iBiology Videos

Jan characterizes the Calcium-Activated Chloride Channels (CaCC) in the TMEM16 family of transmembrane proteins with unknown functions and explains experiments from her lab that aided in the understanding of the molecular role of these channels. As she explains, one family member, TMEM16A, is typically expressed in peripheral cells and is involved in the rhythmical contraction of smooth muscles in the gastrointestinal tract. On the other hand, the TMEM16B CaCC is expressed in multiple brain regions as well as sensory neurons, like photoreceptors, and they have an inhibitory role in these cells.

A dendrite is a tree-like structure in neurons, which receives the incoming signal from adjacent neurons or from sensory stimuli. Dr. Yuh-Nung Jan is interested in understanding the molecular underpinnings that drive dendrite morphogenesis. His laboratory uses the fruit fly larvae as a model organism to study the development of dendritic arborization (da) neurons. Using these neurons, Jan and others have shown that the combinatorial expression of different transcription factors, such as Cut, as well as the interactions between dendrites and between dendrites and epithelial cells is what drives dendrite morphogenesis. In addition, Jan explains the role of Dscam isoforms in the regulation of dendrite-dendrite interactions for proper dendrite patterning.

Jan explains how dendrite morphology relates to the function of neurons. For example, class IV da neurons are photoreceptors and their dendrites form a regular array in the fruit fly larvae to enable the avoidance of noxious signals, like light. On the other hand, class III da neurons are mechanosensors, and they use no mechanoreceptor potential C (NompC) protein to detect gentle touch. Jan and collaborators showed that NompC works by tethering ankyrin repeats to microtubules, providing evidence for the first time that this type of gating mechanosensor mechanism is possible.

What mechanisms do plants have to fight pathogens? In this seminar, Dr. Sheng-Yang He explores plant-pathogen interactions and provides an overview of a plant’s basic immunological responses. As He explains, plants have “resistant” genes, which trigger the immune response after pathogenic infections (effector-triggered immunity). Also, plants immune system can be activated by the recognition of general patterns in pathogens (pattern-triggered immunity). Understanding these interactions could aid in the prevention of disease in plants, which would be beneficial to the agricultural industry and global food security.

He provides evidence on the effect of environmental factors (e.g. humidity) in the development of disease in plants. In order to understand disease susceptibility, He’s laboratory studies the interaction that Arabidopsis has with the bacteria Pseudomonas syringae. He’s laboratory showed that an increase in temperature and humidity increase bacterial disease severity. By genetically creating a plant that is altered in its immune system and water homeostasis, they were able to define the minimal factors that bacteria need to infect the plant. 

Dr. David Bikard’s lab focuses on engineering bacteria with CRISPR to combat microbial pathogens. In this video, he introduces the historical context for using CRISPR in bacteria and then delves into two CRISPR technologies being developed by his lab. Part of his lab is using CRISPR/Cas9 to eliminate antibiotic resistance in bacterial populations. His group is also optimizing a catalytically dead Cas9 (dCas9) to modulate levels of CRISPR-induced transcriptional repression and use it in pooled high throughput screens for gene function.

Microglia are the primary immune cells in the central nervous system. In the brain, they play central roles in proper development and function, as well as dysfunction and disease. In her first talk, Dr. Beth Stevens provides an overview of the many ways microglia cells operate, and how they can both harm and protect the brain. Fairly recent advances in the study of microglia through imaging have allowed researchers to identify different microglia states and study their dynamic roles at different stages of development.

Dr. Stevens dives deeper into the mechanisms that allow microglia to shape the network of connections between neurons in the brain. She provides an introduction to the role of microglia in synaptic pruning, the process of eliminating extra synapses in healthy developing brains. She then goes on to explain how the reactivation of this process affects aging and diseased brains.

Single cell sequencing, as the name implies, allows researchers to examine the genomic information for individual cells. This provides an opportunity to examine cell-to-cell differences and identify cell subtypes, which provides insight into how specific cells function within and respond to their environment. Dr. Eric Chow begins his talk with an overview of single cell sequencing with a focus on RNA. He then goes on to outline the predominant approaches, including plate-based, microfluidic-based, and combinatorial indexing methods. He finishes by addressing approaches to single cell analysis that don’t rely on RNA, including methods that use DNA, proteins, and antibodies. He also reviews some of the benefits and limitations of analysis at the level of individual cells.

The nucleosome is the central organizing structure of the eukaryotic genome. It consists of DNA wrapped around histone proteins. Dr. Karolin Luger shares her discovery of the three-dimensional structure of the nucleosome using X-ray crystallography, which provided a deeper understanding of chromatin organization.