Temporal and spatial expression of a fos-lacZ transgene in the developing nervous system.

A Fos-lacZ transgenic mouse has been described that accurately recapitulates both constitutive and inducible patterns of c-fos expression in adult mice. Here we describe the developmental expression of the transgene in the brain during the early postnatal period. On the day of birth, expression of the transgene is observed in several discrete regions of the CNS; including the olfactory bulb, hippocampus, retrosplenial cortex, parafascicular nucleus of the thalamus, and several cranial nerve nuclei. In these regions, expression declines to adult levels by three weeks. In other regions of the CNS, expression appeared transiently after P0.