Comparison of Fecal Microbiota in Children with Autism Spectrum Disorders and Neurotypical Siblings in the Simons Simplex Collection.

In order to assess potential associations between autism spectrum disorder (ASD) phenotype, functional GI disorders and fecal microbiota, we recruited simplex families, which had only a single ASD proband and neurotypical (NT) siblings, through the Simons Simplex Community at the Interactive Autism Network (SSC@IAN). Fecal samples and metadata related to functional GI disorders and diet were collected from ASD probands and NT siblings of ASD probands (age 7-14). Functional gastrointestinal disorders (FGID) were assessed using the parent-completed ROME III questionnaire for pediatric FGIDs, and problem behaviors were assessed using the Child Behavior Check List (CBCL). Targeted quantitative polymerase chain reaction (qPCR) assays were conducted on selected taxa implicated in ASD, including Sutterella spp., Bacteroidetes spp. and Prevotella spp. Illumina sequencing of the V1V2 and the V1V3 regions of the bacterial 16S rRNA genes from fecal DNA was performed to an average depth of 208,000 and 107,000 high-quality reads respectively. Twenty-five of 59 ASD children and 13 of 44 NT siblings met ROME III criteria for at least one FGID. Functional constipation was more prevalent in ASD (17 of 59) compared to NT siblings (6 of 44, P = 0.035). The mean CBCL scores in NT siblings with FGID, ASD children with FGID and ASD without FGID were comparably higher (58-62 vs. 44, P < 0.0001) when compared to NT children without FGID. There was no significant difference in macronutrient intake between ASD and NT siblings. There was no significant difference in ASD severity scores between ASD children with and without FGID. No significant difference in diversity or overall microbial composition was detected between ASD children with NT siblings. Exploratory analysis of the 16S rRNA sequencing data, however, identified several low abundance taxa binned at the genus level that were associated with ASD and/or first order ASD*FGID interactions (FDR <0.1).

Altered Interactions between the Gut Microbiome and Colonic Mucosa Precede Polyposis in APCMin/+ Mice.

Mutation of the adenomatous polyposis coli (APC gene), an early event in the adenoma-carcinoma sequence, is present in 70-80% of sporadic human colorectal adenomas and carcinomas. To test the hypothesis that mutation of the APC gene alters microbial interactions with host intestinal mucosa prior to the development of polyposis, culture-independent methods (targeted qPCR assays and Illumina sequencing of the 16S rRNA gene V1V2 hypervariable region) were used to compare the intestinal microbial composition of 30 six-week old C57BL/6 APCMin/+ and 30 congenic wild type (WT) mice. The results demonstrate that similar to 12-14 week old APCMin/+ mice with intestinal neoplasia, 6 week old APCMin/+ mice with no detectable neoplasia, exhibit an increased relative abundance of Bacteroidetes spp in the colon. Parallel mouse RNA sequence analysis, conducted on a subset of proximal colonic RNA samples (6 APCMin/+, 6 WT) revealed 130 differentially expressed genes (DEGs, fold change ≥ 2, FDR <0.05). Hierarchical clustering of the DEGs was carried out by using 1-r dissimilarity measurement, where r stands for the Pearson correlation, and Ward minimum variance linkage, in order to reduce the number of input variables. When the cluster centroids (medians) were included along with APC genotype as input variables in a negative binomial (NB) regression model, four of seven mouse gene clusters, in addition to APC genotype, were significantly associated with the increased relative abundance of Bacteroidetes spp. Three of the four clusters include several downregulated genes encoding immunoglobulin variable regions and non-protein coding RNAs. These results support the concept that mutation of the APC gene alters colonic-microbial interactions prior to polyposis. It remains to be determined whether interventions directed at ameliorating dysbiosis in APCMin/+mice, such as through probiotics, prebiotics or antibiotics, could reduce tumor formation.