Connectomics: Mapping the Neural Network Governing Male Roundworm Mating

ScienceDaily (July 26, 2012) — In a study published July 26 online in Science, researchers at Albert Einstein College of Medicine of Yeshiva University have determined the complete wiring diagram for the part of the nervous system controlling mating in the male roundworm Caenorhabditis elegans, an animal model intensively studied by scientists worldwide.


 

The study represents a major contribution to the new field of connectomics — the effort to map the myriad neural connections in a brain, brain region or nervous system to find the specific nerve connections responsible for particular behaviors. A long-term goal of connectomics is to map the human “connectome” — all the nerve connections within the human brain.

Because C. elegans is such a tiny animal- adults are one millimeter long and consist of just 959 cells — its simple nervous system totaling 302 neurons make it one of the best animal models for understanding the millions-of-times-more-complex human brain.

The Einstein scientists solved the structure of the male worm’s neural mating circuits by developing software that they used to analyze serial electron micrographs that other scientists had taken of the region. They found that male mating requires 144 neurons — nearly half the worm’s total number — and their paper describes the connections between those 144 neurons and 64 muscles involving some 8,000 synapses. A synapse is the junction at which one neuron (nerve cell) passes an electrical or chemical signal to another neuron.

“Establishing the complete structure of the synaptic network governing mating behavior in the male roundworm has been highly revealing,” said Scott Emmons, Ph.D., senior author of the paper and professor in the department of genetics and in the Dominick P. Purpura Department of Neuroscience at Einstein. “We can see that the structure of this network has spatial characteristics that help explain how it exerts neural control over the multi-step decision-making process involved in mating.”

In addition to determining how the neurons and muscles are connected, Dr. Emmons and his colleagues for the first time accurately measured the weights of those connections, i.e., an estimate of the strength with which one neuron or muscle communicates with another.

The research was supported by the Medical Research Council (U.K.); the National Institute of Mental Health (R21MH63223) and the Office of Behavioral and Social Sciences Research (OD010943), both of the National Institutes of Health; and the G. Harold and Leila Y. Mathers Charitable Foundation.

Link:

http://www.einstein.yu.edu/news/releases/814/connectomics-mapping-the-neural-network-governing-male-roundworm-mating/

Journal Reference:

  1. T. A. Jarrell, Y. Wang, A. E. Bloniarz, C. A. Brittin, M. Xu, J. N. Thomson, D. G. Albertson, D. H. Hall, S. W. Emmons. The Connectome of a Decision-Making Neural Network. Science, 2012; 337 (6093): 437 DOI: 10.1126/science.1221762

Citation:

Albert Einstein College of Medicine of Yeshiva University (2012, July 26). Connectomics: Mapping the neural network governing male roundworm mating. ScienceDaily. Retrieved July 28, 2012, from http://www.sciencedaily.com­ /releases/2012/07/120726142043.htm

Does Presence of Oxidants Early in Life Help Determine Life Span?

ScienceDaily (July 19, 2012) — Why do we age, and what makes some of us live longer than others? For decades, researchers have been trying to answer these questions by elucidating the molecular causes of aging.


One of the most popular theories is that the accumulation of oxygen radicals over time might be the underlying culprit in aging. Oxygen radicals are chemically reactive molecules that can damage cellular components such as lipids, proteins and nucleic acids, resulting in “oxidative stress.”

The possible link between oxidative stress and aging has led to the proliferation of antioxidant products ranging from dietary supplements to anti-aging creams. However, the role of oxidative stress in aging is still controversial, and the effectiveness of these antioxidants is debatable.

In a paper to be published online July 19 in the journal Molecular Cell, University of Michigan molecular biologist Ursula Jakob and her co-workers measured reactive oxygen species in worms and identified the processes affected by oxidative stress.

Using the small roundworm C. elegans, a popular model organism for aging studies, they made several surprising observations. They found that these animals are forced to deal with very high levels of reactive oxygen species long before old age. High levels of reactive oxygen were found to accumulate during early development (i.e., the childhood of the worm).

Once these worms reached adulthood the levels of reactive oxygen declined, only to surge again later in life. Intriguingly, mutant worm variants that were destined to live a very long time were able to cope much better with reactive oxygen and recovered earlier than short-lived variants.

This finding suggests that the ability to deal with and recover from early oxidative stress might be a harbinger of the lifespan of the animals, according to the U-M researchers.

“We fully expected to see increased levels of reactive oxygen species in older animals, but the observation that very young animals transiently produce these very high levels of oxidants came truly as a big surprise,” said Daniela Knoefler, a doctoral candidate in Jakob’s lab and one of the lead authors of the study.

“Of course, we have no idea whether this is also the case in humans,” said Jakob, a professor in the Department of Molecular, Cellular and Developmental Biology in the College of Literature, Science, and the Arts and a professor in the Department of Biological Chemistry at the Medical School.

“However, there are some convincing studies conducted in mice which show that manipulating metabolism in the first few weeks of life can produce a substantial slowing of the aging process and increase in life span,” Jakob said.

Now, the search is on to discover the mechanism behind this early oxidant accumulation and the fascinating possibility that by manipulating these levels of reactive oxygen early in life, researchers could potentially affect the lifespan of the organisms, Jakob said.

In addition to Knoefler and Jakob, authors of the Molecular Cell paper are Maike Thamsen, Martin Koniczek, Nicholas Niemuth and Ann-Kristen Diederich, all of U-M.

The work was supported by the National Institute of Aging, an Office of the Vice President for Research grant from U-M, the National Center for Research Resources and the National Institutes of Health.

 

Link:

http://ns.umich.edu/new/releases/20640-does-presence-of-oxidants-early-in-life-help-determine-life-span

Citation:

University of Michigan (2012, July 19). Does presence of oxidants early in life help determine life span?. ScienceDaily. Retrieved July 21, 2012, from http://www.sciencedaily.com­ /releases/2012/07/120719132559.htm