Thomas, M. S.; Galletta, B. J.; Ryniawec, J. M.; Amoiroglou, A.; Khan, C.; Fagerstrom, C. J.; Rogers, G. C.; Rusan, N. M.

Centrosome dysfunction is linked to developmental disorders affecting brain and body size, including microcephaly and primordial dwarfism. However, the cellular mechanisms underlying these rare conditions remain poorly understood. In this study, we investigate a rare variant of the centrosome-associated protein Pericentrin, which was discovered in a single family with Majewski/microcephalic osteodysplastic primordial dwarfism type II (MOPD II). Unlike the majority of pathogenic PCNT variants that cause severe protein truncation, the p.Lys3154del variant (delta-K3154) involves a single amino acid deletion a conserved functional domain, providing a unique opportunity to explore PCNT function in MOPD II. To model PCNT-deltaK3154, we examined the effects of Drosophila Pericentrin-like protein (PLP) carrying an orthologous deletion (Plp-deltaR). Our results show that Plp-deltaR animals exhibit smaller tissues that recapitulate MOPD II phenotypes. Behavioral assays revealed defects in climbing and mechanosensation, suggesting impaired sensory cilia function. We also found that Plp-deltaR cells exhibit accelerated mitosis, increased apoptosis, and reduced pericentriolar material recruitment. In silico structural modeling, yeast two-hybrid, and co-immunoprecipitation experiments show that Plp-deltaR produces a protein that disrupts PLP dimerization and PLP interaction with Asterless, another centrosome protein. Overall, modeling the human MOPD II patient variant PCNT-deltaK3154 in Drosophila reveals how a single amino acid deletion affects biological processes from the molecular level to the organismal level. Our work offers new insights into the defective cellular mechanisms underlying MOPD II in patients with the PCNT-deltaK3154 variant, potentially linking the etiology of the disease in these individuals to the loss of a single protein-protein interaction.