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The existence of a genetic disease caused by immotile cilia was reported in a short paper published in 1976.1 The prevalence was estimated to be one person in about 30 000. The following facts made it possible to draw these conclusions.
Cilia from the lung, nose, or elsewhere have a structure that is highly conservative and, moreover, resembles that of the sperm flagellum. The central part of the sperm tail, its axoneme, thus has the same well known 9 + 2 pattern as has a cilium, although it is about 50 μm long whereas the human cilium is only about 6 μm in length (fig1).
Schematic cross section of a ciliary axoneme. The central part of the spermatozoan flagellum has an identical ultrastructure. Nine microtubular doublets surround two central microtubules. The dynein arms are responsible for causing the nine microtubules to slide relative to each other. The nexin links restrict the sliding with the result that the cilium bends.
The ultrastructure of the sperm tail from three infertile men with immotile but otherwise normal spermatozoa had been described in two papers in 19752 ,3; they were found to lack the so-called dynein arms, the structures responsible for generating the movements of cilia or sperm tails.4 The absence of dynein arms had not been described in any other organism, although flagellar (or ciliary) mutants of other types had been described from a unicellular green alga.5 In one of these two papers the spermatozoa of two brothers were examined3 and it was suggested that “the two brothers have a genetic disorder in which the synthesis of the dynein proteins, or their assembly into dynein arms, is defective”.
It was assumed that a genetic defect involving the dynein arms in the sperm tail would affect those in …