The Development of the Inner Ear in Mice Homozygous for Shaker-with-Syndactylism

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Abstract
A reinvestigation of the effects of the gene sy on the inner ear showed that the first abnormalities appear several days earlier than had hitherto been believed, and that they concern the periotic labyrinth and not the otic labyrinth. An excessive amount of mesenchymal tissue is laid down round certain, if not all, parts of the otic labyrinth in 13-day embryos, and as the periotic labyrinth is derived from this tissue it is abnormal. The abnormalities of the otic labyrinth appear at least 4 days later, and consist in a dedifferentiation of the epithelium and its penetration by the periotic mesenchymal tissue. As the otic labyrinth is surrounded by the periotic labyrinth, it is believed that the abnormalities of the former are consequent upon those of the latter, although the underlying mechanism is not understood. A possible connection has been suggested between the three major effects of the gene sy, namely, abnormalities of the inner ear, syndactylism, and defects of ossification involving the whole skeleton.