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Architecture génétique des troubles du spectre autistique dans les îles Féroé

Abstract : Autism Spectrum Disorders (ASDs) are a heterogeneous group of neurodevelopmental disorders characterized by deficits in social interaction and communication as well as the presence of repetitive behaviors and restricted interests. ASD affects approximately one in 68 individuals. They usually occur during the first three years of life but, in some cases, symptoms are recognized later, when social demands increase. There is a strong genetic component to ASD, as indicated by the recurrence risk in families and twin studies. However, the genetic architecture of ASD remains largely unknown because of its extreme heterogeneity. It is very challenging to identify, for each patient, the combination of risk alleles. Our laboratory identified the first genetic pathway associated with ASD – the NLGN-NRXN-SHANK pathway – playing a key role in synaptogenesis during development. There are an increasing number of genes associated with ASDs but few studies have been conducted on epidemiological cohorts and isolated populations. Here, we investigated 357 individuals from the Faroe Islands including 36 patients with ASD, 136 of their relatives and 185 non-ASD controls. Data from SNP array and whole exome sequencing revealed that patients had a higher burden of copy-number variants, higher inbreeding status, higher load of homozygous deleterious mutations, and a higher ASD polygenic risk score compared to controls. We confirmed the role of several ASD-associated loci (NRXN1, ADNP, 22q11 deletion) and identified new truncating (GRIK2, ROBO1, NINL and IMMP2L) or recessive variants (KIRREL3 and CNTNAP2) affecting genes already associated with ASD. We have also identified three novel candidate genes playing key roles in synaptic plasticity (RIMS4, KALRN and PLA2G4A) carrying deleterious de novo mutations in patients without intellectual disability. Overall, for 11% of individuals with ASD, a known genetic cause was identified, for 39% at least one strongly deleterious mutation was identified in a compelling candidate gene and for 50% no obvious genetic cause was detected. In summary, our study provides a better understanding of the genetic architecture of ASD in isolated populations by highlighting both the impact of common and rare variants but also by revealing the role of new genes for ASD. These genes code for proteins that are essential for neurodevelopment. The identification of these factors involved in synapse formation and maintenance could provide new leads to better understand the biological basis of ASD and find novel therapeutic strategies. However, it is necessary to further understand the combined impact of different mutations on neuronal function in order to better characterize the genetic architecture of ASD.
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Coralie Carton-Buonafine. Architecture génétique des troubles du spectre autistique dans les îles Féroé. Sciences agricoles. Université Sorbonne Paris Cité, 2018. Français. ⟨NNT : 2018USPCC117⟩. ⟨tel-02343507⟩

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