Disease Example (trisomy rescue)

Angelman syndrome can be caused by paternal uniparental disomy of chromosome 15 resulting from trisomy rescue of a trisomy 15 zygote (either 47,XY+15 or 47,XX+15) in which the total number of chromosomes in the cell is reduced to 46,XX or 46,XY such that two paternal chromosomes 15 remain.

Prader-Willi syndrome can be caused by maternal uniparental disomy of chromosome 15 resulting from trisomy rescue of a trisomy 15 zygote (either 47,XY+15 or 47,XX+15) in which the total number of chromosomes in the cell is reduced to 46,XX or 46,XY such that two maternal chromosomes 15 remain.

trisomy rescue

Some Clinical Implications

  • Uniparental disomy (UPD) leads to an abnormal phenotype if the chromosome involved has imprinted gene(s) or if UPD results in homozygosity for a pathogenic variant resulting in an autosomal recessive condition.
  • If prenatal diagnostic testing via chorionic villus sampling (CVS) reveals a trisomic cell line involving a chromosome known to have imprinted genes, and follow-up amniocentesis reveals normal fetal chromosomes, UPD testing for the trisomic chromosome should be considered to exclude the possibility that trisomy rescue restored the normal karyotype in the fetal cells, but in doing so, led to UPD.

Last revision: 10-31-16

Related terms: aneuploidy; imprinting; postzygotic; uniparental disomy

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