Autism Speaks, the world's largest autism science and advocacy organization, and an international consortium of researchers, along with participating families, joined together to announce additional new autism genetic discoveries. The results were published today in Science Translational Medicine.
Based on analysis of genomes collected from almost 2,250 individuals, including almost 2,000 with ASD and 246 with intellectual disabilities, and more than 10,000 controls, the researchers found PTCHD1 mutations or copy number variant (CNV) associated with about one percent of the individuals with ASD or intellectual disabilities – almost all of them male – but in none of the control subjects.
"This finding begins to explain the sex bias we see in autism," remarked Autism Speaks Vice President for Scientific Affairs Andy Shih, Ph.D. "PTCHD1 is located on the X chromosome. Since males have one copy of the X chromosome while females have two, they have no 'back up copy' if there is a deleterious variant on the X chromosome."
"We believe that the PTCHD1 gene has a role in a neurobiological pathway that delivers information to cells during brain development – this specific mutation may disrupt crucial developmental processes, contributing to the onset of autism." said Dr. John B. Vincent, Senior Scientist and head of the Centre for Addiction and Mental Health (CAMH) Molecular Neuropsychiatry and Development Laboratory who led the study. "Our discovery will facilitate early detection, which will, in turn, increase the likelihood of successful interventions."
PTCHD1 is part of a neurobiological pathway that determines the development of human embryos. It is one of several genes recently implicated in both ASD and intellectual disabilities. Earlier this year, Autism Genome Project's report in Nature identified PTCHD1 as a genetic risk factor for autism. The current study, running parallel to the AGP study, focused on the molecular characteristics and potential clinical implications of the CNV associated with this specific gene in individuals with ASD.
"Interestingly, the data is also starting to tell us something about the dramatic variety of symptoms observed in the clinic," further explained co-senior author Dr. Stephen Scherer, Senior Scientist and Director of The Centre for Applied Genomics at The Hospital for Sick Children (SickKids), and Director of the McLaughlin Centre at the University of Toronto. "CNV in the protein-coding region tend to travel with intellectual disabilities while CNV in the nearby regulatory regions appear more associated with Asperger's or high-functioning autism. But, as often seems the case, symptoms associated with autism can also be more complex."
While each of these variants, found in this and the earlier AGP studies may only account for a small fraction of the cases, collectively they are starting to account for a greater percentage of individuals in the autism community, as well as providing insights into possible common pathogenic mechanisms. The overlap between autism susceptibility genes and genes previously implicated in intellectual disabilities further supports the hypothesis that at least some genetic risk factors are shared by different psychiatric developmental disabilities.
Finally, identification of a male-linked genetic mutation begins to address the previously unknown basis for often reported skewed male to female ratio in autism.
"Piece by piece, we are discovering genetic mutations that can cause autism. These findings will provide answers for families about what contributed to their autism," said Dr. Shih. "Furthermore, as we have learned from examples involving other genetic risk factors of autism (e.g., Fragile X, Rett, TSC), these genetic findings help us understand the underlying biology of autism, which can lead to the development of novel treatments."
Data was supplied to this study by the Autism Genome Project (AGP) an international autism genetics research consortium co-funded by Autism Speaks, the Medical Research Council, Canadian Institutes of Health Research, Health Research Board (Ireland), Genome Canada, the Hilibrand Foundation and Autistica which seeks to identify genetic risk factors associated with autism spectrum disorders (ASDs).
Autism Speaks provided major funding support to this study, in addition to funding from Genome Canada through the Ontario Genomics Institute, the McLaughlin Centre, the Canadian Institutes of Health Research (CIHR), the Canadian Institute for Advanced Research, the Canada Foundation for Innovation, Ontario's Ministry of Research and Innovation, the Ontario Innovation Trust, the Catherine and Maxwell Meighen Foundation, the National Alliance for Research on Schizophrenia and Depression, the Ontario's Premier's Summit Award in Medical Research, The Centre for Applied Genomics, the Chedoke Health Corporation, the Mayberry Family Fund, the Hamilton Health Sciences Foundation and the SickKids Foundation.
Autism is a complex neurobiological disorder that inhibits a person's ability to communicate and develop social relationships, and is often accompanied by behavioral challenges. Autism spectrum disorders are diagnosed in one in 110 children in the United States, affecting four times as many boys as girls. The prevalence of autism increased 57 percent from 2002 to 2006. The Centers for Disease Control and Prevention have called autism a national public health crisis whose cause and cure remain unknown.
About Autism Speaks
Autism Speaks is North America's largest autism science and advocacy organization. Since its inception in 2005, Autism Speaks has made enormous strides, committing over $142.5 million to research through 2014 and developing innovative new resources for families. The organization is dedicated to funding research into the causes, prevention, treatments and a cure for autism; increasing awareness of autism spectrum disorders; and advocating for the needs of individuals with autism and their families. In addition to funding research, Autism Speaks also supports the Autism Treatment Network, Autism Genetic Resource Exchange and several other scientific and clinical programs. Notable awareness initiatives include the establishment of the annual United Nations-sanctioned World Autism Awareness Day on April 2 and an award-winning "Learn the Signs" campaign with the Ad Council which has received over $235 million in donated media. Autism Speaks' family resources include the Autism Video Glossary, a 100 Day Kit for newly-diagnosed families, a School Community Tool Kit and a community grant program. Autism Speaks has played a critical role in securing federal legislation to advance the government's response to autism, and has successfully advocated for insurance reform to cover behavioral treatments. Each year Walk Now for Autism Speaks events are held in more than 80 cities across North America. To learn more about Autism Speaks, please visit www.autismspeaks.org.
About the Co-Founders
Autism Speaks was founded in February 2005 by Suzanne and Bob Wright, the grandparents of a child with autism. Bob Wright is Senior Advisor at Lee Equity Partners, Chairman and CEO of the Palm Beach Civic Association and served as vice chairman, General Electric, and chief executive officer of NBC and NBC Universal for more than twenty years. He also serves on the boards of the Polo Ralph Lauren Corporation, RAND Corporation and the New York Presbyterian Hospital. Suzanne Wright has an extensive history of active involvement in community and philanthropic endeavors, mostly directed toward helping children. She serves on the boards of several non-profit organizations and is also Trustee Emeritus of Sarah Lawrence College, her alma mater. Suzanne has received numerous awards such as the CHILD Magazine Children's Champions Award, Luella Bennack Volunteer Award, Spirit of Achievement award by the Albert Einstein College of Medicine's National Women's Division and the Weizmann Institute of Science. In 2008, the Wrights were named to the Time 100 list of the most influential people in the world for their commitment to global autism advocacy.