The expression of 350 miRNAs during the rat epididymal development was profiled by a home-made miRNA microarray recently. The results showed that the expression of miR-335 decreased from postnatal day 7 to 49 in the rat epididymis. Few studies on miR-335's roles in the epididymis and its targets have been reported so far. The bioinformatic analysis indicated that one of miR-335's putative targets is RASA1, a known gene related to cell proliferation and anti-apoptosis, which may contribute to the epididymal development. It was found that the overexpression of miR-335 in NIH/3T3 cells caused the suppression of RASA1 expression. The result of luciferase targeting assay confirmed that the mRNA of RASA1 was targeted by miR-335. In addition, it was also found that the temporal expression of RASA? was inverse to that of miR-335 during the epididymal development in the rat. These results indicated that the reduction of miR-335 at least in part caused the upregulation of RASA1 in the rat epididymis. Therefore, miR-335 can be involved in the epididymal development by affecting the expression of RASA1. (C) 2010 Elsevier Inc. All rights reserved.