Mutations in a gene called MECP2 are the cause of Rett Syndrome. Restoration of adequate levels of MECP2 has been shown to undo the damage caused by a mutated copy of the gene, demonstrating the powerful reach of MECP2‘s influence as symptom after symptom disappeared in fully mature mouse models of Rett Syndrome. This astonishing breakthrough presents us with the urgent challenge of determining whether such results can be achieved in humans.
RSRT stimulates, organizes and funds research to defeat this disorder via three essential approaches:
• Treatment – Targeting downstream effects of MECP2 mutations via drugs and/or procedures. This is largely a symptom-by-symptom approach to relieving some of Rett Syndrome’s many manifestations and improving quality of life.
• Basic science – Investing in rigorous science to develop an accurate, detailed knowledge base of the neurobiology of Rett as a direct conduit to the creation of new strategies to overcome it.
• Reversal – Approaches that target the underlying cause of Rett, aberrations in MECP2, in efforts to actualize the 2007 pre-clinical reversal for human clinical application. Included are gene therapy; activation of the silent MECP2 gene on the inactive X; identification and deployment of modifier genes.
The following are the projects that RSRT is supporting financially as well as intellectually categorized by the three approaches. To date almost $20 million have been committed to these projects.
There is a multitude of data suggesting that mice models of Rett have low levels of a neurotrophic factor called BDNF (brain derived neurotrophic factor). BDNF is a very important and complex protein that is implicated in a variety of disorders. Increasing BDNF in the Rett mice models, either genetically or pharmacologically is beneficial. An FDA approved drug for multiple sclerosis called copaxone (or Glatiramer Acetate) is known for increasing BDNF and therefore of interest in treating Rett.
RSRT has committed to funding an open label study of copaxone in two centers, the Tri-State Rett Syndrome Center at Children’s Hospital at Montefiore in the Bronx, under the supervision of Dr. Sasha Djukic, and at Sheba Medical Center in Ramat Gan in Israel under the supervision of Dr. Bruria Ben Zeev. Each center will give copaxone to ten individuals for 6 months. Below is a comparison of the two studies.
|Title||Pharmacological treatment of Rett Syndrome with Glatiramer Acetate (Copaxone)||An open-label exploratory study to investigate the treatment effect of glatiramer acetate (Copaxone) on girls with Rett Syndrome|
|Principal Investigator||Aleksandra Djukic, MD, PhD||Bruria Ben Zeev, MD|
|Location||Children’s Hospital at Montefiore, Bronx||Sheba Medical Center, Ramat Gan, Israel|
|Objectives||Primary: gaitSecondary: cognition, autonomic function, EEG, quality of life||Primary: EEG improvementSecondary: autonomic function, general behavior, communication, hand stereotyping, feeding, gastrointestinal|
|Study Size||10 girls – 10 yrs old and up||10 girls – 6 to 15 yrs old|
|Dose (injections)||Ramp up to 20 mg per day||Ramp up to 20 mg per day|
|Length of study||6 months||6 months|
While copaxone is not going to cure Rett Syndrome we hope that by increasing BDNF we will see improvements in symptoms. The trials are currently recruiting.
Evaluate the outcome of deep brain stimulation (DBS) on cognition in Rett mouse models
Huda Zoghbi, M.D.
Baylor College of Medicine
The use of DBS has revolutionized the treatment of Parkinson’s and is now also used for depression, OCD, Alzheimer’s and more recently in pediatric disorders such as dystonia and Tourette. The availability of Rett mouse models allows us the opportunity to explore potential benefits of this procedure for Rett. Encouraging data can be quickly moved to the clinic.
Therapeutic Approaches to Reversing Forebrain and Brainstem Abnormalities
David Katz, Ph.D.
Case Western Reserve University
This project will seek to determine whether NMDA receptor antagonists can reverse the imbalance of excitation vs inhibition present in the forebrain and brainstem of Rett mice. If so, certain drugs could be quickly moved into clinical trials. Watch a video interview with Dr. Katz.
Testing of selective NMDA receptor modulators
Michela Fagiolini, Ph.D.
Boston Children’s Hospital
A joint collaboration between RSRT, Mnemosyne Pharmaceutical and Boston Children’s Hospital to perform preclinical testing of selective novel NMDA receptor modulators.
Immune modulation as a new therapeutic approach for Rett Syndrome
Jonathan Kipnis, Ph.D.
University of Virginia
Recent data generated in the Kipnis lab demonstrates that immune system and T cells, in particular, are required for normal brain function. T cells, working through soluble factors (cytokines), control synaptogenesis, regulate adult neurogenesis, and affect levels of brain derived neurotrophic factor (BDNF). Depletion or malfunction of T cells correlates with reduced synaptogenesis, decreased levels of BDNF, and impaired brain function. Rett syndrome is associated with motor malfunction, reduced neurogenesis, and deficit in BDNF. Studies indicate that some aspects of T cell function are impaired in Rett patients. Therefore, Kipnis hypothesizes that a malfunction in adaptive immune system (T cells, in particular) in Rett patients contributes, at least in part, to some aspects of disease progression. Thus, if T cell function is improved, the disease can be attenuated and some symptoms might be partially ameliorated. Learn more about this work.
mGluR5 Signaling – Is it Implicated in Rett?
Mark Bear, PhD
Dr. Bear is a pioneering researcher whose thoughtful insight has dramatically advanced the understanding of Fragile X. His seminal work was featured in Forbes late last year.
Like Rett Syndrome, Fragile X is a single gene disorder, but caused by mutations in a gene called Fmr1. When Fmr1 is mutated, protein synthesis fails to shut down leading to an excess. Some years ago Dr. Bear proposed that compounds which can block a certain type of receptor, mGluR5 (which triggers the burst of synaptic protein synthesis) might counteract over-expression of protein and thereby cancel out the damaging effect of Fmr1 deficiency. His theory has proved correct and clinical trials of mGluR5 antagonists are currently ongoing at multiple pharmaceutical companies. Dr. Bear has proposed that just as Fragile X is due to over-synthesis of proteins at the synapse, Rett may be due to under-expression of protein at the same locations. RSRT has committed funding to the Bear lab to first test this hypothesis and if proven correct to explore whether pharmacological manipulations of mGluR signaling will improve any of the mutant mice Rett-like symptoms. The in vivo mouse work will be performed in collaboration with Professor Adrian Bird.
In vivo evaluation of specific drugs in mouse models of MECP2 disorders
Huda Zoghbi, M.D.
Baylor College of Medicine
The Zoghbi lab identified MECP2 mutations as the cause of Rett Syndrome in 1999 and has been very active in the field since. This project is a thorough evaluation of specific drugs which will be tested in the various mouse models of MECP2 disorders: the knockout, the truncated MECP2 and the MECP2 over-expressing mouse lines. Instead of completely lacking the MECP2 gene as in the knockout mouse, the truncated MECP2 mouse expresses the first portion of the MECP2 protein. These animals have milder deficits with a much slower disease progression, and are therefore a model of milder forms of Rett Syndrome. Interestingly, too much MECP2 also causes a severe neurological disease, called MECP2 duplication syndrome. The MECP2 over-expressing mouse carries multiple copies of the MECP2 gene and is a relevant model of MECP2 duplication syndrome in humans. The goal is to speed any promising drugs/compounds to the clinic.
Effect of the serotonin 1a agonist F15599 on respiration and locomotion in a mouse model of Rett syndrome
John M Bissonnette, MD
Oregon Health and Science University
In ongoing experiments we find that the serotonin 1a agonist sarizotan effectively reduces apnea and corrects irregularity in Mecp2 deficient female mice. Sarizotan is a phase II drug that has been evaluated in clinical trials to treat L-dopa induced dyskinesia in Parkinson’s disease. F15599 is a serotonin 1a agonist shown to be effective in rodent models of depression and cognition. It is an attractive candidate that may correct respiratory disorders without affecting locomotion in Rett mice.
Exploring NLX-101 as a potential treatment for breathing abnormalities in Rett Syndrome
Mark Varney, PhD
Neurolixis is a biotech company developing a drug (NLX-101) to treat breathing problems in Rett Syndrome. John Bissonnette, Ph.D. of OHSU, previously tested the drug in mouse models of Rett. These mice exhibit severe breathing difficulties, including apneas and respiratory irregularity, similar to those seen in girls with Rett syndrome. NLX-101 treatment reduced the occurrence of apneas and normalized the irregular breathing patterns without interfering with other behaviors. These data suggest that NLX-101 may represent a promising strategy for treating breathing disturbances in Rett.
Treatment of Osteoporosis in Murine Rett Syndrome Models: A Comparison of Zoledronic Acid vs Teriparatide on Osteoblast Function, Gene Expression and Bone Mass
Jay R. Shapiro, M.D.
Johns Hopkins University
Osteoporosis leading to fractures affects nearly 40% of young children and adults with Rett Syndrome. The pathogenesis of osteoporosis in Rett is not understood and no accepted treatment regimen exists. This project addresses both of these issues.
Novel insights in MeCP2 function suggests new therapeutic strategies
Stavros Lomvardas, Ph.D.
University of California San Francisco
This experiment leverages the discovery that MeCP2 deficient olfactory receptor neurons (ORN) have a very robust readout; they co-express molecules that are never expressed in the same neuron in wild type mice. Dr. Lomvardas will capitalize on this finding to screen for drugs that can reverse the deficit – in other words find drugs, using high throughput screens (HTS) that can turn off one of ectopically expressed molecular markers.
Vitamin D therapy for MeCP2 target Irak1/NF-κB dysregulation
In our previous studies, we identified a number of potential “target” genes of MeCP2 in these important cortical neurons. One of the over-expressed genes is Irak1, a component of the NFkB signaling pathway. We propose to investigate the therapeutic potential of one known inhibitor of NFkB signaling, Vitamin D , in Mecp2 mutant mice. Our proposed experiments will not only add to our understanding of molecular and pathological mechanisms of Rett syndrome, but will also potentially contribute to future therapeutic strategies via Vitamin D or alternative NFkB pathway drugs.
In vivo screen of drugs and drug-like compounds
Andrew Pieper, M.D., Ph.D.
University of Texas Southwestern Medical Center in Dallas
This project tests FDA approved drugs and compounds of interest in mice models of Rett to identify Hits that improve disease-related signs in the animals. Compounds that alleviate the symptoms or progression of the disease in mice will form the basis of advanced drug discovery programs; approved drugs can be fast-tracked to clinical trials.
The MECP2 Consortium is a dynamic collaboration between the laboratories of three distinguished scientists, Adrian Bird, Michael Greenberg and Gail Mandel. Made possible by a $2 million lead gift by RSRT Trustee Anthony Schoener and his wife Kathy, the Consortium was formed to definitively determine how this complex protein, MeCP2, functions and exerts its powerful influence on the human brain. Deep knowledge of its structure and roles in neurological development and maintenance will inform the design of rational treatments for disorders caused by abnormalities in this protein. RSRT has invested $5.2 million in the Consortium thus far.
Three papers to date have been published through the effort of the Consortium. Two papers by the Bird and Greenberg labs deepen our knowledge of the MeCP2 protein and a paper from the Mandel lab opens the door to gene therapy as a treatment option.
Despite almost two decades of research into the molecular mechanisms of MeCP2 function, many questions are yet to be answered conclusively: Is MeCP2 a multifunctional protein or primarily a transcriptional repressor? Does it act at specific sites within the genome or more globally? In which cell types is it functionally relevant? How does it change in response to brain activity? The Consortium is tackling these questions through a series of experiments, some of which are summarized below.
The most pressing unresolved issue concerns the role of MeCP2 in regulating gene expression. The biochemical consequences of MeCP2-deficiency in the brain are complex and have been interpreted in diverse ways. Some have concluded that MeCP2 is an activator of transcription, whereas others have emphasized evidence that its primary role is repression of gene activity. In addition, there are recent reports that MeCP2 regulates cellular processes other than transcription, for example post-transcriptional processing of RNA. With the benefit of powerful new developments in biochemistry, genetics, bioinformatics and imaging the Consortium will mount a multi-pronged attack on this thorny question.
MeCP2 is associated with chromosomes and it is vital to have a detailed picture of exactly where it is bound, especially in cells of the brain. Recent work has suggested that newly appreciated chemical marks on DNA, including hydroxymethylcytosine – which is relatively abundant in the brain – provide landing pads for MeCP2 over and above conventional DNA methylation sites. The Consortium will address this issue by generating high-resolution maps of both DNA modification and MeCP2 binding in neurons and glia.
The original mouse models of Rett syndrome were based on simple removal of the Mecp2 gene. Recent advances in techniques for genetic manipulation allow researchers to create Mecp2 mutations that exactly mimic those found in Rett patients and study their consequences. Consortium scientists will also alter the Mecp2 gene in human neuronal cells and in mice to test hypotheses about how the protein works. The effects of such mutations will be studied in novel ways. For example new imaging methods allow analysis effects on the microscopic substructure of brain cells and the effects on the entire protein composition can be scrutinized. The Consortium will also study the effects of MeCP2-deficiency on different types of cells in the brain, including for example neurons that excite or inhibit electrical activity. By using a broad range of state-of-the-art technologies, within the context of regular data-sharing, the Consortium will attempt to transform our understanding of MeCP2. Its principal belief is that basic biological knowledge of this kind will be essential to inform the Rett therapies of the future.
MECP2 Gene Therapy Consortium
Launched in early 2014 the MECP2 Gene Therapy Consortium is charged with tackling the necessary experiments to get us to clinical trials as quickly as possible. RSRT is investing $1.6 million in this international collaboration.
Brian Kaspar (Nationwide Children’s Hospital)
Stuart Cobb (University of Glasgow)
Steven Gray (UNC Chapel Hill)
Gail Mandel (OHSU)
A Chemical Genetic Approach for Unsilencing Mecp2
Ben Philpot, Ph.D., Bryan Roth, Ph.D., Terry Magnuson , Ph.D.
University of North Carolina at Chapel Hill
These investigators have successfully employed a high-throughput screen to identify compounds that unsilence the gene for Angelman Syndrome, UBE3A. They are now applying the same approach to Rett Syndrome. Using high throughput robotic equipment they are working their way through a library of 20,000 compounds. To learn more about this work we invite you to watch a video of Dr. Philpot describing this work. RSRT is investing $2.2 million in this project.
A High-Throughput Screen to identify compounds that reactivate the functional MECP2 allele in Rett Syndrome
Jeannie Lee, M.D., Ph.D.
Dr. Lee will develop an assay using mouse cells that can detect activation of the MECP2 gene. Utilizing the significant resources of The Broad Institute the assay will undergo a high-throughput screen to identify compounds able to turn on expression of the gene.
An Oligotherapeutics Approach to Treat Rett Syndrome
Jeannie Lee, M.D., Ph.D.
In 2013 RSRT funded a second project in the Lee lab. While the goal of the new award is the same – activate MECP2 – how she proposes to accomplish it is completely novel. The hypothesis of Dr. Lee’s approach rests on an observation that a group of proteins called Polycomb complexes working in concert with a certain type of RNA, called noncoding RNA (lncRNA) are relevant for keeping genes silent on the inactive X. Dr. Lee’s therapeutic strategy is to awaken the MECP2 gene by disrupting the binding that occurs between the lncRNA and the Polycomb complexes.
Identification of drugs or genes that activate the silent MECP2 gene
Antonio Bedalov, M.D., Ph.D.
Fred Hutchinson Cancer Research Center
The gene that is mutated in Rett Syndrome, MECP2, is located on the X chromosome. All females have two X chromosomes in every cell but one is inactivated. The goal of this project is to identify drugs/compounds and/or genes that will activate the silent MECP2 on the inactive X chromosome.
Reactivation of the Inactive X-linked MECP2 Gene as a Therapeutic Strategy for Rett Syndrome
Michael Green, M.D., Ph.D.
University of Massachusetts
We have identified factors that control X chromosome inactivation and based upon this information derived small molecule drugs that can reactivate the silenced MECP2 gene in cell culture. We will continue to study reactivation of the silenced MECP2 gene and, in particular, extend our cell culture results to mouse models of RTT.
Identification of the mechanisms that silence the MECP2 gene on the inactive X chromosome
Marisa Bartolomei, Ph.D.
University of Pennsylvania
A synergistic project to the project above this effort is also focused on activating the silent MECP2 gene on the inactive X. Dr. Bartolomei seeks to identify the molecular mechanisms that keep MECP2 silent in the hopes that these modifications can be reversed with drug(s). It is possible that activating the silent MECP2 may require a combination of loosening up the mechanisms that keep this gene silent in concert with activation drugs identified in the above project.
Identification of gene modifiers that ameliorate Rett symptoms
Monica Justice, Ph.D.
Hospital for Sick Children (Toronto)
An emerging field of interest is that of genetic modifiers that impact the severity of disease. Rett Syndrome is ideal for modifier screening for two reasons: a) it has been shown to be reversible in mice and b) some girls do not have Rett symptoms despite having common mutations in MECP2. This project aims to identify these advantageous modifiers using a forward genetic screen in mice. The knowledge of disease amelioration may provide novel avenues for therapeutic intervention. In a preliminary screen, five lines that carry inherited suppressors, which increase lifespan and decrease other RTT-related symptoms in mice, have been identified. As expected, most of the suppressors act at the level of chromatin remodeling, and may be difficult to target therapeutically. However, one modifier, Sqle, belongs to the cholesterol pathway and suggests statins may be helpful in Rett Syndrome. The screen is ongoing and many more modifiers are likely to be found.
Learn more about this work.
Identification of genetic modifiers in Rett Syndrome
Jeffrey Neul, M.D., Ph.D.
Baylor College of Medicine
This project was awarded in late 2013 and will run in parallel with Dr. Justice’s mouse project. Like with many diseases Rett Syndrome is a spectrum disorder. Some “lucky” girls can walk, run, speak in simple sentences, hold a pencil, follow directions and more. They have mutations in the Rett gene and yet they are spared the classic and devastating symptoms. Why? Their genetic code may hold the answer.
Dr. Neul will sequence the exomes (the protein producing portion of the genome) of high-functioning kids/adults in the hopes that some common variables may point to modifiers which can then become drug targets. Importantly, the sequencing and phenotypic data will be a valuable resource as it will be deposited into the National Database for Autism Research and available to the scientific community.
Watch this video to learn more about this project.
Evaluate the outcome of boosting MeCP2 levels in wildtype cells of female mice
Huda Zoghbi, M.D.
Baylor College of Medicine
Females with Rett Syndrome lack functional MeCP2 in approximately 50% of their neurons while 50% have normal (wildtype) MeCP2. Dr. Zoghbi will explore whether boosting MeCP2 levels in the wildtype cells might enhance the overall neural network activity even in the face of the 50% null cells. Encouraging results could set the foundation for a large scale screen to identify targets that can modulate MeCP2 levels. This knowledge will be critical for Rett Syndrome as well as the MECP2 duplication syndrome.
Adeno-associated Virus-mediated Gene Transfer for the Treatment of Rett Syndrome
Ronald C. Crystal, M.D., Adrian Bird, Ph.D.,
Weill Cornell Medical College, University of Edinburgh
This project also seeks to develop a gene therapy approach to the treatment of Rett but with a different vector than the project outlined above. The vector used will be the new generation AAVrh10 which has shown remarkable gene expression throughout the central nervous system. The Crystal lab is one of only a few in the world that has conducted gene therapy clinical trials in humans. Complimenting the Crystal expertise at gene therapy and clinical trials is Adrian Bird, who brings his deep knowledge of MeCP2 and the Rett animal models. If gene therapy with AAVrh10 is successful in the mice Crystal’s past experience in clinical trial development will prove invaluable.
MECP2 Duplication Syndrome Fund at RSRT
Testing reversibility of the MECP2 Duplication/Triplication Syndrome
Huda Zoghbi, M.D.
Baylor College of Medicine
The dramatic reversal of Rett symptoms in mice described by Adrian Bird in 2007 opened the field to questions that now must also be explored in the MECP2 Duplication Syndrome. We know that in Rett, restoration of proper MeCP2 function in mice only days away from death brought them back to health. Would elimination of the influence of excess MeCP2 in the Duplication Syndrome have a similarly dramatic effect? Dr. Zoghbi’s experiment will yield an answer to this very important questions.
Screening for Compounds to Reduce Levels of MeCP2
Huda Zoghbi, M.D.
Baylor College of Medicine
To conduct a screen to discover compounds that can reduce levels of MeCP2 for the duplication/triplication syndrome.
Gene Therapy Approach to Treating MECP2 Duplication Syndrome
Kevin Foust, Ph.D.
Ohio State University
The duplication syndrome is caused by having an extra copy of the MECP2 gene. In theory, reducing the amount of MeCP2 protein should improve the disease. Dr. Foust will use adeno-associated virus (AAV) to deliver RNA interference to lower the amount of MeCP2 protein. If successful the project will provide proof-of-concept data showing that MeCP2 reduction is a therapeutic option for patients.