ZespÃ³Å‚ Pradera-Williego.pdf

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Prader-Willi syndrome

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Prader-Willi syndrome (PWS) is an uncommon genetic disorder characterized by mental

retardation, decreased muscle tone, short stature, emotional lability and an insatiable appetite

which can lead to life-threatening obesity. The syndrome was first described in 1956 by Drs.

Prader, Labhart, and Willi.

PWS is caused by the absence of segment 11-13 on the long arm of the paternally derived

chromosome 15. In 70-80% of PWS cases, the region is missing due to a deletion. Certain

genes in this region are normally suppressed on the maternal chromosome, so, for normal

development to occur, they must be expressed on the paternal chromosome. When these

paternally derived genes are absent or disrupted, the PWS phenotype results. When this same

segment is missing from the maternally derived chromosome 15, a completely different

disease, Angelman syndrome, arises. This pattern of inheritance — when expression of a gene

depends on whether it is inherited from the mother or the father — is called genomic imprinting.

The mechanism of imprinting is uncertain, but, it may involve DNA methylation.

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Genes found in the PWS chromosomal region code for the small ribonucleoprotein N

(SNRPN). SNRPN is involved in mRNA processing, an intermediate step between DNA

transcripton and protein formation. A mouse model of PWS has been developed with a large

deletion which includes the SNRPN region and the PWS 'imprinting centre' (IC) and shows a

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phenotype similar to infants with PWS. These and other molecular biology techniques may

lead to a better understanding of PWS and the mechanisms of genomic imprinting.

Related diseases

Gene sequence

Genome view see gene locations

Entrez Gene collection of gene-related information

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BLink related sequences in different organisms

The literature

Research articles online full text

Books online books section

OMIM catalog of human genes and disorders

GeneReviews a medical genetics resource

Websites

Prader-Willi Syndrome Association (USA) information, education, and support services

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Prader-Willi syndrome