I Attend the 55th Annual Fly Meeting!

After a long flight across the country from North Carolina, I made it to San Diego for the 55th Annual Drosophila Research Conference. I traveled with two other undergraduates from my lab, and we kept ourselves busy in the plane with card games and coloring books (no joke!). We arrived late, so I missed the opening session. However, I was able to attend the evening mixer and reception. My PI (or boss) Karen Hales was already there, and she introduced us to some of her friends at the conference. We also met other students, including a couple that I had already met on the grad school interview circuit.

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Day 2: Forget a fly gene? Fat chance!

The first full day of the conference began with the presentation of the annual Drosophila image awards, which recognize those "wow!" images or videos that highlight an important feature of fly biology. Afterwards were a series of plenary talks, presented to the entire conference and longer than the concurrent talks that followed later in the day.

The fly genetics community has a long tradition of naming genes creatively, which makes them much easier to remember and the conferences and publications more fun. A current hot area of research that was featured in a plenary talk is the Hippo pathway, so named because flies lacking Hippo are abnormally large. When Hippo is active, the transcription factor Yorkie is prevented from switching on genes that promote cell and tissue growth. Because fly genetics is driven by the identification of mutants, or strains that are deficient in a particular gene, genes are often named after characteristics of the mutant. In Flies lacking the Hippo protein, Yorkie is abnormally active, causing excessive growth. There are many other proteins that feed signals into the Hippo pathway, but one important protein at the cell surface is called Fat (you can imagine why it would be so-named). Intriguingly, Fat also plays roles in cell polarity (differentiating one end from the other) and mitochondrial function.

Another interesting plenary talk discussed CLAMP proteins, which play a role in dosage compensation. Like in humans, male flies have one X and one Y chromosome, while females have two X chromosomes. That poses a problem, because males have half the number of X chromosome genes as females. A mammal would say that females have twice the required number of genes, while a fly would say that males have half the number. In other words, in humans, inactivation of one female X chromosome compensates for this dosage imbalance, but in flies the single male X chromosome is up-regulated by about two-fold.

After the plenary talks I took a long lunch (Mexican food!) in Old Town, followed by the first poster session. I had some good conversations, and as always happens at conferences discussions led to new ideas for experiments. Later in the day was the first set of concurrent talks. One talk on the mechanisms of wound repair humorously incorporated a slide with glaring, villainous eyes to show the "evil" of wounds. The talk ended with a striking implication. It turns out that the molecules and pathways that epithelium (cells on the outsides of tissues, like skin) uses to signal wound repair are in many cases the same as those used by neurons, such as the neurotransmitter dopamine. I remember being surprised when I first learned that skin and neurons come from the same layer of the early embryo, the ectoderm. The presenter pointed out that, while many people would approach the problem from the perspective "Why is epithelium so much like nervous system?", it is actually the opposite. Epithelium is older than nervous system, and probably epithelium invented many of the tricks that the nervous system now depends on. Just ask a sea sponge.

Genes of the day:

four wheel drive, sauron, crimpy, bag of marbles

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While fly genetics might at first seem like a narrow field, it actually encompasses many areas. My own research interests fall within the genetics of processes that happen at the sub-cellular level, specifically mitochondria. At this conference I make sure that I also attend talks that are completely unrelated to my own research area.

I have long been fascinated by evolution, and Drosophila species of fly provide a great opportunity to understand evolution in genetic detail. Drosophila is a diverse genus with many member species, meaning that speciation has occurred over and over again in the time since the first Drosophila species evolved long ago. Matings between the modern species Drosophila melanogaster and Drosophila simulans produce sterile females and inviable (dead!) males. It has long been known that a gene on the X chromosome in Drosophila melanogaster acts in concert with a gene on the 2nd chromosome of Drosophila simulans to create hybrid inviability. However, those genes alone did not fully explain the trait. Using a brute force approach, the presenters screened over 300,000 offspring from Drosophila melanogaster females and mutagenized Drosophila simulans males. They found only 6 males, and all had mutations in the same gene, gfzf (recall that hybrid females are viable but sterile, while the males normally fail to develop). The three genes, one from Drososphila melanogaster and two from Drosophila simulans seem to interact in male hybrid offspring to disrupt the normal cell cycle.

The morning talks were interesting, but the highlight of the day was the workshop on Drosophila male fertility. My PI gave the first talk in the session, and my experiments were the bulk of her presentation. It was very gratifying to see my work presented to colleagues working on similar problems, and I received kind comments afterwards. I work on mitochondrial shaping during spermatogenesis, which involves a quite dramatic transition. Large, round cells containing many mitochondria are, during the process of spermatogenesis, transformed into highly elongate cells containing two giant mitochondria. I don't think too much about the end result (mating), because the developmental processes I study occur before sperm are fully mature. However, I was fascinated (shocked, even!) to learn that there is a genetic method to collect fly semen. The gene fruitless was identified years ago as required for male fertility, not because sperm develop incorrectly but because males fail to correctly court and copulate with females. Not surprisingly, fruitless is expressed in neurons that are required for mating behavior. By using fruitless to "drive" the expression of the ion channel dTrpAI under heat shock conditions, researchers can induce ejaculation on demand by stimulating those same neurons. Remember that next time you are at a dinner party.

Genes of the day:

deadbeat, alien, yuri gagarin

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The highlight of the morning on my last full day was a talk that featured beautiful videos of partitioning of the endoplasmic reticulum during cell division in the early fly embryo. The ER is a huge organelle, and given its importance there is clearly a need for a cellular mechanism to ensure it is cleanly divided between dividing cells. The cells in early fly embryos undergo rapid and synchronized divisions, so fast that in fact the nuclei divide without forming new plasma membranes. For a while, the entire embryo is essentially a giant cell with many nuclei.

If you thought the embryos were weird, you will probably find the mating behavior required to create the embryos in the first place equally strange. In fact, courtship behaviors vary considerably across the many Drosophila species. One major difference Drosophila virilis and the favorite Drosophila melanogaster is that virilis males and females perform duets, while in melanogaster only the male sings. Of course, flies can't sing with mouths or vocal cords, as they have neither. Instead, they vibrate their wings at high frequencies, which can be detected with sensitive instruments. virilis courtship is dynamic. The male and female communicate with one another to time copulation, and the sensory inputs from the duet influence mating behavior. You can find a lot of videos of Drosophila courtship online, even hilariously set to background music.

Genes of the day:

clueless, zelda, dynasore (a drug, not a gene, but I couldn't resist!)

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Day 5: Fly-ing back

It was sad that such a fun conference ended, but after hearing a snippet of the closing session we had to leave for the airport. I am in my last semester of undergrad, and I don't know if I will still be working with flies in the future. Either way, the fly community-and the fly itself-will always have a special place in my heart, the community for its friendliness and collaborative spirit, and the fly for its elegance as a model system.

Images are © Eric Sawyer