the Phenotypic and Genetic Profile of Patients With Early Onset Schizophrenia Associated With Autism Spectrum Disorder.

Overview

Early onset schizophrenia "early dissociative disorder" is a rare disorder with a low incidence of approximately (1/5000 to 1/20000). Its link with autism spectrum disorders remains unknown although both are serious neurodevelopmental diseases. As part of the 2011-2013 Interregional hospital Clinical Research program, University Department of Child and Adolescent Psychiatry Pediatric Hospitals of CHU de Nice Lenval identified patients with a complex phenotype characterized by an early schizophrenia associated with autism spectrum disorders and developmental disabilities in mild to moderate. This phenotype could be a new syndrome. The goal of our project is to define the genetic causes of this phenotype. The technique of high throughput sequencing will be used to obtain the sequence of exomes of these patients and their families. This study will therefore be important to give an accurate diagnosis for patients and their families. Moreover, we believe that this project will identify new genes involved allowing a better understanding of the pathophysiology. Recent studies show the involvement of mutations in several genes (eg NRXN1 and UPF3B) in these different clinical phenotypes. However, the genetic basis of the childhood and early onset schizophrenia are much less well known than those of autism spectrum disorder

Introduction: Early-onset Schizophrenia (EOS) is a rare and severe condition displaying early dissociative disorder (i.e., age of onset \< 18 years). A higher rate of neurodevelopmental abnormalities is observed in EOS compared to adult onset schizophrenia (AOS). Thus, patients affected by EOS typically present intellectual, learning, communication or neuromotor impairments, as well as attention deficit hyperactivity disorder. Early signs of autism spectrum disorders (ASD) are also found in 30% of patients with EOS. Cytogenetics abnormalities, including copy number variations (CNVs), are frequent in neurodevelopmental disorders and have been linked to ASD physiopathology. Implicated genes encode proteins playing a role in brain development, synaptic morphology, plasticity and neurogenesis. In addition, an increasing number of genetic abnormalities are shared by EOS and ASD, suggesting that schizophrenia can be considered a neurodevelopmental disorder. The main objective of the present study is to identify mutations in genes involved in neurodevelopmental pathways in our cohort of patients affected by both EOS and ASD. Method and analysis: We describe here a multicenter study in a pediatric population named "Exploration and characterization of genetic and phenotypic profile of the 'early dissociative disorder' associated with autism spectrum disorder (GenAuDiss)". The study started in April 2014. The inclusion criteria are: age 7 to 22 years, diagnoses of EOS with co-morbid ASD and IQ \> 50; as well as parents and siblings of the included patients. We perform standardized psychiatric assessments (MINI, K-SADS-PL, PANSS, SANS, TCI 226, and AQ) and neurocognitive evaluations (IQ, TMT A/B, and verbal fluency). Then, we study variants of the coding part of the DNA (exome), using next generation sequencing (NGS) process on trio (mother, father, and child). Divers bio-informatics tools such as RVIS and PolyPhen-2 will be used to prioritize the potential candidate genes. The inclusion period of this study will end in November 2019. Ethics and dissemination: The study protocol was approved by the Ethics Committee 'Sud Méditerrané V' (number 14.002) and by the French National Agency for Medicines and Health Products Safety (ANSM 2013-A01699-36). All patients, their parents and siblings signed informed consent upon enrolment in the study. Results of the present study should help to unravel the molecular pathology of EOS, paving the way for an early therapeutic intervention