2016
Gatlinburg Conference Symposium
SS‐17 Symposium Title: Prenatal Risk Factors for Autism Spectrum Disorders: Advancing our Understanding through Integrated Epidemiological and Preclinical Studies Chair: Melissa D. Bauman1 Overview: Given the prevalence and societal impact of ASD spectrum disorders (ASD), there is an urgent need to identify risk factors, determine the underlying neural basis and ultimately develop novel therapeutic and pharmacological interventions. This is a daunting challenge for ASD research because of the inherent complexity of the human brain, our lack of understanding of disease neurobiology underlying ASD and the incredible heterogeneity of this disorder. There is a growing consensus that ASD is actually a number of distinct brain disorders each caused by a complex interplay of different genetic and environmental factors. Here we highlight progress in our understanding of prenatal risk factors that have been identified through epidemiological studies and then systematically evaluated in preclinical models. New findings from recent ASD epidemiological studies investigating environmental exposures, genetic factors, and their interplay will be presented. Preclinical studies evaluating in utero exposure to (i) valproic acid, (ii) autism associated maternal auto‐antibodies and (iii) maternal immune activation will be highlighted as examples of basic science approaches. The discussion will focus on maximizing translational studies to advance our understanding of ASD. Paper 1 of 4 Paper Title: Epidemiology of Autism Spectrum Disorders: Investigating Perinatal Risk Factors Authors: Lisa Croen2 Introduction: Although the initial manifestations of autism spectrum disorders typically do not appear until several months or years after a child is born, the results of research studies conducted over the past 50 years provide overwhelming evidence that factors operating around the time of pregnancy and birth are at play. Methods: Epidemiologic studies have played a crucial role in the identification of prenatal risk factors for autism, and in directing basic science studies focused on elucidating underlying biologic mechanisms. Results: In this talk, findings from recent studies investigating the role of maternal immune system function during pregnancy in autism will be presented. Studies utilizing biospecimens collected from expectant mothers and their newborns will be highlighted. Discussion: Future directions and preclinical approaches to further evaluate findings from human epidemiology studies will be discussed. 1
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University of California, Davis Kaiser Permanente Division of Research Page 1 of 4 2016
Gatlinburg Conference Symposium
SS‐17 Paper 2 of 4 Paper Title: Prenatal Valproic Acid Exposure as a Preclinical Model for the Study of Autism Spectrum Disorders (ASD): Assessing ASD‐Like Social and Communicative Behaviors in Rats Authors: Sarah Raza3, Bryan Kolb4, Sergio M. Pellis4, Robbin Gibb4 Introduction: Autism Spectrum Disorder (ASD) is characterized by impairments in social interactions, communication, and repetitive behaviors. Currently, preclinical research is focusing on the development of environmental animal models of ASD to better understand the underlying neurobiological mechanisms. However, validation of these animal models is contingent upon the ability to simulate the clinical features of ASD, such as deficits in social function. The present study assessed whether juvenile rats exposed prenatally to valproic acid (VPA) exhibit deficits in social play that are consistent with the socio‐communicative deficits in ASD. Given the cognitive, emotional, and communicative demands on animals during social play, the present study provides a detailed analysis of the social play of VPA‐exposed rats. Methods: Pregnant Long‐Evans dams were administered an acute oral dose of VPA (800mg/kg) on gestational day 12.5 (Raza et al., 2015). Thirty‐two female rats (16 VPA, 16 control) born to the VPA‐exposed and control dams were utilized. Juvenile play fighting and the associated ultrasonic vocalizations (USVs) were assessed between PN29‐PN34. To investigate playful interactions, the frequency of playful attack, defensive tactics, and the rate of USV calling per bout of play fighting were examined. Non‐playful behaviors ‐ frequency of mounting and body shakes ‐ were also assessed. It was predicted that VPA‐
treated rats should play less than controls and the frequency of emitting USVs would be reduced. Results: While VPA and control rats did not differ in their frequency of launching attacks or in the probability of defending against an attack, significant differences in the use of defensive tactics were observed. That is, VPA rats were significantly less likely to turn to supine and more likely to remain standing when defending themselves, suggesting that in the VPA rats bodily contact is limited. Moreover, although the VPA rats tended to vocalize less frequently overall during play, the difference was not statistically significant. The rate of calling, however, revealed that the VPA rats called significantly less often than expected for the number of times they initiated play, suggesting reduced communicative ability. With respect to non‐playful behaviors, VPA rats mounted each other more often than the control rats and were more likely to perform body shakes, indicative of altered sexual behavior and stereotypy. Discussion: The present study supports the validity that in utero exposure to VPA produces a viable rodent model for the study of ASD, especially with respect to studying sociality. While the VPA‐treated rats appeared to be as motivated to play as control rats (i.e., comparable rates of playful attack), they limited the contact involved in playful wrestling. It appears that the rewards offered by playing may have been altered, reducing the pleasure to be gained from the physical contact usually associated with play. This may also explain the reduced rate of emitting USVs relative to the amount of play initiated, reflecting a deficit in communicative ability. This discordance between vocalizing and play, and the reduction in contact‐promoting tactics, may reflect altered socio‐communicative function and dysregulation of pragmatics in social relations, characteristics of ASD. Furthermore, elevated frequencies of mounting and body shaking at this early developmental stage may be indicative of accelerated sexual maturation and stereotypic behavior, two additional characteristics of ASD. These data suggest that prenatal VPA exposure disrupts some aspects of being able to communicate effectively and engage partners in dynamic interactions ‐ deficits consistent with those seen in ASD ‐ thus, validating the VPA rodent model as a useful preclinical tool to study ASD. 3
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University of Alberta University of Lethbridge Page 2 of 4 2016
Gatlinburg Conference Symposium
SS‐17 Paper 3 of 4 Paper Title: Maternal Anti‐Fetal Brain IgG Autoantibodies and Autism Spectrum Disorders: Translational Approaches to Determine Underlying Mechanism Authors: Judy Van de Water1 Introduction: Several studies have found a correlation between the presence of circulating maternal autoantibodies and neuronal dysfunction in the neonate. Specifically, maternal anti‐brain autoantibodies, which may access the fetal compartment during gestation, have been identified as one risk factor for developing Autism Spectrum Disorder (ASD). Methods: Studies by our laboratory elucidated seven neurodevelopmental proteins recognized by maternal autoantibodies, whose presence is associated with a diagnosis of maternal autoantibody related (MAR) autism in the child. Preclinical approaches utilizing mice, rat and nonhuman primate models have been carried out to evaluate the underlying neurobiology of autoantibody‐mediated pathology. Results: Animal model studies using gestational transfer of purified IgG from mothers of children with ASD, have shown that the autoantibodies associated with MAR autism induce long‐term behavioral changes in gestationally‐exposed offspring. Recent convergent findings from both mouse and nonhuman primate models indicate that prenatal exposure to these antibodies impact brain growth trajectories and parallel features from clinical ASD studies. Discussion: A better understanding of the mechanisms that drive autoantibody generation and autoantibody‐mediated pathology is necessary to further translate this research into a clinical application. Future preclinical research efforts will be discussed. Page 3 of 4 2016
Gatlinburg Conference Symposium
SS‐17 Paper 4 of 4 Paper Title: Prenatal Immune Challenges and Altered Neurodevelopment: Novel Findings and Future Directions from Preclinical Models in Rats and Nonhuman Primates Authors: Melissa Bauman1 Introduction: Women exposed to infection during pregnancy have an increased risk of giving birth to a child who will later develop autism, schizophrenia (SZ) or other central nervous system (CNS) disorders. In order to implement preventative prenatal care approaches, we much first understand why some, but not all, women who experience infection during pregnancy have a child who will later develop a neuropsychiatric disease. A number of factors, including genetic susceptibility, the sex of the fetus, the intensity of the infection and the maternal and/or fetal response, as well as the precise timing of the immune challenge likely influences the degree to which prenatal immune challenge alters fetal brain development and may ultimately determine which disease phenotype (SZ, autism, other CNS disorders) is expressed. Methods: Sophisticated animal models are needed to understand how these genetic and environmental risk factors contribute to an increased risk of neuropsychiatric disorders in exposed offspring and to develop novel preventative strategies. Here we present novel findings from two preclinical models of maternal immune activation (MIA) utilizing the nonhuman primate and the laboratory rat. Pregnant dams from each species were injected with a viral mimic, polyic, to stimulate the maternal immune response. Longitudinal brain and behavioral development of the offspring were evaluated to determine the impact of prenatal immune challenge. Results: New findings from the nonhuman primate model indicate that prenatal immune challenge yields behavioral impairments in sensorimotor gating relevant to a number of neurodevelopmental disorders. Novel findings from the rat model indicate that the severity of the maternal immune response, as indexed by cytokine profiles and sickness behaviors, influences offspring neurodevelopment. Discussion: A better understanding of the mechanisms that drive maternal immune activation pathology is necessary to further translate this research into a clinical application. Preclinical models are critical for these efforts. The strength of integrating cross‐species preclinical approaches will be discussed. Page 4 of 4