The specific causes of and contributors to autism spectrum disorders (ASDs) remain shrouded in medical mystery despite ongoing research, repeated press mentions and blossoming public interest. Most experts agree that the condition's roots are genetic, but new research indicates that non-inherited abnormalities in a particular sequence of chromosomes heighten a child's susceptibility to the disorder and may be responsible for as many as 1 in 100 cases.
In a multi-institutional study under the banner of the nonprofit Autism Consortium, researchers combed through the largest-ever accumulated data pool of autistic individuals and their families, examining the DNA of more than 1,400 patients with some form of autism spectrum disorder and their unaffected parents. The distinct and quite simply fascinating patterns observed by the research team revolve around chromosome 16: several of the autistic children in the study (approximately 1% of the entire sample) were found to be missing the same 25-gene segment of the chromosome related to inter-cellular communication and external behavior patterns. This tiny irregularity may have profound repercussions on the rest of the genome with a particularly stark influence on neurological development. While the roles played by particular chromosomes in the human genome have yet to be fully fleshed out, abnormalities in the 16th have been linked to a number of developmental disorders as well as physical abnormalities like underdeveloped lungs, congenital heart defects and asymetrical facial features.
None of the parents of these children bore the same genetic deformations, illuminating the spontaneous nature of a phenomenon that appears to occur due to a mutation in egg or spermatozoa around the period of conception. In a closely related variation, several of the autistic children in the study group had two copies of the given chromosome. In these cases, however, parents shared their children's anomalies, indicating that this trait is one acquired via heredity and may serve as a recessive gene leaving children more susceptible to the development of ASDs. Future research projects will aim to further explore this link. While the 1% estimate does not look particularly impressive on paper, the extreme rarity of this chromosomal anomaly, combined with its exponentially larger presence among the autistic patient sample, very strongly implies a causal relationship between the two variables. The chromosome 16 deletion pattern is not strictly limited to autistic individuals, but it was observed in only 2 control patients in a group of 20,000, and these numbers only further streamline its sphere of influence.
This study will most likely not produce any revolutionary changes in autism treatment, but every step forward, no matter how small, is a welcome development. The genetic roots of ASDs are multi-faceted, and chromosome 15 is more commonly believed to factor into the autism equation, but this study draws a clear connection between number 16 and a small percentage of affected children. At the very least, many patients diagnosed with autism will now be tested for this particular anomaly, and further testing using chromosome 16 as a springboard will inevitably teach us more about the disorder as a whole. If the study leads to more effective approaches applying to even a portion of the stated 1% of the autistic population, it could prove invaluable. And considering that nearly 1 in 150 American children now qualify for an ASD diagnosis, that number is anything but a paltry sum.
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