New & Noteworthy
Yeast, More Interesting than your Parents Think
April 23, 2013
Are you tired of getting asked why you study yeast? And having your grandma’s eyes glaze over when you try to explain your latest research result to her? Well, we here at SGD have decided to help you out.
We have revamped our “What are yeast?” page to make it even better. We’ve stripped out a lot of the jargon making it much simpler for the nonscientist to read. Not only that, but we’ve consolidated the information onto a single page so you won’t have to link out so much to find what you are looking for.
So now when your mom asks why you’re wasting your time on yeast, you don’t have to tear your hair out and try to explain it to her. We’ve done the work for you.
You can send her to our reworked page where she can see what makes yeast such an ideal organism to study. She’ll learn that we share a whole lot with yeast even though they are single-celled. Our cells are set up similarly, we share lots of the same genes, and yeast are way easier to grow and manipulate than a person. She’ll see we’ve learned a lot about cancer, Alzheimer’s, Lou Gehrig’s Disease, and so on from our little friends. She’ll learn how useful they are for making existing medicines better and finding new ones. And that’s just a couple of the sections!
After reading this, your friends and family will realize there is much more to yeast than making bread or wine (although these are awesome as well). They will see how useful yeast is for understanding us and they will have a newfound respect for the work you do. At least we hope they will!
Community Wiki Updated
April 22, 2013
SGD’s Community Wiki now has a new look and a clearer organization, making it even easier for you to share important information with the yeast community. Use the wiki to record facts about your favorite gene, post a job opening or meeting announcement, or add links to yeast resources. Please contact the SGD help desk for an account that will allow you to log in and add to the wiki.
When Half a Loaf is Too Much
April 18, 2013
One of the ways you can tell a human cell is cancerous is by taking a peek at its genome. Instead of the orderly 23 pairs of chromosomes seen in a normal cell, the cancerous one has a jumbled mess of a genome. There are extra chunks sticking here and there, chunks missing, and lots of other oddities.
Half a loaf may be better than none but the same is not always true for genes. Sometimes having just one copy can be very bad indeed.
Besides looking untidy, this sort of chaos also causes something called copy number variation (CNV). In CNV, there are either more or less than the usual two copies of some genes. Having the wrong number of copies of certain genes can definitely cause problems.
There is some debate out there about whether CNV causes a cell to go cancerous or if it is just an effect of the cancer. In a new study, de Clare and coworkers provide strong evidence that for many genes in the yeast Saccharomyces cerevisiae, having just one copy in a diploid background leads to faster growth, poor cell cycle control, and an aversion to apoptosis (programmed cell death). This argues strongly that CNV can actually cause a cell to go cancerous. This suggestion is strengthened further by the fact that many of the genes they identified are orthologs of human genes that exist as single copies in certain cancers.
Earlier studies from this group looked at the growth rates of over 5,800 heterozygous diploid yeast mutants, each missing one copy of a particular gene, and found around 600 that actually grew faster than wild type. You might not expect such a high number at first blush, since it seems like a single celled organism would have evolved to grow as fast as it can. The authors hypothesized that there must be a strong selective advantage to having these genes, outweighing the fact that they slow down growth.
Looking more closely, they found that the genes in this set were significantly more likely than the average gene to have functions that keep the genome stable, such as DNA damage repair. They were also highly conserved across the Ascomycete fungi, confirming their importance.
The next step was to see whether there might be any connection to human cancer. They took a subset of these genes – 30 genes involved in DNA repair and sister chromatid segregation – and compared them to human genes. Nineteen of the yeast genes had a human ortholog, and 17 of those human genes exist as a single copy in many cancers, suggesting that having only one copy of these genes may contribute to a cell’s cancer phenotype.
If copy number variation of those genes contributes to cancer in human cells, does it confer a cancer-like phenotype on yeast? The researchers found that the heterozygous yeast mutants showed characteristics of cancer cells such as altered cell cycle, a decrease in apoptosis, and lowered sensitivity to anti-cancer drugs. So the increased growth conferred by the mutations comes with a high cost: increased genome instability and cancer-like symptoms.
Because this cancer-like phenotype occurs in yeast, it will be an excellent model to study exactly how particular genes contribute to it. But these findings could also have a more immediate impact on cancer treatment. Certain experimental cancer treatments work by decreasing the activity of the proteins produced by some of these genes. If a treatment only partly knocks down the activity, then it may actually encourage cancer growth. It would mimic the effects of having a single copy of a gene. The authors actually show that this is the case in yeast for some of the drugs they tested.
And this isn’t a worry just for the drug targets themselves. The drugs aren’t completely specific…they can affect other genes too, again mimicking the effects of having a single copy of one of these other genes. Add to this the fact that each genomically jumbled cancer cell may have different proportions of genes, and you have quite a mess. As usual, yeast can swoop in and save the day.
Scientists may be able to use this and other yeast libraries to quickly screen varying amounts of potential new drugs for their effects on growth. Not only that, they’ll be able to identify what pathways these drugs are hitting in addition to the one(s) that are targeted. This should make the process of drug optimization move ahead much more quickly. Thanks yeast!
by D. Barry Starr, Ph.D., Director of Outreach Activities, Stanford Genetics
Finally, Microbes Get the Recognition They Deserve
April 15, 2013
Anyone reading the SGD blog knows that the yeast Saccharomyces cerevisiae is an amazing little organism. Not only does it give us bread, wine and beer, but it also is an invaluable tool in understanding human biology. It has helped us better understand cancer, Alzheimer’s, and lots of other diseases, not to mention basic biological processes like gene regulation and cell cycle control. This little one celled beast is the rock star of biology!
And now, finally, government is starting to take notice. In a 58-0 vote, the Oregon House recently decided that yeast should be the official state microbe. If the Senate and the governor agree, then yeast will be getting the recognition it deserves. Take that, C. elegans, Drosophila, and all of you other model organisms!
Yeast is getting recognition for beer, but it is so much more!
Unfortunately, this recognition is not for yeast’s scientific value. Craft beer making is huge in Oregon, and designating yeast as the official state microbe is a way of celebrating this important state industry. Given all of yeast’s other important contributions to the well-being of us all, this feels a bit like celebrating Hugh Jackman for his role as Wolverine in X-Men while ignoring his roles on Broadway or his role as Jean Valjean in Les Miserables. Yes, he was great in X-Men, but that is an incomplete picture of him as an actor. Same thing with yeast.
Yeast should be celebrated for wine and bread, for medicines like anti-malarials and antifungals, for the deep biological understanding it has given us, and even for its possible future as a source for biofuels. Still, this honor is way better than nothing, and at least yeast will be the first microbe officially recognized by a state. Well, it will be if Oregon hurries.
Hawaii is voting on an official state microbe too, Flavobacterium akiainvivens. This bacterium was discovered by a high school student during a science fair project and is only found in the state of Hawaii. The Oregon senate should vote soon, or yeast will be the second officially recognized microbe.
Of course, the bill could die in the Senate. This is what happened in Wisconsin back in 2009 when their House passed a bill making Lactococcus lactis the official state microbe. This bacterium is important for making Wisconsin’s famous cheese but it wasn’t important enough for the Senate to approve it as Wisconsin’s official state microbe. Hopefully Oregon won’t make the same mistake with yeast.
by D. Barry Starr, Ph.D., Director of Outreach Activities, Stanford Genetics