If we want to understand how the brain creates memories, and how genetic disorders distort the brain’s machinery, then the fragile X gene is an ideal place to start. That’s why the Stephen T. Warren Memorial Symposium, taking place November 28-29 at Emory, will be a significant event for those interested in neuroscience and genetics.
Stephen T. Warren, 1953-2021
Warren, the founding chair of Emory’s Department of Human Genetics, led an international team that discovered Read more
At a time when COVID-19 appears to be receding in much of Georgia, it’s worth revisiting the start of the pandemic in early 2020. Emory virologist Anne Piantadosi and colleagues have a paper in Viral Evolution on the earliest SARS-CoV-2 genetic sequences detected in Georgia.
Analyzing relationships between those virus sequences and samples from other states and countries can give us an idea about where the first COVID-19 infections in Georgia came from. We can draw Read more
A new paper in PNAS from geneticist Steve Warren and colleagues illustratesÂ the complexity of the protein disrupted in fragile X syndrome. It touches on how proposed drug therapies that address one aspect of fragile X syndrome may not be able to compensate for all of them. [For a human side of this story, read/listen to this recent NPR piece from Jon Hamilton.]
Fragile X syndrome is the most common single-gene disorder responsible for intellectual disability. Most patients with fragile X syndrome inherit it because a repetitive stretch of DNA, which is outside the protein-coding portion of the fragile X gene, is larger than usual. The expanded number of CGG repeats silences the entire gene.
However, simple point mutations affecting the fragile X protein are possible in humans as well. In the PNAS paper, Warren’s team describes what happens with a particularly revealing mutation, which allowed researchers to dissect fragile X protein’s multifaceted functions. Read more
A studyÂ published in Pediatrics this week tracks “adaptive behavior” asÂ children and adolescents with fragile X syndrome are growing up. This isÂ the largest longitudinal study to date in fragile X, which isÂ the leading inherited cause of intellectual disability and the leading single-gene risk factor for autism spectrum disorder.
Adaptive behavior covers a range of everyday social and practical skills, including communication, socialization, and completing tasks of daily living such as getting dressed. In this study, socialization emerged as a relative strength in boys with fragile X, in that it did not decline as much as the other two domains of adaptive behavior measured: communication and daily living skills.
The “socialization as relative strength in fragile X” findings meshes with a growing awareness in the autism field, summarized nicely here by Jessica Wright at the Simons Foundation Autism Research Initiative, thatÂ fragile X syndrome symptoms are often distinct from those in autism spectrum disorder.
One key distinction between the disorders, for example, is in social interactions. Children with autism and those with fragile X syndrome both shy away from social contact, have trouble making friends and avert their gaze when people look at them.
But children with fragile X syndrome often sneak a peek when the other person turns his back, researchers say. Children with autism, in contrast, seem mostly uninterested in social interactions.
â€œChildren with fragile X syndrome all have very severe social anxiety that plays a big role in the perception that they have autism,â€ saysÂ Stephen Warren, professor of human genetics at Emory University School of Medicine in Atlanta. â€œThey are actually interested in their environment; they are just very shy and anxious about it.â€
A clinical trial testing a therapy for children with fragile X syndrome is closing down, after the sponsoring company announced that the drug, called arbaclofen, was not meeting its goals.
Readers of Emory Health magazine may remember Samuel McKinnon, an arbaclofen study participant who was featured in a 2012 article and video (below).
â€œWe were surprised,â€ Samuelâ€™s mother Wendy told us Monday. â€œBut we knew going in that there were no guarantees.â€
She reports that Samuel has made significant progress in the last couple of years. He likes playing and talking with the family’s new puppy, Biscuit. Samuel’s language skills have Ray Ban outlet blossomed and he will be headed to second grade this fall. But itâ€™s hard to say whether thatâ€™s mainly because of the experimental drug or because Samuel has been continuing to grow and work hard in school and in therapy, she says.
A sizable fraction of patients in the study appeared to benefit from the drug, just not the majority of them, says Emory genetics chair Steve Warren.
An article in the April 2011 issue of Nature Medicine highlights the mechanistic overlap between autism and epilepsy.
By studying how rare genetic conditions known to coincide with both epilepsy and autismâ€”such as Rett syndrome, fragile X syndrome and tuberous sclerosisâ€”unfold at an early age, neuroscientists are finding that both disorders may alter some of the same neural receptors, signaling molecules and proteins involved in the development of brain cell synapses.
Gary Bassell, PhD
Emory cell biologist Gary Bassell and his colleagues have been taking exactly this approach. Recently they published a paper in Journal of Neuroscience, showing that the protein missing in fragile X syndrome, FMRP, regulates expression of an ion channel linked to epilepsy. This could provide a partial explanation for the link between fragile X syndrome and epilepsy.
The Nature Medicine article also mentions a drug strategy, targeting the mTOR pathway, which Bassell’s group has been exploring with fragile X syndrome.
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.
â€œThis 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,â€ he says.
If the brain acts like a computer, which of the brain’s physical features store the information? Flashes of electricity may keep memories and sensations alive for the moment, but what plays the role that hard drives and CDs do for computers?
A simple answer could be: genes turning on and off, and eventually, neurons growing and changing their shapes. But it gets more complicated pretty quickly. Genes can be regulated at several levels:
at the level of transcription — whether messenger RNA gets made from a stretch of DNA in the cell’s nucleus
at the level of translation — whether the messenger RNA is allowed to make a protein
at the level of RNA localization — where the mRNAs travel within the cell
Each neuron has only two copies of a given gene but will have many dendrites that can have more or less RNA in them. That means the last two modes of regulation offer neurons much more capacity for storing information.
Gary Bassell, a cell biologist at Emory, and his colleagues have been exploring how RNA regulation works in neurons. They have developed special tools for mapping RNA, and especially, microRNA — a form of RNA that regulates other RNAs.
In the dendrites of neurons, FMRP seems to control where RNAs end up
Fragile X mental retardation protein (FMRP), linked to the most common inherited form of mental retardation, appears to orchestrate RNA traffic in neurons. Bassell andÂ pharmacologist Yue Feng recently received a grant from the National Institute of Child Health and Development to study FMRP’s regulation of RNA in greater detail. The grant was one of several at Emory funded through the American Recovery and Reinvestment Act’s support for the NIH.
In the video interview above, Bassell explains his work on microRNAs in neurons. Below is a microscope image, provided by Bassell, showing the pattern of FMRP’s localization in neurons.