Contralateral translocation of progenitor retinal cells observed on bifurcation of the primordial eye field is predicted by the Inversion Hypothesis

Rodger Guy Loosemore


Though counter-intuitive, the origins of vertebrate forebrain contralaterality as proposed by the Inversion Hypothesis, are nonetheless eminently predictable. The hypothesis proposes that contralaterality developed to support an evolving single frontal eye in ancestral craniates, predating bilateral vision and development of the optic chiasm. Its most empirically accessible prediction claims that on bifurcation of the embryonic primordial eye field, the majority of progenitor retinal cells (PRCs) must cross the midline to become mature retinal cells in the contralateral eye, in the process creating an incipient optic chiasm. Here we show, by way of a focused review, that, despite a general belief to the contrary, such a translocation has previously been demonstrated in both zebrafish and Xenopus frog embryos.


Contralaterality; optic primordium; optic chiasm; Inversion Hypothesis


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