A longevity gene product, Sir2 (silent information regulator 2) is a NAD-dependent histone deacetylase involved in longevity in yeasts, worms and flies. The mammalian homolog of Sir2, SIRT1(sirtuin 1), has been shown to play important roles related to anti-aging effects (regulating apoptosis, stress tolerance, insulin resistance, and fat metabolism). Recently, SIRT1 expression has been demonstrated to occur at as early as embryonic day 10.5 in mice. SIRT1 during developing period may be involved in the mechanism of developmental origins of adult diseases, such as diabetes and cardiovascular disease. To investigate the contribution of SIRT1, it is important to reveal the distribution of this protein during development. In the present study, we demonstrated the distribution of immunoreactivity of SIRT1 in mouse organs during prenatal and neonatal development by staining a wide variety of serial sections. The SIRT1 immunoreactivity was strongly observed in the neuroepithelial layer, dorsal root ganglion, trigeminal ganglion, eyes, roots of whiskers, and internal organs, including the testis, liver, heart, kidney, and lung during the fetal period. Neurons which had finished migrating still showed relatively strong immunoreactivity. The immunoreactivity was completely absorbed by the blocking peptide in an absorption test. During the postnatal period, the immunoreactivities in most of these organs, except the heart and testis weakened, with the liver most dramatically affected. As SIRT1 expression was demonstrated in a wide variety of developing organs, further study to investigate prenatal factors which affect SIRT1 expression and its activity is important.
