Maternal disomy and Prader-Willi syndrome consistent with gamete complementation in a case of familial translocation (3;15) (p25;q11.2)

Am J Med Genet. 1998 Jun 30;78(2):134-9.


Maternal uniparental disomy (UPD) for chromosome 15 is responsible for an estimated 30% of cases of Prader-Willi syndrome (PWS). We report on an unusual case of maternal disomy 15 in PWS that is most consistent with adjacent-1 segregation of a paternal t(3;15)(p25;q11.2) with simultaneous maternal meiotic nondisjunction for chromosome 15. The patient (J.B.), a 17-year-old white male with PWS, was found to have 47 chromosomes with a supernumerary, paternal der(15) consisting of the short arm and the proximal long arm of chromosome 15, and distal chromosome arm 3p. The t(3;15) was present in the balanced state in the patient's father and a sister. Fluorescent in situ hybridization analysis demonstrated that the PWS critical region resided on the derivative chromosome 3 and that there was no deletion of the PWS region on the normal pair of 15s present in J.B. Methylation analysis at exon alpha of the small nuclear ribonucleoprotein-associated polypeptide N (SNRPN) gene showed a pattern characteristic of only the maternal chromosome 15 in J.B. Maternal disomy was confirmed by polymerase chain reaction analysis of microsatellite repeats at the gamma-aminobutyric acid receptor beta3 subunit (GABRB3) locus. A niece (B.B.) with 45 chromosomes and the derivative 3 but without the der(15) demonstrated a phenotype consistent with that reported for haploinsufficiency of distal 3 p. Uniparental disomy associated with unbalanced segregation of non-Robertsonian translocations has been reported previously but has not, to our knowledge, been observed in a case of PWS. Furthermore, our findings are best interpreted as true gamete complementation resulting in maternal UPD 15 and PWS.

Publication types

  • Case Reports

MeSH terms

  • Adolescent
  • Chromosomes, Human, Pair 15*
  • Chromosomes, Human, Pair 3*
  • DNA Methylation
  • Female
  • Genetic Complementation Test
  • Genomic Imprinting*
  • Germ Cells
  • Humans
  • In Situ Hybridization, Fluorescence
  • Male
  • Microsatellite Repeats
  • Pedigree
  • Prader-Willi Syndrome / genetics*
  • Translocation, Genetic*