Sleep Architecture in Mice Is Shaped by the Transcription Factor AP-2β

Abstract

The molecular mechanism regulating sleep largely remains to be elucidated. In humans, families that carry mutations in TFAP2B, which encodes the transcription factor AP-2β, self-reported sleep abnormalities such as short-sleep and parasomnia. Notably, AP-2 transcription factors play essential roles in sleep regulation in the nematode Caenorhabditis elegans and the fruit fly Drosophila melanogaster Thus, AP-2 transcription factors might have a conserved role in sleep regulation across the animal phyla. However, direct evidence supporting the involvement of TFAP2B in mammalian sleep was lacking. In this study, by using the CRISPR/Cas9 technology, we generated two Tfap2b mutant mouse strains, Tfap2b^K144 and Tfap2b^K145 , each harboring a single-nucleotide mutation within the introns of Tfap2b mimicking the mutations in two human kindreds that self-reported sleep abnormalities. The effects of these mutations were compared with those of a Tfap2b knockout allele (Tfap2b^-). The protein expression level of TFAP2B in the embryonic brain was reduced to about half in Tfap2b^+/- mice and was further reduced in Tfap2b^-/- mice. By contrast, the protein expression level was normal in Tfap2b^K145/+ mice but was reduced in Tfap2b^K145/K145 mice to a similar extent as Tfap2b^-/- mice. Tfap2b^K144/+ and Tfap2b^K144/K144 showed normal protein expression levels. Tfap2b^+/- female mice showed increased wakefulness time and decreased nonrapid eye movement sleep (NREMS) time. By contrast, Tfap2b^K145/+ female mice showed an apparently normal amount of sleep but instead exhibited fragmented NREMS, whereas Tfap2b^K144/+ male mice showed reduced NREMS time specifically in the dark phase. Finally, in the adult brain, Tfap2b-LacZ expression was detected in the superior colliculus, locus coeruleus, cerebellum, and the nucleus of solitary tract. These findings provide direct evidence that TFAP2B influences NREMS amounts in mice and also show that different mutations in Tfap2b can lead to diverse effects on sleep architecture.

Keywords: Char syndrome; mouse; sleep; transcription factor.