One of the regions responsible for the symptoms of idic(15) syndrome is the critical PWS/AS-region named after the Prader-Willi and/or Angelman syndromes. Isodicentric chromosome 15 and autism
For more than 12 years, scientists have noticed that some individuals with autism also have idic(15). In fact, idic(15) is the most frequently identified chromosome problem in individuals with autism. (A chromosome anomaly involves extra or missing chromosomal material, not changes within the genes such as Fragile X syndrome). It is suggested that the co-occurrence of autism and idic(15) is not by chance. There may be a gene or genes in the 15q11-q13 region that is/are related to the development of autism in some individuals.Genetic research studies of individuals without chromosome anomalies also support this idea that an autism-related gene may be present in 15q11.2-q13.1 Specifically, research studies found that certain DNA markers from the (15q1.2-q13.1) region were found more often in individuals with autism than in individuals without autism. Although these DNA markers are too small to be genes, they suggest that researchers may be getting close to finding an autism gene in this region.A recent study reported the introduction of two extra copies of just a single gene present in the 15q11.2-q13.1 region, Ube3a, into mice to model the gene copy number expressed in the brain in idic(15). These mice displayed autism-related behavioral deficits including impaired social interaction, reduced ultrasonic vocal communication, and increased repetitive behavior (self-grooming). Diagnosis
The extra chromosome in people with idic(15) can be easily detected through chromosome analysis (karyotyping). Additional tests are usually required.
Isodicentric 15, also called marker chromosome 15 syndrome, idic(15), partial tetrasomy 15q, or inverted duplication 15 (inv dup 15), is a chromosome abnormality in which a child is born with extra genetic material from chromosome 15. People with idic(15) are typically born with 47 chromosomes in their body cells, instead of the normal 46. The extra chromosome, which is classified as a small supernumerary marker chromosome, is made up of a piece of chromosome 15 that has been duplicated end-to-end like a mirror image. It is the presence of this extra genetic material that is thought to account for the symptoms seen in some people with idic(15). Individuals with idic(15) have a total of four copies of this chromosome 15 region instead of the usual two copies (1 copy each on the maternal and paternal chromosomes). The syndrome is also often referred to by the term Chromosome 15q11.2-q13.1 Duplication Syndrome, shortened to Dup15q Syndrome, or marker chromosome 15 syndrome (mainly in the United States). Dup15q Syndrome includes both idic(15) and interstitial 15q11.2-q13.1, another type of duplication that causes similar clinical traits. The extra chromosome is occasionally found in the mosaic state, i.e. some of the cells carry the marker chromosome. However, mostly because of the markers instability and tendency to be lost during cell division (mitosis), some cells are completely normal with 46 chromosomes. Occasionally, cells may have more than one idic(15), resulting in 48 or 49 chromosomes in all or some of their cells.