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Reelin Associated With Restricted and Stereotyped Behavior Based on Principal Component Analysis on Autism Diagnostic Interview-Revised

Ulrika Roine, Samuli Ripatti, Karola Rehnström, Timo Roine, Helena Kilpinen, Ida Surakka, Juho Wedenoja, Tero Ylisaukko-oja, Elli Kempas, Jaana Wessman, Irma Moilanen, Marja-Leena Mattila, Marko Kielinen, Katja Jussila, Saara Suomalainen, Esko Pulkkinen, Lennart von Wendt and Leena Peltonen

Background: Twin and family studies have indicated a strong genetic component in autism spectrum disorders, and genetic studies have revealed highly heterogeneous risk factors. The range and severity of the symptom presentation also vary in the spectrum. Thus, symptom-based phenotypes are putatively more closely related to the underlying biology of autism than the end-state diagnosis.

Methods: We performed principal component analysis on Autism Diagnostic Interview-Revised algorithm for 117 Finnish families and 594 families from the Autism Genetic Research Exchange (AGRE). The resulting continuous component scores were used as quantitative phenotypes in family-based association analysis. In addition, K-means clustering was performed to cluster and visualize the results of the PCA. Unaffected siblings were included in the study.

Results: The components were interpreted as Social Component (SC), communication component and Restricted and Stereotyped Behavior Component (RSBC). K-means clustering showed that, especially in SC, the range of the symptom severity was increased by the siblings. The association of neuroligin 1 with SC was increased, compared to a previous study where only the end-state diagnosis was used. In RSBC, the range of the symptom severity of siblings overlapped greatly with that of patients, which could explain why no association of reelin was found in previous studies in which only the end-state diagnosis was used, but a significant association of reelin with RSBC was now found in the Finnish families (Bonferroni-corrected p=0.029 for rs362644). Although, the Finnish sample is isolated and genetically very homogeneous, compared to the heterogeneous background of AGRE families, many single-nucleotide polymorphisms in reelin, showed modest association with RSBC in the AGRE sample, too.

Conclusions: This study demonstrates how the quantitative phenotypes can affect the association analyses, and yields further support to the use of siblings in the study of complex neuropsychiatric disorders.