Xu C F, Chambers J A, Nicolai H, Brown M A, Hujeirat Y, Mohammed S, Hodgson S, Kelsell D P, Spurr N K, Bishop D T, Solomon E
Somatic Cell Genetics, Imperial Cancer Research Fund, London, United Kingdom.
Genes Chromosomes Cancer. 1997 Feb;18(2):102-10.
BRCA1 is a tumour suppressor gene located on chromosome band 17q21. It is estimated that mutations in the BRCA1 gene account for approximately 45% of the breast cancer families and almost all of the breast/ovarian cancer families. We have used single strand conformation polymorphism analysis, direct sequencing, allele specific oligonucleotide hybridisation, and reverse transcription polymerase chain reaction (RT-PCR) to look for mutations in the BRCA1 gene in 49 breast or breast/ovarian cancer families. Five distinct mutations, three novel and two previously observed, were detected in seven families. Each novel mutation was identified in one family: 3896delT in exon 11, a splicing mutation in the intron 9-exon 10 junction, and an inferred regulatory mutation. The 185delAG in exon 2 was found in three families sharing the same haplotype, but this haplotype is different from that shared by the Ashkenazi Jewish families, suggesting that the 185delAG in our families may have arisen independently. Another previously reported mutation, the 3875del4 in exon 11, was identified in one family. Of the 49 families examined, linkage analyses for both the BRCA1 and the BRCA2 regions were performed on 33 families, and mutations in the BRCA1 gene were identified in all but one family that have a lod score above 0.8 for BRCA1. All of the mutations cause either a truncated BRCA1, or loss of a BRCA1 transcript, thus are likely to be functionally disruptive. In addition, we found that alternative splicing is a common phenomenon in the processing of the BRCA1 gene. Seven variant BRCA1 transcripts were identified by RT-PCR; all but one maintained the BRCA1 open reading frame. We believe that alternative splicing may play a significant role in modulating the physiological function of BRCA1.
BRCA1是一种位于17号染色体17q21带的肿瘤抑制基因。据估计，BRCA1基因的突变约占乳腺癌家族的45%，几乎涵盖了所有的乳腺癌/卵巢癌家族。我们运用单链构象多态性分析、直接测序、等位基因特异性寡核苷酸杂交以及逆转录聚合酶链反应（RT-PCR），对49个乳腺癌或乳腺癌/卵巢癌家族的BRCA1基因进行突变检测。在7个家族中检测到5种不同的突变，其中3种为新发现的突变，2种为先前已观察到的突变。每个新突变分别在一个家族中被鉴定出来：外显子11中的3896delT、内含子9 - 外显子10连接处的剪接突变以及一个推测的调控突变。外显子2中的185delAG在3个具有相同单倍型的家族中被发现，但该单倍型与德系犹太人家庭所共有的单倍型不同，这表明我们所研究家族中的185delAG可能是独立产生的。另一个先前报道的突变，即外显子11中的3875del4，在一个家族中被鉴定出来。在所检测的49个家族中，对33个家族进行了BRCA1和BRCA2区域的连锁分析，除了一个BRCA1基因lod值高于0.8的家族外，其余家族均鉴定出了BRCA1基因的突变。所有这些突变要么导致BRCA1截短，要么导致BRCA1转录本缺失，因此很可能在功能上具有破坏性。此外，我们发现可变剪接是BRCA1基因加工过程中的一种常见现象。通过RT-PCR鉴定出7种可变的BRCA1转录本；除一种外，其余均保持BRCA1开放阅读框。我们认为可变剪接可能在调节BRCA1的生理功能方面发挥重要作用。
