NPAS2 as a transcriptional regulator of non-rapid eye movement sleep: genotype and sex interactions.

Because the transcription factor neuronal Per-Arnt-Sim-type signal-sensor protein-domain protein 2 (NPAS2) acts both as a sensor and an effector of intracellular energy balance, and because sleep is thought to correct an energy imbalance incurred during waking, we examined NPAS2's role in sleep homeostasis using npas2 knockout (npas2-/-) mice. We found that, under conditions of increased sleep need, i.e., at the end of the active period or after sleep deprivation (SD), NPAS2 allows for sleep to occur at times when mice are normally awake. Lack of npas2 affected electroencephalogram activity of thalamocortical origin; during non-rapid eye movement sleep (NREMS), activity in the spindle range (10-15 Hz) was reduced, and within the delta range (1-4 Hz), activity shifted toward faster frequencies. In addition, the increase in the cortical expression of the NPAS2 target gene period2 (per2) after SD was attenuated in npas2-/- mice. This implies that NPAS2 importantly contributes to the previously documented wake-dependent increase in cortical per2 expression. The data also revealed numerous sex differences in sleep; in females, sleep need accumulated at a slower rate, and REMS loss was not recovered after SD. In contrast, the rebound in NREMS time after SD was compromised only in npas2-/- males. We conclude that NPAS2 plays a role in sleep homeostasis, most likely at the level of the thalamus and cortex, where NPAS2 is abundantly expressed.

The neuronal PAS domain protein 3 transcription factor controls FGF-mediated adult hippocampal neurogenesis in mice.

The neuronal PAS domain protein 3 (NPAS3) gene encoding a brain-enriched transcription factor was recently found to be disrupted in a family suffering from schizophrenia. Mice harboring compound disruptions in the NPAS3 and related NPAS1 genes manifest behavioral and neuroanatomical abnormalities reminiscent of schizophrenia. Herein we demonstrate that Npas3-/- mice are deficient in expression of hippocampal FGF receptor subtype 1 mRNA, most notably in the dentate gyrus. In vivo BrdUrd-labeling shows that basal neural precursor cell proliferation in the dentate gyrus of Npas3-/- mice is reduced by 84% relative to wild-type littermates. We propose that a deficiency in adult neurogenesis may cause the behavioral and neuroanatomical abnormalities seen in Npas3-/- mice, and we speculate that impaired neurogenesis may be involved in the pathophysiology of schizophrenia.

Altered patterns of sleep and behavioral adaptability in NPAS2-deficient mice.

Animal behavior is synchronized to the 24-hour light:dark (LD) cycle by regulatory programs that produce circadian fluctuations in gene expression throughout the body. In mammals, the transcription factor CLOCK controls circadian oscillation in the suprachiasmatic nucleus of the brain; its paralog, neuronal PAS domain protein 2 (NPAS2), performs a similar function in other forebrain sites. To investigate the role of NPAS2 in behavioral manifestations of circadian rhythm, we studied locomotor activity, sleep patterns, and adaptability to both light- and restricted food-driven entrainment in NPAS2-deficient mice. Our results indicate that NPAS2 plays a substantive role in maintaining circadian behaviors in normal LD and feeding conditions and that NPAS2 is critical for adaptability to food restriction.