Fig. 1.

Pumilio proteins are required for embryogenesis and normal growth. (A) Immunofluorescence staining of Pum1 in wild-type ESCs. Pum1 is diffusely cytoplasmic and is enriched in the nuclear periphery of some mitotic cells (arrows). Nuclei were counterstained with DAPI (blue). (B) Immunofluorescence staining of e2.5 morulae (Upper) and e3.5 blastocysts (Lower). Pum1 is expressed in both inner cell mass (ICM) and trophoblast (TB) cells, with greater cytoplasmic expression levels in the ICM. (C and D) Phenotype of P28 (C) and 11-mo-old (D) wild-type (wt), Pum1^+/−, and Pum1^−/− littermates. Pum1^−/− mice have a hunched appearance that becomes more prominent with age and weigh 43% less than wild-type mice (D, Upper Right). (E and F) Body weight (in grams) of wild-type (solid line), Pum1^+/− (dashed line), and Pum1^−/− (dotted line) littermates at P1, P7, P14, P21, and P28. P28 Pum1^−/− mice weigh 35% less than wild-type mice. Error bars indicate SEM. *P value < 0.01. (G) Deviation of the ratio of observed from expected genotypes of a Pum1^+/−; Pum2^+/− x Pum1^+/−; Pum2^+/− mating at e3.5 (dark gray, n = 52), e8.5 (light gray, n = 36), e9.5 (pink, n = 21), e12.5 (red, n = 23), and P1 (dark red, n = 127). The observed ratio of Pum1^−/−; Pum2^+/− pups is 65% less than expected at P1. No Pum1^−/−; Pum2^−/− pups were recovered at e9.5, e12.5, and 1dpp. * and ***indicates P < 0.01 and <0.001, respectively. (H) Morphology and average weight (in grams) of P1 wild-type, Pum1^+/−; Pum2^−/−, and Pum1^−/−; Pum2^+/− littermates. Pum1^+/−; Pum2^−/− pups weigh 29% less than WT littermates; Pum1^−/−; Pum2^+/− pups weigh 38% less than WT littermates, have no milk in their stomachs, and die within 24 h of birth. (I) Phenotype of P28 Pum-deficient mice; Pum1^−/− mice are smaller than Pum2^−/− mice and Pum1^+/−; Pum2^+/− mice, which are both indistinguishable from wild type at this age.