van Schaarenburg Rosanne A, Daha Nina A, Schonkeren Joris J M, Nivine Levarht E W, van Gijlswijk-Janssen Danielle J, Kurreeman Fina A S, Roos Anja, van Kooten Cees, Koelman Carin A, Ernst-Kruis Margot R, Toes Rene E M, Huizinga Tom W J, Lankester Arjan C, Trouw Leendert A
Department of Rheumatology, Leiden University Medical Center, Leiden, The Netherlands.
Department of Nephrology, Leiden University Medical Center, Leiden, The Netherlands.
Immunobiology. 2015 Mar;220(3):422-7. doi: 10.1016/j.imbio.2014.10.005. Epub 2014 Oct 18.
C1q deficiency is a rare genetic disorder that is strongly associated with development of systemic lupus erythematosus (SLE). Several mutations in the coding regions of the C1q genes have been described that result in stop-codons or other genetic abnormalities ultimately leading to C1q deficiency. Here we report on a Dutch boy suffering from recurrent infections with a complete C1q deficiency, without any SLE symptoms.
The presence of C1q in serum was assessed using ELISA and hemolytic assay. By western blot we examined the different C1q chains in cell lysates. We identified the mutation using deep-sequencing. By qPCR we studied the mRNA expression of C1qA, C1qB and C1qC in the PBMCs of the patient.
Deep-sequencing revealed a homozygous mutation in the non-coding region of C1qB in the patient, whereas both parents were heterozygous. The mutation is located two nucleotides before the splice site of the second exon. In-silico analyses predict a complete abrogation of this natural splice site. Analyses of in vitro cultured cells from the patient revealed a lack of production of C1q and intracellular absence of C1qB in the presence of C1qA and C1qC peptides. Quantitative PCR analysis revealed total absence of C1qB mRNA, a reduced level of C1qA mRNA and normal levels of C1qC mRNA.
In this study we report a new mutation in the non-coding region of C1qB that is associated with C1q deficiency.
C1q缺乏是一种罕见的遗传性疾病，与系统性红斑狼疮（SLE）的发生密切相关。已描述了C1q基因编码区的几种突变，这些突变导致终止密码子或其他基因异常，最终导致C1q缺乏。在此，我们报告一名患有复发性感染且C1q完全缺乏但无任何SLE症状的荷兰男孩。
使用酶联免疫吸附测定（ELISA）和溶血测定评估血清中C1q的存在。通过蛋白质印迹法，我们检测了细胞裂解物中不同的C1q链。我们使用深度测序鉴定了该突变。通过定量聚合酶链反应（qPCR），我们研究了患者外周血单核细胞（PBMC）中C1qA、C1qB和C1qC的mRNA表达。
深度测序显示该患者C1qB的非编码区存在纯合突变，而其父母均为杂合子。该突变位于第二个外显子剪接位点前两个核苷酸处。计算机分析预测该天然剪接位点将完全失效。对患者体外培养细胞的分析显示，在存在C1qA和C1qC肽的情况下，缺乏C1q的产生且细胞内不存在C1qB。定量PCR分析显示完全不存在C1qB mRNA，C1qA mRNA水平降低，C1qC mRNA水平正常。
在本研究中，我们报告了C1qB非编码区一个与C1q缺乏相关的新突变。
