TL;DR: The connections between cilia and developmental signalling have begun to clarify the basis of human diseases associated with ciliary dysfunction, and the cilium represents a nexus for signalling pathways during development.
Abstract: The primary cilium has recently stepped into the spotlight, as a flood of data show that this organelle has crucial roles in vertebrate development and human genetic diseases. Cilia are required for the response to developmental signals, and evidence is accumulating that the primary cilium is specialized for hedgehog signal transduction. The formation of cilia, in turn, is regulated by other signalling pathways, possibly including the planar cell polarity pathway. The cilium therefore represents a nexus for signalling pathways during development. The connections between cilia and developmental signalling have begun to clarify the basis of human diseases associated with ciliary dysfunction.
TL;DR: Genetic analysis shows that Wim, Polaris and the IFT motor protein Kif3a are required for Hedgehog signalling at a step downstream of Patched1 (the Hedgehog receptor) and upstream of direct targets of hedgehog signalling.
Abstract: Intraflagellar transport (IFT) proteins were first identified as essential factors for the growth and maintenance of flagella in the single-celled alga Chlamydomonas reinhardtii. In a screen for embryonic patterning mutations induced by ethylnitrosourea, here we identify two mouse mutants, wimple (wim) and flexo (fxo), that lack ventral neural cell types and show other phenotypes characteristic of defects in Sonic hedgehog signalling. Both mutations disrupt IFT proteins: the wim mutation is an allele of the previously uncharacterized mouse homologue of IFT172; and fxo is a new hypomorphic allele of polaris, the mouse homologue of IFT88. Genetic analysis shows that Wim, Polaris and the IFT motor protein Kif3a are required for Hedgehog signalling at a step downstream of Patched1 (the Hedgehog receptor) and upstream of direct targets of Hedgehog signalling. Our data show that IFT machinery has an essential and vertebrate-specific role in Hedgehog signal transduction.
TL;DR: The data reveal that BBS may be caused by defects in vesicular transport to the cilium, and a complex composed of seven highly conserved BBS proteins is identified, the BBSome, which localizes to nonmembranous centriolar satellites in the cytoplasm but also to the membrane of the cILium.
TL;DR: Cilia — tiny hair-like organelles attached to the cell surface — are located on almost all polarized cell types of the human body and have been adapted as versatile tools for various cellular functions, explaining why cilia-related disorders can affect many organ systems.
Abstract: Defects in the function of cellular organelles such as peroxisomes, lysosomes and mitochondria are well-known causes of human diseases. Recently, another organelle has also been added to this list. Cilia--tiny hair-like organelles attached to the cell surface--are located on almost all polarized cell types of the human body and have been adapted as versatile tools for various cellular functions, explaining why cilia-related disorders can affect many organ systems. Several molecular mechanisms involved in cilia-related disorders have been identified that affect the structure and function of distinct cilia types.
TL;DR: A motility in the flagella of the green alga Chlamydomonas that is unrelated to dynein-based flagellar beating is reported, and groups of nonvesicular, lollipop-shaped structures positioned between the outer doublet microtubules and the flagingllar membrane may be responsible for intraflagella transport.
Abstract: We report a motility in the flagella of the green alga Chlamydomonas that is unrelated to dynein-based flagellar beating. This motility, referred to as intraflagellar transport, was observed as the rapid bidirectional movement of granule-like particles along the length of the flagella. Intraflagellar transport could be experimentally separated from other, previously reported, nonbeat flagellar motilities. EM of flagella showed groups of nonvesicular, lollipop-shaped structures positioned between the outer doublet microtubules and the flagellar membrane. Movement of these complexes along the length of the flagella may be responsible for intraflagellar transport.