背景:直到最近,原发性家族性脑钙化(PFBC)已由四个基因确定,SLC20A2,PDGFRB,PDGFB和XPR1。目前尚无研究分析中国人群PDGFB基因突变情况。
目的:在无SLC20A2突变的大型中国PFBC患者队列中筛选PDGFB基因突变。
方法:我们招募了192例PFBC患者,包括21例指标病例和171例散发病例,在我们的研究中。收集所有参与者的外周静脉血样本进行基因组DNA提取。通过聚合酶链反应(PCR)扩增PDGFB的编码序列,然后进行直接测序。通过生物信息学分析评估鉴定的变体对蛋白质功能的潜在影响。
结果:三个错义变体(c.35G>T,c.232C>T,在五名散发性PFBC患者中发现了PDGFB的一个无义变体(c.610C>A)和一个无义变体(c.220G>T)。在来自相同种族背景的2名健康对照中发现了变异c.35G>T,而c.220G>T,500个对照中不存在c.232C>T和c.610C>A。c.220G>T(p。E74*)在谷氨酸残基编号74的位置产生了终止密码子。c.232C>T(p。R78C)发生在高度保守的区域,并被至少两个计算预测程序预测为破坏性的,这表明该变异可能在PFBC中具有因果作用。尽管变体c.610C>A(p。P204T)也发生在一个高度保守的区域,两个计算预测程序预测它很可能是良性的,提示该变体对PFBC的作用不确定。
结论:本研究确定了一种可能的致病变异(p。E74*)和两个具有不确定意义的变体(p。R78C和p.P204T)在PDGFB中。仍需要对这些变体的PDGF-B功能性表达的进一步研究以证实致病作用。
BACKGROUND: Until recently, primary familial brain calcification (PFBC) has been determined by four genes, SLC20A2, PDGFRB, PDGFB and XPR1. No studies have been carried out to analyze the gene mutation of PDGFB in Chinese population.
OBJECTIVE: To screen mutations of PDGFB gene in a large cohort of Chinese PFBC patients with no SLC20A2 mutations.
METHODS: We recruited 192 PFBC patients, including 21 index cases and 171 sporadic cases, in our study. Peripheral venous blood samples of all included participants were collected for genomic DNA extraction. The coding sequence of PDGFB was amplified by polymerase chain reaction (PCR) followed by direct sequencing. The potential effects of the identified variants on protein function were assessed by bioinformatics analysis.
RESULTS: Three missense variants (c.35G>T, c.232C>T, and c.610C>A) and one nonsense variant (c.220G>T) of PDGFB were identified in five sporadic PFBC patients. The variant c.35G>T was found in 2 healthy controls from the same ethnic background, whereas c.220G>T, c.232C>T and c.610C>A were absent from 500 controls. c.220G>T (p.E74*) produced a stop codon in the place of the glutamicacid residue number 74. c.232C>T (p.R78C) occurred at highly conserved regions and were predicted as damaging by at least two computational predictive programs, suggesting that this variant were likely to have a causal role in PFBC. Although variant c.610C>A (p.P204T) also occurred at a highly conserved region, it was predicted to be most likely benign by two computational predictive programs, suggesting an uncertain role of this variant on PFBC.
CONCLUSIONS: The present study identified one likely pathogenic variant (p.E74*) and two variants of uncertain significance (p.R78C and p.P204T) in PDGFB. Further studies of PDGF-B functional expression for these variants are still required to confirm the pathogenic effect.