Fragile X Mutant Mouse Models

David Nelson, PhD, FRAXA Investigator

With $375,000 in grants from the FRAXA Research Foundation since 2009, Dr. David Nelson has developed an impressive array of advanced mouse models of Fragile X, at Baylor College of Medicine. These models are available to investigators worldwide on request. This resource has been essential for a broad, rapid distribution of Fragile X and related gene mouse models and has increased the pace of Fragile X research.

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Repurposing Drugs to Dampen Hyperactive Nonsense-Mediated Decay in Fragile X Syndrome

With a $90,000 grant from the FRAXA Research Foundation, Dr. Lynne Maquat and Dr. Tatsuaki Kurosaki will investigate nonsense-mediated mRNA decay (NMD) in Fragile X. NMD is a “housekeeping” process that cells use to prevent faulty proteins from being made. But there is too much of it in Fragile X syndrome. There are already available drugs that suppress NMD – including caffeine.

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Fruit Flies to Model and Test Fragile X Treatments

Dr. Tom Jongens and Dr. Sean McBride study Fragile X Fruit Flies

Dr. Jongens and his collaborators have found an insulin-like protein in the fly brain that is overexpressed in the Fragile X mutant fly, leading to increased activity of the insulin signaling pathway. Furthermore, they found that certain behavioral patterns in the Fragile X flies can be rescued by expressing the FX gene just in insulin producing neurons in the fly brain. In the mutant, there are other changes in the signaling pathways, including a decrease in cAMP and elevation in PI3K, mTOR, Akt and ERK activity. They now propose to study 2 medicines used for diabetes: pioglitazone (increases cAMP and decreases Akt and ERK) and metformin (inhibits mTOR), in flies and mice to validate the potential efficacy of these novel therapeutics for Fragile X.

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FRAXA Grant to Nahum Sonenberg, PhD — Effects of metformin in Fmr1 knockout mouse model of Fragile X syndrome

Nahum Sonenberg

Mis-regulation of activity-dependent protein synthesis is one of the major cellular abnormalities found in Fragile X. Upstream neuronal signaling regulates a large cluster of enzymes called the mTORC1 complex, which in turn regulates protein synthesis. This complex is also controlled by cellular energy levels via the metabolic sensor AMP-activated Protein Kinase (AMPK). AMPK is a highly conserved kinase that is activated under conditions of energy stress, when intracellular ATP levels decline and intracellular AMP increases.

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Computational Analysis of Neural Circuit Disruption in Fragile X Model Mice

Computer modeling of the brain offers the hope of predicting how the brain responds to varying conditions, but these models have been rather primitive until recently. The Sejnowski team at the Salk Institute, who specialize in computational models of neural networks, will take the results of previous FRAXA-funded projects and incorporate them into their advanced computer models of brain function.

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Bcl-xL Inhibition as a Therapeutic Strategy for Fragile X Syndrome

Scientists have found increases in the numbers of neurons in brain regions of autistic children, suggesting a problem in developmental programmed cell death pathways. One of the most important effectors of neuronal survival during brain development is the “anti-cell death” protein Bcl-xL. While the normal function of Bcl-xL is to maintain a healthy number of neurons and synapses, over-expressed Bcl-xL can cause an overabundance of synaptic connections. This may be happening in Fragile X.

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Small Molecules To Target r(CGG) Expansions to Treat Fragile X Syndrome

With a 2-year, $90,000 grant from FRAXA Research Foundation, Dr.’s Matthew Disney and Wang-Yong Yang worked to correct the underlying problem in Fragile X: the silencing of the Fragile X gene (FMR1) and the resulting lack of FMRP (Fragile X Mental Retardation Protein). Their approach was to use novel small molecules to target the abnormal CGG repeats before the FMR1 gene.

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Potassium Channel Modulators to Treat Fragile X

With $246,000 in funding from FRAXA over 2012-2014, the Yale University team of Leonard Kaczmarek, PhD, showed that loss of FMRP leads to an increased Kv3.1 potassium currents and decreased Slack potassium currents in neurons. Both of these changes impair timing of action potentials in auditory neurons (and likely others throughout the brain). The team also found that the firing pattern of neurons in response to repeated stimulation is severely abnormal in Fragile X mice. Based on these results, they are collaborating with the UK-based company Autifony to develop and test advanced compounds which may reverse these deficits.

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