In a study published in Journal of Proteome Research, >180 proteins have been spatially mapped to specific subcellular compartments in cells with motile cilia using multiplex immunohistochemistry. The high-resolution data is available in the HPA Tissue resource, and aids in further functional mapping of proteins with limited evidence.

Motile cilia are complex structures regulated by thousands of genes, essential for various physiological functions like respiration and reproduction. Their dysfunction can result in severe conditions like primary ciliary dyskinesia (PCD), highlighting the need for a deeper molecular understanding of their specific ciliary compartments. Interestingly, ciliated cells harbor multiple proteins with limited evidence on biological function, as defined by Functional Evidence (FE) scores, a grading system developed by the Human Proteome Project (HPP). Building upon the HPA antibody validation pipeline, a high-throughput workflow combining multiplex immunohistochemistry with image analysis was developed. Based on signal overlap with a panel of marker proteins outlining the cilium (CL), the transition zone (TZ), the rootlet (RL), the cytoplasm, and the nucleus of ciliated cells, the spatial subcellular localization of 187 motile cilia proteins was mapped across five different tissue types from both respiratory (nasopharynx and bronchus) and reproductive tracts (fallopian tube, endometrium and cervix). Out of the 187 analyzed proteins, 73% have FE scores 2-5, suggesting that further evidence is needed to establish these proteins' biological function. The detailed information at the tissue, cellular, and subcellular levels thus offered new insights into the presumed functions of these proteins in motile cilia. Another important finding is that expression patterns varied between tissues, suggesting that motile cilia proteins are not universally expressed across the different epithelia. The pipeline constitutes a promising resource for comprehensive mapping of the motile cilia proteome, and a first step toward identifying cilia proteins for functional studies to understand the molecular mechanisms underlying ciliopathies.

Link to the proteins analyzed in ciliated cells

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