Interaction between SNP and age on PHV was detected for four SNPs that had a main effect (p<0.05) on PHV1 and/or PHV2 (Table 2). For SNPs rs6854783 in HHIP and rs10946808 in HIST1H1D adult height increasing alleles increased PHV in infancy but not in puberty (p = 0.045 and 0.0093). SNPs rs11107116 (in SOCS2, see Figure 1 for velocity by genotype and age), and rs12459350 (DOT1L), showed an effect on PHV in puberty but not in infancy (p = 0.0030 and 0.047). Given the strong biological argument for differential effects at different ages [14], we considered the SOCS2 and HIST1H1D interactions as suggestive and we also found a possible biological explanation for the SOCS2 interaction. The HHIP and DOT1L interactions are borderline significant (just below p<0.05) but for the former there is also a possible biological explanation (see Discussion).
