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BackgroundAutism spectrum disorder (ASD) is still diagnosed through behavioral observation, due to a lack of laboratory biomarkers, which could greatly aid clinicians in providing earlier and more reliable diagnoses. Metabolomics on human biofluids provides a sensitive tool to identify metabolite profiles potentially usable as biomarkers for ASD. Initial metabolomic studies, analyzing urines and plasma of ASD and control individuals, suggested that autistic patients may share some metabolic abnormalities, despite several inconsistencies stemming from differences in technology, ethnicity, age range, and definition of “control” status.MethodsASD-specific urinary metabolomic patterns were explored at an early age in 30 ASD children and 30 matched controls (age range 2–7, M:F = 22:8) using hydrophilic interaction chromatography (HILIC)-UHPLC and mass spectrometry, a highly sensitive, accurate, and unbiased approach. Metabolites were then subjected to multivariate statistical analysis and grouped by metabolic pathway.ResultsUrinary metabolites displaying the largest differences between young ASD and control children belonged to the tryptophan and purine metabolic pathways. Also, vitamin B6, riboflavin, phenylalanine-tyrosine-tryptophan biosynthesis, pantothenate and CoA, and pyrimidine metabolism differed significantly. ASD children preferentially transform tryptophan into xanthurenic acid and quinolinic acid (two catabolites of the kynurenine pathway), at the expense of kynurenic acid and especially of melatonin. Also, the gut microbiome contributes to altered tryptophan metabolism, yielding increased levels of indolyl 3-acetic acid and indolyl lactate.ConclusionsThe metabolic pathways most distinctive of young Italian autistic children largely overlap with those found in rodent models of ASD following maternal immune activation or genetic manipulations. These results are consistent with the proposal of a purine-driven cell danger response, accompanied by overproduction of epileptogenic and excitotoxic quinolinic acid, large reductions in melatonin synthesis, and gut dysbiosis. These metabolic abnormalities could underlie several comorbidities frequently associated to ASD, such as seizures, sleep disorders, and gastrointestinal symptoms, and could contribute to autism severity. Their diagnostic sensitivity, disease-specificity, and interethnic variability will merit further investigation.Electronic supplementary materialThe online version of this article (doi:10.1186/s13229-016-0109-5) contains supplementary material, which is available to authorized users.

Macrocephaly and brain overgrowth have been associated with autism spectrum disorder. We performed a systematic review and meta-analysis to provide an overall estimate of effect size and statistical significance for both head circumference and total brain volume in autism. Our literature search strategy identified 261 and 391 records, respectively; 27 studies defining percentages of macrocephalic patients and 44 structural brain imaging studies providing total brain volumes for patients and controls were included in our meta-analyses. Head circumference was significantly larger in autistic compared to control individuals, with 822/5225 (15.7%) autistic individuals displaying macrocephaly. Structural brain imaging studies measuring brain volume estimated effect size. The effect size is higher in low functioning autistics compared to high functioning and ASD individuals. Brain overgrowth was recorded in 142/1558 (9.1%) autistic patients. Finally, we found a significant interaction between age and total brain volume, resulting in larger head circumference and brain size during early childhood. Our results provide conclusive effect sizes and prevalence rates for macrocephaly and brain overgrowth in autism, confirm the variation of abnormal brain growth with age, and support the inclusion of this endophenotype in multi-biomarker diagnostic panels for clinical use.

SUMMARYWe have previously shown that inactivation of the gene encoding the Arabidopsis thaliana transcription factor DOF AFFECTING GERMINATION 1 (DAG1) renders seed germination more sensitive to both phytochrome B (phyB) and gibberellins (GA). dag1 mutant seeds require less red (R) light fluence and a lower GA concentration than WT to germinate. Here, we show that inactivation of the gene PHYTOCHROME INTERACTING FACTOR 3-LIKE 5 (PIL5) results in down-regulation of DAG1. Inactivation of PIL5 in the dag1 mutant background further increased the germination potential of dag1 mutant seeds, supporting the suggestion that DAG1 is under the positive control of PIL5. Germination of dag1phyB seeds showed a reduced requirement of gibberellins as compared with phyB mutant seeds, both in the presence and in the absence of GA biosynthesis. Furthermore, the GA biosynthetic gene AtGA3ox1 is upregulated in dag1 seeds as compared with the WT, and DAG1 actually binds to the AtGA3ox1 promoter, as shown by chromatin immunoprecipitation experiments. Expression analysis at different time points confirms that AtGA3ox1 is directly regulated by DAG1, while suggesting that DAG1 is not a direct regulatory target of PIL5. Our data indicate that in the phyB pathway leading to seed germination, DAG1 negatively regulates GA biosynthesis and suggest that DAG1 acts downstream of PIL5. In addition, the analysis of hypocotyls of dag1 and phyB mutant plantlets, of plantlets overexpressing phyB in the dag1 mutant, as well as of dag1phyB double mutant suggests that DAG1 may act as a negative regulatory element downstream of phyB also in hypocotyl elongation.