Is MECP2 duplication syndrome inherited ?
Is MECP2 duplication syndrome inherited? MECP2 duplication syndrome is inherited in an X-linked manner. A condition is considered X-linked if the genetic change that causes the condition is located on the X chromosome, one of the two sex chromosomes (the Y chromosome is the other sex chromosome). In males (who have only one X chromosome), a duplication of the MECP2 gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a duplication of one of the two copies of the gene typically does not cause the disorder. Early in the development of females, one of the two X chromosomes is randomly and permanently inactivated in each cell (called X-inactivation). X-inactivation prevents female cells from having twice as many functional X chromosomes as males. Because X-inactivation is usually random, the X chromosome inherited from the mother is active in some cells, and the X chromosome inherited from the father is active in other cells. However, when a female has an X chromosome with a duplicated copy of the MECP2 gene, the abnormal chromosome is often preferentially inactivated in many or all cells. This is called "skewed X-inactivation." It prevents some women with an MECP2 duplication from developing features of the duplication since the extra genetic material is not active. In most cases, MECP2 duplication syndrome is inherited from a mother who has no signs or symptoms of the duplication. Rarely, the condition is not inherited and occurs due to a random event during the formation of the egg or sperm, or in early fetal development. When this happens, it is called a de novo duplication (occurring as a new genetic change for the first time in the affected person).