X chromosome inactivation and female predisposition to autoimmunity.

The human X chromosome is the favorite chromosome of many geneticists because of its peculiar inheritance pattern and unique biology. The peculiar inheritance pattern stems from its hemizygosity in males and gives rise to a disproportionately high number of Mendelian diseases associated with a human chromosome. As high as 70% of the genes with a known function on the X are associated with disease phenotypes. The unique biology, termed Xinactivation, describes the transcriptional silencing of one of its copies in females. A substantial deal of sex differences in health issues has its origins in the genes on the X chromosomes and the X-inactivation process [1]. For example, a single copy of X chromosome in males leads to their vulnerability to X-linked diseases, such as X-linked immunological diseases (Bruton agammaglobulinemia and Wiskott–Aldrich syndrome), Duchenne muscular dystrophy, or a variety of X-linked mental retardation syndromes, such as fragile X syndrome. X Chromosome and Autoimmune Diseases