Magazine article The Exceptional Parent

Genetic Advances in Autism Leading the Way to Improved Care

Magazine article The Exceptional Parent

Genetic Advances in Autism Leading the Way to Improved Care

Article excerpt

BY SILVIA DE RUBEIS, PHD AND JOSEPH D BUXBAUM, PHD

Autism spectrum disorder (ASD) describes a group of neurodevelopmental disorders with a wide range of severity and symptoms. ASD affects one in every 88 children in the USA and manifests with an array ('spectrum') of disabilities. An individual is diagnosed with ASD when s/he is shown to have persistent deficits in (I) social communication and social interaction, and (II) restricted patterns of behavior, interests, or activities [Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V)]. Difficulty with social communication in ASD can manifest even at an early age, with symptoms such as poor eye contact, limited facial and body language, and difficulty understanding nonverbal communication such as facial expressions. Individuals with ASD often have particular difficulty with social interactions. They may have difficulty engaging and main-taining social contacts, connecting with and sharing interests and emotions with their peers, and adjusting their behavior according to social context. Individuals with ASD can also experience repetitive behaviors ('stereotypies'), including repetition of movements (e.g., hand flapping), actions (e.g., flipping objects), or speech (e.g. repeated words or phrases). Children and adults with ASD may also have exceedingly narrowed interests such as fascination for or persistent preoccupation with unusual objects and inflexibility to routines in their daily activities, which can take the form of rituals, insistence of consistency, and distress at small changes. Unusual sensory responses, including, for example, sensitivity to pain/temperature, fixation with lights, or aversion to specific sounds, have also been documented. Individuals with ASD may or may not have language impairments, which often occur in combination with other conditions, such as intellectual disability and seizures. The severity of symptoms can vary significantly: some children are mildly affected, while others are more severely impacted. There is still no medicine for ASD, but appropriate behavioral interventions have strong beneficial effects.

ASD is a complex condition, and many factors contribute to risk. For over 30 years, studies of families and twins have suggested that genetic factors are largely responsible for autism. In identical (monozygotic) twins, who share the same genetic material, if one child has ASD the other twin also has ASD in 7 to 9 out of 10 cases, while in fraternal (dizygotic) twins the concordance drops to 1 out of 10 cases. This predisposition has its roots in mutations in our DNA, the genetic material that contains the instructions for human development and how we function. The DNA is structurally organized in chromosomes, which contain molecular units (genes), each composed of a sequence of nucleotides. Each gene contains exons, which are instructions for creating proteins (each protein carries out specific functions in the cell, thus translating the genetics information of the gene). Although the collection of all exons (exome) contains a substantial portion of meaningful DNA, it only represents 2 percent of the entire genetic repertoire (genome).

Identifying genes underlying a disorder has many important ramifications, discussed briefly below. But one that should be appreciated is that, as gene mutations are identified, the same mutation can be studied in cells in culture (in a petri dish) and in laboratory animals (most often mice). This provides a window into the molecular and cellular changes caused by the mutation, and can lead to a deep understanding of the neurobiology of the condition being studied. This understanding of the neurobiology can in turn lead to potential novel treatments. In ASD, this approach of rational medicine is likely to be the cornerstone of personalized, or individualized, medicine, where treatments are tailored to the specific causes of the ASD. Examples of clinical trials based on this approach include ongoing trials in Fragile X syndrome, Rett syndrome, and Phelan-McDermid syndrome. …

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