Department of Gynecology, Xinyu People's Hospital, Xinyu, 338000, Jiangxi, China.
Department of Obstetrics and Gynecology, The First Affiliated Hospital of Nanchang University, No. 17 Yongwai Zhengjie, Nanchang, 330000, Jiangxi, China.
J Assist Reprod Genet. 2020 Jun;37(6):1489-1495. doi: 10.1007/s10815-020-01783-w. Epub 2020 Apr 30.
Breast cancer susceptibility gene 1/2 (BRCA1/2) is the most important susceptibility gene associated with hereditary ovarian cancer (HOC). We aimed to screen BRAC1 and BRAC2 gene mutations in a member of a hereditary ovarian cancer family in China, and to analyze the structure and function of the mutant protein.
A typical HOC family was selected. Blood samples and pathological tissue samples were taken from the female members of the family. Blood samples from two patients with sporadic ovaries of the same pathological type were taken as a control group. After RNA extraction, PCR amplification was applied and the PCR products were directly sequenced and aligned, prediction and analysis of protein structure and molecular conformation that may be caused by BRCA1/2 mutation.
The whole gene analysis of BRCA1 and BRCA2 in ovarian cancer patients in the family showed that there were 8 mutations in BRCA1 whole gene sequencing, including 3 nonsense mutations (2314C>T, 2543T>C, 4540T>C); two mutations have been recorded, which are associated with cervical cancer (2844C>T) and endometriosis (3345A>G); three newly discovered mutations (3780A>G, 5069A>G, 3326A>T). Among them, 3780A>G and 5069A>G caused amino acid changes, while 3326A>T mutation caused Arg mutation to stop codon. A total of 7 mutations were detected in BRCA2 whole-genome sequencing, including 5 non-significant mutations (3623A>G, 4034T>C, 4790A>G, 6740G>C, 7469A>G); one no-record mutation (1716T>A), and 1 recorded mutation (1342A>C), which was associated with breast cancer and ovarian cancer. BRCA1 (3326A>T) and BRCA2 (1342A>C) mutations were co-existing in patients (II1, II3, and II5) identified as serous adenocarcinoma grade II. Two cases of ovarian serous cystadenocarcinoma with no history of family tumors were normalized for BRCA1/2 gene sequencing. In the gene detection of III generation female, four females with BRCA2 (1342A>C) mutation were found, and one of them also carried the BRCA1 (3326A>T) mutation, who can be considered a high-risk group of HOC in this family. Online protein structure predictions revealed that BRCA1 (3326A>T) mutations mutated AGA at this site to TGA resulting in a translated Arg (arginine) mutation as a stop codon, while BRCA2 (1342A>C) mutated AAT at this site to CAT resulting in a translated Asn mutation to His.
The BRCA1 (3326A>T) and BRCA2 (1342A>C) were detected in the HOC family, which may be the susceptibility gene of the family's HOC. The BRCA1/2 gene screening may be possible to obtain high-risk populations in this family.
乳腺癌易感基因 1/2（BRCA1/2）是与遗传性卵巢癌（HOC）相关的最重要的易感基因。本研究旨在对中国一个遗传性卵巢癌家族的成员进行 BRAC1 和 BRAC2 基因突变筛查，并分析突变蛋白的结构和功能。
选择了一个典型的 HOC 家族。从家族中女性成员身上采集血液样本和病理组织样本。同时采集两名具有相同病理类型的散发性卵巢癌患者的血液样本作为对照组。提取 RNA 后，进行 PCR 扩增，直接对 PCR 产物进行测序和比对，预测和分析 BRCA1/2 突变可能导致的蛋白质结构和分子构象变化。
对家族中卵巢癌患者的 BRCA1 和 BRCA2 全基因分析显示，BRCA1 全基因测序发现 8 个突变，包括 3 个无义突变（2314C>T、2543T>C、4540T>C）；2 个已记录的突变，与宫颈癌（2844C>T）和子宫内膜异位症（3345A>G）相关；3 个新发现的突变（3780A>G、5069A>G、3326A>T）。其中，3780A>G 和 5069A>G 导致氨基酸改变，而 3326A>T 突变导致 Arg 突变至终止密码子。BRCA2 全基因组测序共检测到 7 个突变，包括 5 个非显著突变（3623A>G、4034T>C、4790A>G、6740G>C、7469A>G）；1 个无记录突变（1716T>A）和 1 个记录突变（1342A>C），与乳腺癌和卵巢癌相关。BRCA1（3326A>T）和 BRCA2（1342A>C）突变同时存在于被诊断为 II 级浆液性腺癌的患者（II1、II3 和 II5）中。对两名无家族肿瘤史的卵巢浆液性囊腺癌患者进行 BRCA1/2 基因测序。在对第三代女性的基因检测中，发现了 4 名携带 BRCA2（1342A>C）突变的女性，其中 1 名还携带 BRCA1（3326A>T）突变，可被认为是该家族中 HOC 的高危人群。在线蛋白结构预测显示，BRCA1（3326A>T）突变使该位点的 AGA 突变为 TGA，导致翻译的 Arg（精氨酸）突变成为终止密码子，而 BRCA2（1342A>C）突变使该位点的 AAT 突变为 CAT，导致翻译的 Asn（天冬酰胺）突变成为 His（组氨酸）。
在 HOC 家族中检测到 BRCA1（3326A>T）和 BRCA2（1342A>C），可能是该家族 HOC 的易感基因。BRCA1/2 基因筛查可能有助于确定该家族中的高危人群。
