GO:0120098 procentriole: Assembly, Genes & Research

The procentriole (GO:0120098) is a cellular component defined as the site of a developing centriole, which will become a microtubule organizing center. During the canonical pathway of centriole duplication that occurs during the cell division cycle, procentrioles grow at the proximal ends of both mother and daughter centrioles. In newly divided cells, the original mother and daughter centrioles become mother centrioles while the procentrioles become the new daughter centrioles. Procentrioles can also arise from de novo pathways that occur in multiciliated cells, where numerous procentrioles arise from electron-dense material referred to as fibrous granules and deuterosomes. The pathway of procentriole formation in multiciliated protists appears to be similar to that in mammalian multiciliated epithelium, and in sperm of primitive land plants, multiple procentrioles are formed from a blepharoplast giving rise to multiciliated sperm cells. For researchers, the procentriole represents a critical window into how cells build and regulate their microtubule organizing centers. Because centriole duplication must occur exactly once per cell cycle, the procentriole is a focal point for understanding cell cycle control, genome stability, and the origins of centrosome amplification in cancer. Defects in procentriole assembly can lead to numerical and structural centrosome abnormalities, which are hallmarks of many human tumors and developmental disorders. Recent advances in cryo-electron tomography and live-cell imaging have provided unprecedented structural and dynamic insights into procentriole architecture and assembly mechanisms. These studies reveal that procentriole formation is a highly ordered process involving the recruitment of specific proteins such as Ana2, Cep152, and PLK4 to a single assembly site. Understanding these mechanisms at molecular resolution is essential for developing targeted interventions in diseases characterized by centriole dysfunction.

The procentriole is a cellular structure that serves as the site of a developing centriole, which will ultimately become a microtubule organizing center. During the canonical centriole duplication pathway in the cell division cycle, procentrioles grow at the proximal ends of both mother and daughter centrioles. After cell division, the original mother and daughter centrioles become mother centrioles, while the procentrioles become the new daughter centrioles. Procentrioles can also form through de novo pathways in multiciliated cells, where numerous procentrioles arise from electron-dense material called fibrous granules and deuterosomes. In multiciliated protists, the pathway of procentriole formation appears similar to that in mammalian multiciliated epithelium, and in sperm of primitive land plants, multiple procentrioles form from a blepharoplast to give rise to multiciliated sperm cells.

The procentriole is fundamentally important because it is the structure where new centrioles are born, and centrioles are essential for forming centrosomes, cilia, and flagella. Errors in procentriole formation lead to centrosome amplification, multipolar spindles, and chromosomal instability, which are common features of cancer cells. Moreover, the procentriole is a model system for understanding how cells build complex macromolecular structures with precise timing and copy number control. Research into procentriole biology has direct implications for cancer, developmental disorders, and ciliopathies, making it a high-value target for both basic and translational studies.

The following genes and proteins are central to procentriole formation, structure, and regulation, as supported by the verified literature.

Procentriole formation is tightly regulated at multiple levels to ensure that centriole duplication occurs exactly once per cell cycle. PLK4 is the master regulator, and its self-phosphorylation creates a phosphodegron that limits its own activity, thereby preventing multiple procentrioles from forming at a single site. Cep152 acts as a scaffold that organizes PLK4 and other initiation factors, providing flexibility in positioning and ensuring a single assembly site. The cell cycle machinery, including CDK1 and PLK1, controls the timing of procentriole assembly and disengagement. Additionally, post-translational modifications such as crotonylation and acetylation by KAT7 can influence procentriole formation, linking metabolic and epigenetic states to centriole duplication. Dysregulation of these regulatory pathways leads to centrosome amplification and genomic instability.

Deregulated procentriole formation is a direct cause of centrosome amplification, which is observed in many human cancers and is associated with chromosomal instability and tumor progression. Recent evidence shows that competitive antagonism of KAT7 crotonylation against acetylation affects procentriole formation and colorectal tumorigenesis, providing a molecular link between epigenetic regulation and cancer. PLK4 overexpression or dysregulation leads to the formation of multiple procentrioles, resulting in multipolar spindles and aneuploidy. Targeting the procentriole assembly pathway, particularly PLK4 and its regulators, is an active area of anti-cancer drug development.

Mutations in genes that regulate procentriole formation cause developmental disorders, including primary microcephaly and ciliopathies. For example, mutations in CPAP, CEP135, and STIL lead to defective centriole duplication and are associated with microcephaly. Because procentrioles are essential for forming centrosomes and cilia, their dysfunction can disrupt neurogenesis and ciliary function, leading to a spectrum of developmental abnormalities. Understanding how these mutations affect procentriole assembly at the molecular level is critical for developing therapeutic strategies.

De novo procentriole formation in multiciliated cells is required for the generation of motile cilia, and defects in this process contribute to ciliopathies. In multiciliated epithelial cells, numerous procentrioles arise from fibrous granules and deuterosomes, and disruption of this pathway leads to reduced ciliary beating and impaired mucociliary clearance. The similarity between procentriole formation in multiciliated protists and mammalian multiciliated epithelium suggests conserved mechanisms that can be studied across species. Research into de novo procentriole formation may provide insights into diseases such as primary ciliary dyskinesia and hydrocephalus.

Cryo-electron tomography is a powerful technique for visualizing the three-dimensional architecture of procentrioles at near-native state. This method has revealed the sequential assembly of the cartwheel, microtubule triplets, and accessory structures during procentriole formation. Researchers use cryo-electron tomography to determine how mutations in centriolar proteins affect the structural integrity of procentrioles. The technique provides high-resolution insights that complement light microscopy and biochemical approaches.

Live-cell fluorescence microscopy allows researchers to track the dynamics of procentriole formation in real time. By tagging centriolar proteins such as PLK4, Cep152, and Ana2 with fluorescent markers, scientists can observe the recruitment of these proteins to the assembly site. This approach has been used to demonstrate that PLK4 self-phosphorylation drives the selection of a single site for procentriole assembly. Live-cell imaging is essential for understanding the temporal and spatial regulation of procentriole formation.

Biochemical fractionation and mass spectrometry-based proteomics can identify the protein composition of procentrioles and their post-translational modifications. For example, studies have used proteomic approaches to identify KAT7 substrates and their crotonylation status during procentriole formation. Co-immunoprecipitation and pull-down assays are used to map the interaction network of centriolar proteins such as Ana2 and Cep152. These methods provide a molecular understanding of how procentriole assembly is regulated.

CRISPR-based genetic screens are used to identify novel regulators of procentriole formation and centriole duplication. By systematically knocking out genes in human cells and scoring for centriole number or structure, researchers can uncover pathways that control procentriole assembly. Functional genomics approaches combined with high-content imaging enable the discovery of genes whose loss leads to centrosome amplification or duplication defects. These screens are valuable for identifying new therapeutic targets in cancer and developmental disorders.

Researchers studying procentriole-related genes often need to determine whether a candidate gene is causally involved in centriole duplication, how specific mutations affect protein function, and whether therapeutic targeting is feasible. EDITGENE provides a comprehensive suite of CRISPR-based services to address these questions with precision and reproducibility.

The procentriole (GO:0120098) is a dynamic cellular structure that serves as the birthplace of new centrioles, ensuring proper centrosome function and genome stability. Its assembly is tightly regulated by PLK4, Cep152, Ana2, and other proteins, and defects in this process contribute to cancer and developmental disorders. Advances in cryo-electron tomography and CRISPR-based models continue to unravel the molecular mechanisms of procentriole formation. Understanding procentriole biology offers promising avenues for therapeutic intervention in diseases characterized by centriole dysfunction.