Although the presence of Azin2 mRNA in mouse spermatids suggested that AZIN2 may have a role in spermiogenesis, other studies showing AZIN2 immunoreactivity in mast cells as well as in BI-D1870 Leydig cells and ovarian luteinized cells have related AZIN2 with the release of serotonin and steroid hormones. In addition, our studies using real-time RT-PCR detected significant Azin2 mRNA levels in several mouse tissues, including pancreas and adrenal glands, similar to those existing in brain. Since the analysis of Azin2 mRNA levels gives only a partial view of the expression of the gene and it is not clear whether the available antibodies against AZIN2 may react with other proteins Nilotinib different to AZIN2, we decided to generate a transgenic mice with a truncated Azin2 gene fused to the bacterial lacZ gene under control of the Azin2 promoter, in order to carry out a more detailed analysis of the cellular patterns of AZIN2 expression in mouse tissues. This Azin2 transgenic mouse model could be also useful to progress in the knowledge of the physiological function of AZIN2. We report here that Azin2 is expressed, as previously known, in testis and brain, but interestingly also in pancreas and adrenal glands, reinforcing the idea that this protein may have a role in the function of endocrine secretory cells. Next, we carried out a histochemical analysis of lacZ expression in different mouse tissues. Only heterozygous mice were used for b-D-galactosidase histochemical staining. Azin2bGeo/+ mice did not display any evident phenotype. It is important to note that the gene product from the recombinant allele comprises the Nterminal 92 amino acid residues of native AZIN2, the critical sequence that drives AZIN2 to its subcellular localization in the Endoplasmic Reticulum-Golgi Intermediate Compartment, and therefore it can be considered that the pattern of b- D-galactosidase staining might be informative of the native localization of AZIN2. Amidst those tissues, we detected histochemical signal in testis, pancreas, epididymis, brain and adrenal gland. Lung and other tissues expressing lower levels of b-Dgalactosidase did not show any detectable staining. Endogenous b-D-galactosidase activity at experimental conditions was only detectable in proximal epithelium of the epididymis. As mentioned in the introduction, the high expression of Azin2 mRNA in testis and brain is a widely known fact. The histochemical analysis of b-D-galactosidase in the testis revealed that the protein was mainly expressed in the inner part of the seminiferous tubules, where spermatids and spermatozoa are located.