The cells, which are the building blocks of our body, contain small structures called chromosomes. There are 46 chromosomes in total made up of 23 pairs. You inherit one of each pair from your mother and the second from your father. Because half of our chromosomes are from our mother and half are from our father we become a mix of both of our parents.
One pair of chromosomes contains information which determines which sex you will be and this pair differs in men (XY) and women (XX). Chromosomes take the form of a long length of a chemical called deoxyribonucleic acid (DNA). This DNA can be split into smaller segments known as genes. Genes act as the blue print for our body, telling cells what proteins to make, and ultimately determining what features we have and how we will grow and develop.
MECP2 duplication syndrome comes about when an individual has an extra copies of the region of DNA on the X chromosome which contains the MECP2 gene. This means that the individual will have one more copy of the MECP2 gene than normal. The region of the X chromosome involved is termed Xq28, so this condition is also often referred to as Xq28 duplication syndrome. MECP2 is just one of the many genes that lie within the Xq28 segment of the X chromosome. Boys are far more likely to be affected by having an extra copy of the MECP2 gene due to an Xq28 duplication. This is because boys have only a single X chromosome, whereas girls have a second, normal X chromosome which can usually cancel out the effects of having a duplication on the other chromosome. There are however some rare occasions when girls may also be affected.
The area of DNA that is duplicated on the X chromosome can vary . Sometimes, other genes can also be duplicated along with the MECP2 gene. The number of genes which are duplicated can vary between one patient and the next. Overall, it is duplication of the MECP2 gene which appears to lead to most symptoms, though as a general rule, the more genes that are duplicated, the more severe the symptoms will be. A lot of research is currently focused at looking into the other genes that can be duplicated along with MECP2 and trying to find out what effect these other genes have on the symptoms of the syndrome.
How do you test for MeCP2 duplication syndrome?
Until recently it was not possible to locate this duplication of DNA because it is so small it can’t be seen under a microscope. However a new techniques, including those called array comparative genomic hybridization (aCGH or microarray analysis) and multiplex ligation-dependent probe amplification (MLPA), mean it is now possible to detect the duplication. DNA is usually obtained for testing from cells in a blood sample, though sometimes enough DNA can be obtained from a saliva sample.