iBiology Videos

Richard Harland begins his talk by asking how a fertilized egg goes from a single cell to a complex, multicellular organism during vertebrate development.  He explains that amphibians, and in particular Xenopus laevis, are an excellent system for addressing this question.  For example, early experiments by Spemann and Mangold in newt embryos were the first to demonstrate the presence of an “organizer” region, and more recent studies in Xenopus have identified many signaling molecules that control embryogenesis. Throughout his talk, Harland shows stunning movies to illustrate the beauty and complexity of early frog development.

During gastrulation, cell movements result in a massive reorganization of the embryo from a simple spherical ball of cells, the blastula, into a multi-layered organism. In his second video, Harland simplifies this complex phase of frog development by breaking it down into 7 separate steps and describing the specific cell rearrangements associated with each step.

Harland introduces the signaling molecules responsible for specifying distinct tissues in the embryo.  He explains how signaling effectors, such as beta-catenin and Nodal/PSmad2, become localized in the blastula by determinants  set up in the egg, and how these signals induce the formation of the mesoderm layer. He also describes classic experiments from the 1990s showing that the organizer is necessary to pattern the mesoderm into tissues such as muscle and neural plate. Harland then focuses on experiments from his lab that identified the molecules expressed in the organizer that specify dorsal cell fate.

Diabetes is a devastating disease which takes an enormous toll on both human life and healthcare spending worldwide.  Dr. Frances Ashcroft begins her talk by explaining that blood glucose must be controlled within narrow limits. In a healthy person, insulin is released from the pancreatic beta cells in response to a rise in blood sugar, which stimulates the uptake of glucose into muscle, liver and fat and so restores the blood glucose to its resting level. Diabetes occurs when the beta cells do not release enough insulin, resulting in chronically high blood sugar levels.  There are several types of diabetes: type 1 occurs because the beta cells are damaged by autoimmune attack; type 2, the most common form, is usually due to a combination of insulin resistance and decreased insulin secretion and is exacerbated by obesity and age; monogenic diabetes results from a mutation in a single gene.   Neonatal diabetes is a rare monogenic form of diabetes that presents at, or shortly after, birth. Ashcroft explains that in 1984, she and her colleagues found that the function of an ATP-sensitive potassium channel (KATP channel) in the plasma membrane of pancreatic beta cells is critical for linking increased blood glucose levels to insulin secretion. They postulated that a mutation that caused the KATP channel to be permanently open would impair insulin release.  Twenty years later, these mutations were identified and shown to be the cause of neonatal diabetes.

The first video is a shortened version in which Dr. David Baltimore introduces the different types of viruses, and defines how viruses are classified depending on their genetic material. Using HIV as an example, Baltimore explains what constitutes an equilibrium versus a non-equilibrium virus, and shows how the discovery of the reverse transcriptase helped scientist understand viruses.

Cryo-Electron Microscopy (Cryo-EM) is a form of transmission electron microscopy in which a beam of electrons is transmitted through a frozen-hydrated sample, and is used to study the molecular structure of biological samples. In this lecture, Dr. Yifan Cheng overviews the principles of Cryo-EM, and describes how advances in this technique have allowed scientists to solve biological structures to atomic resolution.

For decades, a strange neurological disease has plagued snakes around the world. The snakes tie themselves into knots, exhibit strange behaviors, and eventually die. In this talk, Dr. Joseph DeRisi describes how using genome sequencing his lab uncovered the mysterious agent responsible for this disease, which turned out to be an ancient arenavirus.

TOR, the Target of Rapamycin, is now known to be a central controller of cell, tissue and organism growth and an important molecule in many human diseases including cancer, cardiac hypertrophy, diabetes and obesity. Michael Hall explains how the fortuitous decision, in 1991, to investigate the action of rapamycin in yeast led to the discovery of TOR.

The conversion of atmospheric carbon dioxide (CO2) to biomass via photosynthesis is the foundation for all of our food and energy. Tobias Erb explains how his lab is working to design, build and optimize pathways for synthetic CO2 fixation. By combining enzymes from multiple organisms with “re-engineered” enzymes and optimizing the processes, Erb and his lab generated a synthetic cycle that fixes CO2 more energy efficiently than photosynthesis. In the future, they plan to test the system in artificial cells and to transplant it into bacteria and chloroplasts.  The video exemplifies the general rules and principles of building synthetic metabolism.

How does the brain translate sensory stimuli into a behavior? In his first iBiology talk, Dr. Florian Engert explains that larval zebrafish are an excellent model to tackle this question. Larval zebrafish are tiny, translucent, and genetically tractable vertebrates.  By making transgenic fish with labelled neurons, it is possible to visualize neuronal activity in the entire brain of a living and awake fish.  Engert introduces the virtual behavior simulators that his lab members use to trigger and measure neuronal activity in the fish.