Gene dosage of independent dynein arm motor preassembly factors influences cilia assembly in < i > Chlamydomonas reinhardtii < /i >

by Gervette M. Penny, Susan K. Dutcher

Motile cilia assembly utilizes over 800 structural and cytoplasmic proteins. Variants in approximately 58 genes cause primary ciliary dyskinesia (PCD) in humans, including the dynein arm (pre)assembly factor (DNAAF) geneDNAAF4. In humans, outer dynein arms (ODAs) and inner dynein arms (IDAs) fail to assemble motile cilia when DNAAF4 function is disrupted. InChlamydomonas reinhardtii, a ciliated unicellular alga, theDNAAF4 ortholog is calledPF23. Thepf23-1 mutant assembles short cilia and lacks IDAs, but partially retains ODAs. The cilia of a new null allele (pf23-4) completely lack ODAs and IDAs and are even shorter than cilia frompf23-1. In addition, PF23 plays a role in the cytoplasmic modification of IC138, a protein of the two-headed IDA (I1/f). As most PCD variants in humans are recessive, we sought to test if heterozygosity at two genes affects ciliary function using a second-site non-complementation (SSNC) screening approach. We asked if phenotypes were observed in diploids with pairwise heterozygous combinations of 21 well-characterized ciliary mutantChlamydomonas strains. Vegetative cultures of single and double heterozygous diploid cells did not show SSNC for motility phenotypes. When protein synthesis is inhibited, wild-typeChlamydomonas cells utilize the pool of cytoplasmic proteins to assemble half-length cilia. In this sensitized assay, 8 double heterozygous diploids withpf23 and otherDNAAF mutations show SSNC; they assemb...

Source: PLoS Genetics - March 18, 2024 Category: Genetics & Stem Cells Authors: Gervette M. Penny Source Type: research