Oral-aboral axis specification in the sea urchin embryo II. Mitochondrial distribution and redox state contribute to establishing polarity in Strongylocentrotus purpuratus.

摘要: The initial asymmetry that specifies the oral–aboral (OA) axis of sea urchin embryo has long been a mystery. It was shown previously OA polarity can be entrained in embryos by imposing respiratory asymmetry, with most oxidizing side tending to develop as oral pole. This suggests one earliest observable asymmetries along incipient axis, redox gradient established higher density and/or activity mitochondria on prospective embryo, might play causal role establishing axis. Here, we examine origin and functional significance this early gradient. Using MitoTracker Green, show are asymmetrically distributed unfertilized egg Strongylocentrotus purpuratus, maternal is maintained zygote. Vital staining indicates inherits highest tends into correlation holds when redistributed centrifugation eggs or transfer purified zygotes, indicating an asymmetric mitochondrial distribution entrain polarity, possibly through effects intracellular state. In support possibility, find specification ectoderm suppressed cultured under hypoxic conditions enforce relatively reducing effect reversed overexpression nodal, zygotic marker whose localized expression suffices organize entire state upstream nodal expression. We therefore propose threshold level oxidation required effectively activate precocious attainment within blastomeres containing results consequent