He Ning, Zahirieh Alireza, Mei Yan, Lee Brian, Senthilnathan Sean, Wong Betty, Mucha Bettina, Hildebrandt Friedhelm, Cole David E, Cattran Daniel, Pei York
Division of Nephrology, Toronto General Hospital, University Health Network and University of Toronto, Toronto, Ontario, Canada.
Clin J Am Soc Nephrol. 2007 Jan;2(1):31-7. doi: 10.2215/CJN.02690806. Epub 2006 Oct 25.
Recessive NPHS2 (podocin) mutations account for up to approximately 30% of steroid-resistant idiopathic FSGS in children and are associated with a reduced risk for disease recurrence after renal transplantation. R229Q, a missense variant that is present in 3.6% of the white population, has been implicated as a common disease-causing mutation. Given these clinical implications, we examined the role of NPHS2 mutations in a cohort of patients with adult-onset FSGS. We used denaturing HPLC to screen for heterozygous and homozygous gene variants in PCR-amplified DNA fragments that contained all exons and splice junctions of NPHS2. Bidirectional sequencing was performed to define all of the gene variants detected. With the use of the denaturing HPLC in a single-blind pilot study, 40 of 43 known NPHS2 mutations were detected from 22 pediatric patients with FSGS to establish a test sensitivity of 93%. This screen then was applied to 87 adult patients with idiopathic FSGS (15 steroid-sensitive, 63 steroid-resistant, and nine familial cases). In this latter cohort, compound heterozygous mutations were detected only in one patient with steroid-sensitive FSGS (R229Q and Q285fsX302) and no homozygous mutations. Overall, R229Q accounted for eight (80%) of ten of the putative mutant alleles that were detected in the study cohort. Contrary to the pediatric experience, recessive NPHS2 mutations are rare in this study population, suggesting that the pathogenesis of FSGS in adults may differ from that in children. These data do not support R229Q as a disease-causing mutation for steroid-resistant FSGS.
隐性NPHS2（足突蛋白）突变在儿童类固醇抵抗性特发性局灶节段性肾小球硬化症（FSGS）中占比高达约30%，且与肾移植后疾病复发风险降低相关。R229Q是一种错义变异，在3.6%的白种人群中存在，被认为是一种常见的致病突变。鉴于这些临床意义，我们研究了NPHS2突变在一组成人起病的FSGS患者中的作用。我们使用变性高效液相色谱法（denaturing HPLC）在包含NPHS2所有外显子和剪接位点的PCR扩增DNA片段中筛选杂合子和纯合子基因变异。进行双向测序以确定所有检测到的基因变异。在一项单盲初步研究中，使用变性高效液相色谱法从22例FSGS患儿中检测到43个已知NPHS2突变中的40个，测试敏感性为93%。然后将该筛查应用于87例成人特发性FSGS患者（15例类固醇敏感型、63例类固醇抵抗型和9例家族性病例）。在这后一组患者中，仅在1例类固醇敏感型FSGS患者中检测到复合杂合突变（R229Q和Q285fsX302），未检测到纯合突变。总体而言，R229Q在研究队列中检测到的10个推定突变等位基因中占8个（80%）。与儿童患者的情况相反，隐性NPHS2突变在该研究人群中很少见，这表明成人FSGS的发病机制可能与儿童不同。这些数据不支持R229Q作为类固醇抵抗型FSGS的致病突变。
