Molecular study of the Prader-Willi syndrome: deletion, RFLP, and phenotype analyses of 50 patients

Am J Med Genet. 1991 Oct 1;41(1):54-63. doi: 10.1002/ajmg.1320410116.


Deletion and RFLP studies with 5 cloned DNA markers localized at 15q11.2 were performed in 50 patients with the Prader-Willi syndrome (PWS). A one-copy density (deletion) for at least one of 4 loci, D15S9, D15S11, D15S10, D15S12, was detected in 32 (64%) of the 50 patients; deletions of each of the 4 loci were found in 29, 30, 29, and 28 patients, respectively. Three patients showed 4 or more copy density for D15S12 locus, in addition to deletions. The remaining 18 patients showed two-copy densities for each of the 4 loci. A common site of rearrangements among our 32 patients as well as the reported patients seemed to be confined to a segment between D15S9 and D15S11, suggesting the putative PWS gene locus in this segment. Of 6 patients who have cytologic deletions but did not show any molecular deletions, 3 have normal size of hands and feet, and 4 have normally pigmented skin and hair. The normal pigmentation was also observed in 3 patients who had small molecular deletions in the examined 5-locus segment. These observations may support the conception of contiguous gene syndrome. RFLP analysis demonstrated maternal uniparental isodisomy of chromosomes 15 in both a patient with 45,t(15q;15q) and a karyotypically normal patient. Based on the results of the present study, a new model is proposed to explain the occurrence of PWS with a variety of chromosome abnormalities, including partial monosomy, disomy, trisomy, and/or tetrasomy for 15q11.2. The normal development may require an even or more "number ratio" of paternally derived allele(s) to maternally derived allele(s) of the gene(s) localized at 15q11.2, and a disturbance of the ratio would lead to the PWS phenotype.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Blotting, Southern
  • Child
  • Child, Preschool
  • Chromosome Deletion*
  • Chromosome Mapping
  • Chromosomes, Human, Pair 15*
  • DNA Mutational Analysis
  • Female
  • Humans
  • Infant
  • Male
  • Phenotype
  • Polymorphism, Restriction Fragment Length
  • Prader-Willi Syndrome / genetics*
  • Translocation, Genetic / genetics