RESUMEN
Restricted and repetitive behavior (RRB) is a group of heterogeneous maladaptive behaviors. RRB is one of the key diagnostic features of autism spectrum disorders (ASDs) and also commonly observed in Prader-Willi syndrome (PWS). In this study, we assessed RRB using the Repetitive Behavior Scale-Revised (RBS-R) in two ASD samples (University of Illinois at Chicago [UIC] and University of Florida [UF]) and one PWS sample. We compared the RBS-R item endorsements across three ASD cohorts (UIC, UF and an ASD sample from Lam, The Repetitive Behavior Scale-Revised: independent validation and the effect of subject variables, PhD thesis, 2004), and a PWS sample. We also compared the mean RBS-R subscale/sum scores across the UIC, UF and PWS samples; across the combined ASD (UIC + UF), PWS-deletion and PWS-disomy groups; and across the combined ASD sample, PWS subgroup with a Social Communication Questionnaire (SCQ) score ≥15, and PWS subgroup with a SCQ score <15. Despite the highly heterogeneous nature, the three ASD samples (UIC, UF and Lam's) showed a similar pattern of the RBS-R endorsements, and the mean RBS-R scores were not different between the UIC and UF samples. However, higher RRB was noted in the ASD sample compared with the PWS sample, as well as in the PWS subgroup with a SCQ score ≥15 compared with the PWS subgroup with a SCQ score <15. Study limitations include a small sample size, a wide age range of our participants, and not controlling for potential covariates. A future replication study using a larger sample and further investigation into the genetic bases of overlapping ASD and RRB phenomenology are needed, given the higher RRB in the PWS subgroup with a SCQ score ≥15.
RESUMEN
BACKGROUND: SLC25A12 was previously identified by a linkage-directed association analysis in autism. In this study, we investigated the relationship between three SLC25A12 single nucleotide polymorphisms (SNPs) (rs2056202, rs908670 and rs2292813) and restricted repetitive behavior (RRB) traits in autism spectrum disorders (ASDs), based on a positive correlation between the G allele of rs2056202 and an RRB subdomain score on the Autism Diagnostic Interview-Revised (ADI-R). METHODS: We used the Repetitive Behavior Scale-Revised (RBS-R) as a quantitative RRB measure, and conducted linear regression analyses for individual SNPs and a previously identified haplotype (rs2056202-rs2292813). We examined associations in our University of Illinois at Chicago-University of Florida (UIC-UF) sample (179 unrelated individuals with an ASD), and then attempted to replicate our findings in the Simons Simplex Collection (SSC) sample (720 ASD families). RESULTS: In the UIC-UF sample, three RBS-R scores (ritualistic, sameness, sum) had positive associations with the A allele of rs2292813 (p = 0.006-0.012) and with the rs2056202-rs2292813 haplotype (omnibus test, p = 0.025-0.040). The SSC sample had positive associations between the A allele of rs2056202 and four RBS-R scores (stereotyped, sameness, restricted, sum) (p = 0.006-0.010), between the A allele of rs908670 and three RBS-R scores (stereotyped, self-injurious, sum) (p = 0.003-0.015), and between the rs2056202-rs2292813 haplotype and six RBS-R scores (stereotyped, self-injurious, compulsive, sameness, restricted, sum)(omnibus test, p = 0.002-0.028). Taken together, the A alleles of rs2056202 and rs2292813 were consistently and positively associated with RRB traits in both the UIC-UF and SSC samples, but the most significant SNP with phenotype association varied in each dataset. CONCLUSIONS: This study confirmed an association between SLC25A12 and RRB traits in ASDs, but the direction of the association was different from that in the initial study. This could be due to the examined SLC25A12 SNPs being in linkage disequilibrium with another risk allele, and/or genetic/phenotypic heterogeneity of the ASD samples across studies.
