KPNA7, an oocyte- and embryo-specific karyopherin α subtype, is required for porcine embryo development

Coordinated partitioning of intracellular cargoes between nuclear and cytoplasmic compartments is critical for cell survival and differentiation. The karyopherin α/β heterodimer functions to import cytoplasmic proteins that possess classical nuclear localisation signals into the nucleus. Seven karyopherinαsubtypes have been identified in mammals. The aim of this study was to determine the relative abundance of transcripts encoding seven karyopherinαsubtypes in porcine oocytes and embryos at discrete stages of cleavage development, and to determine the developmental requirements of karypopherinα7 (KPNA7), an oocyte and cleavage stage embryo-specific karyopherinαsubtype. We hypothesised that knockdown of KPNA7 would negatively affect porcine cleavage development. To test this hypothesis, in vitro matured and fertilised porcine oocytes were injected with a double-stranded interfering RNA molecule that targeted KPNA7; nuclei were counted in all embryos 6 days after fertilisation. Embryos injected with KPNA7-interfering RNAs possessed significantly lower cell numbers than their respective control groups (P<0.05). In vitro binding assays also suggest that KPNA7 may transport intracellular proteins that possess unique nuclear localisation signals. Our data suggest that embryos have differential requirements for individual karyopherinαsubtypes and that these karyopherinαsubtypes differentially transport intracellular cargo during cleavage development.