目的探讨肾脏特异性表达新基因Collectrin在大鼠5/6肾切除残余肾组织中的表达变化，为Collectrin基因功能研究提供线索。方法建立慢性肾衰大鼠5/6肾切除模型，分为对照组（10只）、手术组（12只）和依那普利治疗组（12 只），采用逆转录2PCR和Western蛋白印迹、免疫组织化学技术检测手术后2、8和16周大鼠肾组织Collectrin的表达变化。结果在对照组中，随着大鼠周龄的增长大鼠Collectrin mRNA表达逐渐减少。2,8,16周分别为，11690109，1138±0104，1121±0109，（P<0105）；在术后2，8，16周，手术组（2133±0107，1185±0120，1147±0117）Collectrin表达明显高于对照组（1169±0109，1138±0104，1121±0109，P<0105；经依那普利治疗，Collectrin 表达明显减少；手术组Collectrin的表达在手术后2周明显增加，随着慢性肾衰的进Collectrin的表达逐渐减少。2，8，16周分别为2133±0107，1185±0120，1147±0117（P<0105）。Collectrin蛋白的表达情况与Collectrin mRNA表达情况相一致。结论Collectrin的表达随大鼠周龄的增长而减少；在5/6肾切除残余肾组织中，Collectrin的表达与肾脏的增生、肥大的病生理变化相关。

为探讨collectrin在人类疾病中的作用，利用人类collectrin同源性引物，经末端cDNA快速扩增法分离获得人collectrin基因全长序列并对collectrin 进行生物信息学分析及定位表达研究。结果发现，人类llectrin （GenBank 登录号为AF229179）基因全长含1345 bp，开放阅读框架编码222个氨基酸。在核苷酸和氨基酸水平，与小鼠collectrin序列分别有8619%和8714%同源性。生物信息学分析结果提示，collectrin为一个25kD的具有一个信号肽和一个跨膜区的跨膜糖蛋白。人类collectrin与人类血管紧张素转换酶相关的羧基肽酶（ACE2）具有4718%高度同源性。人多组织Northern杂交结果显示：collectrin基因为人类肾脏特异性表达基因。原位杂交及免疫组化证实，与小鼠collectrin 特异表达于集合管细胞不同，人collectrin基因mRNA及其蛋白产物除位于肾脏集合管细胞外，远曲肾小管细胞也有表达。由此推论，人类collectrin 基因为肾脏特异性表达基因，与人类血管紧张素转换酶相关的羧基肽酶具有高度同源性，可能为血管紧张素转换酶（ACE）基因家族的新成员。

Accumulation of extracellular matrix (ECM) in the glomerular mesangium is a common feature of many progressive renal diseases. Angiotensin II (Ang II) plays a major role in the progression of chronic kidney diseases in part by induction of ECM. However, the precise molecular signals responsible for this effect are unknown. To explore possible molecular mechanisms of ECM production related to Ang II, we screened and identified genes up-regulated by Ang II in cultured human mesangial cells (MC). Detection of up-regulated genes was determined by mRNA populations from human MC with and without Ang II stimulation (10-6mol/l, 24h) by suppression subtractive hybridization. Reverse Northern blot analysis was performed to screen for differentially expressed genes. Full-length cDNAs of three novel genes were isolated by rapid amplification of cDNA ends (RACE)-polymerase chain reaction (PCR). One of these novel genes, AngRem104, was further investigated by Northern blot, Western blot and reverse transcription (RT)-PCR. The bioinformatics analysis implied that AngRem104 coded for a nuclear protein that was widely expressed in various normal human tissues. Moreover, up-regulation of ngRem104 induced by Ang II was time-dependent and was dosedependently blocked by the Ang II type 1 receptor antagonist, Losartan. Interestingly, we also demonstrated that AngReam104 was associated with increased fibronectin expression. We conclude that AngRem104 is a novel human gene that is related to the expression of fibronectin and that is up-regulated by Ang II in human MC. These findings may lead to new insights into the mechanisms of glomerular sclerosis associated with Ang II

Collectrin, a novel homolog of angiotensin-converting enzyme-related carboxypeptidase (ACE2), was identified during polymerase chain reaction-based cDNA subtraction and up-regulated in 5/6 ablated kidneys at hypertrophic phase. Collectrin, with 222 amino acids, has an apparent signal peptide and a transmembrane domain; the sequence is conserved in mouse, rat, and human and shares 81.9% identity. Human collectrin has 47.8% identity with non-catalytic extracellular, transmembrane, and cytosolic domains of ACE2; however, unlike ACE and ACE2, collectrin lacks active dipeptidyl carboxypeptidase catalytic domains. The collectrin mRNA transcripts are expressed exclusively in the kidney. In situ hybridization reveals its mRNA expression in renal collecting ducts, and immunohistochemistry shows that it is localized to the luminal surface and cytoplasm of collecting ducts. Immunoprecipitation studies, using [35S]methionine-labeled renal cortical and inner medullar collecting duct cells, i.e. M-1 and mIMCD-3, indicate that the protein size is; 32kDa. During the development of mouse kidney, mRNA signal is detectable at day 13 of gestation, and the protein product is observed in the ureteric bud branches. Its expression is progressively increased during later stages of the gestation extending into the neonatal periods and then is decreased in adult life. Up-regulated expression of collectrin in the hypertrophic kidneys after renal ablation and restricted spatio-temporal expression during development indicates a possible role (s) in the process of progressive renal failure and renal organogenesis.

AngRem104 is a novel gene recently identified in human mesangial cells induced by angiotensin II. cDNA microarray was performed to screen the functional genes related to AngRem104. Thirty-one genes were up-regulatedwhile 2 genes were down-regulated. Of all the up-regulated genes, fibronectin, one of the major extracellular matrixes, was up-regulated with over-expression of AngRem104.