Fellows gathered at the National Museum of the American Indian in downtown Washington D.C. for a day away from the lab—but not away from science! The annual fellows retreat is always a highly anticipated event where fellows can share research stories and learn firsthand about exciting career opportunities. This year’s retreat was no exception. Keynotes by a Nobel Prize winner and a successful—very successful—business owner, intriguing talks by NICHD fellows, and scientific updates from some of the institute’s principal investigators packed the day. A full agenda can be found at http://retreat.nichd.nih.gov/.
Missed this year’s meeting? Fear not. Several NICHD fellows have graciously volunteered to recap each of the talks here.
Physicists and Biologists, Unite!
By Valerie Virta, PhD
“I wonder what I learned in graduate school? Maybe they didn’t know anything back then,” joked Dr. Eric Wieschaus, professor at Princeton University and 1995 Nobel Prize winner, referring to how much developmental biologists have discovered over the past few decades. Dr. Wieschaus delivered the morning’s keynote address, which focused on the relationship between gene activity and cellular mechanics.
Once cells know what they are by gene expression, that almost immediately translates to cell behavior, Dr. Wieschaus explained. To examine this phenomenon, his lab uses microscopy and mathematical modeling to study cellular invagination during Drosophila gastrulation, a time during fruit fly development that lacks cell division, has very little migration, and, most importantly, is fast!
Dr. Wieschaus relies on two recent advances in microscopy: two-photon microscopy and light-sheet confocal microscopy. These, combined with a software program called the Embryo Development Geometry Explorer (EDGE I & EDGE II), enable a dynamic reconstruction of cellular morphogenesis. But what really gives his work an “edge” is that his team mathematically models the physical forces exerted by cells during invagination to develop hypotheses about cell shape changes. “My lab has been invaded by physicists,” he said, with a smile.
Their goal using mathematical models for cell mechanics is to find the simplest possible model that accounts for all quantitative data. Oleg Polyakov, a recently defended graduate student, constructed a mathematical model that treated invagination like a bunch of springs, or an elastic surface. During invagination, cells first pinch into a placodal shape and then eventually undergo dramatic cell shape changes. The team hypothesized that, like a spring, the cell stores energy in the lateral membrane during the first stage of shape change and releases it to apical-basal stretchiness during the next. The key is the relative stretchiness between the lateral and basal surfaces.
To test this model, Dr. Wieschaus’s group injected inert fluorescent beads into the cytoplasm of the gastrulating fly embryo to see if cellular flow followed the predictions of the model. They found that cells flowed as if they were a continuous viscous liquid. This led them to ask if a lateral membrane is necessary for invagination. Using a double mutant that fails to incorporate membranes during celularization, lightheartedly called slam dnk (pronounced slam-dunk), they still observed viscous movement, but ultimately invagination failed and the embryo died.
Their results led them to conclude that the lateral plasma membrane is needed to store potential energy like a spring, driving the second phase of invagination. Dr. Wieschaus urged the audience to think about invagination during fruit fly gastrulation as global movements rather than the behavior of individual cells. To conclude his talk, he offered that the right way to think about the mechanics of cell shape change is to unite the views of physicists and biologists, an approach that clearly has worked for him.
Of Mice, Zebrafish, and Men: Fellow Presentations 1 & 2
By Joanna Cross
After an engaging welcome and keynote address, the morning continued with two fellow presentations by Dr. Amber Stratman and Dr. Katerina Nella.
Dr. Amber Stratman, a postdoc in Dr. Brant Weinstein’s lab, started the session with a new way of thinking about cancer therapy. Tumors rely on a good blood supply, making anti-angiogenic therapies—which help prevent the formation of blood vessels—a promising therapeutic approach. However, some tumors evade these therapies by increasing levels of signaling molecules in angiogenic (blood vessel forming) pathways. One of these molecules, Vascular Endothelial Growth Factor (VEGF), relies on the recycling of another molecule called phosphoinositide.
Using both zebrafish and cell culture, Dr. Stratman inhibited the recycling of phosphoinositide to prevent angiogenesis. Excitingly, the method was successful. Tumors increased their levels of VEGF to compensate, which in turn depleted phosphoinositide more rapidly. Dr. Stratman continued her studies in a tumor-producing mouse model and discovered that inhibiting phosphoinositide recycling indeed reduced tumor growth! Dr. Stratman is currently carrying out chemical screens to identify and validate compounds that inhibit phosphoinositide recycling to continue this novel approach to cancer therapy.
If this wasn’t engaging enough, Dr. Katerina Nella moved the session into a more clinical setting by presenting her work, in collaboration with Dr. Deborah Merke, on a new method for administering therapies to patients suffering from Congenital Adrenal Hyperplasia (CAH). These patients have depleted cortisol levels, which are responsible for circadian rhythms (including sleep cycles). Conventional therapy is administered orally and focuses on replacing the steroid hormones cortisol and aldosterone in combination with preventing excess of a third steroid hormone, androgen. However, this method is often ineffective in suppressing androgen levels without administering greater than physiological normal cortisol levels.
Dr. Nella is conducting a Phase I-II clinical trial to test a new administration method – Continuous Subcutaneous Hydrocortisone Infusion (CSHI). This method uses a pump under the skin that keeps cortisol at typical physiological levels using similar or lower doses than conventional treatment. The trial assessed four adult patients on this new treatment method over the course of six months. The patients were using conventional oral administration at the start of the trial, which functioned as the baseline. At two and six months, Dr. Nella conducted serial hormone sampling to investigate levels of 17OH-Progesterone, an important biomarker of CAH androgen control. To conclude a memorable session, Dr. Nella informed us that the trial has been successful so far, with all patients tolerating CSHI well, showing significant reduction of androgens.
Moving Forward: Scientific Update with Dr. Jennifer Lippincott-Schwartz
By Libby Barksdale, PhD
Muscle fibers and cardiomyoctes, or heart cells, are obvious examples of cells that contract. But contraction is a fundamental property of all cells and is necessary for cell motility, which, in turn, is necessary for numerous developmental and regenerative processes. Most motile cells in multicellular organisms utilize a crawling movement, and this was the focus of Dr. Jennifer Lippincott-Schwartz’s Scientific Update.
Cells “crawl” by constantly extending and retracting their lamellae, the flattened portions of cells pointed in the direction of movement. Lamellae are enriched in actin filaments and myosin II—the same proteins responsible for muscle contraction—as well as focal adhesions that connect cells to their substrates. Using a combination of cutting-edge imaging and protein labeling techniques, Dr. Lippincott-Schwartz and her lab visualized the 3D organization of actin and myosin in lamella to better understand contractile activity in moving cells.
There are three types of actin filament-based fibers in the lamella: arcs, dorsal stress fibers, and anchor stress fibers. “Think about a tent,” Dr. Lippincott-Schwartz said. “Arcs create tension on dorsal stress fibers analogous to how canvas puts stress on a tent to shape it.” The anchor stress fibers serve as “stakes for the tent.” This is certainly a helpful image, but tents are stationary. . . and not flat, unless something has gone terribly wrong. So how does this translate into a moving cell and a flattened lamella?
At the “front” of the lamella is a region called the lamellipodium, where a meshwork of actin filaments continuously builds up and breaks down, driving the extension and retraction, respectively, of the leading edge. Occasionally during a retraction phase, the cell lays down a focal adhesion, which anchors the cell in the new position. After multiple cycles, the cell moves incrementally forward. At the same time, myosin II clusters individual actin filaments together and rearranges them into arcs. Dorsal stress fibers join the focal adhesions with the newly formed arcs (think tent stakes). As new arcs form, more mature arcs move away from the leading edge and farther back into the lamella. Myosin II builds up on the mature arcs and, similar to sarcomeric contraction in muscles, pulls on the arcs causing them to contract. Thus as the actin arcs contract and move away from the cell edge, the dorsal stress fibers joined to them behave as levers pivoting at focal adhesion “hinges” to pull down the dorsal surface of the lamella.
To test this model, the lab inhibited the dorsal contractile system, which resulted in a puffy lamella. But even more telling, adding the contractile system induced flattening behavior in a non-flat cell. So if you’re having trouble setting up your tent on a camping trip this summer, just think about a cell’s dorsal contractile system. You’ll get it.
Raising a Toast to Obesity Resistance: Fellow Presentations 3 & 4
By Apratim Mitra, PhD
The post-lunch fellow presentations showcased two important health issues facing society at present – obesity and alcoholism. First, Dr. Edra London (Stratakis lab) covered the contribution of RIIα, an enzymatic subunit of protein kinase A (PKA), to diet-induced obesity (DIO) in mice. Second, Dr. Nader Shahni Karamzadeh (Gandjbakhche lab) presented his use of a sophisticated computational approach to find characteristics that distinguish brains of alcoholics from normal subjects.
PKA is an important component of metabolic pathways linked to obesity, but the contribution of its widely expressed subunit RIIα is unclear. Dr. London and colleagues found that disruption of RIIα produced leaner mice that were resistant to DIO, supporting their hypothesis that RIIα plays an important role in the process. Interestingly, this effect appeared limited to female mice, which not only showed improved glucose tolerance, but also reduced intake of the high-fat diet (HFD).
Dr. London surmised that lowered body fat and the altered preference for fatty feed were possibly linked to changes in PKA signaling. They confirmed this with subsequent experiments that revealed striking increases in PKA activity in brain and adipose tissue of the RIIα knockout (KO) mice. In summary, removal of RIIα resulted in leaner mice as a result of lower fat intake and higher energy expenditure that correlated with higher PKA activity. Dr. London emphasized the potential of RIIα as a therapeutic target for obesity and the importance of the RIIα-knockout mice for understanding the role of PKA in food intake and energy balance.
Next we learned about a novel mechanism to identify alcoholism. The detrimental effects of excessive alcohol consumption on various functions of the brain are well known. Researchers use electroencephalography (EEG) to measure and record brain activity over short periods of time with electrodes attached to the scalp. Dr. Karamzadeh asked whether it was possible to distinguish between alcoholics and normal subjects on the basis of brain activity measured via EEG. To this end, he developed a novel technique, termed Relative Brain Signature (RBS). In brief, he extracted meaningful features from EEG profiles of known alcoholic and control subjects to generate a “fingerprint” of the respective groups. Dr. Karamzadeh then used these fingerprints to calculate the likelihood that a patient was alcoholic or not. Validation of RBS using a public repository of EEG data revealed its impressive accuracy, as this method was able to correctly classify individuals 85 percent of the time. Dr. Karamzadeh expressed the hope that his results could lead to identification of functional biomarkers and possible early warning signs of alcoholism.
Genetic Basis of Brittle Bones: Scientific Update with Dr. Joan Marini
By Sudhir Rai, PhD
The scientific update sessions were designed to highlight some of the latest research updates in biomedical research. For the second update of the day, Dr. Joan Marini, chief of the NICHD Bone and Extracellular Matrix branch, presented some of her recent findings on the genetic basis of bone disease.
Osteogenesis Imperfecta (OI), also known as brittle bone disease, is a clinically heterogeneous connective tissue disorder characterized by bone fragility and deformity. OI is usually caused by mutations in type I collagen, a major protein component of extracellular matrix in bone and skin. These mutations are usually dominant and account for 85 to 90 percent of OI cases. An important question, however, is what causes recessive OI. One day, while Dr. Marini and her colleagues sat around a conference table, they began listing proteins that interact with type I collagen. Then, they went down the list.
With the power of molecular biology and whole exome sequencing, she identified and characterized numerous genes involved in OI, such as collagen prolyl 3-hydroxylation complex, cartilage associated protein (CRTAP), LEPRE1, and PPIB. She also identified additional disease loci responsible for recessive OI, such as FKBP10, SERPINH1, SP7/OX, and SERPINF1. While FKBP10 and SERPINH1 code for collagen chaperones resident in the ER, products of the latter two genes are not directly involved in collagen production or secretion, but instead are key factors in osteoblast differentiation and activity.
Thanks to Dr. Marini’s research, we have a better understanding of how very rare mutations in specific genes affect the structure of type I collagen, and how this leads to the OI symptoms observed in these patients. This research opens doors for basic and clinical scientists to further explore the mechanism behind OI disease and hopefully develop versatile treatment tools.
Do What You Love: Career Keynote with Dr. Sherri Bale
By Michael Dambach, PhD
In today’s challenging job market, many fellows are choosing career paths outside of the traditional academic setting. Breakthroughs in basic research coupled with technological innovation are creating new opportunities that did not exist in the past for scientists. However, the path to obtaining a position outside of the university setting is not always intuitive, leading to frustration and uncertainty. That’s what made this year’s career keynote address at the tenth annual NICHD fellows retreat all the more refreshing.
Former NIAMS section head Dr. Sherri Bale presented “Life after NIH: taking the road less traveled,” and indeed it was. Dr. Bale believes she was “born a scientist.” It just took her a while to come to this realization. She attended four different colleges along the way and worked as an EMT, cytogenetics technician, waitress, and bartender before earning her Bachelor’s degree in biology from Clark University. On being a bar tender, Dr. Bale quipped, “it was fun and sort of like chemistry.” However, it was her experience as a cytogenetics tech in the chromosome biology lab at Massachusetts General Hospital that ultimately led her to the University of Pittsburgh, where she earned a MS in genetic counseling, followed by a PhD in statistical genetics.
She next followed her then husband to the NIH, where he was beginning a fellowship in medical genetics at the clinical center. At the time this program was only open to physicians, but over many beers, Dr. Bale persuaded the director of the program to allow her to join. She spent the next 16 years at NIH, where she first completed a postdoc and then served as section head investigating the genetic basis of rare hereditary diseases of the skin.
It was in this capacity that she interacted with many families afflicted with hereditable diseases that desperately wanted to know the genetic status of their children. Commercial genetic diagnostic labs didn’t exist, so in 2000, Dr. Bale left the NIH and co-founded GeneDx with her former staff scientist. In 2006, BioReference laboratories acquired GeneDx, and Dr. Bale’s initial personal investment of $14,000 resulted in a multi-million-dollar profit just six years later. Currently, she serves as Managing Director of GeneDx and Sr. Vice President of BioReference Labs. Dr. Bale’s best advice for current fellows is to “do what you love, and the rest will fall into place.”