Development of left/right symmetry and asymmetry, Kartagener's syndrome, and cerebral laterality.
The anteroposterior and the dorsoventral axes plus two semiaxes orthogonal to the median plane can give enantiomorphic positional information to the two halves of the embryo. This kind of positional information can both determine the development of bilateral symmetry and mark left and right. Left/right asymmetry may be caused by a generative programme that operates on the three orthogonal coordinates of one side. The chirality of the asymmetry will thus depend on which side the programme operates. Kartagener's syndrome can be explained by considering that a ciliation-or-division switch involved in gastrulation assigns the generative programme to one side by creating a difference in the growth rate between the two halves of the embryo: in the syndrome a defect of ciliation blocks the switch, and the generative programme is assigned randomly. The model may be of particular utility for cerebral L/R asymmetries, for which a distinction from truncal L/R asymmetries is proposed.
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D000818:Animals; D005314:Embryonic and Fetal Development; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007619:Kartagener Syndrome / Q000209:etiology* / Q000503:physiopathology; D051381:Rats