Similar metabolic pathways are affected in both Prader-Willi Syndrome and Congenital Myasthenic Syndrome-22

Funding Summary

Dr. Creemers has found that PWS has molecular similarities to another genetic disorder called CMS22. Individuals with CMS22 deficiency also have hypotonia and poor growth, followed by the development of hyperphagia.  Here the lab will evaluate if the protein associated with CMS22 (PREPL) can rescue the PWS neonatal characteristics, using a mouse model of PWS.

Dr. Theresa Strong, Director of Research Programs, shares details on this project in this short video clip.

Lay Abstract

Congenital myasthenic syndrome 22 (CMS22) is a neuromuscular disorder caused by defects in the PREPL gene that leads to similar phenotypes as PWS. CMS22 patients suffer from neonatal muscle weakness, failure to thrive, and growth delays . Later in childhood, patients will have a great appetite resulting in rapid weight gain and obesity. Because of the similarities with PWS, we hypothesized that the disease mechanisms of PWS and CMS22 are similar at the molecular level. Therefore, we have recently compared mice with PWS and CMS22 and observed a very similar disruption in the molecular switches that control appetite and food intake. Moreover, we have compared PWS and CMS22 patient skin cells and observed that the mitochondria the energy factories of the cell are also similarly impaired . This mitochondrial disruption can possibly be the basis for the muscle weakness observed in PWS and CMS22 patients. Because of these similarities, we hypothesized that we could improve PWS symptoms by giving the PWS cells an extra dose of PREPL (the gene causal for CMS22). Excitingly, we observed that mitochondrial defects in PWS patient skin cells fully recovered upon overexpression of PREPL. This is exciting to us as it shows that activating only 1 gene can have such a significant beneficial effect for PWS patient cells. For this reason, we believe that acting on PREPL has the potential to be a new therapeutic approach for PWS patients in the future. In this research project, we aim to progress these rescue studies from PWS cells to a PWS mouse model. Specifically, we will work with a PWS mouse model that dies shortly after birth due to respiratory defects caused by muscle weakness. We will use gene therapy to increase PREPL expression in these mice before birth, which possibly will restore muscular strength in these mice resulting in survival and growth. This is a simple readout which, if successful, will provide evidence that acting on PREPL has beneficial effects in a mouse model for PWS . In summary , we will evaluate if expression of only 1 gene (PREPL) can fully restore normality of some of the PWS phenotypes observed in mice In the future, we aim to develop new treatments for PWS patients aimed at upregulating PREPL.

Research Outcomes: Public Summary

This project established the technical and conceptual feasibility of prenatal gene delivery as a therapeutic strategy for Prader–Willi syndrome (PWS). A critical first outcome was the successful development and validation of rAAV2/9 vectors encoding both the long and short isoforms of PREPL, the key gene implicated in CMS22 pathology. The long isoform has been shown to be able to rescue the mitochondrial pathology in PWS patient fibroblasts. Both PREPL isoforms were confirmed to be robustly expressed in vitro, with the long isoform showing correct mitochondrial localization and enzymatic activity.
In vivo proof of concept studies further demonstrated the feasibility of prenatal viral delivery. Optimization of in utero injection procedures resulted in the successful birth of live pups following partial embryonic injection with an rAAV GFP control vector. Preliminary analyses of the liveborn pups revealed GFP expression in multiple tissues, confirming effective prenatal gene transduction. These findings provide critical evidence that prenatal rAAV mediated gene delivery can achieve tissue level expression at early postnatal stages. Together, these results represent an important step toward therapeutic intervention in PWS. The successful validation of PREPL vectors and the demonstration of prenatal delivery feasibility directly support the translational potential of PREPL replacement strategies aimed at improving early survival and developmental outcomes in PWS mouse models.