Eugene Bell Center


Akash Srivastava, a student in the Brown-MBL Graduate Program in Biological and Environmental Sciences, successfully defended his Ph.D. dissertation entitled “Transdifferentiation of Liver to Pancreas” on August 18 at Brown University. Srivastava, a student in the Molecular Biology, Cell Biology and Biochemistry Department (MCB) at Brown, conducted his research at the MBL’s Eugene Bell Center for Regenerative Biology and Tissue Engineering under the advisement of MBL Associate Scientist Marko Horb. His doctoral committee members also included Rich Freiman, Kristi Wharton, and Eric Morrow from the MCB Department.

Srivastava’s doctoral research helped to elucidate the molecular mechanisms involved in transdifferentiation of liver to pancreas in the frog Xenopus laevis. He identified a previously unknown role of a highly conserved beta-catenin inhibitor protein (Chibby) in transdifferentiation of liver to pancreas and in normal pancreas development. His research also provided a better understanding of the function of Wnt/beta catenin signaling in pancreas development. Funding for his research came from the Horb lab at with grant support from the National Institutes of Health.

After completing his final manuscripts, Srivastava plans to work as a validation consultant in the pharmaceutical industry.

Akash Srivastava defends his thesis at Brown University for his Ph.D. in the Brown-MBL Graduate Program.

Akash Srivastava defends his thesis at Brown University for his Ph.D. in the Brown-MBL Graduate Program.

By Laurel Hamers

One of the brain’s amazing abilities is self-repair: Although injury or illness may disrupt neural circuits, many connections will reform over time.

Artur Llobet, an MBL Research Awardee from the University of Barcelona, is spending his second consecutive summer in the Whitman Center for Visiting Research investigating olfactory neuron repair in Xenopus laevis, the African clawed frog.

Calcium labeling of olfactory sensory neurons' presynaptic terminals in a Xenopus laevis tadpole. Photo credit: Artur Llobet

Labelling of presynaptic terminals of olfactory sensory neurons in a Xenopus laevis tadpole using calcium green dextran. Image is pseudocolored so that yellow represents higher and blue lower calcium concentration.
Photo and caption: Artur Llobet

“One of the advantages of working with frogs is that they have fantastic regenerative capabilities,” says Llobet. Tadpoles are able to repair damaged neural circuits in a few days, making them ideal test subjects.

Llobet is working with a transgenic line of Xenopus tadpoles that express green fluorescent protein (GFP) in their neurons, allowing him to easily see the neural connections. Last year, he studied the timeframe of Xenopus neural repair by measuring how long snipped olfactory nerves took to regrow. Now, he is trying to understand in greater detail the mechanisms behind the repair process.

Neurons pass electrochemical messages between each other at junctions called synapses; when a neuron fires, the voltage change propagates along the nerve fiber (axon) and calcium increases at the presynaptic terminal, which releases neurotransmitters. By labeling the tadpoles’ synaptic terminals with calcium indicators, Llobet can visualize the functionality of the re-grown connections and determine when during the repair process the new synapses start signaling.

“In a GFP animal, we can see that the nerve has re-grown, but we don’t know if that nerve is actually working or not,” says Llobet. “So we look at the synapses and see whether the calcium concentration increases when we stimulate olfactory sensory neurons.” This calcium accumulation indicates that the new nerve is not just present, but also functional.

By examining neural repair in frogs, scientists hope to gain insight into this process in more complex systems such as the human brain.

Llobet’s research is taking place through the National Xenopus Resource (NXR) at the MBL, a center that maintains breeding stocks of frogs and provides training on advanced imaging and experimental technologies. According to Llobet, the specialized resources offered by the NXR make this research project possible. He is one of six MBL Research Awardees in 2014 to be using the animals and research services of the NXR, which is one of 28 National Institutes of Health-funded Animal Resource Centers nationwide and a cornerstone facility of the MBL’s Bell Center for Regenerative Biology and Tissue Engineering.

Carlo Bocconcelli, a senior at Falmouth Academy and student researcher working in the lab of MBL scientist Joel Smith under the guidance of postdoctoral associate Sarah Tulin, won second place in the Intel International Science Fair Competition, held last week in Los Angeles. Carlo’s project involved developing a method for detecting regulatory regions in the sea urchin genome which produced promising results the lab intends to submit for publication this summer. Carlo will be joining Harvard’s freshman class this coming fall. Congratulations, Carlo!

CARLO