Interpreting the Impact of ASD Gene Mutations Using Pluripotent Stem Cells

The autism genome is comprised of genes that directly regulate protein expression and genes that indirectly regulate activity by turning on or off genes that affect protein expression. The latter genes are described as  “epigenetic” and are influenced by both genetic mutations and environmental factors. What is not known is whether epigenetic mutations affect downstream processes related to autism like altering connections or function of brain cells. This project will use human induced pluripotent stem cells, or iPSCs, with a mutation of a gene called SETD1A that controls epigenetic gene regulation to examine the effects of mutations on gene expression in different types of cells. In addition, this fellow will examine how these mutations affect brain cell shape and functionality. Finally, they will investigate whether these effects are reversible, leading the way to new therapies that can help those with ASD.

Females are less likely to receive an autism diagnosis than males and several studies are examining the biological, psychological, and developmental reasons for this disparity. One theory is that language abilities and patterns in females are superior to males, possibly reflecting better social ability, which may contribute to lower diagnostic rates. This study will look at a measure of language called prosody, or the rhythm, tone and pattern used during spoken language. Studies around prosody in autistic females are lacking, mostly because there are fewer girls with an autism diagnosis who can participate in research on prosody. This fellow will examine prosody in males and females with and without autism, and compare prosody to assessments of social function and interest. These results will inform caregivers, educators, and clinicians when considering a possible autism diagnosis for girls.

Individuals with a mutation in ASH1L exhibit symptoms of profound autism, as well as several medical comorbidities. Building on this fellow’s expertise in pre-clinical models of ASH1L-related autism, the fellow will advance to a natural history study of human patients with this mutation, and their families. In addition, the fellow will collect EEG data from families and identify potential biomarkers of this gene mutation. These are critical steps that enable future drug development and seizure treatment. When the study is complete, the findings have potential to guide development of new drugs to treat symptoms of profound autism, including those with and without an ASH1L mutation.

More and more evidence is pointing to sex-related differences in gene expression as a potential explanation of the male sex bias in autism diagnosis. This study will examine the role of a gene called MYT1L that has been linked to autism. Mouse models will examine the expression of this gene in the cortex (where there is no evidence of a sex difference in expression of MYT1L) and compare it to expression in the hypothalamus (where there are sex-specific differences linked to social behaviors). The fellow will also examine social learning in males and females and count neurons to look for both behavioral and cellular changes. This will determine where in the brain sex-differential effects in social behavior originate, providing evidence for more targeted intervention strategies in males and females with autism.

Siblings have the potential to shape the developmental trajectories of individuals with autism. Early studies have shown the positive impact that a sibling can have on the outcome of an autistic brother or sister. However, these studies were unable to identify which particular aspects of being a sibling contribute most to this effect. This study will leverage existing data from about 5,000 families across multiple longitudinal studies to understand the role of a sibling in longer-term adaptive behavior, and to better identify specific factors that may influence this benefit. Findings from this research may inform intervention planning to maximize adaptive skill development across time and optimize outcomes in those with autism. The results may also provide important insight into the needs of undiagnosed siblings who may themselves need support.

Autism has a well-established and prominent 4:1 male: female bias in diagnosis, but the biological basis for this difference remains unknown. One possible theory is that the presence of estrogen may play a role in the activity of brain cells that turn neurons on or off, which is part of the “excitation/inhibition” theory in autism. To test this theory, this fellow will create different types of neurons using induced pluripotent stem cells from both males and females with autism, with and without a rare genetic variation in an autism gene called neurexin. Then, estrogen will be applied to these cells and gene expression and functioning of different cell types will be compared. This gene-by-environment study will help identify the role of estrogen during development as a component in the later biological and behavioral features of females compared to males with autism.

Recent research has implicated the gene PTCHD1 on the X chromosome as contributing to the causes of autism and intellectual disability, but there is still very little known about what it does and how it leads to changes in the brain. This project will be the first-ever attempt to determine the function of the PTCHD1 protein in its natural biological setting. Cells will be manipulated to create mutations in PTCHD1, then turned into neurons, and then the proteins that are expressed will be measured. Finally, the fellow will measure how these proteins interact in the brain. This will enhance our understanding of how this gene interacts with the rest of the brain and expand the range of therapeutic approaches intended to target specific types of dysfunction in people with autism.

Oversensitivity to touch is common in autism and can lead to discomfort and harm. In some cases, people with autism avoid other people’s touch but seek out tactile stimulation through self- stimulatory behaviors. Self-stimulation can be anything from finger tapping to headbanging, which is harmful and dangerous. While the differences in the brain’s response to different types of touch have been studied in neurotypical people, there is little information on the different responses in people with autism. This fellow will examine how the autistic brain responds to different types of touch, ultimately providing a biological basis for determining why some touch is avoided while some is sought out, which could improve therapy for dangerous self-stimulatory behaviors.

Rett Syndrome is caused by a mutation on the X chromosome at MeCP2. Girls with Rett Syndrome share many features of autism, including delayed or lack of language development, impaired fine motor skills, repetitive behaviors and cognitive disability. MeCP2 activity is also regulated by environmental factors and has been implicated in autism when a genetic cause has not been identified. This fellow will look closely at changes in MeCP2 binding and how it regulates gene expression by isolating different types of neurons at different ages to determine which are critical in the progression of symptoms. The fellow will also employ a sophisticated analysis of machine learning techniques to integrate the data to predict how MeCP2 activity regulates different neuron types at different points in development. This will allow scientists to move closer to providing patients with targeted approaches to interventions.

2011Baylor College of MedicineChristie BuchoveckyMonica Justice

2011University of California Santa BarbaraJessica BradshawRobert Koegel