Clin Lab. 2024 Aug 1;70(8). doi: 10.7754/Clin.Lab.2024.240245.
Prader-Willi syndrome (PWS, MIM 176,270) and Angelman syndrome (AS, MIM 105,830) are caused by imprinting defects of chromosome 15q11-13, with loss of maternal gene expression causing AS and paternal gene expression causing PWS. The diagnosis, once established in most cases by using a methylation-specific PCR test, enables appropriate therapeutic interventions and avoids the need for further investigations. Genetic testing for PWS/AS is limited in Sri Lanka (and in other low- and middle-income countries), mainly because parents are unable to pay for testing as these are not funded by the health service.
Ninety cases (46 female) with clinical features suggesting PWS (n = 37) and AS (n = 53), referred by a pediatric endocrinologist and a pediatric neurologist, were recruited. Clinical information and blood samples were obtained following informed consent. DNA was extracted and methylation-specific PCR (MS-PCR) was performed following bisulfite modification of DNA by using an in-house method and a kit. Results were validated using known positive controls. Parent-child trio DNA samples were used in cases with confirmed PWS and AS to determine if the disease was due to a deletion or uniparental disomy. The cost of the MS-PCR testing of the two modification methods and the microsatellite analysis was determined.
Among the suspected PWS cases, 19/37 were positive, while 5/53 of the suspected AS cases were positive. The lower identification rate of AS is probably related to the overlap of clinical features of this condition with other disorders. The kit-based modification method was more reliable, less time-consuming, and cost-effective in our laboratory.
The kit-based modification followed by MS-PCR described in this study enables more affordable genetic testing of suspected PWS/AS cases, and this is likely to improve patient care by targeting appropriate therapy for the affected cases. Parental genetic counselling is made possible regarding the low recurrence risk, especially where a deletion or uniparental disomy is confirmed. In MS-PCR, negative cases with a strong clinical suspicion of AS, UBE3A mutation testing is required. In addition, imprinting center mutation/deletion testing may also be needed in strongly clinically suspected, MS-PCR negative PWS and AS cases.
普拉德-威利综合征（PWS，MIM 176,270）和安格曼综合征（AS，MIM 105,830）是由 15q11-13 染色体印迹缺陷引起的，母源基因表达缺失导致 AS，父源基因表达缺失导致 PWS。大多数情况下，通过甲基化特异性 PCR 检测可明确诊断，这有助于进行适当的治疗干预，并避免进一步的检查。在斯里兰卡（和其他中低收入国家），PWS/AS 的基因检测受到限制，主要是因为父母无力支付检测费用，因为这些检测没有得到医疗服务的资助。
招募了 90 名（46 名女性）有临床特征提示 PWS（n=37）和 AS（n=53）的病例，这些病例是由儿科内分泌学家和儿科神经学家转诊的。在获得知情同意后，采集临床信息和血样。DNA 提取后，采用实验室自建方法和试剂盒进行亚硫酸氢盐修饰，然后进行甲基化特异性 PCR（MS-PCR）。采用已知阳性对照验证结果。在确诊的 PWS 和 AS 病例中，使用亲子三核苷酸 DNA 样本确定疾病是否由缺失或单亲二体性引起。确定了两种修饰方法和微卫星分析的 MS-PCR 检测成本。
在疑似 PWS 病例中，19/37 例阳性，而在疑似 AS 病例中，5/53 例阳性。AS 较低的识别率可能与该疾病的临床特征与其他疾病重叠有关。试剂盒修饰法在我们实验室中更可靠、耗时更少、更具成本效益。
本研究中描述的基于试剂盒的修饰方法结合 MS-PCR，使疑似 PWS/AS 病例的基因检测更具成本效益，这有望通过为受影响病例提供适当的治疗来改善患者护理。对于确认缺失或单亲二体性的病例，可进行父母遗传咨询，告知低复发风险。在 MS-PCR 中，对于具有强烈临床怀疑的 AS 阴性病例，需要进行 UBE3A 基因突变检测。此外，在强烈临床怀疑、MS-PCR 阴性的 PWS 和 AS 病例中，也可能需要进行印记中心突变/缺失检测。
