments for this debilitating disease.

Want to read the articles?  Unfortunately, they are behind a paywall, but you can see the abstracts here:

O’Rourke et al. (2015) C9orf72 BAC Transgenic Mice Display Typical Pathologic Features of ALS/FTD. Neuron. Volume 88, Issue 5, p892–901, 2 December 2015 Article

Peters et al. (2015) Human C9OFR72 Hexanucleotide Expansion Reproduces RNA Foci and Dipeptide Repeat Proteins but Not Neurodegeneration in BAC Transgenic Mice. Neuron. Volume 88, Issue 5, p902–909, 2 December 2015 Article

Read the Article from PN News that I contributed to here

Personalized Medicine: A Cure for HIV

Personalized Medicine – finding the right treatment for the right patient at the right time – is quickly becoming a buzzword both in the medical field but also to the public. But is it just hype? No!  I discussed a number of examples of how personalized medicine is currently be used in breast cancer in a previous post. In this and future posts, I’ll talk about a few fascinating emerging examples of the promise of personalized medicine.  These are NOT currently being used for patient treatment as part of standard of care, but could be someday.

HIV

HIV lentivirus

The Human Immunodeficiency Virus (HIV), the cause of AIDS, is a virus that attacks the immune system.  This attack prevents immune cells from fighting other infections.  The result of this is that the patient is more likely to acquire other infections and cancers that ultimately kill them.  When first discovered in the early 1980s, HIV infection was a death sentence. Untreated, survival is 9 to 11 years.  In the past 30 years, antiviral treatments have been developed that, when taken as prescribed, essentially make HIV infection a chronic disease, extending life to 25-50 years. But there is no cure for HIV, and as of 2012, over 35.3 million people were infected with the virus.

The lack of a vaccine to prevent the disease or of a cure to treat those infected isn’t because no one is trying. Since the virus was identified as the cause of the disease, scientists have been working to find a prevention or cure (along with developing all of the antiretroviral drugs that delay/treat the disease). I’m not going to discuss all of this interesting research (though it is worthy of discussion), instead I’m going to talk about one patient, Timothy Ray Brown, who was cured of HIV/AIDS through a stroke of genetic understanding and luck!

Brown was HIV positive and had been on antiretroviral therapy for over 10 years when he was diagnosed with leukemia in 2007. His leukemia – Acute Myeloid Leukemia (AML) – is caused by too many white blood cells in the bone marrow, which interferes with the creation of red blood cells, platelets and normal white blood cells. Chemotherapy and radiation are used to treat AML by wiping out all of the cells in the bone marrow – both the cancer cells and the normal cells. Brown’s doctors then replaced the cells in the bone marrow with non-cancerous bone marrow cells of a donor.  This is called a stem cell transplant, and it is commonly used to treat leukemia – often resulting in long term remission or a cure of the disease.

But the really cool part of this story isn’t the treatment itself.  Rather it’s that that Brown’s doctor selected bone marrow from a donor that had a mutation in the gene CCR5. So what? The CCR5 protein is found on the outside of the cells that the HIV virus infects. CCR5 is REQUIRED for the virus to get inside the cell, replicate, and kill the cell. Without CCR5, HIV is harmless. There is a deletion mutation in CCR5 called delta32 that prevents HIV from binding to the cell and infecting it.  Blocking HIV from getting into the cell prevents HIV infection.  In fact, it’s been found that some people are naturally resistant to HIV infection because they have this deletion. Two copies of the gene are found in 1% of the Caucasian population, and it’s thought that this mutation was selected for because it also prevents smallpox infection.
HIV_ccr5So Brown’s doctors repopulated his bone marrow with cells that had the CCR5-delta32 mutation.  This didn’t just cure his leukemia but it also prevented the HIV from infecting his new blood cells, curing his HIV. He is still cured from HIV today!

What does this mean for others who are infected with HIV? Is a stem cell transplant going to work for everyone?  Unfortunately, no. This mutation is very rare, so finding donors with this mutation isn’t feasible.  Plus, this is a very expensive therapy that comes with risks such as graft-versus-host disease from the mismatch between the person receiving the transplant and the transplanted cells themselves. However, there are possible options to overcoming these challenges, including “gene editing.” In this method, T cells from HIV-positive patients would be removed from the body and then gene editing would be used to to make the CCR5-delta32 mutation in these cells.  These cells could then be re-introduced into the patient.  With the mutation, HIV won’t be able to infect these T cells, which would hopefully cure the disease, while avoiding some of the major graft-versus-host side effects. A small clinical trial tested this idea in 2014 (full article can be found in the New England Journal of Medicine), and HIV couldn’t be detected in one out of four patients who could be evaluated. Although this is a preliminary study using an older gene-editing technique, it shows promise for “personalized gene therapy” to potentially cure HIV.

What does it mean when I have genes that increase my “risk” of disease? Like Alzheimer’s?

The last few posts (here and here) have been about people who have carrier mutations.  These people have one recessive gene mutation that they could pass on to their child.  If the child inherits two recessive genes (one from each parent), they will get the disease.  That’s how it works with recessive diseases that are caused by one gene.  About 4,000 diseases are caused by mutations in one gene (either in dominant or recessive genes).  But that leaves all of the other diseases…

Since we’re still talking about genetics, let’s stick to diseases that are caused at least in
part by gene mutations as compared to diseases caused by infection, for example.  There are many diseases that are caused by mutations in multiple genes (the technical word for this is polygenic). In these cases, no one gene can be identified as the single cause of the disease.  The genes that are involved in causing the disease can be on many different chromosomes in many different locations on these chromosomes and only if mutated in combination will someone get the disease.  And these mutations may only cause the disease if exposed to a certain environmental factor (like cigarette smoke).

disease_polygenic

If this sounds confusing and complicated to you – it is.  Scientists find it confusing and complicated too. It’s much more difficult to pinpoint the exact genes that cause a  disease if there is more than one mutation in more than one gene.  It’s like a puzzle, but you don’t know the number of pieces in advance or what the puzzle looks like.  So if you fit two pieces together (or identify two genes that are mutated), you don’t know if you have completed the puzzle and figured out what is causing a disease or if you need to look deeper.

Scientifically, this is a complicated question, but for the patient who doesn’t care how many genes cause the disease, what does it mean to them? What does this mean for risk?  If a gene is found to be associated with a polygenic disease, mutations in this gene may increase or decrease your risk of that disease.  But unlike genes cause by dominant or recessive genes, no one can say for sure 100% either way if you have a particular gene mutation that you will or won’t get a disease.

A great example of this is Alzheimer’s disease.  Only in early onset Alzheimer’s (0.1% of all cases), one dominant genetic mutation the cause of the disease. However, in 99.9% of Alzheimer’s Disease cases, more than one gene is involved (at least three genes, but probably more).  One gene that is well studied in association with Alzheimer’s Disease risk is the gene apolipoprotein E (ApoE, for short).  There are three different versions of the ApoE gene called ApoE2, ApoE3, and ApoE4 – each representing a different mutation in the ApoE gene.  The E2 version (found with 8.4% frequency in the population) is protective against Alzheimer’s Disease.  The E3 version (found with 77.9% frequency in the population) is essentially neutral (neither causing or protecting from disease).  The E4 version (found with 13.7% frequency in the general population) is the one that causes the problems and and increase the risk from 20% in a person who has zero copies of E4 to 91% risk in a person with two ApoE4 copies.  The more copied of E4 the more likely a person is to get Alzheimer’s disease at a younger age as well. And if you’re wondering, this is ABSOLUTE risk, not relative.

alzheimersAlzheimer’s disease is a particularly tricky example to use because there are few, if any, preventative treatments for the disease.  So even if you know that you have two copies of ApoE4, there isn’t much that you can do.  However, there are other diseases, where certain genes increase risk for a disease (like I described for the BRCA mutations and breast cancer risk).  In this case there are potential preventative treatments, though even after those treatments, the decrease in risk is significant but cannot be eliminated.  Overall, it’s important to understand the complexity of disease and how many factors (including unknown factors) can contribute to disease risk and onset. For scientists, knowing the risk factors can help to detect disease early or develop targeted therapies to treat the disease. For doctors, it helps to predict disease risk and tailor treatment.  And for the patient, it helps to know that diseases are complicated and risk isn’t 0% or 100%.

 

What does it mean if I’m a “carrier”?

What does it mean when someone “carries” anything?  The definition of “carry”is to hold or support something while moving somewhere.  Often when you carry something it’s heavy, a burden.  When you’re a genetic carrier, it’s much the same.  You’re holding or supporting a recessive gene mutation as you move around in your normal everyday life.  Even though the recessive gene doesn’t affect you, it’s a genetic burden, because you could pass the trait down to your child.

cfLet’s remind ourselves what it means to have a recessive gene (or re-read the original post referencing 50 Shades of Grey).  You have two copies of every chromosome, and on each of these chromosomes is copies of each gene (called alleles – pronounced AL-eels).  These genes can be slightly different.  In some cases they are different enough that one copy doesn’t work as expected or work at all (these are the “recessive” genes we talked about in an earlier post).  Often the functional copy of the gene can compensate for the copy that doesn’t work right.  But in the case where both copies of the gene don’t work correctly, the person can end up with a disease.  The example that we used previously was cystic fibrosis.  A person will have cystic fibrosis only when the have two copies of the mutated CFTR gene.  The same is true for sickle cell anemia, which is caused by having two mutated copies of the hemoglobin gene called HbgS.  If a person only has one copy of HbgS, the other normal hemoglobin can produce enough hemoglobin to function just fine.  However, if there are two copies of HbgS, the HbgS protein structure collapses in cases where the person doesn’t have enough oxygen and this causes the red blood cells to make a sickle shape.
youandpartnercarrierThere are a number of diseases that are caused by having two copied of a mutated recessive gene (many are listed here).  But again, if you only have one copy, you’re just fine – but you carry that gene mutation. If you have children with someone else who is a carrier (meaning that they also have one copy of a recessive gene that would cause disease), then you have a 25% chance of having a child with that disease, because they have 25% chance of getting two copies of the recessive gene.

This isn’t a huge deal – only 25%, right?  Except that you would never know from looking at someone if they are a carrier.  And you wouldn’t know from living with yourself for all these years if you are a carrier.  And some populations or ethnic groups are more likely than others to be carriers for recessive genes for certain diseases. If you look at the chart below, I have listed a few ethnic groups and diseases which they are often genetic carriers.  After the name of the disease, I have listed the likelihood of someone from that ethnic group being a carrier for a recessive gene that would cause that disease. For Caucasians, if you and 28 people are sitting in a room, one person would carry a mutation in one copy of the CFTR gene that would cause cystic fibrosis. It is estimated that at least one in five Eastern European Ashkenazi Jewish individuals is a carrier of one gene that would cause a genetic disorder.

carrierSo what should you do now that you know that you could be a carrier for gene that could cause a disease.  There are options – the first one being doing nothing at all.  You could also look at your family history.  Are there people in your family or your partners family with a recessive genetic disease like Wilson Disease or Tay-Sachs?  If so, you may want to get tested for common recessive genes. On the other hand even without family history, if you are from a particular ethnic group such as Ashkenazi Jew, you may be encouraged to get tested no matter what (see an interesting guidance about this here) before or during pregnancy.  There is also the possibility that you want to be prepared, and before you and your partner get pregnant that both of you are tested for common carriers. Next post, we’ll talk more about what you can do if you are a carrier.

 

 

 

 

What are examples of diseases caused by one gene?

Mutations. We know what they are.  Mutations change a gene, which can change the protein.  And this change in the protein can be either neutral, good or bad.  Let’s finally talk about how these mutations can be bad.

There are over 4,000 diseases that are caused by mutations in just one gene.  This means that if there is a mutation in one copy of the gene (if dominant) or both copies of the gene (if recessive), there is nearly 100% likelihood that you will get the disease.  Let’s look at some common examples.

Cystic Fibrosis

cfThis is a genetic disease of the lung that is caused by a recessive gene called the cystic fibrosis transmembrane conductance regulator (or CFTR for short). This gene makes a protein that transports chloride across the cell membrane.  The most common mutation in this gene is a deletion that causes a frameshift, which makes a much shorter protein.  This shorter protein doesn’t work properly at transporting chloride and results in fluid build up in the lungs and other organs that leads to cystic fibrosis (also known as CF).

Since this is a recessive disease, what this means is that you need TWO copies of the mutated CFTR gene to get cystic fibrosis. Remember those genetic squares we used to figure out what the possibility of a child inheriting a particular allele of a gene?  Let’s look at one for CFTR.  If you imagine that the normal CFTR gene (the one that isn’t mutated) is “C” (shown in blue) and the mutated CFTR gene is “c” (shown in orange).  If each parent has one copy of the non-mutated and one copy of the mutated CFTR gene Cc, then they have a 25% chance of having a child with CFTR.  Why?  Because only a child with two copies of the recessive trait (which in this case is the mutated CFTR gene) will have cystic fibrosis.

Huntington Disease

This is an example of a dominant mutation that causes a disease.  The huntingtin genehuntingtin
has a region that has lots of repeats of one codon CAG. Most people have less than 36 repeats of CAG.  However, if a person has more than 36 repeats, it creates a protein that is toxic to brain cells – exactly how and why it is toxic isn’t really well understood.  Since this is a dominant mutation, you only need one copy of this mutated gene to get Huntington’s disease.  So if you have one parent with the Huntingtin mutation (shown as H*), which means they have one copy of the Huntingtin gene with >36 CAGs, then a child has a 50% chance of also inheriting Huntington’s disease (HH*)

Now you may be wondering, how do we know if the mutation will be dominant or recessive?  That’s a complicated question.  In part, you may know if you look at the family history.  A disease caused by a dominant mutation will be inherited by more often by the children of an affected parent whereas a recessive mutation is less likely to be inherited because it is only inherited when both parents have one copy of the recessive gene.  Another option is to study the function of the mutation protein and see how the mutation in the gene affects the function of the protein.  Since there are two copies of every gene, if one copy is mutated, the second copy of the gene could compensate for this mutation (in the case of cystic fibrosis).  In other cases, the mutation could cause such dysfunction that even with the normal protein around, it still causes disease (like Huntingtin’s).

How do mutations change proteins?

We’ve talked about mutations and how they can be good, bad or neutral, but how does that work exactly?  This is the nitty gritty. Remember back to how DNA is transcribed into messenger RNA which is then translated into the protein?  This is based on a three letter code – where each 3 letters of the RNA makes on amino acid. (If you’re interested in knowing how 4 nucleotides, which have 64 possible combinations makes only 20 amino acids, see my Answers page). If you change one of these amino acids a number of things can happen.

To make it easier, let’s pretend that these codons make the sentence “DNA HAS ALL YOU CAN ASK FOR” (see the picture below).  You may change one letter and it doesn’t change the meaning of the sentence (or the function of the protein) at all, making it a “silent” mutation. You may change one letter and it does change the meaning, but maybe not significantly – this is a missense mutation.  You may have a mutation that stops the sentence early – this would make a protein that is shorter than it’s supposed to be and probably will cause the protein to function improperly.  This is a nonsense mutation. Finally, you may add or remove one or many nucleotides which shifts the letter of the sentence so that they no longer make any sense.  These frameshift mutations also will affect the protein, and likely not in a good way.

protein_mutationsNow you can see how small changes may or may not affect the protein.    It’s interesting because it helps really explain how ONE nucleotide change can affect a protein and cause disease.  Also, if you think about the effect one nucelotide change can have, it helps us understand how finding and understanding these changes can be important for diagnosing disease.

 

How do genes affect traits? It’s just like “50 Shades of Grey”

In “50 Shades of Grey”, there isn’t any mention of molecular biology or genetics, but maybe there should be, because it’s a great example of how to explain how genes affect traits. And yes, I’m talking about dominance. Don’t get too excited – there won’t be any photos or explicit descriptions of sexy time (aka business time, if you’re  Flight of the Conchords fan).  We’re going to be talking about dominant and recessive genes.

You have two copies of each gene – one on each chromosome – and these are called alleles.  One allele is from your mother and one from your father, and these genes can be slightly different.  In some cases, the gene is dominant, which means that the variant of the trait that it is responsible for will take over – this would be represented by the dominatrix or Mr Grey.  Other genes are considered recessive – or the submissive, Anastasia Steele.  Christian Gray is the boss and what he says goes.  Only when the dominant person isn’t around does the submissive get to do what it wants.
dominant_and_recessiveAnother way to think of this is if you have a bully.  The dominant bully will take over whenever any other kids are around.  Only when the bully isn’t there, can the other kids do what they want.

What does this mean in genetics?  First, let’s get some terminology out of the way.  The dominant gene is usually represented in capital letters (for simplicity let’s call it gene “A”) and the recessive gene is in lowercase “a”.  Whenever the dominant trait, A, is present on one chromosome, that trait will be visible.  So if you have two As (AA) or one dominant and one recessive gene (Aa), you’ll only see the dominant trait.  Only when you have two recessive genes (aa) will you see the recessive trait.

punnetsquareLet’s give an example using eye color.  Let’s say that the dominant gene trait (A) is from brown eyes and the recessive trait (a) is for blue eyes.  With AA or Aa, you will have brown eyes, and with aa you will have blue eyes.  If you look at the image on the right, you may be having nightmares back to high school biology.  All this is representing are the possibilities of what trait a child might have depending on the parents genes.  If each of the parents has one copy of A and one copy of a, the child will randomly get either the A allele or the a allele from each parent. The boxes represent those possibilities.  From there you can ask and answer some really interesting questions – what’s the likelihood that with two Aa parents that the child will have blue eyes?  What do you think?  The answer is here.

What we have just discussed is what’s called “Mendelian Genetics” or “Mendelian Inheritance” named after the Monk Gregor Mendel who in the 1800s discovered these rules with dominant and recessive genes in pea plants.  What’s most interesting for us, besides being able to understand traits like eye color, is that over 4,000 diseases can be attributed to a single gene, either because it was inherited or by chance.

 

Book Club – The Genome

genomeOur second book club book is The Genome The Autobiography of a Species in 23 Chapters written by the fabulous popular science author Matt Ridley.  So why do you think there are 23 chapters to this book? Do you remember how many pairs of chromosomes humans have?  Have 23 chromosomes, and Ridley devotes one chapter to each chromosome. The chapters weave stories about genes that are found on each of the chromosomes and how they affect our life (e.g., blood groups) or disease (e.g., Huntington’s disease). He also takes the time to provide information about the history of human evolution, genetics and biology, bringing the biology and its implications all together. What’s interesting about this book is that it was published 2 years before the first draft of the human genome sequence was complete in 2001.  It would be interesting to see how different this book would be if written today, 16 years later with the added knowledge and technology.

Besides really enjoying Ridley’s books, he was a visiting scientist at Cold Spring Harbor Laboratory, where I attended graduate school.  He presented to graduate class (which only had 6 people in it) in my first year Scientific Exposition and Ethics class two years after this book was written.  He also received an honorary doctorate from my graduate school the year before I received my PhD.  Although we met only briefly, his insight and ability to describe science is impressive and all of his books are worth a read.

For more Book Club books, click here.

What is a gene and what does it do?

Genome – it has the word “gene” built into it. But what exactly is a gene? You may remember that the genome is made up of DNA, long strings of bases called A, T, C, and G.  There are certain strings of bases, called a genes, that code for proteins, and proteins are the molecules that do all the stuff in your cells.

Perfectly clear, right?  Of course not, so let’s start with an analogy.  Let’s imagine that one chromosome is a chapter of a book, but the book is written in such a way that the sentences with meaning are mixed in with random letters.  All of the letters are part of the English alphabet, but some of them are written in such a way that they make sense and have meaning – like the sentences written in red below. This is just like your DNA.  Some of the DNA makes readable sentences (genes) and other DNA in between these genes doesn’t (this used to be called junk DNA, but now we know better – more on that later!).
gene_analogy

Each of these genes makes a protein (the how of this is a topic for another post).  Let’s give a few examples of genes and proteins that you may be familiar with.  Insulin is a protein that is coded for by the insulin gene. Insulin is important in regulating blood sugar, and people with diabetes often need to inject the insulin protein to help regulate blood sugar.  Another example is the lactase gene.  This gene codes for a protein that makes the enzyme that breaks down lactose.  A decrease in the amount (also known as the “expression”) of the lactase gene is what causes lactose intolerance in adults.

An analogy that is used all of the time is to think of DNA as a blueprint for something – let’s say a car.  Each gene is a blueprint for a different part of the car – a steering wheel, a brake, or a headlight and the protein that each of these individual blueprints make is the steering wheel, brake or headlight itself.  The genome is all of the blueprints put together to make the entire car.  So what does this mean to you?  Imagine if the blueprint for the brake was a little wrong and the brake on your car didn’t work quite right…the car won’t exactly function as intended. It’s the same with genes.  If the gene isn’t quite right, it can make a protein that isn’t quite right, and this can cause the body to not function quite right (causing disease).

gene_protein

And just in case you’re sitting there and still thinking about blueprints and steering wheels and book chapters and codes, let’s summarize how the Genome, DNA, genes, and proteins are all connected in this image here:
dna_and_genes

 

Why does everyone, including me, like astronomy so much? OR – how I became a biologist.

Photo Feb 17, 6 57 16 PMI LOVED SPACE.  I loved space so much that in the sixth grade I spent most of my time at recess – without shame – with a friend planning on how to create a tractor beam (for those who aren’t complete geeks, that’s the force in Star Trek that allowed the Enterprise to latch on to other spaceships).  Our solution – a very big, long rope. Completely ignoring my fear of heights or adventure rides, I was convinced that I was going to be the female Jean-Luc Picard.  And as everyone else wrote in their sixth grade yearbooks how they wanted to be a teacher, doctor or lawyer, I wanted to be an aerospace engineer (and I honestly cannot believe that I’m showing the proof with my sixth grade yearbook photo).

"Aequorea victoria" by Mnolf - Photo taken in the Monterey Bay Aquarium, CA, USA. Licensed under CC BY-SA 3.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Aequorea_victoria.jpg#mediaviewer/File:Aequorea_victoria.jpg

“Aequorea victoria” by Mnolf – Photo taken in the Monterey Bay Aquarium, CA, USA. Licensed under CC BY-SA 3.0 via Wikimedia Commons

With this deep-seeded love of astronomy, you may be asking yourself how I became a biologist?  In my senior year of high school, I attended a Boston University Medical Center program called City Lab.  This was a six week program that my mom drove my friend Missy and me to (an hour each way in rush hour traffic) so that we could do a lab experiment.  Each week, we spent several hours in the Boston University lab doing different parts of the experiment I describe below.

gfprabbitThe goal of this experiment was to take a piece of DNA that coded for the green fluorescent protein (also known as GFP) and put it into a piece of DNA that could make bacteria glow green.  We haven’t talked in detail about genes or protein expression yet, so I’ll stick to the basics. GFP is from a jellyfish called aequorea victoria, and it’s what makes the jellyfish glow green (see above).  A scientist isolated this one gene, and if transferred properly into another organism, it can make that organism glow green.  And yes, people have tried this.  People have created GFP rabbits and mice and…NO, NOT PEOPLE.  Why not?  Well, first, because it’s highly unethical to do genetic engineering in people for no clinical reason (and having glowing eyebrows will not cure any disease).  Also it’s very difficult to manipulate the DNA in humans for a variety of reasons that we will discuss when talking about gene therapy.

So, at City Lab our job was to cut the GFP gene using restriction enzymes (which are essentially DNA gpfbacteriascissors that cut DNA in a specific place) and then insert the GFP gene into another piece of DNA using ligase (essentially, DNA glue).  This  new piece of DNA (called a bacterial expression vector) makes the GFP protein in bacteria cells.  When the GFP protein is expressed in bacterial cells, the bacteria glow green (like the picture to the right).  It was easy to figure out if your six weeks of effort was worth it if your bacteria glowed green.

OUR EXPERIMENT WAS THE ONLY ONE THAT WORKED. Not only had we understood how a piece of DNA worked, moved it from one place to another, but we then were able to get it to do something in a bacterial cell.  At the time, I didn’t realize that this was what scientists called “recombinant DNA technology”.  I didn’t know that this was used all of the time in the laboratory as a foundation of molecular biology studies.  I had no idea that someday I would be managing a facility that stored hundreds of thousands of these pieces of DNA to help researchers worldwide with their experiments.  I only knew the thrill of “discovery” and I wanted more.

That’s how I became a biologist #tbt