There is a lot of folklore about left-brain, right-brain differences—the right side of the brain is supposed to be the creative side, while the left is the logical half. But it’s much more complicated than that. Marnie Halpern studies how left-right differences arise in the developing brain and discovers the genes that control this asymmetry.

Using the tiny zebrafish, Danio rerio, Halpern explores how regional specializations occur within the neural tube, the embryonic tissue that develops into the brain and spinal cord. The zebrafish is ideal for these studies because its basic body plan is set within 24 hours of fertilization. By day five, young larvae are able to feed and swim, and within three months they are ready to reproduce. They are also prolific breeders. Most importantly the embryos are transparent, allowing scientists to watch the nervous system develop and to identify mutants easily.

In the course of studying a mutation that produced fused eyes analogous to those of the mythological Cyclops, Halpern and a team from Vanderbilt University discovered that the affected gene codes for a protein signal that acts in the early embryo, then later reappears on the left side of the neural tube. This unexpected finding led her to explore where in the larval brain the molecular asymmetry resided and to determine its purpose.

Notable structural specializations are found within a precise region of the fish forebrain, and Halpern found that the signal influences whether they end up on the left or the right side. Remarkably, a member of the very same protein family had previously been shown to control the left and right differences in our internal organs, such as the characteristic rightward looping and left positioning of the heart, the counterclockwise coiling of the intestines, and the placement of the pancreas on the left and the gall bladder and liver on the right side of the body.

The Halpern laboratory has studied diverse problems using this versatile fish and its powerful genetics, initiating new projects to understand the basis of neural tube defects, to study patterning of the skeleton, and to visualize digestive physiology, projects that have enabled former trainees to establish unique research directions in their own laboratories. Other current interests of the Halpern group include the genetic regulation of myelination—the process of myelin synthesis. Myelin is the insulating material that forms around the axons of neurons to expedite their electrical activity and that is compromised in multiple sclerosis.

Halpern is also very involved in outreach. Among her activities she runs a speakers program with the Baltimore public schools, Women Serious About Science, which encourages girls from diverse backgrounds to pursue careers in science. She received her B.Sc. in biology from McMaster University and her master’s at the McMaster University Medical Centre. She then went on to Yale for her Ph.D. and did postdoctoral work at the Institute of Neuroscience, University of Oregon. She joined the Carnegie staff in 1994. For more see the Halpern lab

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Yixian Zheng
March 11, 2020

Baltimore, MD— Carnegie’s Director of Embryology Yixian Zheng is one of 15 scientists awarded a grant from the Gordon and Betty Moore Foundation to support research on symbiosis in aquatic systems.

For the past two years, Zheng and her colleagues have been working to elucidate the molecular mechanisms of endosymbiosis in the relationships between coral and jellyfish and the photosynthetic algal species that they host. She has been building on Carnegie’s longstanding tradition of model organism development to begin revealing the genetics underlying the uptake and sustenance of symbiotic dinoflagellates by the soft coral species Xenia.

“I have always

Illustration courtesy of Navid Marvi and Andres Aranda-Diaz.
March 5, 2020

Baltimore, MD—Antibiotics can make easy work of infections. But how do they affect the complex ecosystems of friendly bacteria that make up our microbiome?

“When a doctor prescribes antibiotics, it sets up a multi-faceted experiment in your gastrointestinal system,” explains Carnegie’s Will Ludington “What can it teach us about the molecular principles of species interactions in nature?”

New work led by Ludington and Stanford University’s K.C. Huang set out to answer this challenging question and discovered a new form of antibiotic tolerance. Their findings, which have important health implications, are published by eLife.

Bellymount allows researchers to peer into the live tissue of the fruit fly gut.
March 2, 2020

Baltimore, MD— They say a picture is worth 1,000 words. But what about a real-time window into the complexity of the gastrointestinal system? 

A new research tool allowed biologists to watch in real time the cell renewal process that keeps gut tissue healthy, as well as the interactions between bacterial species that make up the microbiome. Their work, led by Lucy O’Brien and KC Huang of Stanford University and Carnegie’s Will Ludington, was recently published by PLOS Biology.

The system, dubbed Bellymount, allowed researchers to peer into the live tissue of the fruit fly gut and better understand the many complex, overlapping processes occurring

Fetal Oocyte Attrition prevention, courtesy Marla Tharp and Navid Marvi.
January 16, 2020

Baltimore, MD— A woman’s supply of eggs is finite, so it is crucial that the quality of their genetic material is ensured. New work from Carnegie’s Marla Tharp, Safia Malki, and Alex Bortvin elucidates a mechanism by which, even before birth, the body tries to eliminate egg cells of the poorest quality. Their findings describing this mechanism are published by Nature Communications.

“Some organisms produce a large number of offspring, many of which don’t survive to adulthood; females in these species continually produce new egg cells throughout their reproductive lives,” Bortvin explained. “But in mammals, females are born with a fixed

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The Zheng lab studies cell division including the study of stem cells, genome organization, and lineage specification. They study the mechanism of genome organization in development, homeostasis—metabolic balance-- and aging; and the influence of cell morphogenesis, or cell shape and steructure,  on cell fate decisions. They use a wide range of tools and systems, including genetics in model organisms, cell culture, biochemistry, proteomics, and genomics.

 

The Spradling laboratory studies the biology of reproduction. By unknown means eggs reset the normally irreversible processes of differentiation and aging. The fruit fly Drosophila provides a favorable multicellular system for molecular genetic studies. The lab focuses on several aspects of egg development, called oogenesis, which promises to provide insight into the rejuvenation of the nucleus and surrounding cytoplasm. By studying ovarian stem cells, they are learning how cells maintain an undifferentiated state and how cell production is regulated by microenvironments known as niches. They are  also re-investigating the role of steroid and prostaglandin hormones in controlling

The Marnie Halpern laboratory studies how left-right differences arise in the developing brain and discovers the genes that control this asymmetry. Using the tiny zebrafish, Danio rerio, they explores how regional specializations occur within the neural tube, the embryonic tissue that develops into the brain and spinal cord.

The zebrafish is ideal for these studies because its basic body plan is set within 24 hours of fertilization. By day five, young larvae are able to feed and swim, and within three months they are ready to reproduce. They are also prolific breeders. Most importantly the embryos are transparent, allowing scientists to watch the nervous system develop and to

The Gall laboratory studies all aspects of the cell nucleus, particularly the structure of chromosomes, the transcription and processing of RNA, and the role of bodies inside the cell nucleus, especially the Cajal body (CB) and the histone locus body (HLB).

Much of the work makes use of the giant oocyte of amphibians and the equally giant nucleus or germinal vesicle (GV) found in it. He is particularly  interested in how the structure of the nucleus is related to the synthesis and processing of RNA—specifically, what changes occur in the chromosomes and other nuclear components when RNA is synthesized, processed, and transported to the cytoplasm.

Evolutionary geneticist Moises Exposito-Alonso joined the Department of Plant Biology as a staff associate in September 2019. He investigates whether and how plants will evolve to keep pace with climate change by conducting large-scale ecological and genome sequencing experiments. He also develops computational methods to derive fundamental principles of evolution, such as how fast natural populations acquire new mutations and how past climates shaped continental-scale biodiversity patterns. His goal is to use these first principles and computational approaches to forecast evolutionary outcomes of populations under climate change to anticipate potential future

Staff Associate Kamena Kostova joined the Department of Embryology in November 2018. She studies ribosomes, the factory-like structures inside cells that produce proteins. Scientists have known about ribosome structure, function, and biogenesis for some time. But, a major unanswered question is how cells monitor the integrity of the ribosome itself. Problems with ribosomes have been associated with diseases including neurodegeneration and cancer. The Kostova lab investigates the fundamental question of how cells respond when their ribosomes break down using mass spectrometry, functional genomics methods, and CRISPR genome editing.

Kostova received a B.S. in Biology from the

Sally June Tracy applies cutting-edge experimental and analytical techniques to understand the fundamental physical behavior of materials at extreme conditions. She uses dynamic compression techniques with high-flux X-ray sources to probe the structural changes and phase transitions in materials at conditions that mimic impacts and the interiors of terrestrial and exoplanets. She is also an expert in nuclear resonant scattering and synchrotron X-ray diffraction. She uses these techniques to understand novel behavior at the electronic level.  Tracy received her Ph.D. from the California Institute of

The Ludington lab investigates complex ecological dynamics from microbial community interactions using the fruit fly  Drosophila melanogaster. The fruit fly gut carries numerous microbial species, which can be cultured in the lab. The goal is to understand the gut ecology and how it relates to host health, among other questions, by taking advantage of the fast time-scale and ease of studying the fruit fly in controlled experiments.