Hi
Rett syndrome is a classic example of a Mendelian chromatin disease
in which pathogenesis occurs as a result of altered chromatin
states at gene loci that are distinct from the one that is mutated.
Explain how this happens. Why are individuals with Rett syndrome
almost exclusively female?
Best wishes
Mohammad Amin
Rett syndrome is a striking disorder that occurs nearly exclusively in
females and meets all criteria for being an X-linked dominant disorder that is usually lethal in hemizygous males. The disease mechanism is thought to reflect abnormalities in the regulation of a set of genes in the developing brain; the cause of male lethality is unknown but presumably reflects a requirement during early development for at least one functional copy of the MECP2 gene on the X chromosome that is mutated in this syndrome.
For a better understanding of what Shima has adequately described please read
https://academic.oup.com/hmg/article/11/2/115/812000/Insight-into-Rett-syndrome-MeCP2-levels-display
MECP2 is responsible for Rett syndrome, its more easy to see in females, as in males it has been linked to lethality. Nevertheless, there are males affected with it. https://www.sciencedaily.com/releases/2006/08/060812090802.htm
Dear Seyed, Rett syndrome (also known as RTT in OMIM) is caused by mutation in the gene encoding methyl-CpG-binding protein-2 (MECP2) on chromosome Xq28.
Rett syndrome is typically caused by mutations in the MECP2 gene that result in underexpression or underactivity of the gene. MECP2 duplication syndrome is caused when there are extra copies of the MECP2 gene in cells resulting in overexpression and overactivity of the gene.
MECP2 is a tightly regulated gene. Because females have two copies, one on each X chromosome, about half of their MECP2 genes still produce the MeCP2 protein, so they are adversely affected but survive. Since males only have one X, if the MECP2 gene is damaged they may produce very little or no MeCP2 protein. As a result, they do not survive. Nevertheless, some defects in the MECP2 gene may result in less severe underexpression, and males with these specific mutations do survive, so there are boys with Rett syndrome but they are rare relative to affected girls.
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