Generation and functional characterization of a conditional Pumilio2 null allele.

The highly conserved RNA binding protein PUF (Pumilio/FBF) family is present throughout eukaryotes from yeast to mammals, with critical roles in development, fertility and the nervous system. However, the function of the mammalian PUF family members remains underexplored. Our previous study reported that a gene-trap mutation of Pum2 results in a smaller testis but does not impact fertility and viability. Although the gene-trap mutation disrupted the key functional domain of PUM protein-PUM-HD (Pumilio homology domain), but still produced a chimeric Pum2-β-geo protein containing part of PUM2, raising a question if such a chimeric protein may provide any residual function or contribute to the reproductive phenotype. Here, we report the generation of a conditional PUM2 allele, when knocked out, producing no residual PUM2 and hence a complete loss-of-function allele. We also uncovered small but significant reduction of male fertility and viability in the mutants, suggesting requirement of PUM2 for male fertility and viability.