Deletions Within Certain Chromosome Can Lead to Autism Development

Autism spectrum disorder is considered a rather complex genetic disorder, mainly because numerous studies related to genetics reveal that not all identical twins have ASD. These studies have led researchers to conclude that there is something else associated with the onset of ASD. Yet, is it genetics or is it related with the environment?

A recent study has found that deletions within a small area of the chromosome 22 increase the risk of autism. The deletions within this area are known as 22q11.2 because they are situated right near the center of the chromosome 22 at a location labeled q11.2. What’s more, they are associated with conditions such as autism and schizophrenia, as well as digestive and heart problems. In a majority of cases, these deletions cover the entire region, yet in about 15% of cases, they merely affect one of four areas within 22q11.2.

Almost 50% of children with autism have this trait

Researchers have found that one of these areas is associated with autism because five out of twelve children with a deletion have autism. Controversy, zero out of eight children have a deletion in any of the other three areas. “That’s a pretty high rate,” said Robert Schultz, lead researcher and director of the Center for Autism Research at the Children’s Hospital of Philadelphia.

The study, published in Molecular Autism, involved the participation of thirty-three children with a small deletion and thirteen children with a small duplication in 22q11.2. Schultz and his fellow colleagues evaluated twenty of the children for the onset of autism and of this group, twelve showed a deletion between two points, marked as A and B, within the region.

“Our study hints that duplication of genes in this region might be more specific for autism than the deletion is,” said Schultz. The other eight children had alterations that affected the areas that ran along points B to D. The points A, B, C, and D are blocks of repetitive DNA. The evaluations led the research team to discover that five of the children with a deletion A-B had autism and none of the other children outside of these two points did. “The findings are really interesting — particularly that the rate of autism was zero,” said Carrie Bearden, professor of psychiatry and biobehavioral sciences and psychology at the University of California.

Previous research supports the new findings

The study was rather limited because of the small population sample. “These kids were only assessed because they have developmental disorders of some sort,” said Elliott Sherr, professor of neurology and pediatrics at the University of California. This is due to the fact that these mutations are rare and discoveries need to be replicated. Yet, this particular study showed a link with previous studies’ findings. In fact, a study conducted back in 2014 showed that individuals with a low activity rate of two genes, known as PRODH and COMT, within the A-B points are more prone to developing autism. In addition, a study conducted last year by Schultz and his team found that deletion of a third gene, known as RANBP1, increases the risk of autism. In a recent study, Schultz and his team defined one autistic child to have a duplication in 22q11.2 that contains the genes RANBP1 and COMT. 

Read on to learn more about what these results mean for children with autism.