Pacrg, short for Parkin co-regulated gene, shares a bidirectional promoter with the Parkinson's disease-associated gene Parkin. It is involved in multiple biological processes. In sperm development, it forms a complex with MEIG1 in the manchette, which is crucial for sperm flagellum assembly [1,3,5]. In cilia, it is part of the inner junction of axonemal doublet microtubules and regulates ciliary motility [2]. It also has roles in cellular signaling, influencing gustatory plasticity and longevity in Caenorhabditis elegans [4].

Gene-knockout (KO) mouse models have been instrumental in understanding Pacrg's function. In male germ-cell-specific DNALI1-deficient mice, the localization of Pacrg within the manchette is affected, leading to abnormal sperm morphology and male infertility, highlighting its importance in sperm differentiation [1]. In Pacrg-deficient mice, MEIG1 no longer localizes to the manchette, and the transport of cargos like SPAG16L to build the sperm flagella is disrupted, emphasizing its role in sperm flagella formation [5].

In conclusion, Pacrg plays essential roles in sperm development, ciliary motility, and cellular signaling. The use of KO mouse models has revealed its significance in these processes, especially in relation to male infertility. Understanding Pacrg's functions provides insights into the mechanisms underlying sperm-related disorders and ciliary-associated diseases.