Biology

Seminars

Upcoming Seminar

February 17, 4:10 PM; Biology B-19
Reed College Post-Doc Talks

All Biology Department Seminars are free and open to the public. Seminars take place Fridays at 4:10 PM in B-19 in the basement of the Biology Building on the Reed College Campus (unless otherwise noted on the schedule). Seminars are immediately preceded by a service of coffee, tea, and other refreshments.

The Reed College campus is located in southeast Portland at 3203 SE Woodstock Blvd. (Online maps are available for getting to Reed and for the Campus).

2016-17 Schedule

Fall

4:10-5:00 in Biology B-19 (unless otherwise noted).
Directions to Reed.

Sept 2Transmission of an epigenetic “memory of germline” from parents to offspring in C. elegans
Susan Strome, University of California, Santa Cruz
Sponsor: Lamfrom Fund

Abstract: How epigenetic memory is passed from parents to offspring and through development are areas of intense investigation. In C. elegans, both sperm and oocytes transmit a memory of gene repression and gene expression to embryos in the form of modified histones, methylated H3K27 for repression and methylated H3K36 for expression. During DNA replication modified histones are passed to daughter chromatids and can provide chromatin memory for a few cell divisions. Histone-modifying enzymes (PRC2 for repression and MES-4 for expression) are needed to replenish histone modifications and provide long-term chromatin memory. Such memory is required for development of the next generation of germ cells.

Sept 9The Road from DNA to Fish-hunting Cone Snail Venoms and Beyond
Baldomero Olivera, University of Utah
Sponsor: Lamfrom Fund

General Theme: Chemical Interactions between Organisms. Specific research focus: discovery and characterization of venom components, identification of their molecular targets, and an exploration of potential biomedical applications in venomous marine snails.

Sept 13
Time: 12:10 PM
Forensic DNA transfer: Your DNA goes places you have never been.
Dr Georgina Meakin, University College London
Sponsor: Liu Fund

Georgina conducts and directs research into the transfer and persistence of DNA and other trace evidence. She is particularly interested in the indirect transfer of DNA and how this affects the evaluation of trace DNA in casework. She collaborates with DNA experts from across the world to progress and raise the profile of this important area of research. Georgina still consults in casework to ensure that her research addresses the critical issues faced in forensic science practice, and also lectures on the Crime and Forensic Science MSc programme.

Sept 16
Location: Kaul
Student Summer Research Fellows Poster Session

Join students from Biology, Chemistry, Math, Physics, and Psychology as they present the results of their summer research and projects.

Sept 23Probing Mechanisms that Regulate Differentiation in the Growing Zebrafish Retina.
Kara Cerveny, Reed College
Sponsor: Liu Fund

Maintaining neurogenesis in growing tissues requires a tight balance between progenitor cell proliferation and differentiation. In the zebrafish retina, neuronal differentiation proceeds in two stages with embryonic retinal progenitor cells (RPCs) of the central retina accounting for the first rounds of differentiation, and stem cells from the ciliary marginal zone (CMZ) being responsible for late neurogenesis and growth of the eye. In this study, we analyse two mutants with small eyes that display defects during both early and late phases of retinal neurogenesis. These mutants carry lesions in gdf6a, a gene encoding a BMP family member previously implicated in dorsoventral patterning of the eye. We show that gdf6a mutant eyes exhibit expanded retinoic acid (RA) signalling and demonstrate that exogenous activation of this pathway in wild-type eyes inhibits retinal growth, generating small eyes with a reduced CMZ and fewer proliferating progenitors, similar to gdf6a mutants. We provide evidence that RA regulates the timing of RPC differentiation by promoting cell cycle exit. Furthermore, reducing RA signalling in gdf6a mutants re-establishes appropriate timing of embryonic retinal neurogenesis and restores putative stem and progenitor cell populations in the CMZ. Together, our results support a model in which dorsally expressed gdf6a limits RA pathway activity to control the transition from proliferation to differentiation in the growing eye.

Sept 30How to Win at Being a Biology Major
Biology Resources Workshop
Sponsor: Eliis Fund

Reed College offers many resources to help students be successful both at Reed and beyond. Come meet some of the people from around campus who can help out and learn about what they can do for you!

Oct 7Evolution of vocal patterns of Xenopus: retuning a hindbrain circuit during species divergence
Charlotte Barkan, Visiting Scholar- Reed College, PhD candidate- Columbia University
Sponsor: Ellis Fund

Circuits underlying motor patterns of closely related species provide an ideal framework in which to study how evolutionary forces shape behavioral variation. Male African clawed frogs produce a species-specific advertisement call to attract female mates. Xenopus laevis is the most well-studied species in terms of its vocal behavior and underlying anatomy and physiology. The clade that includes X. laevis also includes 3 other species that diverged ~8.5 million years ago. All 4 of these species produce advertisement calls that include fast trill­­­s – trains of fast rate (~60 Hz) sound pulses. However, their calls differ substantially between species in measures of trill duration and period. I examined the premotor circuit underlying vocal patterning in three of these species: X. laevis, X. petersii, and X. victorianus. I used extracellular recordings to find that a premotor nucleus, DTAM, which is part of the vocal central pattern generator, is the likely source of species-variation of vocal patterns. Species-specific trill duration and period are intrinsic to the region of the hindbrain that includes DTAM. Next, I used blind whole-cell patch recordings in DTAM of X. laevis and X. petersii to examine the cells that encode trill duration and period. I identified homologous populations of premotor vocal cells in both species that code for trill duration and period in a species-specific manner. Together, these results support an autonomous role of the DTAM circuit for generation of species variation in call duration and period.

Oct 14No seminar, Friday before Fall break
Oct 21No seminar, Fall break
Oct 28Do motor neurons regulate vocal rhythms? And other unconventional questions in neuroscience.
Erik Zornik, Reed College
Sponsor: Liu Fund

Many motor behaviors are generated by circuits called central pattern generators (CPGs) that can produce rhythmic motor patterns without patterned input. In a canonical view, vertebrate motor systems operate in a top-down manner: rhythmic activity produced by the CPG leads to activation of motor neurons, which in turn activate muscles. My group studies the vocal CPG of the frog, Xenopus laevis, as a means of identifying fundamental principles that govern motor production. In contrast to the top-down view of a “textbook” motor circuit, we found evidence that motor neurons may be essential players in the production of vocal patterns. Specifically, we have discovered that motor neurons project to and modify the activity of vocal CPG neurons. When this feedback projection is blocked, the vocal CPG becomes incapable of generating vocal patterns. These results indicate a unique circuit property in which motor neurons are essential components of the CPG, not mere relays between the CPG and muscles. This work supports the notion that motor neuron involvement in vertebrate CPG function may be the rule rather than the exception.

Nov 4Using actin to put our heads (and tails) in the right place
Margot Quinlan , University of California, Los Angeles
Sponsor: Lamfrom Fund

Cells contain structural elements, collectively referred to as the cytoskeleton. The cytoskeleton is more dynamic than its name implies. A dynamic cytoskeleton is critical for many processes, including cell polarity, division, and motility. In early development, cell polarity leads to establishment of the major body axes (e.g., where the head and tail go). We are studying two proteins that stimulate formation of actin filaments, the nucleators Spire (Spir) and Cappuccino (Capu), and are essential to polarity establishment during early development. Spir and Capu collaborate to build an actin mesh that traverses the Drosophila oocyte throughout mid-oogenesis. The presence of the mesh and its timely removal are both critical to polarity establishment. In the Quinlan lab, we combine the power of Drosophila genetics with physical biochemistry and cell biology. Our goal is to develop a mechanistic understanding of Spir and Capu, advancing our knowledge of the cytoskeleton and how it is controlled. This conserved pair of proteins co-exists in other polar cells, including neurons and epithelial cells in mammals. Thus we anticipate that what we learn about Spir and Capu in Drosophila oogenesis will be applicable to our understanding of fundamental biological principals and disease in all animals.

Nov 11Evolution and ecology of color variation in damselflies
Idelle Cooper , James Madison University
Sponsor: Ellis Fund

Sexual selection, more so than natural selection, is posited as the major cause of sex differences. Dr. Cooper's research shows the ecological correlations between solar radiation levels and sexual dimorphism in body color of a Hawaiian damselfly.

Nov 18Insights into the origin of virulence from model organisms
Arturo Casadevall, Albert Einstein College of Medicine of Yeshiva University
Sponsor: Lamfrom Fund

The germ theory of disease was a landmark moment in human progress because it catalyzed progress that greatly reduced mortality from infectious diseases. However, the germ theory left unanswered two major questions that have preoccupied scientists for the past century: 1) why are some microbes pathogenic and others not? 2) why are some hosts susceptible and others not? To these question can be added the deeper question: how does the capacity for virulence emerge in some microbes? For microbes acquired from other hosts virulence, which includes many common pathogenic microbes, disease often results from host-microbe interactions that perturb host homeostasis. However, for the set of pathogenic microbes that are acquired directly from the environment, the origin of virulence is less clear, since those microbes have no need for animal virulence for their survival. Among the best candidates to study these problems are pathogenic fungi, which provide clear example of pathogenic microbes acquired from other hosts and directly from the environment. Studies with the fungus Cryptococcus neoformans have provided insight in how virulence can emerge in the environment through pressures that have no relation to the final host. C. neoformans is often found in the same environmental niches as amoeba, and fungal-amoeba interactions have been proposed to select for traits that also allow it to survive in mammalian hosts, in a process that has been called accidental virulence. A comparison of the interaction between amoeba and mammalian phagocytic cells reveals remarkable similarities in intracellular survival strategy despite the enormous phylogenetic distances for these two cellular hosts. Many of the virulence factors that are needed for C. neoformans virulence in mammals are also needed for survival against amoeba predation. The experience with C. neoformans has now been corroborated for several other pathogenic fungi. The environmental predatory selection hypothesis can also explain the non-specific nature of environmental fungal pathogens. Furthermore consideration of host susceptibility to fungal pathogens provides a fertile ground for re-thinking evolutionary processes including great mammalian radiation and the end of the age of reptiles after the events at the Cretaceous-Tertiary boundary.

Nov 25No seminar, Thanksgiving break
Dec 2No seminar, Thesis Parade

Spring

4:10-5:00 in Biology B-19 (unless otherwise noted).
Directions to Reed.

Feb 17
Reed College Post-Doc Talks
Sponsor: Ellis Fund
Feb 24
Aly Uy and Floria Mora-Kepfer Uy, University of Miami
Sponsor: Liu Fund

Our research program explores the origin of biological species, using tropical birds as the primary study organism. We use a combination of observational, experimental and molecular approaches to study populations that are on the verge of becoming new species, providing us with unique and natural experiments to understand how new species evolve.

Mar 3
Fikadu Tafesse, Oregon Health and Science University
Sponsor: Liu Fund

The profound success of pathogens such as Mycobacterium tuberculosis and HIV in causing disease depends on their ability to successfully utilize the host’s cellular machinery for their own advantage to avert its immune system. Understanding these pathways or processes essential for the life cycle of these pathogens is crucial, as it represents potential targets for new drug strategies.

Mar 24
T. M. Murali , Virginia Tech
Sponsor: Liu Fund

Dr. Murali's work focuses on problems in computational systems biology. He works in the area of cellular response networks and their building blocks (network legos), gene function prediction (GAIN, Art, MENGO), host-pathogen protein-protein interactions (prediction, landscape) biclustering algorithms and their applications (xMotif, visualisation, XcisClique, Arabidopsis CO2, RankGene), and conserved protein interaction modules (GraphHopper). He is also interested in the problem of identifying ligand migration pathways in proteins such as myoglobin.

Mar 31
Mike Behrenfield, Oregon State University
Sponsor: Liu Fund

Description of Research: Physiological-ecology of marine algae, biogeochemcial cycles, remote sensing of the biosphere, novel optical approaches to understanding algal ecology/physiology, biochemistry and biophysics of photosynthesis, physiological responses of plants to environmental stresses, and regional and global ecological modeling, climate change and carbon cycling.

Apr 7
STARS Talks

Brief lectures presented by thesis students about their thesis projects

Apr 14
Jasmine Crumsey, Cornell University
Sponsor: Ellis Fund

Dr. Crumsey is interested in understanding the ecological effects of animal communities on ecosystem function and ecological responses of animal communities to environmental change. Current projects focus on characterizing ecological responses through the application of stable isotope analysis to specimen collections held by natural history museums. Her research aims to link temporal patterns in the isotopic composition of small mammal tissues (Blarina brevicauda, Microtus pennsylvanicus, and Microtus californicus) to temporal patterns of regional land use, nitrogen deposition, and climate over the past 150 years.

Apr 21
Kristen Kwan, University of Utah
Sponsor: Liu Fund

Dr. Kwan's lab studies the cellular and molecular mechanisms underlying tissue morphogenesis: the process by which a group of cells achieves its proper cellular organization and shape. Using the vertebrate eye as a model, we want to understand how the cells that comprise the vertebrate optic cup – neural retina, retinal pigmented epithelium, and lens – form the stereotyped structure that is critical for visual function. Developmental defects in eye morphogenesis represent a common cause of serious visual impairment in newborns.