Dr. Andy Singson – Reproductive success in model organism C. elegans
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Dr. Andy Singson – Reproductive success in model organism C. elegans


(music playing) Dr. Andy Singson: We’re interested in understanding
reproductive processes and there’s a lot of things that are required for reproductive
success, but what we’re mainly focused on is how sperm and eggs actually get together
at the moment of conception. Reproductive success is a subject of great medical, social,
and economic importance. The events of fertilization are fairly well described, however their molecular
underpinnings are poorly understood, and so we would like to understand how sperm and
egg interact with each other, not just from the point of view understanding fertilization,
per se, but also understanding the universal cell biology of how cells communicate with
each other. That’s important for our development, and progression of disease, and things like
that. There’s also a lot of compelling reasons to study the fertilization process. In the
US, about one in six couples have fertility issues. The other side of that equation is
we also want to have effective contraceptive strategies. We of course would love to do
all of our experiments on humans to understand human reproductive biology, but there’s many
practical and ethical reasons why we cannot do that. So, we turned to a model system,
in our case a small nematode worm called Caenorhabditis elegans. C. Elegans comes in two sexes, hermaphrodite
and a male. C. elegans is a good model system for representing fertilization because one,
they are reproductively mighty. A single hermaphrodite work can have anywhere from 200 to 300 progeny
on its own. If it meets up with a male, it can have literally thousands of progeny. So,
if we find mutations that severely affect fertility, it’s quite dramatic, a worm that’s
only having one or two or no progeny vs a worm that’s having hundreds of progeny is
really quite easy to spot, and so it allows us to really find a needle in the haystack
were we have specific mutations that affect the reproductive success of the animal. Another
nice thing about the worm is that they’re transparent so we can actually watch events
surrounding fertilization in live animals. Nematode sperm look a little different from
the sperm most people are used to seeing, so rather than having a tail and swimming,
nematode sperm are amoeboid and crawl, so they have a pseudopod. So, rather than putting
a propeller in the back, they have a sort of tractor-treads in front and it drags the
cell body behind it. Actually, in the great scheme of things, sperm are followed to, the
way sperm look, is quite diverse in that sperm are adapted to the environment which they
have to function. Some sperm morphological types are actually quite mysterious and we
can’t explain exactly why sperm are a particular size, or have particular structures on them,
but that’s one of the things that we hope to learn about them. I’ve been here since
2000, so about 9 years now. So, when we first arrived, we primarily focused on mutants that
affected the sperms ability to fertilize the egg. So, what we have identified is basically
sort of cellular molecular velcro. Molecules that sit on the surface of sperm and allow
it to recognize when it came in contact with the egg. Recently we identified a protein
on the surface of the egg, an interesting insight that we got from discovering this
molecule was that molecules that are involved in diverse functions also could be involved
in fertilization. Our research is primarily aimed at understanding the diversity of reproductive
strategies, and that technologies hopefully arise out of that, but we don’t do it with
an eye towards developing some sort of new contraceptive strategy or treatment for specific
types of infertility. (music playing)

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