One hundred years of centrioles: the Henneguy-Lenhossek theory, meeting report.

an international conference took place in the Lederle Graduate Research Tower of the University of Massachusetts at Amherst, with funding provided by the Richard Lounsbery Foundation, New York City. Its title marked the centennial of centriolekinetosome research and commemorated the two founders of the field: Mihaly Lenhossek (1863–1937), the Hungarian neurobiologist and relative of conference attendee Andrew Szent-Györgyi, and prominent French histologist Louis Félix Henneguy (1850–1928). The enigmatic centriole, a barrel-shaped structure that sits at the mitotic poles in nearly all animal cells, presents a wide variety of form and function in different taxa. Well known as the site of astral microtubule emergence, the same [9(3)+0] microtubule structure, the kinetosome (or basal body), subtends all undulipodia (eukaryotic flagella and cilia). This polyfunctional organelle has even been shown to confer cell polarity throughout the cell cycle, by determining the number, orientation and polarity of mitotic and interphase microtubules, even in breast cancer cells [8]. Because of the near-ubiquity and identical ultrastructure of centriole-kinetosomes (C-Ks) across eukaryotic taxa, together with the highly conserved nature of the C-K proteins centrin and tubulin, evolutionists believe that C-Ks originated in the earliest eukaryotes, perhaps as long as 2000 million years ago. Subsequent divergence has led to a myriad of C-K-associated elaborations, from the calcium-modulated spasmoneme of Vorticella to the paraxonemal rod (transverse undulipodium) of Peridinium and the cochlear kinocilium of our inner ear sensory epithelium. As mitotic structures, centrioles are altogether absent from some major taxa (e.g. plants, yeasts, rhodophytes [red algae], and cellular slime molds). As basal bodies of undulipodia, kinetosomes occur in the vast majority of eukaryotic phyla. Amoebomastigotes such as Naegleria, however, produce and resorb kinetosomes with every life history transition between amoeboid and mastigote phases [7]. Uni mutants in Chlamydomonas [5] and “monster” ciliates with inverted orientation of the infraciliature [13], respectively, have shown that a nuclear mutation can delay kinetosomal reproduction in one system, while in another, kinetosome reproduction is partially independent of nuclear control. In short, C-K-related controversy has mushroomed over the past 100 years in concert with our growing appreciation of the bewildering number of variations on the theme. In April 1898, Lenhossek published a paper entitled “Über Flimmerzellen” wherein he showed that kinetosomes, the bodies at the bases of the rat sperm tails, were identical to those of cilia lining the epididymis. He further proposed that these kinetosomes were identical to centrioles, and that from the centrioles originated the spindle. In the same month Henneguy, working on silkworm spermatocytes, independently published the same interpretation in Archives d’Anatomie Microscopique, Tome I. The two founders of C-K theory courteously agreed to equally share the credit. Their contribution, that mitotic centrioles and ciliary basal kinetosomes are essentially the same structure, descends to us today as Henneguy-Lenhossek theory. As anticipated by these 19th century scientists, we can now say that centriole-kinetosomes give rise to all undulipodial shafts (i.e., axonemes) as well as to microtubular elements of the cytoskeleton. The conference began on the evening of Wednesday, June 24, with open discussion entitled “The centriole’s new clothes: a century of controversy at the cell center,” moderated by Chandler Fulton of Brandeis University. Discussion centered around the perplexing questions that still remain after many lifetimes of research: How did centriole-kinetosomes first evolve? Why are they absent in many taxa? What kinds of selection may have driven their secondary loss in plants, yeasts 233