Document Type


Publication Date



DOI: 10.1371/journal.pgen.1010796; PMCID: PMC10298753


Motile and non-motile cilia play critical roles in mammalian development and health. These organelles are composed of a 1000 or more unique proteins, but their assembly depends entirely on proteins synthesized in the cell body and transported into the cilium by intraflagellar transport (IFT). In mammals, malfunction of non-motile cilia due to IFT dysfunction results in complex developmental phenotypes that affect most organs. In contrast, disruption of motile cilia function causes subfertility, disruption of the left-right body axis, and recurrent airway infections with progressive lung damage. In this work, we characterize allele specific phenotypes resulting from IFT74 dysfunction in human and mice. We identified two families carrying a deletion encompassing IFT74 exon 2, the first coding exon, resulting in a protein lacking the first 40 amino acids and two individuals carrying biallelic splice site mutations. Homozygous exon 2 deletion cases presented a ciliary chondrodysplasia with narrow thorax and progressive growth retardation along with a mucociliary clearance disorder phenotype with severely shorted cilia. Splice site variants resulted in a lethal skeletal chondrodysplasia phenotype. In mice, removal of the first 40 amino acids likewise results in a motile cilia phenotype but with little effect on primary cilia structure. Mice carrying this allele are born alive but are growth restricted and developed hydrocephaly in the first month of life. In contrast, a strong, likely null, allele of Ift74 in mouse completely blocks ciliary assembly and causes severe heart defects and midgestational lethality. In vitro studies suggest that the first 40 amino acids of IFT74 are dispensable for binding of other IFT subunits but are important for tubulin binding. Higher demands on tubulin transport in motile cilia compared to primary cilia resulting from increased mechanical stress and repair needs could account for the motile cilia phenotype observed in human and mice.

Journal Title

PLoS Genet





First Page


Last Page


MeSH Keywords

Humans; Animals; Mice; Cilia; Tubulin; Proteins; Ciliopathies; Amino Acids; Mammals; Cytoskeletal Proteins


Mice; Cilia; Tubulin; Proteins; Ciliopathies; Amino Acids; Mammals; Cytoskeletal Proteins


Grant support

MS acknowledges funding from the European Research Council (ERC) (ERC starting grant No. 716344 to MS) and from the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Project-ID 431984000–SFB 1453) and Germany’s Excellence Strategy CIBSS—EXC-2189—project ID 390939984 under Germany’s Excellence Strategy. GJP funding was provided by National Institutes of Health grant R01 GM060992. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Publisher's Link: