Molecular genetic diagnostics of Prader-Willi Syndrome: a validation of linkage analysis for the Chinese population.

Prader-Willi Syndrome (PWS) is a genetic disorder that is difficult to detect, particularly at an early age. PWS is caused by disruption of normal, epigenetically controlled gene function in the chromosome 15q11-q13 region. Clinical symptoms are difficult to diagnose in infants and only become clearer at later ages as the patients develop hyperphagia and morbid obesity. Molecular genetic tests are able to definitively diagnose PWS and allow early diagnosis of the syndrome. High resolution cytogenetic testing, methylation-specific PCR (MS-PCR), and linkage analysis are routinely used to diagnose PWS. To establish a linkage analysis method for Chinese patients, this study identified a useful set of STR markers in the typical PWS deletion and adjacent area, for linkage analysis in two Chinese families with PWS offspring. Using this method, the authors confirmed that one patient had a paternal deletion in chromosome 15q11-q13 and the other patient had maternal uniparental heterodisomy of chromosome 15. MS-PCR and high resolution chromosome G-banding also confirmed this diagnosis. This linkage analysis method can detect both deletion and uniparental disomy, thus providing valuable information for genetic counseling and the opportunity to analyze the relationship between the genotype and phenotype of PWS.