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New hope for Prader-Willi syndrome

Duke Health researchers have identified a drug-like small molecule that, in animals, appears to be an effective treatment for a genetic disorder called Prader-Willi syndrome. Studies in mice and human cell lines indicate other gene-based diseases might also benefit.


Prader-Willi syndrome is a syndrome characterized by poor feeding, with slow growth and weak muscles in infancy, followed by excessive eating, obesity and behavioral problems in childhood. It occurs in about one of every 15,000 births and has no cure.

If their findings continue to be verified in human studies, the Duke University developed drug could become the first treatment option for Prader-Willi syndrome.


The concept of this study could also apply immediately to other similar types of genomic imprinting disorders in which children inherit an active copy of a gene from only one parent.


"Our findings are promising and indicate that we may have a path forward for the first time to treat the severe, life-limiting features of this genetic disorder," said Yong-hui Jiang, M.D., Ph.D., associate professor in Duke's departments of Pediatrics and Neurobiology. Jiang is senior author of a study published online Dec. 26 in the journal Nature Medicine. http://www.nature.com/ni/journal/vaop/ncurrent/full/ni.3654.html


In most cases of Prader-Willi syndrome, a gene on the father's region of chromosome 15 is missing, and the mother's copy is silent (or non-functioning).

Jiang's team focused on activating the mother's silent gene on her chromosome to recover gene function lost on the father's chromosome.


Researchers screened more than 9,000 compounds. Using fluorescent markers on mouse embryonic fibroblasts, connective tissue producing collagen, they could see which molecules triggered cells to glow. Glowing indicated which were activating the maternal copy of the Prader-Willi gene.

A class of small molecules known as G9a inhibitors glowed, both in the mouse model of Prader-Willi syndrome and in human cells from patients with the disorder. G9a is an enzyme important in gene regulation.


The G9a inhibitors also appeared to have a therapeutic effect. When mice with Prader-Willi syndrome were treated with these small molecule drugs during infancy, they lived longer and had more normal growth.


"Our findings suggest that G9a inhibitors may play a role in regulating the silencing of parental chromosomes on certain genes that require an imprinting process for normal function," Jiang added. "This could provide a new insight for the molecular mechanism of genomic imprinting."

Abstract
Toll-like receptor (TLR) activation contributes to premalignant hematologic conditions, such as myelodysplastic syndromes (MDS). TRAF6, a TLR effector with ubiquitin (Ub) ligase activity, is overexpressed in MDS hematopoietic stem/progenitor cells (HSPCs). We found that TRAF6 overexpression in mouse HSPC results in impaired hematopoiesis and bone marrow failure. Using a global Ub screen, we identified hnRNPA1, an RNA-binding protein and auxiliary splicing factor, as a substrate of TRAF6. TRAF6 ubiquitination of hnRNPA1 regulated alternative splicing of Arhgap1, which resulted in activation of the GTP-binding Rho family protein Cdc42 and accounted for hematopoietic defects in TRAF6-expressing HSPCs. These results implicate Ub signaling in coordinating RNA processing by TLR pathways during an immune response and in premalignant hematologic diseases, such as MDS.

Study authors include Jing Fang, Lyndsey C Bolanos, Kwangmin Choi, Xiaona Liu, Susanne Christie, Shailaja Akunuru, Rupali Kumar, Dehua Wang, Xiaoting Chen, Kenneth D Greis, Peter Stoilov, Marie-Dominique Filippi, Jaroslaw P Maciejewski, Guillermo Garcia-Manero, Matthew T Weirauch, Nathan Salamonis, Hartmut Geiger, Yi Zheng & Daniel T Starczynowski

Subject terms: Leukaemia Toll-like receptors

The study received support from the National Institutes of Health (HD077197, R01GM103893) and the Foundation for Prader-Willi Syndrome Research.
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Jan 13, 2017   Fetal Timeline   Maternal Timeline   News   News Archive   


A class of small molecules, known as G9a inhibitors,
may play a role in turning off parental chromosomes.

BLUE represents father's chromosomes;
PINK represents mother's chromosomes

Image Credit:Prader Willi USA

 


 


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