Daily Archives: June 24, 2017

24 Jun 2017

Two new papers show how rare genetic mutations are helping scientists understand more about the processes that go wrong in the amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) spectrum. A hallmark of these diverse conditions is the abnormal clumping of the nuclear protein TDP-43 in the cytoplasm. In the June 6 Nature Communications, researchers led by David Kang, University of South Florida, Tampa, reported that mutations in the mitochondrial protein CHCHD10 induced TDP-43 translocation from the nucleus to the cytoplasm and poisoned mitochondria and synapses. In a second paper, Yongchao Ma and colleagues from Northwestern University Feinberg School of Medicine, Chicago, debut a new ALS gene, UBQLN4, identifying a variant in a woman with familial ALS. Their paper, published May 2 in eLIFE, shows that the D90A substitution in the ubiquilin impairs proteasome function and causes abnormal sprouting and branching of motor axons in model systems. The results further highlight the role of protein homeostasis in neuronal health and disease.

Kangs intriguing work suggests that wild-type CHCHD10 maintains TDP-43 nuclear localization and protects against TDP-43 toxicity, while disease-related mutations of CHCHD10 have opposite, damaging effects, said Ronald Klein, Louisiana State University Health in Shreveport. The work also adds significantly to the importance of mitochondrial function in neurodegenerative diseases, Klein wrote in an email toAlzforum.

The discovery, just over two years ago, of mutations in the mitochondrial protein CHCHD10 (short for coiled-coil-helix-coiled-coil-helix domain containing protein 10) in several families with amyotrophic lateral sclerosis/ frontotemporal dementia (ALS-FTD) suggested for the first time that dysfunction in the organelles, the cells power plants, could cause motor neuron disease (see Jun 2014 newsand Oct 2014 news).Scientists know little about the function of CHCHD10, which sits inside the mitochondria as part of a protein complex that stabilizes cristae, the organelles membrane folds. In patients with ALS-associated CHCHD10 mutations, mitochondria appear disorganized and dysfunctional (Genin et al., 2015).

Kang set out to understand how CHCHD10 mutations affect protein function, and whether they also impact TDP-43 accumulation and toxicity. To get at those issues, the researchers first turned to the roundworm Caenorhabditis elegans, whose single CHCHD10 homolog, har-1, includes both the arginine-15 (R15) and serine-59 (S59) residues that are mutated in ALS/FTD. Co-first author Courtney Trotter found that har-1 knockouts developed movement problems similar to those seen in worms overexpressing TDP-43. The animals crawled more slowly on an agar plate, and curled up when dropped in liquid, rather than thrashing about like wild-type worms. Their mitochondria appeared to be in poor health. They produced more superoxide than mitochondria from normal worms. Introducing a human CHCHD10 transgene into the har-1 knockouts completely normalized their behaviorthe transgenic worms crawled and swam normally, and their mitochondrial superoxide hovered at control levels. In contrast, human CHCHD10 bearing either the R15L or S59L mutation did not compensate at all, suggesting that the mutations caused a loss of CHCHD10function.

As the two other first authors, Jung-A. Woo and Tian Liu, worked their way through studies on mammalian cells, primary neurons, and finally mouse brains in vivo, they saw the same pattern. Loss of CHCHD10 function, either by knockdown or by overexpression of mutated protein, spelled trouble for mitochondria, disrupting their structure, increasing superoxide production, and causing expression of mitochondrial genes to decrease by half. In primary mouse hippocampal neurons, CHCHD10 mutant expression led to a 50 percent reduction in synaptic markers drebrin and synatophysin as visualized by confocal microscopy. All told, the results suggest the loss of CHCHD10 function in these models poisons mitochondria and zaps synapses.Does any of this affect TDP-43? In the primary neurons, TDP43 exclusively localized to the nucleus, but after knockdown of CHCHD10 or expression of the mutants, a fraction of the TDP-43 moved to the cytoplasm, reaching as far as neuritic processes. Expression of CHCHD10 mutants doubled the cytosol/nuclear ratio of TDP-43 over that seen in wild-type cells. Recent work suggests TDP-43s toxicity stems from its localization to mitochondria (Jul 2016 news). Indeed, under the influence of CHCHD10 mutants, nearly half of the cytosolic TDP-43 deposited inmitochondria.

TDP-43 (red) normally resides in the nucleus but in NIH3T3 mouse fibroblasts expressing R15L or S59L CHCHD10 mutations (second and third rows), it leaches into the cytoplasm, where it localizes with the mitochondrial outer membrane protein TOM20 (green). [Courtesy of DavidKang.]

The CHCHD10 variants also enhanced TDP43 toxicity. Adenovirus-mediated expression of TDP-43 in the brains of young mice caused synaptic markers to drop by 50 and 39 percent in the dentate gyrus and CA3 region of the hippocampus, respectively. Co-expression of CHCHD10 prevented the decline, and expression of either mutant exacerbated it. The results establish that CHCHD10 mutations influence toxicity of TDP43 in neurons, however, the researchers have yet to test this in motor neurons or cortical neurons, the cell types affected in ALS orFTD.

While the work connects CHCHD10 to TDP-43, many questions remain. How does CHCHD10 influence where TDP-43 localizes, and why do the mutations cause TDP-43 to appear in the cytoplasm? Co-immunoprecipitation hinted that CHCHD10 and TDP-43 physically associate, but that mutations do not disrupt this interaction. We have to work out the details, Kang said, noting that their next studies will focus on the mechanisms of CHCHD10 and TDP-43 translocations and theirregulation.

The second report details how a newly discovered ALS variant in UBQLN4 disrupts a different and equally fundamental homeostatic mechanismthe regulated recycling of proteins via the ubiquitin proteasome system. Ubiquilins deliver proteins to the proteasome. UBQLN1 and UBQLN2 are linked to Alzheimers disease and FTD/ALS, but this is the first time UBQLN4 variants have been linked to disease. Ma worked with coauthor Teepu Siddique, whose lab identified the variant through targeted gene sequencing in 267 familial and 411 sporadic ALS cases. One patient carried the single amino acid change, from aspartate to alanine at position 90. None of 332 in-house controls, or more than 60,000 people in a sequencing consortium database, had the change, suggesting it may be the pathogenicvariant.

To test this, first author Brittany Edens expressed wild-type or D90A UBQLN4 in cultured mouse spinal cord neurons, and found the mutant increased neurite number. In zebrafish embryos, the mutant induced abnormal motor neuron branching as well. These morphological effects accompanied inhibition of the proteasome and upregulation of -catenin, one of UBQLN4s target proteins and an important regulator of neuronal development. Treatment with the -catenin inhibitor quercetin reversed the mutant effects on morphology in neurons andzebrafish.

This is an interesting first report linking UBQLN4 to ALS, said Lihong Zhan of the University of California, San Francisco, who was not involved with the work. Zhan told Alzforum hed like to see how the mutation behaves in models more relevant to ALS, such as age-related neuron death. Ma agreed that the models are mainly developmental, but considers them still relevant for ALS, as early life events may render the neurons vulnerable later. The models used in the study were short-term expression systems; Ma told Alzforum they are now working on additional models that will enable a more thorough examination of the mutants impact across the lifespan. He hopes that -catenin, or other substrates of UBQNL4, could become useful therapeutic targets in ALS.Pat McCaffrey

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ALS/FTD Genes Reveal Pathways to Pathology - Alzforum

Xconomy Boston

One of the years most closely watched clinical studies could lead to a landmark approval of a gene therapy and throw wide open the debate over how to pay for expensive drugs. The first drips of data have emerged.

Bluebird Bio (NASDAQ: BLUE) says the first three patientsof 15 total expectedhave had good results from a revised version of its LentiGlobin gene therapy to treat certain genetic variants of the rare blood disease beta-thalassemia, which causes severe anemia and requires frequent transfusions.

Bluebird has changed the way it manufactures the product, which requires extracting a patients bone marrow cells, altering their DNA outside the body, then reintroducing the cells to the patient. This study, called NORTHSTAR-2, is the first test of the improved process, which regulators said last year would not require rewinding its clinical program back to the beginninga sigh of relief at the time for the company and its shareholders.

Caveats abound. The results are not only a small sample size, they are also early. Typically data from three patients in a study would not be worth singling out. But Bluebird, of Cambridge, MA, is trying to produce a type of medicine never approved before in the U.S. (Two have been approved in Europe, but one never took hold.)

And the FDA has already shown willingness to consider approval of medicines for rare diseases based on tiny sample sizeswith considerable controversy, in the case of a drug approved last year to treat Duchenne muscular dystrophy.

In one NORTHSTAR-2 patient, the healthy version of the blood protein hemoglobin has reached normal levels six months after a single dose of treatment. The second patients healthy hemoglobin levels are rising but lower than the first patient after three months. The third patient is only two months out from treatment.

For patients with good results, the treatments staying power will be crucial. Bluebird wants it to be a one-time cure, as of course will patients. Insurers will undoubtedly want the samebut what to do if something that costs hundreds of thousands or more than a million dollars, stops working after a few years?

Bluebird officials say they have already begun talking to payers about pay for performance arrangements. Our hope is to tie outcomes of the patient to the value generated, says chief financial and strategic officer Jeff Walsh. It can come in many different forms. (Xconomy reported on several creative drug-pricing ideas in this article.)

Bluebird hopes to make a case for approval for beta-thalassemia before U.S. and European regulators, perhaps in 2019, using data from the NORTHSTAR-2 trial and from previous trials that used the older LentiGlobin version. The main goal of NORTHSTAR-2 is for patients to produce enough of their own healthy hemoglobin to eliminate the need for regular blood transfusions. The first patient has reached that goal, says chief medical officer David Davidson.

The new version of LentiGlobin product, among other things, squeezes more copies of the correct gene into each targeted cellmore shots on goal to change each malfunctioning cell for the better, in other words.

The NORTHSTAR-2 patient with six months of results to report has fared better than similar beta-thalassemia patients six months after they received the previous version of LentiGlobin in a study called HGB-204. The NORTHSTAR-2 patient is producing 13.3 g/DL of hemoglobin, within the normal range for a woman; the median production among 10 HGB-204 patients after six months was 9.7 g/DL.

A doctor working on the study is presenting the data, along with updates from its LentiGlobin treatment for sickle cell disease, at the European Hematology Association meeting this weekend.

Alex Lash is Xconomy's National Biotech Editor. He is based in San Francisco.

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Bluebird Reports Early Results From Upgraded Gene Therapy - Xconomy

How might the shift towards personalized medicine and towards precision medicinetwo related but different conceptsimpact cancer care within the United States healthcare system? That question was explored in some depth during a presentation entitled, Using Precision Medicine and Personalized Medicine to Build a Patient-Centered Strategy, the first presentation given on June 15, during the Health IT Summit in Boston, held at Bostons Revere Hotel, and sponsored by Healthcare Informatics. The presentation was given by Kristin Darby, CIO at the Boca Raton, Fla.-based Cancer Treatment Centers of America, and John Halamka, M.D., CIO at Beth Israel Deaconess Medical Center in Boston.

After explaining in some detail the broad treatment philosophy and strategy at Cancer Treatment Centers of America, Darby noted that There are a lot of paradigm shifts going on as we start to change our industry, and some of the themes involved in oncology are similar to those emerging across U.S. healthcare as a whole. Among them, she said, are the move from predictive to reactive care, from sick care to wellness, and moving towards care thats specific to a patient. And when you look at precision medicine, there are specifics that can be determined about the classification of disease at the molecular level, rather than organ or body location.

What about the two terms? Personalized medicine and precision medicine are terms that are often used interchangeably, Darby said. But there is a difference, she pointed out. Precision medicine focuses on the specific needs of a patient and their known response to specific biomarkers. Patients typically go through genomic testing, and the results are tested based on known biomarkers, and their treatment is then adjusted. Meanwhile, personalized medicine can include precision medicine as one of its components, but also includes such things as lifestyle, patient preferences, and the patients lifestyle.

Darby went on to say that, As you start to look at the value of precision medicinehistorically, prior to this, the approach has been population-based, with the same approach for everyone, and only a certain percentage of those approaches working. And when it comes to oncology, those approaches kill healthy genes as well as diseased genes. But with personalized medicine, you take into account elements important to the patient. And it also includes looking at lifestyle and other factors that can really help the patient individually. She said that a famous quote from science fiction writer Isaac Asimov applies here: One of the saddest things in life, he said, is that science gains knowledge much faster than society gains wisdom, she said. And you can see that with precision medicine: advances are happening at such a rapid rate that individuals cannot absorb the new knowledge.

Kristin Darby and John Halamka, M.D. on June 15

Darby continued, Thats where technology comes in, to help individual patients. And typically, most healthcare providers are doing partial genome sequencing, which might include a 300-gene panel, followed by targeted therapies for specific abnormalities. What youll see sometime in the near future, she said, is an evolution of maturity where, when the test is done, the goal is to move that to time of diagnosis. And we believe at Cancer Treatment Centers of America that well continue to move closer to diagnosis in order to avert going through failed rounds of care. Often, she said, patients dont pursue genomic testing until after two or three rounds of treatment have already failed; meanwhile, overall health tends to decline with each round of chemotherapy. In contrast, she said, in the future, a personalized approach to treatment will be available. And it will mature from partial genome sequencing to full genome sequencing, which will look at healthy DNA. And instead of just looking at DNA, from a targeted therapy perspective, the abnormality causing the disease may only affect the patient as its expressed. And with proteomics, physicians will be able to offer more specific, targeted treatment.

Darby went on to share with the audience a case study that had been approved for public sharing, by the patient involved. The patient is Christine Bray, who was diagnosed at the age of 30 with metastatic ovarian cancer in 2010, when her youngest daughter was just three months old. Bray was given five months to live. Her goal was to survive at least a few years, so that her youngest daughter would have a memory of her. She went through a horrendous experience, with numerous treatments and surgeries, Darby said of Bray. Then she came to CTCA in Philadelphia, and received advanced genomic testing, which identified a therapy that would target the tumors genetic mutation (everolimus). It was when she got her third diagnosis of recurrence that she came to CTCA. And it was identified that she would benefit from genetic testing, and received targeted therapy. Within three months, she was cancer-free and has lived a normal life for five years now, with no evidence of disease. That shows the promise of precision medicine.

Read more here:
At the Health IT Summit in Boston, a Fresh Look at the Emergence of Personalized Medicine - Healthcare Informatics