NEUROTHERAPY · Cellular Mechanisms and Therapies for Rett Syndrome

Cellular mechanisms and therapies for Rett syndrome

Rett syndrome (RTT) is a devastating neurodevelopmental disorder that affects one in ten thousand girls and has no cure. The majority of RTT patients display mutations in the gene that codes for the methyl-CpG binding protein two (MeCP2). Mouse mutants of MeCP2 have been generated and they represent valid models for studying the neurobiology of the disease and for testing possible treatments. Clinical observations and neurobiological analysis of mouse models suggest that defects in the expression of MeCP2 protein compromise the development of the central nervous system, especially synaptic and circuit maturation. Thus, agents that promote brain development and synaptic function, such as Insulin-like growth factor one (IGF1), are good candidates for ameliorating the symptoms of RTT. IGF1 and its active peptide, (1-3)IGF1, cross the Blood Brain Barrier and (1-3)IGF1 ameliorates the symptoms of RTT in a mouse model of the disease, therefore they are ideal treatments for RTT. Neurotherapy focuses on finding suitable therapies for RTT and in particular, tests the safety and efficacy of Insulin-like growth factor one (IGF1) for relieving the symptoms of RTT in animal models and in human patients. We advanced the field of Rett research and therapies with cellular, animal and clinical studies. At the cellular level, we examined the effects of IGF1 and (1-3)IGF1 in primary cortical cultures and measure the expression levels of markers for intracellular pathways and synaptic function. We find that both treatments activate the IGF1 receptor and enhance the expression of synaptic markers, however, they activate different intracellular pathways. Furthermore, (1-3)IGF1 administration increases the expression of endogenous IGF1, suggesting a direct interaction between the two molecules. The results show that the two molecules increase the expression of synaptic proteins through activating different cellular mechanisms. In collaboration with Prof. Sur at Massachusetts Institute of Technology, we performed animal studies to assess the ability of IGF1 to promote brain circuitry maturation in a mouse model of RTT. Using a paradigm that allows the study of cortical circuitry in vivo, we found that animal mutants for MeCP2 show an impaired ability of cortical networks to respond to activity-related stimuli, while administration of IGF1 restores the properties of cortical network observed in control mice. Finally, for the clinical investigations, we performed a pilot study to establish whether there are major risks associated with IGF1 administration in RTT patients. Although IGF1 has been authorised for paediatric use it was necessary to establish whether it is safe and well tolerated in RTT patients. Six young girls with classic RTT received IGF1 subcutaneous injections twice a day for six months and they were regularly monitored by their primary care physicians and by the unit for RTT in Versilia Hospital (Italy). The main possible side effects of IGF1 are: hypoglycaemia, tonsillar hypertrophy, hyperplasia, seizures. We addressed these issues in an open label trial on six RTT patients. The drug was administered subcutaneously twice a day for six months. The girls were monitored each three month starting the day of the first administration until six months from the last application. We found that the treatment did not cause any side effect and it was well tolerated by the patients. This pilot study supports the use of IGF1 in patients with RTT. Further studies are planned to assess the benefits of the treatment. Altogether these studies significantly advanced the therapeutics for RTT and this has a huge impact for the families of the patients affected by the disorder. More broadly, these studies impact the therapeutics for autism and other neurodevelopmental disorders where there is a defect in hypoconnectivity. In future we plan to continue exploring new therapeutics for neurodevelopmental disorders performing similar studies with drugs analogue to IGF1 and its derivates. During the research period, the fellow attended and was invited to several international meetings and she trained three MSc students and one PhD student. The fellow has been involved in activities to disseminate the knowledge to the wider -non scientific public: she made a communication to a local television to explain to the public about the importance of mice models and international collaboration for the treatment of RTT. In addition, she has been actively involved in the programme for disadvantaged students in Trinity College. The programme aimed at promoting the diffusion of neuroscience among disadvantaged students and at increasing their interest in continuing with higher education. The IRG helped the reintegration of the fellow; however she still has a temporary appointment in the host institution.

Data: CORDIS, © European Union