FRAXA Research Foundation is excited to announce our 2017 Research Grants aimed at finding specific treatments and ultimately a cure for fragile X syndrome. Several of these projects are funded with generous support from our partner organizations: Autism Science Foundation, The Pierce Family Fragile X Foundation, and the Fragile X Research Foundation of Canada.
Autophagy is a Novel Therapeutic Target of Impaired Cognition in Fragile X Syndrome
Autophagy is a natural process of programmed degradation and recycling of components of cells. It’s the cells’ system of cleaning house. In fragile X syndrome, autophagy seems to be underactive.
Dr. Zukin and colleagues have previously studied a particular “master regulator” protein, the mammalian target of rapamycin complex 1 (mTORC1), and found that it is overactivated in the hippocampus of fragile X mice. Too much mTORC1 leads to too little of the cleanup system (‘autophagy’) and therefore too much of many other proteins.
The Zukin team will examine whether impaired autophagy causes impaired learning in fragile X mice. They will also investigate whether it can explain the differences seen in the structure of spine-like protrusions on dendrites (connections between neurons), which in fragile X mimic an immature morphology (shape). Then they will look for novel therapeutic strategies that target the autophagy pathway to rescue autophagy and learning in fragile X mice.
Correcting Fragile X-associated Deficits by Targeting Neonatal PKCepsilon Signaling in the Brain
Probal Banerjee, PhD, Principal Investigator
Tatyana Budylin, FRAXA Fellow
The Reason for this Study
Fragile X syndrome (FXS) occurs due the silencing of the X-linked gene Fmr1, and it is known that the protein product (FMRP) of the Fmr1 gene controls expression of other proteins. However, it is unclear how the deficiency of FMRP leads to impairments. So far no mechanistic pathway has been found to link FMRP to FXS.
Discovery of FXS-associated Defects at the Molecular Level
Dr. Banerjee’s team is addressing this information gap by studying PKCe, which is one among the many gene products that are regulated by FMRP. By studying fragile X knockout (KO) mice, which lack FMRP, they have observed that PKCe expression is significantly suppressed in a hormone-secreting center of the brain, the hypothalamus, and the cognitive hub, hippocampus, which regulates hypothalamic activity. They also observed suppression of the sociability hormone oxytocin in the hypothalamus. Simultaneously, increased cell-surface localization of an excitation-causing protein, AMPAR, in the hippocampal nerve cells presumably increased anxiety in the KO mice.
Therapeutic Strategy for Permanent Correction of FXS-associated Defects
The scientists have attempted to compensate for suppressed PKCe signaling by treating the KO mice at an early age with the selective PKCe stimulator DCPLA. Quite strikingly, this resulted in a therapeutic correction of oxytocin expression in the hypothalamus, normalization of cell-surface AMPAR localization in the hippocampus, and correction of later-life hyper-anxiety and autistic-like social behavior deficits in adulthood! Thus, for the first time, this project brings the promise of elucidating a pathway that is compromised in the KO mice and uses a therapeutic strategy to correct the signaling pathway shortly after birth. This strategy is likely to correct early neurodevelopment in the brain and thereby afford a global, permanent correction of neuroconnectivity and behavior in the FXS mice.
The impression that fragile X mouse studies do not translate to human therapy is often based on treatments that are offered beyond the point of critical development when the brain can best be nudged to form the right connections. Therefore, it is highly important to conduct preclinical studies such as this during early brain development. Such studies will have a greater likelihood of eventually translating into successful human clinical trials.
Auditory Dysfunction in Fragile X Syndrome, Role for the Sound Localization Pathway
This FRAXA research grant will allow Elizabeth McCullagh, PhD and Achim Klug, PhD to investigate whether neural circuits which process sound are altered in fragile X syndrome. There is a specific circuit which allows us to discriminate between competing sound sources, helping us focus on a sound source of interest such as with a conversation partner. This is the aptly named “cocktail party effect”. The team will measure alterations in this circuit in fragile X syndrome. If clear differences are found, they could be used as potential biomarkers for FXS.
Achim Klug, PhD
Neural Markers of Cognitive, Language, and Behavioral Deficits in Children with Fragile X
With this grant, the team will identify and characterize brain-based markers that predict cognitive, language, and behavioral deficits in young children with fragile X syndrome. Using EEG, a low cost, non-invasive technique, they will measure brain activity in response to sensory stimuli, and correlate this with cognitive, language, and behavioral ratings. The brain-based markers can then be used in future fragile X clinical trials as objective measures for targeted outcomes.
Results from this study should facilitate development of targeted drug and behavioral based interventions. While other research groups have used EEG to study subjects with fragile X, this project will work with much younger children at an earlier stage of development.
Carol Wilkinson MD, PhD
MicroRNA Mediated Astroglial GLT1 Dysregulation in Fragile X
Glutamate is the major excitatory neurotransmitter in the brain. Abnormal regulation of glutamate has been implicated in many neuropsychiatric disorders, including autism, schizophrenia, and fragile X syndrome. It is thought that glutamate levels outside of the nerve cells are elevated and causes nerves more “excited” and induces many symptoms in humans with fragile X and also in mice bred to mimic fragile X syndrome.
Much of glutamate metabolism depends on astrocytes, the versatile and abundant cells nestled between all the neurons of the brain. Extracellular glutamate (which floats around in between brain cells) is regulated by one of the most abundant proteins in the brain, the glutamate transporter GLT1, which is expressed mainly by astrocytes. Previous studies from the Yang lab at Tufts University School of Medicine have found that there is a decrease of this critical glutamate transporter GLT1 in fragile X mice.
This group has shown that removing the fragile X protein from astrocytes decreases the astrocytes’ ability to sweep up excess glutamate. They have recently identified a few small RNA molecules called microRNA that are involved in the regulation of GLT1. With the help of this research grant, they are now exploring how these microRNAs changes underlie decreased GLT1 expression. The Yang lab is also testing whether these microRNAs can restore astrocytes’ ability to reduce extracellular glutamate levels, thus hold the potential to become new therapies for fragile X syndrome.
Haruki Higashimori, PhD
Yuqin Men, PhD
Aberrant Insulin Signaling in a Mouse Model of Fragile X
Insulin signaling is known to be dysregulated in diabetes and cancer, and has lately been described to be implicated in cognitive dysfunctions in neurodegenerative disorders such as Alzheimer’s disease. Furthermore, dysregulation of insulin signaling might also be associated with autism. Funded by FXRFC and FRAXA research grants, this study will systematically investigate the impact of insulin signaling on autistic-like behaviors, synaptic plasticity, spine morphology and mRNA translation in the mouse model of fragile X syndrome.
Ilse Gantois, PhD