IgA肾病患者Cosmc基因表达低下原因探讨

Causes of reduced expression of Cosmc gene in IgA nephropathy patients

目的探讨IgA肾病（IgAN）患者核心181，3半乳糖基转移酶伴侣蛋白（Cosmc）表达低下的原因，到底是基因突变还是外源性抑制。方法40例IgAN患者、16例非IgAN。肾小球。肾炎患者、21例健康对照被纳入本研究。直接测序方法测定Cosmc基因外显子区域的核酸序列。免疫磁珠分离IgAN患者、非IgAN肾小球肾炎患者和健康对照者外周血B淋巴细胞，并分别在RPMI-1640及RPMI—1640＋脂多糖（LPS）中培养72h。实时荧光RT—PCR方法测定Cosmc基因的mRNA表达水平。结果（1）IgAN患者Cosmc基因外显子区域没有共同突变位点，仅在2例患者中发现2处错义突变和2处无意义突变，而且这些突变并不影响患者Cosmc基因的表达：（2）IgAN患者外周血B淋巴细胞的基础Cosmc基因表达显著降低，为健康对照组的31％。（3）经RPMI-1640培养后，IgAN患者Cosmc基因的表达水平升高至基础值的219％。RPMI—1640＋LPS组Cosmc基因的上调受到明显抑制。（4）健康对照Cosmc基因的表达不受RPMI-1640和LPS的影响。结论IgAN患者外周血B淋巴细胞Cosmc基因表达低下可能与基因突变无关，而是受外源性抑制因素影响所致．

Objective To clarify whether the Cosmc gene down-regulation in lgA nephropathy （IgAN） patients is resulted from genetic disorders or external suppressions. Methods Forty IgAN patients, 16 non-IgAN glomemlonephritis patients and 21 healthy controls were enrolled in the study. Genomic DNA was extracted and then Cosmc gene was amplified and sequenced. Peripheral B lymphocytes were isolated and cultured with RPMI-1640 alone or plus lipopolysaccharide （LPS）. The Cosnw mRNA expression levels at baseline, after RPMl-1640 culture or RPMI-1640＋LPS treatment were measured respectively by real-time RT-PCR. Results （1） Only 2 missense mutations and 2 silent mutations were detected in coding frame region of Cosmc gene in 2 IgAN patients. （2） The baseline Cosmc gene expression level was significantly lower in IgAN patients （31% of that in healthy controls） than that in healthy controls. （3） Relative quantification PCR indicated that Cosmc mRNA expression level was significantly increased （219% of baseline） after RPMI-1640 culture, and treatment of LPS could strongly inhibit this effect. （4） The Cosmc gene expression of healthy control was not affected by RPMI-1640 or LPS. Conclusion It is not genetic disorders but external suppression to cause the down-regulatlon of Cosmc gene mRNA expression in IgAN.