Hegde explains that although the protein localization system usually operates accurately, it does sometimes fail. This can be due to genetic mutations, stress within an organelle, or just intrinsic inefficiencies that accompany any complex process. As a graduate student, Hegde used a cell-free in vitro system to study the translocation of prion protein into the… Continue Reading
iBiology Podcasts
Ramanujan Hegde Part 3: Recognition of Protein Localization Signals
Proteins that are secreted from the cell or localized to the plasma membrane need first to be translocated into the lumen of the ER or inserted into the ER membrane. Thousands of proteins, each with a unique signal sequence, move through this pathway. How does the protein translocation machinery recognize these diverse signals and correctly… Continue Reading
Ramanujan Hegde Part 1: Compartmentalization of Proteins Inside Cells
Cells are organized into many different compartments such as the cytosol, nucleus, endoplasmic reticulum (ER), and mitochondria. Almost all proteins are made in the cytosol, yet each cellular compartment requires a specific set of proteins. How does the cell regulate protein localization to be sure that proteins end up where they should? In his first… Continue Reading
Richard Harland Part 1: Early Frog Development: How to Make a Tadpole
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… Continue Reading
Richard Harland Part 2: The Cellular Basis of Gastrulation
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. Continue Reading
Richard Harland Part 3: Early Frog Development: How to Make a Tadpole or a Twin
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… Continue Reading
Frances Ashcroft Part 1: Diabetes: A Global Pandemic
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,… Continue Reading
David Baltimore Part 1: Introduction to Viruses
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… Continue Reading
Yifan Cheng Part 1: Single Particle Cryo-EM
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… Continue Reading
Joseph DeRisi: Genome Sequencing for Pathogen Discovery
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. Continue Reading
Michael Hall: The Story of TOR Target of Rapamycin
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… Continue Reading
Tobias Erb: Realizing Synthetic Carbon Dioxide Fixation
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… Continue Reading
Florian Engert Part 1: Fish in the Matrix: Neuronal Activity and Animal Behavior in Virtual Environments
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… Continue Reading
Daniel Colon Ramos Part 2: Mechanisms of Neuronal Synapse Assembly and Function: Lessons from C. elegans
Dr. Colón-Ramos describes his group’s finding of a previously-unknown metabolic subcompartment that powers synaptic function. His group observed that under conditions of energy stress, glycolytic proteins, which are normally diffusely distributed in cells, co-localize to a punctate structure adjacent to synapses. The local formation of these complexes is required for the synaptic vesicle cycle and… Continue Reading
Daniel Colon Ramos Part 3: Actuating Memory: How C. elegans Remembers a Learned Behavioral Preference
Colón-Ramos discusses how his group uses the approaches they have developed to reduce system’s level questions, like behavior, to cell biological questions at the synapse. He describes his lab’s discovery that two plasticity mechanisms—sensory adaptation and presynaptic plasticity—act within a single cell in C. elegans to encode thermosensory information and actuate a temperature-preference memory. The integration of… Continue Reading
Florian Engert Part 3: Neural Circuits Governing Operant Conditioning
Engert describes work done with collaborators to develop a robust operant learning assay for larval zebrafish. Using this assay and techniques for measuring neuronal activity in tethered, awake fish, they are beginning to decipher what happens in a vertebrate brain while the animal is learning. Continue Reading
Florian Engert Part 2: Gain Control: Neuronal Activity and Animal Behavior in Virtual Environments
Neuronal activity can be triggered by either external stimuli or by stimuli that are a result of your own actions. In his second talk, Engert explains how his lab measured and compared neuronal activity in response to these two types of stimuli. Using a set up where larval zebra fish are immobilized with drugs, yet… Continue Reading
David Drubin Part 2: Actin Dynamics and Endocytosis in Yeast
Drubin describes how his lab began studying actin dynamics and endocytosis in yeast using two-color, real-time fluorescence and kymographs. These tools enabled his team to confirm that actin regulated clathrin-mediated endocytosis. They discovered that BAR and F-BAR proteins stabilized the process by acting as a scaffold for actin and facilitating invagination and fission of the… Continue Reading
David Drubin Part 1: Introduction: Actin, Endocytosis and the Early Days of Yeast Cell Biology
Actin forms many cellular structures and regulates a variety of critical biological processes. Dr. David Drubin’s lab focuses on studying actin in the context of membrane trafficking. In his first iBiology seminar, Drubin recounts seminal research done using the intracellular pathogen Listeria that uncovered how the bacteria harnesses phagocytosis and actin polymerization to facilitate motility…. Continue Reading
David Drubin Part 3: Actin Dynamics and Endocytosis in Mammalian Cells
Drubin explains how he and his lab transferred their knowledge of endocytosis in yeast to determine how actin dynamics are harnessed to drive endocytic traffic in mammalian cells. In mammalian cells, his team observed the importance of actin-dynamin interactions in clathrin-dependent endocytosis. Interestingly, they found variability in endocytic site morphology and dynamics. Studies using stem… Continue Reading
David Drubin Part 4: Actin Assembly in Budding Yeast
Drubin explains how endocytosis can be used as a system to dissect the mechanisms of actin dynamics in yeast. He focuses on his lab’s research on three key processes: actin disassembly, filament capping and Arp2/3 nucleation. By giving an overview of the importance of actin dynamics in regulating a single cell process, endocytosis, Drubin highlights… Continue Reading
Daniel Colon Ramos Part 1: Cell Biology of the Neuronal Synapse and Behavior in C. elegans
A fundamental question in neuroscience is how synapses are assembled in living animals to produce behaviors and store memories. Dr. Daniel Colón-Ramos and his lab address these questions by studying the cell biology of the neuronal synapse. In the first part of his seminar series, he introduces approaches his group has pioneered and implemented to… Continue Reading
Yifan Cheng Part 2: Single Particle Cyro-EM of Membrane Proteins
Cheng shows how his laboratory has used Cryo-EM to study the atomic resolution of membrane proteins. It is challenging to use conventional methods to study membrane protein structure, given that the 3D structure of most membrane proteins is dependent on their interaction with the phospholipid bilayer. Cheng describes how his laboratory has overcome these challenges… Continue Reading
Eleanor Bath: Understanding Female Aggression in Fruit Flies
Why do females fight? For over a century, biologists thought that female aggression was uncommon in the animal kingdom. In this lecture, Dr. Eleanor Bath dispels that notion and shows that female aggression in fruit flies increases after mating. More specifically, she shows that semen and a small protein in the male ejaculate lead to… Continue Reading