 Autism Spectrum Disorders ASD are diagnosed clinically, based on key symptoms. As ASD phenotypic variability is large, and symptoms can manifest at different ages and degrees, the clinical diagnosis is challenging. To date, there remains an unmet need for a valid and reliable endophenotype that would facilitate ASD diagnosis early in life, enable efficient study of ASD risk factors, and eventually serve as a useful biomarker to inform the development of effective therapies and assess treatment response in future clinical trials. 