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PI3 kinase

Fragile X: preclinical portfolio for PI3k drug strategy

Research in mice shows that a pharmacological strategy can alleviate multiple behavioral and cellular deficiencies in a mouse model of fragile X syndrome (FXS), the most common inherited form of intellectual disability and a major single-gene cause of autism spectrum disorders.

The results were published online last week by Neuropsychopharmacology, and were presented at the NFXF International Fragile X Conference in Cincinnati.

When the compound GSK6A was given to mice lacking the Fmr1 gene, an established animal model of fragile X syndrome, it relieved symptomatic behaviors, such as impaired social interactions and inflexible decision making, which can be displayed by humans with fragile X syndrome.

The findings indicate that treatment with GSK6A or a similar compound could be a viable strategy for addressing cognitive and behavioral problems in fragile X syndrome; this would need to be tested directly in clinical trials. GSK6A inhibits one particular form of a cellular signaling enzyme: the p110β form of PI3 (phosphoinositide-3) kinase. A closely related p110β inhibitor is already in clinical trials for cancer.

Video from the iBook “Basic Science Breakthroughs: Fragile X Syndrome”. Narration by Emory genetics chair Stephen Warren, whose team identified the gene responsible for fragile X.

“Our results suggest that p110β inhibitors can be repurposed for fragile X syndrome, and they have implications for other subtypes of autism spectrum disorders that are characterized by similar alterations of this pathway,” says Gary Bassell, PhD, professor and chair of cell biology at Emory University School of Medicine.

“Right now, no proven efficient treatments are available for fragile X syndrome that are targeted to the disease mechanism,” says Christina Gross, PhD, from Cincinnati Children’s. “We think that p110β is an appropriate target because it is directly regulated by FMRP, and it is overactivated in both mouse models and patient cell lines.”

The paper represents a collaboration between three laboratories: two at Emory led by Bassell and Shannon Gourley, PhD, and one at Cincinnati Children’s, led by Gross. Gourley is based at Yerkes National Primate Research Center; see this earlier item on her collaboration with Bassell here.

While the researchers are discussing clinical trials of p110β inhibitors in fragile X syndrome, they say that long-term studies in animals are needed to ensure that undesirable side effects do not appear. More here.

With respect to clinical trials, the fragile X community has been disappointed before. Based on encouraging studies in mouse models, drugs targeting mGluR5 glutamate receptors were tested in adolescents and adults. mGluR5 drugs did not show clear benefits; recent re-evaluation suggests the choice of outcome measures, the ages of study participants and drug tolerance may have played a role.

Warren played a major role in developing the mGluR5 approach and Emory investigators were part of those studies. More recently, clinical trials for one of the mGluR5 medications were revived in younger children and Emory is a participating site. Also, see this 2016 discussion in Spectrum with Elizabeth Berry-Kravis on the fragile X mouse model; Bassell, Gross and Gourley have made some inroads on the limitations Berry-Kravis describes.

Posted on by Quinn Eastman in Neuro Leave a comment

Fragile X syndrome: building a case for a treatment strategy

New research in mice strengthens a potential strategy for treating fragile X syndrome, the most common inherited form of intellectual disability and a major single-gene cause of autism spectrum disorder.

The results, published April 23 in Cell Reports, suggest that a drug strategy targeting a form of the enzyme PI3 (phosphoinositide-3) kinase could improve learning and behavioral flexibility in people with fragile X syndrome. The PI3 kinase strategy represents an alternative to one based on drugs targeting mGluR5 glutamate receptors, which have had difficulty showing benefits in clinical trials.

Research led by Emory scientists Gary Bassell, PhD and Christina Gross, PhD had previously found that the p110β form of PI3 kinase is overactivated in the brain in a mouse fragile X model, and in blood cells from human patients with fragile X syndrome.

Now they have shown that dialing back PI3 kinase overactivation by using genetic tools can alleviate some of the cognitive deficits and behavioral alterations observed in the mouse model. Drugs that target the p110β form of PI3 kinase are already in clinical trials for cancer.

“Further progress in this direction could lead to a clinical trial in fragile X,” says Bassell, who is chair of Cell Biology at Emory University School of Medicine. “The next step is to test whether this type of drug can be effective in the mouse model and in human patient cells.” Read more

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New drug strategy against fragile X

Even as clinical trials examining potential treatments for fragile X syndrome gain momentum, Emory scientists have identified a new strategy for treating the neurodevelopmental disorder.

In a paper recently published in Journal of Neuroscience, a team led by cell biologist Gary Bassell shows that PI3 kinase inhibitors could restore normal appearance and levels of protein production at the synapses of hippocampal neurons from fragile X model mice. The next steps, studies in animals, are underway.

“This is an important first step toward having a new therapeutic strategy for fragile X syndrome that treats the underlying molecular defect, and it may be more broadly applicable to other forms of autism,” he says.

A recent Nature Biotechnology article describes pharmaceutical approaches to autism and fragile X.

Posted on by Quinn Eastman in Neuro 1 Comment