Functional and molecular characterization of a non-human primate model of autism spectrum disorder shows similarity with the human disease

ARTICLE https://doi.org/10.1038/s41467-021-25487-6 OPEN Functional and molecular characterization of a non-human primate model of autism spectrum disorder shows similarity with the human disease 1234567890():,; Satoshi Watanabe 1 ✉, Tohru Kurotani1, Tomofumi Oga 1, Jun Noguchi1, Risa Isoda1, Akiko Nakagami1,2, Kazuhisa Sakai1, Keiko Nakagaki1, Kayo Sumida3, Kohei Hoshino 4, Koichi Saito3, Izuru Miyawaki4, Masayuki Sekiguchi5, Keiji Wada5, Takafumi Minamimoto 6 & Noritaka Ichinohe1 ✉ Autism spectrum disorder (ASD) is a multifactorial disorder with characteristic synaptic and gene expression changes. Early intervention during childhood is thought to benefit prognosis. Here, we examined the changes in cortical synaptogenesis, synaptic function, and gene expression from birth to the juvenile stage in a marmoset model of ASD induced by valproic acid (VPA) treatment. Early postnatally, synaptogenesis was reduced in this model, while juvenile-age VPA-treated marmosets showed increased synaptogenesis, similar to observations in human tissue. During infancy, synaptic plasticity transiently increased and was associated with altered vocalization. Synaptogenesis-related genes were downregulated early postnatally. At three months of age, the differentially expressed genes were associated with circuit remodeling, similar to the expression changes observed in humans. In summary, we provide a functional and molecular characterization of a non-human primate model of ASD, highlighting its similarity to features observed in human ASD. 1 Department of Ultrastructural Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan. 2 Department of Psychology, Japan Women’s University, Kawasaki, Kanagawa, Japan. 3 Environmental Health Science Laboratory, Sumitomo Chemical Co., Ltd., Konohana-ku, Osaka, Japan. 4 Preclinical Research Laboratories, Sumitomo Dainippon Pharma Co., Ltd., Konohana-ku, Osaka, Japan. 5 Department of Degenerative Neurological Diseases, National Institute of Neuroscience, National Center of Neurology and Psychiatry, Kodaira, Tokyo, Japan. 6 Department of Functional Brain Imaging, National Institutes for Quantum and Radiological Science and Technology, Chiba, Chiba, Japan. ✉email: ; NATURE COMMUNICATIONS | (2021)12:5388 | https://doi.org/10.1038/s41467-021-25487-6 | www.nature.com/naturecommunications 1 ARTICLE A NATURE COMMUNICATIONS | https://doi.org/10.1038/s41467-021-25487-6 utism spectrum disorder (ASD) is a highly prevalent neurodevelopmental disorder that affects >1% of the population, of which 85% are idiopathic with no direct evidence of specific genetic causes1,2. ASD is characterized by impaired social interaction and communication, repetitive behaviors, and restricted interests. Currently, its core symptoms cannot be cured and there is a need to develop pharmacological therapy. People with ASD typically show delayed development of social and language skills and are diagnosed at ~3 years old. However, early behavioral signs are predictive of pre-existing abnormalities in circuit development. Early behavioral intervention is recommended for children diagnosed with ASD, and better outcomes are expected if it is started earlier3. Thus, there is an urgent need to identify biological abnormalities both to understand the pathogenesis and to develop effective pharmacological treatments that can be started during the early developmental stage. ASD is often discussed as a synaptopathy and there is evidence regarding synaptic dysfunction at both the structural and molecular levels. Dendritic spines in cortical neurons, which are postsynaptic to excitatory synapses and a proxy for synaptic density, are affected in people with ASD4,5. Consistent with this, multiple ASD-related genes are involved in synaptic functions6. Normal synaptic development proceeds in a precisely regulated manner, where excessive synaptic formation in the early postnatal stage is followed by pruning7–9. Synaptic development involves two processes: genetically programmed synaptogenesis and activity-dependent remodeling. Impairment of these processes is likely to adversely affect normal circuit generation with consequent ASD symptoms. ASD affects primate-specific brain areas involved in social functions unique to primates (e.g., the medial prefrontal cortex)10,11. Moreover, the developmental expression pattern of some genes is primate specific12,13, and proteome data suggest primate-specific synaptic functions14. Different molecular networks between humans and rodents may limit the utility of rodent models for human diseases, and therefore, ASD primate models have advantages over rodent models (also see ref. 15). The common marmoset (Callithrix jacchus), a small New World monkey, is well suited for studies on neurodevelopmental diseases, and previous studies from our laboratory have described similarities in neuronal structure and synaptic development to humans8,16. Further advantages are that marmosets are easy to handle, mature rapidly, and are reproductively efficient. We established an ASD marmoset model by administering valproic acid (VPA) in utero17,18. VPA, an antiepileptic drug, increases the risk of ASD in offspring19 by inhibiting histone deacetylase (HDAC) and DNA methylation20; furthermore, it has been used to generate ASD model animals21,22. VPA-exposed marmoset offspring present with abnormalities in social behavior17,18, axon bundle structure23, and neuroimmune cells24, which are consistent with human data. During early postnatal development, the brain experiences drastic changes in neural circuit organization and gene expression. Synaptogenesis is highest at the neonatal period7, and experience-dependent remodeling of the circuit follows in childhood25. Indeed, sensitive periods of language acquisition and social learning occur in childhood26. Gene expression also changes rapidly during the neonatal period as synapses develop12,27. Genes with similar developmental dynamics form a module of functionally related genes27. Temporally related modulations in synaptic structure or function and gene expression will link ASD-related synaptic phenotypes with molecular functions. Accordingly, we investigated synaptic development using acute brain slices from the dorsomedial prefrontal cortex of a VPA-induced ASD marmoset model at the ages of birth (0 M), 2 3 months (3 M), and 6 months (6 M), which can be taken to correspond to neonatal, infancy, and puberty periods, respectively8,16. We also analyzed gene expression modulations at these ages. The present study indicated concurrent changes in synaptic and molecular phenotypes with development. Synapses of the model animal were underdeveloped in neonates, which was different from synaptic overdevelopment commonly observed in the model at puberty and in human ASD. Synaptic plasticity was transiently enhanced during infancy. We also clarified behavioral outcomes at infancy, since ASD symptom (...truncated)