Clinical-neurologic, cytogenetic and molecular aspects of the Prader-Willi and Angelman Syndromes

Arquivos de Neuro-Psiquiatria

João M. De Pina-neto²  Victor Evangelista F. Ferraz²  Greice Andreotti De Molfetta²  Jess Buxton¹  Sarah Richards¹  Sue Malcolm¹ 

[1],University of São Paulo Medical School of Riberião Preto Department of Genetics

关键词: medical genetics;    mental retardation;    Prader-Willi syndrome;    Angelman syndrome;    molecular genetics;    PCR (polymerase chan reaction);    Southern blot;    genética médica;    deficiência mental;    síndrome de Prader-Willi;    síndrome de Angelman;    genética molecular;    PCR (polymerase chain reaction);    Southern blot;   

DOI  :  10.1590/S0004-282X1997000200006

来源: SciELO

【 摘 要 】

The Prader-Willi syndrome (PWS) and the Angelman syndrome (AS) are human neurogenetic disorders involving the imprinting mechanism, at the 15q11-13 chromosome region. The predominant genetic defects in PW are 15q 11-13 deletions of paternal origin and maternal chromosome 15 uniparental disomy. In contrast, maternal deletions and paternal chromosome 15 uniparental disomy are associated with a different neurogenetic disorder, the AS. In both disorders, these mutations are associated with parent-of-origin specific methylation at several 15q 11-13 loci. We studied 5 patients suspect of PWS and 4 patients suspect of AS who were referred to the Medical Genetics Unit at the University Hospital of Medical School from Ribeirão Preto. Our objective was to establish the correct clinical and etiological diagnosis in these cases. We used conventional cytogenetics, methylation analysis with the probe KB 17 (CpG island of the SNRPN gene) by Southern blotting after digestion with the Xba I and Not I restriction enzymes. We studied in patients and their parents the segregation of the (CA)n repeats polymorphisms by PCR, using the primers 196 and IR4-3R. All the patients had normal conventional cytogenetical analysis. We confirmed 3 cases of PWS: one by de novo deletion, one by maternal chromosome 15 uniparental disomy and one case with no defined cause determined by the used primers. We confirmed 2 cases of AS, caused by de novo deletion at the 15q 11-13 region, and one case with normal molecular analysis but with strong clinical characteristics.

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