Running For Research - PWSToday is the second day of PWS Awareness month.
Fact #2: PWS is caused by a lack of active genetic material in a particular region of chromosome 15 (15q11-q13). Normally, individuals inherit one copy of chromosome 15 from their mother and one from their father. The genes in the PWS region are normally only active on the chromosome that came from the father. In PWS, the genetic defect causing the inactivity of chromosome 15 from the father (paternal chromosome 15) can occur in one of three ways: deletion, uniparental disomy and imprinting defect.
PWS by Deletion: Most often, part of the chromosome 15 that was inherited from the person’s father is missing, or deleted, in this critical region. This small deletion occurs in approximately 70% of cases and usually is not detectable with routine genetic analysis such as amniocentesis.
PWS by UPD: Another 30% or so of cases occur when an individual inherits two chromosome 15s from their mother and none from their father. This scenario is termed maternal uniparental disomy (UPD).
PWS by Imprinting Defect: Finally, in a very small percentage of cases (1-3%), a small genetic mutation in the Prader-Willi region causes the paternal chromosome 15 genetic material (although present) to be inactive. Clementine has PWS caused by UPD. It is thought that UPD occurs through a process called ” chromosome rescue”. During the initial formation of egg or sperm cells or in early fetal development, a trisomy ( 3 copies of chromosome 15 instead of the normal 2 copies) of chromosome 15 is detected. The developing fetus attempts to rid itself of one of the three copies of chromosome 15 ( this trisomy is not compatible with life) and in doing so, it sheds the father’s copy of chromosome 15 leaving 2 of the mother’s copies. Thus the creation of a uniparental disomy. I know this a lot of information to take in so I will leave it at that for today. If anyone is interested in learning more about the genetics surrounding PWS, please click here: https://medlineplus.gov/…/condition/prader-willi-syndrome/
If you would like to make a donation to Running for Research ♥ Prader-Willi Syndrome, please click the Donate button below.
Thank you for reading!