Rett syndrome genetic variants now available for advance testing, diagnosis & research

Despite the identification of gene mutations in methyl CpG binding protein 2 (MECP2) being linked to Rett syndrome (RS), research has been hindered by the lack of commercially available reference materials. Through collaboration between the Centers for Disease Control and Prevention (CDC) and members of the clinical-laboratory and non-profit–research communities, 35 DNA samples containing many common RS genetic variants have now been characterized and made publicly available, eliminating a major stumbling-block for investigators and opening the possibility of earlier, more accurate diagnosis of Rett syndrome, reports The Journal of Molecular Diagnostics.

The study was conducted via the CDC Genetic Testing Reference Materials Coordination Program (GeT-RM), which aims to help the genetic testing community obtain appropriate and well-defined reference materials for inherited genetic disorders, including cancer and infectious diseases. Researchers selected eight cell lines from RS patients already available from the National Institute of General Medical Sciences' Coriell Cell Repository, which contained six of the most common mutations that cause RS, as well as one additional point mutation. In addition, DNA was obtained from 27 newly established cell lines derived from blood samples from Rett patients, which included a number of other MECP2 variants. Two of the samples were from males.

The samples were sent for DNA sequence and deletion/duplication analyses (using MLPA, semi-quantitative PCR, or array) to College of American Pathologist–accredited clinical genetic testing laboratories, and each sample was tested in between two to five laboratories. The investigators found that the results were concordant among laboratories and assay platforms.

"The panel of 35 publicly available genomic DNA samples developed and characterized as part of this study contains a wide variety of point mutations, deletions, and duplications in both male and female samples that can be used by clinical laboratories to ensure the quality of Rett syndrome testing," asserts Dr. Kalman.

Point mutations or deletions/insertions of the MECP2 gene, which regulates aspects of brain development as well as the expression of other genes, were discovered to be associated with most cases of RS in 1999. However, since there are still no FDA-approved assays for Rett syndrome, laboratories have developed their own tests but need reference materials to standardize their techniques, validate assays, and meet regulatory and accreditation requirements. Ideally, the reference materials should be well characterized and contain the variants most commonly seen in RS patients.

What is Rett syndrome?

Rett syndrome is a neurodevelopmenal disorder that affects girls almost exclusively. It is characterized by normal early growth and development followed by a slowing of development, loss of purposeful use of the hands, distinctive hand movements, slowed brain and head growth, problems with walking, seizures, and intellectual disability.