Histone 4 acetylation regulates behavioral individuality in zebrafish

Behavioral individuality arises even in isogenic populations under identical environments, but its underlying mechanisms remain elusive. We found that inbred and isogenic zebrafish (Danio rerio) larvae showed consistent behavioral individuality when swimming freely in identical wells or in reaction to stimuli. We also found that behavioral individuality depends on the histone acetylation levels. Individuals with high levels of histone 4 acetylation behaved similar to the average of the population, but those with low levels deviated and showed behavioral individuality. More precisely, we found behavioral individuality to be related to individuality in histone 4 acetylation of a set of genomic regions related to neurodevelopment. We found evidence that this modulation depends on a complex of Yin Yang 1 (YY1) and histone deacetylase 1 (HDAC1). We suggest, using stochastic modelling, that this complex is part of the molecular machinery giving individuality in histone acetylation in neurodevelopmental genes ultimately responsible for behavioral individuality.