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^-6 mol/l, 24 h) 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 AngRem104 induced by Ang II was time-dependent and was dose-dependently 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. (Hypertens Res 2003; 26: 225-235)