van Hattem W A, Brosens L A A, de Leng W W J, Morsink F H, Lens S, Carvalho R, Giardiello F M, Offerhaus G J A
Department of Pathology, University Medical Center Utrecht, Utrecht, The Netherlands.
Gut. 2008 May;57(5):623-7. doi: 10.1136/gut.2007.142927. Epub 2008 Jan 4.
BACKGROUND/AIMS: Juvenile polyposis syndrome (JPS) is a rare autosomal dominant disorder characterised by multiple gastrointestinal juvenile polyps and an increased risk of colorectal cancer. This syndrome is caused by germline mutation of either SMAD4 or BMPR1A, and possibly ENG. PTEN, originally linked to Cowden syndrome and Bannayan-Riley-Ruvalcaba syndrome, has also been associated with JPS. By direct sequencing, germline mutations are found in only 30-40% of patients with a JPS phenotype. Therefore, alternative ways of inactivation of the known JPS genes, or additional genes predisposing to JPS may be involved. In this study, a comprehensive genetic analysis of SMAD4, BMPR1A, PTEN and ENG is performed through direct sequencing and multiplex ligation-dependent probe amplification (MLPA) in JPS patients.
Archival material of 29 patients with JPS from 27 families was collected. Direct sequencing and MLPA analysis were performed to search for germline defects in SMAD4, BMPR1A, PTEN and ENG.
A germline defect in SMAD4, BMPR1A or PTEN was found in 13 of 27 (48.1%) unrelated JPS patients. Nine mutations (33.3%) were detected by direct sequencing, including six (22.2%) SMAD4 mutations and three (11.1%) BMPR1A mutations. MLPA identified four additional patients (14.8%) with germline hemizygous large genomic deletions, including one deletion of SMAD4, one deletion of exons 10 and 11 of BMPR1A, and two unrelated patients with deletion of both BMPR1A and PTEN. No ENG gene mutations were found.
Large genomic deletions of SMAD4, BMPR1A and PTEN are a common cause of JPS. Using direct sequencing and MLPA, a germline defect was detected in 48.1% of JPS patients. MLPA identified 14.8% (4/27) of these mutations. Since a substantial percentage of JPS patients carry a germline deletion and MLPA is a reliable and user-friendly technique, it is concluded that MLPA is a valuable adjunct in JPS diagnosis.
背景/目的：青少年息肉病综合征（JPS）是一种罕见的常染色体显性疾病，其特征为多个胃肠道青少年息肉以及结直肠癌风险增加。该综合征由SMAD4或BMPR1A的种系突变引起，可能还有ENG。PTEN最初与考登综合征和班纳扬-莱利-鲁瓦尔卡巴综合征相关，也与JPS有关。通过直接测序，仅在30%-40%具有JPS表型的患者中发现种系突变。因此，可能涉及已知JPS基因失活的其他方式，或导致JPS的其他基因。在本研究中，通过直接测序和多重连接依赖探针扩增（MLPA）对JPS患者进行了SMAD4、BMPR1A、PTEN和ENG的全面基因分析。
收集了来自27个家庭的29例JPS患者的存档材料。进行直接测序和MLPA分析以寻找SMAD4、BMPR1A、PTEN和ENG中的种系缺陷。
在27例无关的JPS患者中的13例（48.1%）中发现了SMAD4、BMPR1A或PTEN的种系缺陷。通过直接测序检测到9个突变（33.3%），包括6个（22.2%）SMAD4突变和3个（11.1%）BMPR1A突变。MLPA鉴定出另外4例患者（14.8%）存在种系半合子大基因组缺失，包括1例SMAD4缺失、1例BMPR1A外显子10和11缺失，以及2例无关患者同时缺失BMPR1A和PTEN。未发现ENG基因突变。
SMAD4、BMPR1A和PTEN的大基因组缺失是JPS的常见原因。使用直接测序和MLPA，在48.1%的JPS患者中检测到种系缺陷。MLPA鉴定出其中14.8%（4/27）的突变。由于相当比例的JPS患者携带种系缺失且MLPA是一种可靠且用户友好的技术，得出结论MLPA在JPS诊断中是一种有价值的辅助手段。
