Qin Wei, Zhong Xiang, Fan Jun Ming, Zhang Ying Juan, Liu Xian Rong, Ma Xing Yi
Division of Nephrology, Sichuan University West China Hospital, 37# Guoxue Xiang, Wu Hou District, Chengdu, Sichuan Province 610041, People's Republic of China.
Nephrol Dial Transplant. 2008 May;23(5):1608-14. doi: 10.1093/ndt/gfm781. Epub 2008 Jan 17.
IgA(1) aberrant O-glycosylation is one of the main pathogeneses of IgA nephropathy (IgAN), and the core I beta3-Gal-T-specific molecular chaperone (Cosmc) mRNA expression of IgAN patients was significantly decreased. This study tried to clarify whether the down-regulation was a result of genetic disorders or external suppressions.
Sixty-five IgAN patients, 23 non-IgAN glomerulonephritis patients and 21 normal controls were recruited. Genomic DNA was extracted and the Cosmc gene was PCR amplified and directly sequenced. Peripheral B lymphocytes of IgAN patients and normal controls were isolated, and cultured with RPMI-1640 alone or with lipopolysaccharide (LPS) for 72 h. The Cosmc mRNA expression levels at baseline, after RPMI culture or RPMI + LPS treatment were measured by real-time RT-PCR.
(1) The whole coding frame region of the Cosmc gene was successfully amplified and directly sequenced. Four single nucleotide polymorphisms were detected in two IgAN patients. Two were missense mutations and the others were silent mutations. However, they are different from each other, and unrelated to expression levels; (2) the baseline Cosmc mRNA expression in IgAN patients was significantly lower than normal controls (Ct(COSMC/GAPDH) 1.29 +/- 0.08 versus 1.20 +/- 0.01, 31% of normal controls); (3) the Cosmc mRNA expression level of IgAN patients was remarkably increased after the RPMI culture (1.22 +/- 0.12 versus 1.29 +/- 0.08, 219% of the baseline level), while not in normal controls and (4) treatment with LPS (culture with RPMI + LPS) could strongly inhibit the expression of Cosmc mRNA (1.25 +/- 0.01 versus 1.22 +/- 0.12, 61% of the RPMI treatment group).
No common Cosmc gene mutation was detected. Significantly increased Cosmc expression was observed in plasma-free culture, while LPS could significantly inhibit it, which suggested that it might not be genetic disorders but external suppression that causes the low Cosmc mRNA expression in IgAN.
IgA(1)异常O-糖基化是IgA肾病（IgAN）的主要发病机制之一，IgAN患者的核心Iβ3-半乳糖基转移酶特异性分子伴侣（Cosmc）mRNA表达显著降低。本研究试图阐明这种下调是遗传紊乱还是外部抑制的结果。
招募65例IgAN患者、23例非IgAN肾小球肾炎患者和21例正常对照。提取基因组DNA，对Cosmc基因进行PCR扩增并直接测序。分离IgAN患者和正常对照的外周血B淋巴细胞，分别单独用RPMI-1640或与脂多糖（LPS）一起培养72小时。通过实时RT-PCR测量基线、RPMI培养后或RPMI + LPS处理后的Cosmc mRNA表达水平。
（1）成功扩增并直接测序了Cosmc基因的整个编码框区域。在两名IgAN患者中检测到四个单核苷酸多态性。两个是错义突变，其他是沉默突变。然而，它们彼此不同，且与表达水平无关；（2）IgAN患者的基线Cosmc mRNA表达明显低于正常对照（Ct(COSMC/GAPDH) 1.29±0.08对1.20±0.01，为正常对照的31%）；（3）RPMI培养后IgAN患者的Cosmc mRNA表达水平显著增加（1.22±0.12对1.29±0.08，为基线水平的219%），而正常对照则未增加；（4）LPS处理（RPMI + LPS培养）可强烈抑制Cosmc mRNA的表达（1.25±0.01对1.22±0.12，为RPMI处理组的61%）。
未检测到常见的Cosmc基因突变。在无血浆培养中观察到Cosmc表达显著增加，而LPS可显著抑制其表达，这表明导致IgAN中Cosmc mRNA低表达的可能不是遗传紊乱而是外部抑制。
