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Description:
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Prader-Willi syndrome (PWS) is a contiguous gene syndrome involving several imprinted genes in
15q11-q13 which can occur by three different molecular mechanisms, ie, large deletions (70-75%),
maternal UPD (25-30%), or imprinting mutations (2-5%) (Glenn
CC et al, 1997; Nicholls
RD, 1998; Nicholls
RD and Knepper JL, 2001; Bittel
DC, Butler MG, 2004). See individual entries for 15q.
Cases of PWS having microdeletion suggest that loss of SNORD116@ (the HBII-85 cluster) and/or
SNORD19A (HBII-438A)
snoRNAs
cause the key characteristics of PWS (Sahoo
T et al, 2008; Gallagher
RC et al, 2002; de
Smith et al, 2009; Duker
AL et al, 2010). Studies on a family with complete deletion of the HBII-52 cluster have
excluded a major role for this cluster in PW (Runte
M et al, 2004).
Deletion of murine MBII-85 snoRNA (equivalent to human SNORD116@, small nucleolar RNA, C/D box 116
cluster) caused postnatal growth retardation, with about 15% postnatal lethality indicating a
functional role for the MBII-85 snoRNA (Skryabin
BV et al 2007).
The mouse phenotype resulting from disruption of Necdin suggests a role for human NDN in PWS
(Muscatelli
F et al, 2000).
Some of the phenotypic features of Magel2 knockout mice resemble Prader-Willi syndrome features
(neonatal growth retardation, excessive weight gain after weaning, and increased adiposity with
altered metabolism in adulthood) (Bischof
JM et al, 2007).
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