Abstract
Hyperserotonemia is the most replicated biochemical abnormality associated with autism spectrum disorders (ASD). However, previous studies of serotonin synthesis, catabolism, and transport have not elucidated the mechanisms underlying this hyperserotonemia. Here we investigated serotonin sulfation by phenol sulfotransferases (PST) in blood samples from 97 individuals with ASD and their first-degree relatives (138 parents and 56 siblings), compared with 106 controls. We report a deficient activity of both PST isoforms (M and P) in platelets from individuals with ASD (35% and 78% of patients, respectively), confirmed in autoptic tissues (9 pineal gland samples from individuals with ASD—an important source of serotonin). Platelet PST-M deficiency was strongly associated with hyperserotonemia in individuals with ASD. We then explore genetic or pharmacologic modulation of PST activities in mice: variations of PST activities were associated with marked variations of blood serotonin, demonstrating the influence of the sulfation pathway on serotonemia. We also conducted in 1645 individuals an extensive study of SULT1A genes, encoding PST and mapping at highly polymorphic 16p11.2 locus, which did not reveal an association between copy number or single nucleotide variations and PST activity, blood serotonin or the risk of ASD. In contrast, our broader assessment of sulfation metabolism in ASD showed impairments of other sulfation-related markers, including inorganic sulfate, heparan-sulfate, and heparin sulfate-sulfotransferase. Our study proposes for the first time a compelling mechanism for hyperserotonemia, in a context of global impairment of sulfation metabolism in ASD.
Highlights
Introduction According to the Diagnostic andStatistical Manual of Mental Disorders, fifth edition (DSM-5), the core symptoms of autism spectrum disorders (ASD) comprise deficits in social communication and interaction, and repetitive and restricted behaviors, which include sensory abnormalities
We showed that phenol sulfotransferases (PST) activities were decreased in patients with ASD, and that this decrease was correlated with hyperserotonemia, proposing a compelling mechanism for hyperserotonemia in ASD
Whereas in the rat 3′-phosphoadenosine-5′-phosphosulfate (PAPS) and sulfate availability limit sulfation capacity, in mice and humans sulfotransferase activity limits the maximum rate of sulfoconjugation[39]
Summary
Introduction According to the Diagnostic andStatistical Manual of Mental Disorders, fifth edition (DSM-5), the core symptoms of autism spectrum disorders (ASD) comprise deficits in social communication and interaction, and repetitive and restricted behaviors, which include sensory abnormalities. The heritability of ASD is high (>80%)[1] and
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