Sp1 variant in COLIA1 affects bone density prior to and during puberty in females. aBMD and BMC age, sex, and population ancestry-specific Z-scores were calculated and further adjusted for height-for-age Z-scores. A. Main effects by genotype for lumbar spine and femoral neck aBMD Z-scores. B. Puberty interactions by genotype for lumbar spine and femoral neck aBMD Z-scores. T1, Tanner stage 1 (pre-pubertal); T2-T4, Tanner stages 2 to 4 (pubertal); T5, Tanner stage 5 (post-pubertal). P-values in column A are for the main variant associations; P-values in column B are for the variant-puberty stage interactions. TBLH, total body less head.