The Hedgehog (Hh) signaling pathway plays an important role in various biological processes, including pattern formation, cell fate determination, proliferation, and differentiation. Hh function is mediated through its membrane receptor Patched. Herein, we have characterized a novel Patched-domain containing gene Ptchd3 in mouse. Messenger RNA of Ptchd3 was exclusively detected in the testis, and existed in two isoforms Ptchd3a, and Ptchd3b. The expression of these two mRNA isoforms was shown to be developmentally regulated in testes, and specifically found in male germ cells. Further analysis revealed that the Ptchd3 protein was located on the midpiece of mouse, rat and human sperm. Collectively, these results indicate that Ptchd3 is a novel male germ cell-specific gene and may be involved in the Hh signaling to regulate sperm development and/or sperm function. (C) 2007 Elsevier Inc. All rights reserved.