Effects of butyrate on the expression and epigenetic modifications of the γ- and β-globin genes. Mononuclear cells from 5 patients with SCD (+, ×, □, ▵, ○) were cultured into BFU-E–derived colonies in the absence and presence of butyrate. mRNA levels were measured by quantitative real-time RT-PCR and expressed as percentage γ/(β + γ) and percent β/(β + γ). The levels of acetylation of histones H3 and H4 are expressed in relative units and are presented as the sum of acH3 and acH4 (acH3 + acH4). The levels of DNA methylation at the promoters of γ- and β-globin genes are expressed as the mean of methylation levels at all CpG sites (ie, 5 sites for γ-globin and 3 sites for β-globin). Solid horizontal lines represent the mean values for every condition.