The X chromosome and fragile X mental retardation |
| |
Authors: | Oostra B A Willemsen R |
| |
Affiliation: | Department of Clinical Genetics, Erasmus MC, Rotterdam, The Netherlands. b.oostra@erasmusmc.nl |
| |
Abstract: | Fragile X syndrome represents the most common inherited cause of mental retardation. It is caused by a stretch of CGG repeats within the fragile X gene, which increases in length as it is transmitted from generation to generation. Once the repeat exceeds a threshold length, no protein is produced, resulting in the fragile X phenotype. Both X chromosome inactivation and inactivation of the FMR1 gene are the result of methylation. X inactivation occurs earlier than inactivation of the FMR1 gene. The instability to a full mutation is dependent on the sex of the transmitting parent and occurs only from mother to child. For most X-chromosomal diseases, female carriers do not express the phenotype. A clear exception is fragile X syndrome. It is clear that more than 50% of the neurons have to express the protein to ensure a normal phenotype in females. This means that a normal phenotype in female carriers of a full mutation is accompanied by a distortion of the normal distribution of X inactivation. |
| |
Keywords: | |
本文献已被 PubMed 等数据库收录! |
|