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Chaolin Zhang
Chaolin Zhang, PhD, associate professor of systems biology

A new study by researchers in Dr. Chaolin Zhang’s lab at Columbia’s Department of Systems Biology details a novel computational method that models how RNA-binding proteins (RBPs) recognize specific sites in the target RNA transcripts, precisely and accurately. The researchers’ findings include identification of entirely new motifs (RNA sequence patterns), and their research in complex RNA regulation contributes to our understanding of the molecular basis of disease and conditions, and down the road, could aid in the development of targeted therapies. 

The study, led by Dr. Zhang, associate professor of systems biology, with senior co-authors Suying Bao, PhD, and Huijuan Feng, PhD, appears today in Molecular Cell

RNA has traditionally been considered mere “messengers” that transfer genetic information from DNA to proteins that ultimately carry out cellular functions. However, it is now increasingly appreciated that RNA can be tightly regulated to control gene expression and diversity protein products. RNA-binding proteins (RBPs) are at the center of such regulation, with important roles in many cellular processes, including cell function, transport, and location. Gaining mechanistic insights of the binding specificity of RBPs in a genome-wide scale helps advance our knowledge of gene regulation.

“RNA-binding proteins are crucial for gene expression,” says Dr. Feng, coauthor of the study and post-doctoral research scientist in the Zhang lab. “RNA is heavily regulated, and when this regulation goes wrong, instabilities or disease could occur.”  

 

PCF Challenge Award PIs
Principal investigators on the PCF Challenge Award grant, from left to right: Andrea Califano, Michael Shen and Charles Drake.

Columbia University Irving Medical Center experts in prostate cancer will lead a new team research project that tests a novel approach for personalized cancer treatment. 

The two-year project, funded by a $1 million Challenge Award from the Prostate Cancer Foundation (PCF) , combines cutting-edge techniques that include computational methods for targeted drug therapy, single-cell RNA sequencing and novel cancer immunotherapy. The combined approaches are behind a proof-of-concept clinical trial for patients with lethal metastatic prostate cancer.  

PCF Challenge Awards fund projects that bring together experts from a number of related fields to form a team focused on the creation of innovative, effective therapies for advanced prostate cancer. As part of Columbia’s grant, the new clinical trial will take place at the James J. Peters VA Medical Center (also known as the Bronx VA), a partner of Columbia University Irving Medical Center (CUIMC) and New York-Presbyterian .

PCF is recognized as the leading philanthropic organization for prostate cancer research. For the team at Columbia’s Herbert Irving Comprehensive Cancer Center (HICCC ), receiving a Challenge Award from the foundation was more than just an exciting achievement. It underscores CUIMC’s continued commitment to strengthen and expand its expertise in prostate cancer research and care through investments in faculty recruitment, enhanced emphases on bolstering basic science research and clinical trials centered on the disease and direct engagement with PCF. 

Researchers at the Vagelos College of Physician & Surgeons are rewriting the course of scientific investigation, intent on speeding up the process of discovery that will help patients with cancer, Alzheimer’s disease, diabetes, and other intractable diagnoses.

In cancer, Andrea Califano, Dr, the Clyde and Helen Wu Professor of Chemical and Systems Biology and chair of the Department of Systems Biology, decided to turn cancer treatment theory on its head. The first wave of research in pursuit of personalized oncology focused on clues embedded within individual tumors. Decode the nucleic acids gone awry within the DNA of a particular patient’s cancer, or so the thinking goes, to identify treatments tailored to target that specific mutation.

It’s a fine theory, says Dr. Califano in the article, but investigators still have a lot of work to do before the vast majority of cancers yield to that approach. “Only maybe 25 percent of patients have a mutation that could be defined as actionable,” he says.

For more than a decade, Dr. Califano has championed what might be considered an end run around cancer mutations, focusing instead on identifying and blocking the networks of normal proteins—known as master regulators—hijacked by deranged DNA to spur tumor formation and sustain tumor growth. Prevent the signals those proteins send on behalf of a cancerous mutation, and the cancer itself screeches to a halt.

Suying Bao, PhD
Suying Bao, PhD

Suying Bao, a postdoctoral research scientist in the Chaolin Zhang lab , has been named an inaugural Precision Medicine Research fellow by Columbia’s Irving Institute of Clinical and Translational Research . The two-year fellowship aims to train postdocs to use genomics and complex clinical data to improve personalized and tailored clinical care and clinical outcomes. 

This fellowship “will provide me with more opportunities to translate my findings from basic science research into clinical application,” says Bao, “and pave my way towards an independent researcher in this field.” 

Bao’s expertise lies in RNA regulation at the interface of systems biology, ranging from the specificity of protein-RNA interaction to function of specific splice variants. RNA regulation is critical in proper cellular function; gaining deeper insights into this complex molecular mechanism will promote the development of precision medicine therapies. 

In this project, Bao is aiming to develop new approaches to identify causal noncoding regulatory variants (RVs) modulating post-transcriptional gene expression regulation, such as RNA splicing and stability.  “A majority of genetic variants associated with human diseases reside in noncoding genomic regions with regulatory roles,” notes Bao. “Thus, elucidating how these noncoding regulatory variants contribute to gene expression variation is a crucial step towards unraveling genotype-phenotype relationships and advancing precision medicine for common and complex diseases.”

To identify these RVs, she will leverage massive datasets of high-throughput profiles of gene expression and protein-RNA interactions generated from large cohorts of normal and disease human tissues and cell lines by multiple consortia, such as ENCODE, GTEx and CommonMind, and develop innovative computational methods of data mining. 

LIN28 Selectively Modulates Subclass Let-7 miRNAs
The proposed model of selective Let-7 microRNA suppression modulated by the bipartite LIN28 binding.(Image courtesy of Zhang Lab)

A new study led by Chaolin Zhang, PhD , assistant professor of systems biology , published today as the cover story of  Molecular Cell , sheds light on a critical RNA-binding protein that is widely researched for its role in stem cell biology and its ties to cancer progression in multiple tissues.

The LIN28 RNA-binding protein, initially found in worms about 15 years ago, is specifically expressed in stem cells.  It became well known because the protein is one of the four factors that were used to “reprogram” skin cells to induced pluripotent stem cells, or iPSCs, a breakthrough that was awarded the Nobel Prize in 2012. More recently, it was determined that the LIN28 RNA-binding protein can also be reactivated in cancer to drive tumor growth and progression. Due to its critical importance in developmental and cancer biology, scientists want to understand the role LIN28 plays at the molecular level. This new study provides some understanding of how the LIN28 protein suppresses a specific family of microRNAs, called Let-7, which are selectively lost in cancer.

“Let-7 microRNAs are the major downstream targets controlled by LIN28 identified so far. While LIN28 is mostly found in stem cells, Let-7 is only detected in differentiated cells because of stem cell-specific suppression by LIN28. However, the interplay between the two is still not well understood,” says Dr. Zhang, who is also a member of Columbia University’s Center for Motor Neuron Biology and Disease . “This study contributes to our understanding of how LIN28 suppresses Let-7, as well as provides a refined model for this important, rather complex molecular pathway.”

 

In neurons lacking Rbfox, the AIS is disrupted, impairing neuron’s ability to fire action potentials.
The Rbfox protein is a master regulator of neuronal RNA splicing that is demonstrated to be pivotal to establish the mature RNA splicing program in neurons. In neurons lacking this protein, an axonal cytoskeletal structure called “axon initial segment” is disrupted, impairing neuron’s ability to fire action potentials. (Image courtesy of Zhang Lab).

Neurons, or nerve cells, in the brain communicate with each other by transmitting electric signals, or firing action potentials, through long processes named axons (which send out signals) and dendrites (which receive signals). The capability of firing action potentials, among other functions of mature neurons, has to be acquired during development and neuronal maturation. However, the molecular mechanisms governing this complex process are so far poorly understood.

To peel away at the intricate layers that govern the development of neurons, a research team led by Chaolin Zhang, PhD, Assistant Professor in Systems Biology and Biochemistry and Molecular Biophysics and Hynek Wichterle, PhD, Associate Professor in Pathology & Cell Biology, Neuroscience, and Neurology , at the Center for Motor Neuron Biology and Disease , Columbia University Medical Center, focuses on a level of molecular regulation called alternative splicing. Alternative splicing is a process of generating multiple transcripts and protein variants by joining different combinations of coding segments. This process is highly dynamic during neural development with dramatic switches of splicing patterns in thousands of genes, which produce a repertoire of protein products required at specific developmental stages.

A key regulator of alternative splicing is the Rbfox family of proteins, which are enriched in neurons and previously were linked to neurodevelopmental disorders, including autism, schizophrenia, and epilepsy.

Peter Sims Lab Wins CZI Award

Assistant Professor Peter Sims and postdoctoral research scientist Jinzhou Yuan displaying their platform for automated single-cell RNA sequencing. (Photo: Lynn Saville)

Assistant Professor Peter Sims, PhD , has been awarded an inaugural Chan Zuckerberg Initiative (CZI) award for gene sequencing research that will help advance the Human Cell Atlas project. Launched in 2016 by a cohort of world-leading scientists, the Human Cell Atlas is a high-profile endeavor whose goal is to identify and define every cell type of the human body and create a collection of maps that will describe the cellular basis of health and disease.

With the support of CZI, founded by Facebook CEO Mark Zuckerberg and his wife, Priscilla Chan, Dr. Sims and his group in the Department of Systems Biology will receive grant funding to pilot a revolutionary technique for high throughput single-cell sequencing. Called SCOPE-Seq, the novel, economical method conducts RNA sequencing coupled with live imaging of the same individual cell on a large scale.

“We hope that our approach will provide functional insights into the novel cell types that will be discovered by the Human Cell Atlas effort that cannot be obtained from genomic analysis alone,” said Dr. Sims.

Raul Rabadan
Raul Rabadan

Fellow Systems Biology Professor Raul Rabadan, PhD , who directs the Center for Topology of Cancer Evolution and Heterogeneity, also is gaining support from CZI in a collaboration led by Tom Maniatis, PhD, who won the grant for their research to construct an atlas of gene activity of all cells in the human spinal cord. Dr. Maniatis chairs the Department of Biochemistry and Molecular Biophysics, directs Columbia's Precision Medicine Initiative and is a principal investigator at Columbia's Mortimer B. Zuckerman Mind Brain Behavior Institute.

Sexual reproduction may have never become possible if organisms hadn’t evolved a way to restrain the immune system during fertilization, according to a new study from the lab of Sagi Shapira, PhD, assistant professor of systems biology.

The study, published today in Immunity, took an in-depth look at how vertebrate eggs are fertilized.

To fight invading pathogens, all organisms (including vertebrate cells) are programmed to detect and attack any DNA and foreign RNA found outside of the nucleus in the cell’s cytoplasm. It’s usually a safe bet that any DNA found in the cytoplasm is from a foreign microbe, because the cell’s own DNA is safely sequestered in the nucleus. But during fertilization, DNA and RNA from sperm may be briefly exposed to the cytoplasm of an egg—and to the danger of being recognized and attacked.

For fertilization to succeed, Dr. Shapira reasoned that something must prevent the immune system from attacking DNA during fertilization and searched for candidates in the genome.

The search revealed a gene called NLRP14, which encodes a protein that Dr. Shapira’s laboratory demonstrated to play a role in the innate immune system. Without NLRP14, the immune system induces a strong inflammatory response to DNA and RNA found in the cytoplasm, and the fertilization process comes to a halt.

The finding could lead to new ways to treat infertility or develop novel contraceptives.
NLRP14 and related genes are found in many other organisms, Dr. Shapira says, “and safeguarding the genetic material is hardwired into every organism. So, evolving machinery to inhibit that process in gametes may have been a prerequisite for the evolution of sexual reproduction.”

The finding could lead to new ways to treat infertility (about 2 percent of people carry a NLRP14 mutation) or, conversely, to develop novel contraceptives.

In addition, since NLRP14 suppresses a critical arm of the immune system, it may serve as a viable therapeutic target for tuning immune responses in various disease states (i.e., to dampen in the case of autoimmune diseases like IBD, asthma, and lupus, and enhance in the case of cancer).

Andrew Anzalone and Sakellarios ZairisMD/PhD students Andrew Anzalone and Sakellarios Zairis combined approaches based in chemical biology, synthetic biology, and computational biology to develop a new method for protein engineering.

The ribosome is a reliable machine in the cell, precisely translating the nucleotide code carried by messenger RNAs (mRNAs) into the polypeptide chains that form proteins. But although the ribosome typically reads this code with uncanny accuracy, translation has some unusual quirks. One is a phenomenon called -1 programmed ribosomal frameshifting (-1 PRF), in which the ribosome begins reading an mRNA one nucleotide before it should. This hiccup bumps translation “out of frame,” creating a different sequence of three-nucleotide-long codons. In essence, -1 PRF thus gives a single gene the unexpected ability to code for two completely different proteins.

Recently Andrew Anzalone, an MD/PhD student in the laboratory of Virginia Cornish, set out to explore whether he could take advantage of -1 PRF to engineer cells capable of producing alternate proteins. Together with Sakellarios Zairis, another MD/PhD student in the Columbia University Department of Systems Biology, the two developed a pipeline for identifying RNA motifs capable of producing this effect, as well as a method for rationally designing -1 PRF “switches.” These switches, made up of carefully tuned strands of RNA bound to ligand-sensing aptamers, can react to the presence of a specific small molecule and reliably modulate the ratio in the production of two distinct proteins from a single mRNA. The technology, they anticipate, could offer a variety of exciting new applications for synthetic biology. A paper describing their approach and findings has been published in Nature Methods.

Saeed TavazoieSaeed Tavazoie, a professor in the Columbia University Department of Systems Biology, has been named a recipient of a 2015 National Institutes of Health Transformative Research Award. The grant will support research to develop state-of-the-art experimental and computational methods for comprehensively mapping and modeling all pairwise molecular interactions inside cells. 

The Transformative Research Award is a part of the NIH Common Fund’s High-Risk, High-Reward Research program, which provides critical funding to scientists it recognizes as being exceptionally creative and who propose particularly innovative approaches to solving key problems in biomedical research. The Transformative Research Award is designed to support projects that use methods and perspectives that are unconventional and untested, but show great potential to create or overturn fundamental paradigms.

Alex Lachmann
Alex Lachmann during his presentation to the RNA-Seq "boot camp."

In June 2015, the Columbia University Department of Systems Biology held a five-part lecture series focusing on advanced applications of RNA-Seq in biological research. The talks covered topics such as the use of RNA-Seq for studying heterogeneity among single cells, RNA-Seq experimental design, statistical approaches for analyzing RNA-Seq data, and the utilization of RNA-Seq for the prediction of molecular interaction networks. The speakers and organizers have compiled a list of lecture notes and study materials for those wishing to learn more. Click on the links below for more information.

Tuuli LappalainenTuuli Lappalainen has joined Columbia University as an assistant professor in the Department of Systems Biology. Dr. Lappalainen is a specialist in the analysis of RNA sequencing data, with research interests including functional variation in the human genome, population genetic background of variation in the human genome, and interpretation of genome function.

Dr. Lappalainen joins the Department of Systems Biology in co-appointment with the New York Genome Center (NYGC), where she will also serve as a Junior Investigator and Core Member. Based in lower Manhattan, NYGC is a consortium made up primarily of New York-area institutions that is designed to translate promising genomics-based research into new strategies for treating, preventing, and managing disease. This co-appointment with Columbia University — an institutional founding member of the NYGC — will enhance collaboration between the two institutions. (Read an interview with Dr. Lappalainen at the New York Genome Center website.)

Dr. Lappalainen earned her PhD in genetics at the University of Helsinki, Finland, and held appointments as a postdoctoral researcher in at the University of Geneva Medical School, Switzerland and at the Stanford University School of Medicine. She is the chair of the analysis group for the Genetic European Variation in Health and Disease (Geuvadis) Consortium’s RNA sequencing project, a member of the analysis group for the National Institute of Health’s Genotype Tissue Expression (GTEx) project, and a member of the analysis and functional interpretation groups for the 1000 Genomes Project.

An extensive microRNA-mediated network of RNA-RNA interactions

Genome-wide inference of sponge modulators identified a miR-program mediated post-transcriptional regulatory (mPR) network including ~248,000 interactions.

For decades, scientists have thought that the primary role of messenger RNA (mRNA) is to shuttle information from the DNA to the ribosomes, the sites of protein synthesis. However, new studies now suggest that the mRNA of one gene can control, and be controlled by, the mRNA of other genes via a large pool of microRNA molecules, with dozens to hundreds of genes working together in complex self-regulating sub-networks.

In work published in the journal Cell, Andrea Califano, José Silva, and colleagues analyzed gene expression data in glioblastoma in combination with matched microRNA profiles to uncover a posttranscriptional regulation layer of surprising magnitude, comprising more than 248,000 microRNA (miR)-mediated interactions. These include ∼7,000 genes whose transcripts act as miR “sponges.” When two genes share a set of microRNA regulators, changes in expression of one gene affects the other. If, for instance, one of those genes is highly expressed, the increase in its mRNA molecules will “sponge up” more of the available microRNAs. As a result, fewer microRNA molecules will be available to bind and repress the other gene’s mRNAs, leading to a corresponding increase in expression.

Although such an effect had been previously elucidated, the range and relevance of this kind of interaction had not been characterized.