DisAp is a novel kinetodesmal fiber component that is essential for force-dependent fiber elongation and the alignment of basal body orientation in multiciliary arrays.

SummaryBasal bodies and centrioles are conserved microtubule-based organelles the improper assembly of which leads to a number of diseases, including ciliopathies and cancer. Tubulin family members are conserved components of these structures that are integral to their proper formation and function. We have identified the e-tubulin gene in Tetrahymena thermophila and detected the protein, through fluorescence of a tagged allele, to basal bodies. Immunoelectron microscopy has shown that e-tubulin localizes primarily to the core microtubule scaffold. A complete genomic knockout of e-tubulin has revealed that it is an essential gene required for the assembly and maintenance of the triplet microtubule blades of basal bodies. We have conducted site-directed mutagenesis of the e-tubulin gene and shown that residues within the nucleotide-binding domain, longitudinal interacting domains, and C-terminal tail are required for proper function. A single amino acid change of Thr150, a conserved residue in the nucleotide-binding domain, to Val is a conditional mutation that results in defects in the spatial and temporal assembly of basal bodies as well as their stability. We have genetically separated functions for the domains of e-tubulin and identified a novel role for the nucleotide-binding domain in the regulation of basal body assembly and stability.

Centrins are a family of small calcium-binding proteins found at basal bodies. The family can be separated into two groups based on sequence homology to the human centrins. The model organism Tetrahymena was used to show that the two centrin groups have similar but distinct functions at basal bodies.