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Comorbidity and Synapse Biology in Clinically Overlapping Psychiatric Disorders

Periodic Reporting for period 3 - COSYN (Comorbidity and Synapse Biology in Clinically Overlapping Psychiatric Disorders)

Reporting period: 2019-01-01 to 2020-06-30

COSYN is a state-of-art, bench-to-bedside programme focused on personalised therapeutics. COSYN has integrated outstanding European academic and two large Pharma partners to exploit genomic findings for intellectual disability (ID), autism (ASD), and schizophrenia (SCZ). We capitalize on comorbidity, from clinic to cells and synapses to help understanding these disorders. Our ultimate intention is to facilitate development of individualized treatment to reduce the impacts of these conditions on people.
COSYN has used our team’s access to large patient samples across the EU to find rare genetic variants of strong effect in patients with clinical comorbidity. These now include cells from 22q11DS, ID, and ASD patients. Since the start of the project, COSYN partners have analysed the clinical comorbidity profiles to select these cases which include the main psychiatric diagnosis (ID, ASD, SCZ), but also ID severity, psychosis, epilepsy, other psychiatric features (ADHD, depression, panic disorder), other behavioural problems, dysmorphism, other medical diagnoses, and available functional data. In addition, the inheritance status and predicted impact of the rare variants were analysed. Finally, practical considerations are taken into account to select the most suitable cases for COSYN (particularly whether we have the synaptic tools to study the neuronal impact of the genetic variant). Additional criteria include whether we can reasonably add to the world’s literature, if the predicted effect is expected to be cell autonomous, and the degree to which existing pharma compounds can engage with the gene product. Using these criteria, the 10 most suitable cases have been selected, our clinical teams have visited these patients and cells obtained for iPS and neuron generation. Currently, 19 of 20 samples are available for cellular studies in COSYN (10 cases for 22q11 and 9 for ID). 10 cases for ASD are in progress, and 10 for SCZ will be identified in the coming years.
Using these samples as a starting point, we have set out to understand comorbidity by comparing symptom and syndrome overlap with novel neurobiological criteria and to elucidate mechanisms of comorbidity using neurobiology for the major genomic clue of synaptic dysfunction to unravel the cellular mechanisms of comorbidity.
We have generated novel neuronal cell models by using micro-lithography to generate micro-islands of support cells (glia cells) to allow single neurons to grow and form synapses onto themselves in culture (autapses). We have optimized and characterized these cultures in terms of in vitro maturation and synapse formation. Many in vitro differentiation and maturation procedures have been compared to find the optimal in vitro model and be able to generate novel neurobiological criteria and to elucidate mechanisms of comorbidity using these criteria. We have used patch clamp physiology to characterize synapse maturation and function in vitro and to standardize procedures of systematic analysis of synapses from the selected patients. Furthermore, we have introduced modern genome editing (CRISPR/Cas9) to correct genetic variants in the patient cell lines or to (re-)create the same mutations in a standard (non-patient) cell line. We have established a quality control pipe-line with exome sequencing of all patient in vitro cell lines to identify any confounding genetic rearrangements that regularly emerge during re-programming of the primary (skin) cells and gene editing. Only cell models that pass the stringent QC (approximately 50%) are used for cellular analysis. These novel cellular models provide unique opportunities to discover synaptic deficits associated with these rare genetic variants of strong effect and to build future cell models for compound screening and therapy design. In addition to these novel models, COSYN also exploits conventional cell culture models for high content screening (cellomics) and synapse recordings.
For the existing cell lines, multiple advanced neuroscience platforms have been used to evaluate an extensive set of molecular and cellular parameters, and to identify alterations in synaptic biology. The analyses on 22q11 samples, and comparison to 22q11 mouse models, are now completed and the consortium is working on new cell models for comorbidity, especially for ID and ASD.
COSYN partners are now completing the analysis of the first genome editing projects (CRISPR/Cas9), especially for STXBP1 and UNC13A. Mutations in these genes cause ‘SNAREopathies’, a complex mix of comorbid symptoms, prominently those related to ID and ASD. The extensive synaptic analyses provide new insights into the molecular functions of these genes and possible differences between human synapses and previously characterize rodent model synapses. These studies also form the basis for the analyses of engineered mutations in STXBP1, precisely mirroring the mutations detected in some of our patient samples. In this way COSYN will be able to perform side-by-side comparisons between patient-own and engineered cell models.
For the final phase of the project, a selection of the cellular models is now being up-scaled to provide “industry-standard” cellular assays for compound screening. The first reagents have recently been shipped to our Pharma partner Lundbeck for the first pilots. During the remainder of the project, we will refine diagnostic tools, use novel genomic and cellular features to improve disease classification and discriminate specific patient subtypes. Where possible we will design case studies, with our Pharma partners, in precision medicine: to identify patients with a genetic change whose consequences can be reproducibly ameliorated in vitro by an approved medication. Such case studies will be recommended to the patient and clinician as a double-blinded, N-of-one crossover case study to evaluate the clinical utility of a medication precisely indicated for that person. For a subgroup of patients we create medication that would tremendously improve their quality of life.
COSYN is a crucial next step in “decoding” the genetic findings via intensive focus on the clinical and molecular comorbidities of ID, autism, and schizophrenia.