Fig. 3

L1 promoter is hypomethylated in preterm neonates and its methylation is restored upon Early Intervention at NICU discharge. a Schematic representation of human (Hs) LINE-1 (L1): 5′ untranslated region (5′UTR) that contains the internal promoter, open reading frame 1 (ORF1), and open reading frame 2 (ORF2). ORF2 includes endonuclease (EN), reverse transcriptase (RT), and cysteine-rich domains (C); poly (A) tract (An). Within the L1 promoter are highlighted: CpG island (CpG 1–19), the neural-specific CpG (CpG 11–19, as reported in [31]), and YY1-binding site. b, c Methylation analysis of b L1 promoter and c L1 promoter neural-specific CpG 11–19 performed on genomic DNA extracted from whole cord blood of full-term (n = 20) and preterm neonates (n = 19) at birth and from whole peripheral blood of preterm infants at NICU discharge treated with standard care (n = 16) or early intervention (n = 17). In b, ***p < 0.001, full-term vs preterm; *p = 0.015, full-term vs standard care; **p = 0.008, preterm vs early intervention. in c, **p = 0.001, full-term vs preterm; ***p < 0.001, preterm vs early Intervention; *p = 0.015, standard care vs early intervention, unpaired two-tailed t test. d, e Scatter plot and linear regression line with 95% confidence band of weekly infant massages vs d L1 promoter methylation level (estimate: 1.8, p = 0.017) and vs e L1 promoter neural-specific CpG 11–19 methylation level (estimate: 2.0, p = 0.005) in the early intervention group (n = 17)