Diagnosis of patients with Prader-Willi and Angelman Syndromes: the importance of an overall investigation

Abstract

Seventy-two patients with clinical diagnoses of Prader-Willi (PWS; n = 28 patients) or Angelman syndromes (AS; n = 44 patients) were submitted to chromosome analysis, SNRPN-SNURF exon 1 methylation assay, and microsatellite genotyping. Analysis of the methylation pattern confirmed the PWS diagnosis in 18 out of 28 patients and the AS diagnosis in 20 out of 44 patients. FISH and microsatellite analysis detected a deletion in 30 patients (14 PWS and 16 AS). Eight patients had normal FISH results (4 PWS and 4 AS); microsatellite markers showed that these patients had a uniparental disomy (UPD). Based on this study, we propose a strategy for the routine diagnosis of these syndromes that consists of the following steps: 1) methylation analysis, which does not require parental samples; 2) microsatellite genotyping of patient and parents to differentiate deletions, UPD and imprinting mutations; and 3) FISH for otherwise uninformative cases, and whenever parental samples are not available. Of the 34 patients whose PWS or AS diagnoses were not confirmed by laboratory tests, five presented a small extra marker chromosome, identified in three of them as an inv dup(15). One AS patient carried a balanced t(15;15) translocation associated with paternal UPD. Therefore G-banded chromosome analysis should be performed on all such patients, to detect possible structural rearrangements.

Mini-Review Prader-Willi-like phenotypes: a systematic review of their chromosomal abnormalities

“…It is not easy to see a deletion on 15q11-q13 using an ordinary light microscope. This may be due to the difficulty in visualizing a 3-5 Mb deletion with a light microscope and differences in condensation of band 15q12 (Varela et al, 2002). Therefore, G-banding is not sufficient to diagnose PWS (Gillessen-Kaesbach et al, 1995).…”

Use of microsatellite loci in prenatal and postnatal diagnosis of aneuploidy and uniparental disomy

“…Dodatno, usporedbom alela lokusa STR roditelja i ploda može se odrediti podrijetlo prekobrojnog kromosoma, ako plod ima trisomiju određenog kromosoma. Prednost analize lokusa STR u prenatalnoj i postnatalnoj dijagnostici očituje se i u mogućnosti utvrđivanja podrijetla kromosoma u dijagnostici uniparentne disomije (UPD), kojeg nije moguće utvrditi FISH-om i metodama klasične citogenetike (7). Cilj ovog rada bio je dokazati dijagnostičku vrijednost pri-mijenjenih mikrosatelitskih lokusa na kromosomima 13, 18, 21, X i Y kroz prikaz rezultata analize lokusa STR u Kabinetu za prenatalnu dijagnostiku Klinike za pedijatriju KBC-a Zagreb u 9-godišnjem razdoblju.…”

Elsődleges genetikai vizsgálat Prader–Willi-szindróma igazolására

“…Az uniparentalis disomia, illetve az imprinting defektus további elkülönítésére a mikroszatellita-analízis (MSA) alkalmas. A DNS-metilá-ciós status vizsgálatára további alternatív módszerek is rendelkezésre állnak, mint például a metilációspecifikus polimeráz-láncreakció (MS-PCR), a metilációspecifikus Southern-blot (MS-SB) vagy a nagy felbontású olvadás-pont-elemzés (HRM) [11][12][13]. A DNS-metilációs vizsgálat eredménye a Prader-Willis-szindrómás esetek 99%-ában pozitív, alkalmazásával mind a deletiós, mind az anyai uniparentalis disomia, illetve az imprinting defektus detektálható, míg a leginkább hozzáférhető FISH (floureszcens in situ hibridizáció) csupán a deletiós forma kimutatására alkalmas (ez kb.…”