Maternal rather than embryo hepcidin determines embryo iron endowment. To determine the relative contribution of maternal vs embryo hepcidin to the regulation of embryo iron endowment, Hamp Het and KO females were mated with Hamp Het males to generate Hamp WT, Het, and KO embryos. Mothers and embryos were analyzed on E18.5 for maternal serum iron (A) and liver non-heme iron (B) concentrations. Statistical comparisons were performed by 2-tailed Mann-Whitney rank-sum test for nonnormally distributed values (indicated by * following P values) or 2-tailed t test with Welch’s correction for normally distributed but nonequal variance data sets (indicated by ^# after the P value) for embryo serum iron (C), embryo liver nonheme iron (D), and placenta nonheme iron (E) concentrations. (F) Western blot for FPN and TFR1 from E18.5 Hamp WT, Het, and KO placentas, derived from either Hamp Het mothers and Hamp KO mothers. GAPDH was used as a loading control. FPN was run on 2 separate blots, as indicated by a line; TFR1 was run on a single blot. (G) Quantification of placental FPN across different maternal and embryo genotypes. FPN was normalized to GAPDH for loading. To normalized FPN levels between blots, 4 samples from each of the 2 blots were rerun together on a separate blot. (H) Quantification of placental TFR1 across different maternal and embryo genotypes. TFR1 was normalized to GAPDH. (I) Calculated PIDI, the ratio of placental FPN to TFR1 protein. (C-E, G-I) Statistical differences between groups was determined by 2-way analysis of variance for embryo vs mother Hamp genotype. Mat, maternal.