OSS Funded Research

Your One SMALL Step Funds at Work!

Summary of OSS funding to date, July 21, 2012

All proceeds from One SMALL Step events are applied to advance the Prader-Willi Research Plan, a result of the Prader-Willi Syndrome Research Strategy Workshop organized by the Foundation for Prader-Willi Research in 2009. During the Strategy Workshop, leading scientists in the fields of PWS and Obesity identified gaps in knowledge, prioritized basic clinical and research questions, and identified needed resources, technologies and training. A “Report to the Community” can be found at: http://fpwr.org/prader-willi-syndrome-research-strategy-workshop outlining the results of the workshop. Recomendations from the workshop were then used to formulate the PWS Research Plan, a research strategy jointly developed by FPWR and PWSA(USA).

2011 One SMALL Step contributions were applied towards Phase 1 of the PWS Research Plan.

Phase 1 funding of the PWS Research Plan focused on developing resources:

PWS Molecular Resource Center - a website to promote the sharing of resources, models and information among scientists involved in PWS research
Working Groups – teams of experts working to develop guidelines and recommendations to accelerate research: Obesity Clinical Trials Working Group, Mouse Models Working Group, Mental Health Working Group, and Biorepository/Registry Working Group. See below for details related to each working group. Working Group Details
PWS iPS Cells – A research team led by Marc Lalande at the Connecticut Stem Cell Institute established pluripotent stem cells from individuals with PWS, establishing a critical resource for the PWS research community. The team’s goal is to use the cells to determine a list of genes that are specifically altered in PWS. iPS Cell Details
Training - $50,000 has been set aside to train the “next generation” of PWS clinicians and scientists (funding has not yet been expended)

And addressing three research questions:

What underlies the shift from failure to thrive to excessive hunger in PWS?
Can the maternally silent genes in the PWS chromosome region be selectively reactivated?
What are the cellular phenotype(s) of PWS?

Six research projects were funded addressing the 3 questions listed above:

Q1 Nutritional Aspects of Prader-Willi syndrome and Childhood Obesity: Correlation of Plasma Orexin Levels with Nutritional Phases ($20,000)
Q1 Development of leptin dysregulation in a mouse model of obesity in PWS ($148,600, 2 year grant)
Q2 Small Molecular Screening and Therapeutic Potential for PWS ($50,000)
Q2 Reactivation of maternally-silenced genes in PWS ($49,164)
Q3 Use of Stem cell-derived neurons to identify the molecular basis of the PWS ($50,000)
Q3 Pancreatic and neuro-endocrine cell secretory pathway deficits in PWS ($50,000)

In addition to these One SMALL Step funded projects, FPWR supported an additional project, using non-OSS funds: “Development of appetite-related neural circuits in a mouse model for PWS.”

Next Steps: One SMALL Step Funding for 2012-2013

Funding from our 2013 One SMALL Step events will continue to support working groups and the implementation of their recommendations as well as further developing Phase II of the PWS Research Plan. Additionally, funding has been designated for two grant cycles:

Mental Illness in PWS, $300,000 Applications are due Sept 21, 2012. Details can be found here: http://www.fpwr.org/2012-mental-illness-pws-request-applications

Hyperphagia, $200,000 RFA will be announced following the Hyperphagia Conference in Oct 2012 with an estimated deadline of January/February 2013. http://www.hyperphagia.org/

One SMALL Step Funded Projects, RFA 1

Question 1: What underlies the shift from failure to thrive to excessive hunger in PWS?

Nutritional Aspects of Prader-Willi syndrome and Childhood Obesity: Correlation of Plasma Orexin Levels with Nutritional Phases

Awarded To: Dr. Jennifer Miller, University Florida

Amount Funded: $20,000

Lay Abstract:

Early in infancy, babies with Prader-Willi syndrome (PWS) have no interest in feeding manifested by lack of crying for food and failure-to-thrive requiring assisted feeding with a G-tube, NG tube, or cross-cutting of bottle nipple (phase 1a). There is then a series of transition through five nutritional phases, ending in the classic PWS manifestations of voracious appetite, inability to feel full, food-stealing, taking food from unsavory places such as the garbage can or sink, and obesity (phase 3). Remarkable among the nutritional phases is phase 2a, when the child begins to gain weight rapidly despite no increase in food intake. Individuals with PWS often have excessive daytime sleepiness and sleep abnormalities with early morning awakening typically beginning in phase 2a. Although both problems with sleep and appetite control have been attributed to dysfunction of a specific part of the brain called hypothalamus, to date, there has been no definitive hormonal or metabolic explanation for the brain dysfunction or for the transition from failure-to-thrive to obesity and excessive hunger in PWS. Orexin is a hormone from the brain that promotes wakefulness and appetite. Lack of orexin in the brain has been shown to cause excessive sleepiness and is now thought to cause obesity due to low metabolic rate. Orexin levels in brain fluid have been reported to be low in a few individuals with both PWS and excessive daytime sleepiness, but blood levels have never been studied. We believe that blood orexin levels change over time in individuals with PWS as they transition through the nutritional phases, and that low orexin levels cause excessive sleepiness and obesity by decreasing the metabolic rate. If this study is able to show a relationship between blood orexin levels and the development of obesity and excessive sleepiness, orexin may be a promising medication for individuals with PWS as well as those with other causes of childhood obesity.

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Development of leptin dysregulation in a mouse model of obesity in PWS

Awarded To: Dr. Rachel Wevrick, University Alberta

Amount Funded: $148,600 (2 year grant)

Lay Abstract:

The brain balances energy stores with energy expenditure with little conscious effort. The hypothalamus is a part of the brain that senses levels of a hormone called leptin, which is produced by fat. Excess leptin normally causes a decrease in appetite and increase in activity. This balance is disrupted in obese children who carry mutations in genes in the leptin response pathway. We now have convincing evidence that one of the genes inactivated in children with PWS, namely MAGEL2, is essential for leptin signaling in the hypothalamus. Mice missing Magel2 are obese and underactive. We found that some of the hypothalamus cells that sense leptin do not properly function in mice missing Magel2. These neurons normally act on other neurons through the release of a factor called alpha-MSH. We believe this defect causes the mice to fail to properly balance their food intake and activity levels, leading to obesity. We propose that loss of human MAGEL2 causes the fat accumulation, reduced resting energy expenditure, and contributes to hyperphagia in children with PWS. Thus, the underlying cause of obesity in PWS may have considerable overlap with other genetic disorders that cause severe childhood obesity. In this study, we will examine whether mice lacking Magel2 are unresponsive to leptin from birth, or whether insensitivity happens gradually. We will test whether giving the Magel2 mutant mice a drug that is similar to the missing alpha-MSH causes them to eat less and lose weight. We will also test whether daily administration of this drug prevents the Magel2 mice from becoming obese. In summary, these experiments will determine the best time for interventions that improve sensing of leptin in neonatal and juvenile mice, and test a potential treatment for leptin insensitivity, using an obese mouse model of PWS.

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Question 2: Can the maternally silent genes in the PWS chromosome region be selectively reactivated?

Small Molecular Screening and Therapeutic Potential for PWS

Awarded To: Young-hui Jiang, Duke University

Amount Funded: $50,000

Lay Abstract:

Like most genetic disorders, there is no specific therapeutic intervention targeted to the molecular defect for Prader-Willi syndrome (PWS). The clinical presentations of PWS are caused by paternal deficiency of genes in the chromosome 15q11-q13 region. Recent reports indicate a region between the SNRPN and UBE3A genes harboring SnoRNA clusters is important for the key features of PWS including childhood obesity, hypogonadism, hyperphagia, and developmental delay. The SnoRNAs in the maternal chromosome are structurally intact but transcriptionally silent. Therefore, the simple idea of treating the PWS at molecular level is to find a drug that can unsilence the SnoRNAs from maternal chromosome. The epigenetic mechanism including the DNA methylation and chromatin modification at PWS imprinting center (PWS-IC) regulates the paternal specific expression of genes including Snrpn and SnoRNAs in the hromosome 15q11-q13 region. Application of DNA methylation and histone deacetylation inhibitors (HDAC) can activate the expression of the SNRPN gene from the silent maternal chromosome in cells from PWS patients and PWS mouse model. These observations strongly support a possibility to unsilence the expression of the SnoRNAs from maternal chromosome by other molecular approach through the epigenetic mechanism. Our collaborator, Dr. Bryan Roth’s team, has recently identified a FDA approved drug from small molecule screen that specifically unsilences the Angelman syndrome Ube3a gene from paternal chromosome. Small molecule is a low molecular weight organic compound that binds with high affinity to protein, nucleic acid, or polysaccharide. We hypothesize that small molecule may be able to unsilence the PWS candidate genes including Snrpn and SnoRNAs from maternal chromosome. We propose to identify a drug-like small molecule(s) by screen small molecule library using Snrpn-EGFP as a marker. The proposed study is significant because it will lead to the development of therapeutic intervention to the PWS in humans.

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Reactivation of maternally-silenced genes in PWS

Awarded To: David Segal, UC Davis

Amount Funded: $49,164

Lay Abstract:

This proposal will investigate the development of a gene therapy for Prader-Willi syndrome (PWS). PWS is caused by the loss of a region of human cromosome 15q11-13. Humans have two copies of chromosome 15, one the mother (maternal) and one from the father (paternal). Due to an unusual mechanism called genetic imprinting, the genes affecting PWS are active only on the paternal chromosome. Therefore if these genes get deleted from the paternal chromosome, there are no active copies of these genes remaining in the brain. The genes are intact on the maternal chromosome, but are not active. Here we propose a way to activate the genes on the maternal chromosome. My lab has actually been engineering special proteins designed to turn off these genes, as a method to treat a related disorder called Angelman syndrome. However, by reconfiguring these proteins to activa te the genes rather than repress them, we hypothesize that we can activate the inactive but otherwise normal genes on the paternal chromosome. We will test this hypothesis in a mouse model of PWS. If successful, this would represent an important first step towards a gene therapy for PWS.

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Question 3: What are the cellular phenotype(s) of PWS?

Use of Stem cell-derived neurons to identify the molecular basis of the PWS

Awarded To: Rudolph Leibel, Columbia

Amount Funded: $54,000

Lay Abstract:

Prader-Willi syndrome (PWS) is caused by a loss of expression of specific genes normally expressed only from paternal alleles on chromosome 15. PWS patients display common symptoms, which include feeding difficulties in infancy, loss of muscle tone, rapid weight gain after two years of age, extreme hunger and unrelenting appetite, obesity, and some degree of developmental delay. PWS affects specific brain regions at the cellular level in umans, making stem cell technology a particularly effective method for the study of this disease. Stem cell technologies enable researchers to generate and study the cell types affected by human diseases, creating a model of the „disease in a dish‟. In order to better understand how Prader-Willi syndrome affects cells in the brain, we will transform skin cells from PWS patients into pluripotent stem cells (iPS). Induced pluripotent stem cells can give rise to every cell type in the human body. We will differentiate the iPS cells into brain cells (neurons) characteristic of particular regions of the brain. For example, we will make neurons characteristic of the part of the brain (hypothalamus) that plays a critical role in the control of food intake. The neurons generated from PWS patients will allow us to characterize the molecular and cellular defects that are caused by this genetic syndrome. Understanding how PWS affects the brain at the cellular and molecular level can inform novel therapeutic targets for PWS patients.

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Pancreatic and neuro-endocrine cell secretory pathway deficits in PWS.

Awarded To: Robert Nichols, University Pittsburg

Amount Funded: $50,000

Lay Abstract:

Many advances in recent years have added to our understanding of the genetic causes of PWS, including recognition of it as a disorder of genomic imprinting involving defective genes that normally only function after inheritance from the father. At least a dozen genes appear to contribute to the many clinical problems seen in PWS. Unfortun-ately the exact reasons for development of many of these clinical problems remain elusive. Key among these symptoms are hypoglycemia (low blood sugar) with poor growth and difficulty gaining weight early in life, followed by later excess appetite and life threatening obesity. Using a mouse model of early PWS, we have recently shown that some of the imprinted genes in the critical PWS region affect the production of hormones from specialized cells that are critical for normal growth and body weight, and blood and tissue glucose control. The proposed project will examine these genes to determine how they exert control over production of these hormones and how this is disrupted in PWS. I hypothesize that their abnormal function affects the metabolic balance in the body and directly leads to problems in glucose and weight regulation. A better understanding of these processes will allow the development of new targets for therapy for patients with PWS.

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Development of appetite-related neural circuits in a mouse model for Prader-Willi Syndrome

Awarded To: Sebastien Bouret, Childrens Hospital LA

Amount Funded: $50,000

Lay Abstract:

Prader-Willi syndrome (PWS) is a genetic disease characterized by an insatiable appetite and a variety of behavioral dysregulations. It is known that the brain, and particularly a region of the brain called the hypothalamus, is important to regulating appetite and body weight. We also know that many key physiological processes, including appetite regulation, are established during the perinatal period —that time just prior to and soon after birth – and that hormonal conditions in the babies are key in these processes. Notably, babies with PWS display abnormally elevated levels of the gut-hormone ghrelin and we recently found in our lab that this hormone has marked effects on hypothalamic development. The goal of this research project is to determine, using a mouse model for PWS, whether the elevated levels of ghrelin observed in babies with PWS disrupt the normal development of brain circuits involved in appetite regulation. The results of these experiments promise to provide new insight into the mechanism by which alteration of the early life hormonal environment that occurs in children with PWS, leads to perturbations of neurodevelop-mental events and may result to hyperphagia and obesity in later life. The knowledge we gain from this project may also help determine therapeutic interventions to reduce metabolic and neurological problems associated with PWS.

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