FIG 4.

Mpc1 hypomorphic allele reveals a requirement for mitochondrial pyruvate metabolism in mammalian embryonic development. (A and B) Western blotting (A) and qRT-PCR (B) for Mpc1 and Mpc2 in tissues from e17.5 embryos carrying 0, 1, or 2 copies of the Mpc1 hypomorphic KI allele. Hsc70 is shown as a loading control. The RT-PCR data were normalized to the average of four reference genes as described in Materials and Methods and are presented as means plus SEM relative to the WT (n = 7 or 8 per genotype). (C) [2-¹⁴C]pyruvate incorporation into the total lipid fraction in Mpc1-deficient primary MEFs in the presence of the MPC inhibitor UK-5099 or vehicle (DMSO) (means plus SEM; n = 5). (D) Matings between mice heterozygous for the Mpc1 KI allele do not yield expected Mendelian ratios of offspring at weaning at P21; however, the expected Mendelian ratios were observed in late-gestation litters (embryonic day 17.5). (E) Body weights (means ± SD) of e17.5 embryos from KI/+ intercrosses (n = 17 to 34 from 8 litters). (F) Steady-state lactate concentrations in Mpc1^KI/KI e17.5 liver and brain as determined by enzymatic assay (means plus SEM; n = 6). (G) Steady-state ATP concentrations in liver and brain of Mpc1^KI/KI e17.5 embryos and littermate controls (means plus SEM; n = 5). Significant differences among group means determined by Tukey multiple-comparison test after one-way ANOVA relative to WT and D/+ controls are indicated by asterisks (***, P < 0.001).