The Scientific Basis of Medicine
John S. Axford, Chris A. O'Callaghan in Medicine for Finals and Beyond, 2023
In order to divide successfully, a cell must copy its DNA so that each daughter cell receives its full set of chromosomes. This is achieved by a tightly regulated mitosis following the cell cycle pathway (Figure 2.6). Passage through the cell cycle is controlled by cyclin proteins, in a cascade of phosphorylation events. Each cyclin acts as a catalytic subunit in partnership with a cyclin-dependent kinase (CDK). Upon cyclin binding, CDKs phosphorylate target proteins that are required for cell-cycle progression. CDK-specific inhibitors (CDKIs) bind cyclin–CDK complexes to regulate their activity and can themselves be regulated by other proteins. During mitosis, one member of each chromosome pair becomes attached to a centriole. Centrioles move to opposite ends of the cell, taking the chromosomes with them. In order to prevent inappropriate proliferation of cells, mitosis is tightly controlled, with various checkpoints to ensure that every part of the mitotic process is completed correctly before the next stage begins. Because uncontrolled proliferation is a hallmark of cancer, the cell cycle provides an obvious target for therapy. CDKIs often act as tumour suppressors and are potentially useful anticancer agents.
The Pineal Gland and Melatonin
George H. Gass, Harold M. Kaplan in Handbook of Endocrinology, 2020
Most of the organelles of the mammalian pinealocyte do not differ substantially from those of other mammalian cells. The nucleus may be irregular in shape with indentations of the surface. A prominent nucleolus is present. Both smooth and rough endoplasmic reticulum are consistently reported;72 but Wolfe70 pointed out that in the rat the endoplasmic reticulum is not typical and has referred to it as intergrade endoplasmic reticulum. Clusters of ribosomes, not associated with membranes, are found throughout the cytoplasm. Although mitochondria are generally reported as normal in mammalian pinealocytes, considerable variation in size and shape have been documented.70,73–75 They are relatively numerous in most pinealocytes. Centrioles, although not present in great numbers, have been reported to differentiate into structures called microtubular sheaves (microtubules arranged in sheaves).70–76 The presence of cilia depends on the species studied and on the developmental stage examined. Clabough77 observed cilia in pinealocytes of fetal and neonatal rats, but cilia were absent or very rare in pinealocytes of adult rats.70,78 In some species, such as the mole, cilia may be a characteristic feature of each pinealocyte.54 In this species, the cilia were reported as having filaments in a 9 + 0 arrangement in the shaft, an arrangement also found in photoreceptor cells.
The Ultrastructure of Olfactory and Nasal Respiratory Epithelium Surfaces
D. V. M. Gerd Reznik, Sherman F. Stinson in Nasal Tumors in Animals and Man, 2017
The nonsensory portion of the mammalian vomeronasal organ is rather similar in appearance to the ciliated/microvillous respiratory epithelium.30,76,77 The vomeronasal organ is a small tubular structure lying within the nasal septum next to the anteroventral part of the cavum nasi. It has a narrow duct, which enters the nasal cavity directly or via the nasopalatine duct, the latter running between the nasal and the oral cavities. In microsmatic mammals, e.g., man, the vomeronasal organ is rudimentary or absent.31,75 In cetaceans (e.g., whales and dolphins) main and vomeronasal olfactory organs are reduced or absent. This is ascribed to the migration of the nares from anterior to dorsal regions during cetacean evolution.1,78 The ultrastructure of the mammalian vomeronasal organ has been studied for several species.46,79-82 Cell apices of the sensory cells contain centrioles, but cilia are not developed. The cells have microvilli only.83
Prevalence and natural history of variants in the ANKRD26 gene: a short review and update of reported cases
Published in Platelets, 2022
Hrushikesh Vyas, Ahmad Alcheikh, Gillian Lowe, William S Stevenson, Neil V Morgan, David J Rabbolini
As suggested by its localization, ANKRD26 appears to play a role in centriole biology [41]. Centrioles are important in ciliogenesis and motility. They are components of centrosomes that have been implicated in cancer pathogenesis [56,57]. Centrosome amplification triggers p53-dependent apoptosis through activation of a multiprotein complex known as the PIDDosome [56]. In centrosome amplification (e.g. cytokinesis failure), ANKRD26 recruits the p53-induced death domain protein 1 (PIDD1) to the centriole distal appendages to form part of the PIDDosome [57–59]. When ANKRD26 is inactivated, cells cannot sustain PIDDosome assembly and show enhanced growth following centrosome amplification [57,59]. Whether these actions of ANKRD26 protein play any role in the pathogenesis of ANKRD26-RT is unknown.
Microcephaly and chorioretinopathy associated with TUBGCP4: a case report and a review of the literature
Published in Ophthalmic Genetics, 2023
Claudia Yahalom, Russell L Woods, James D Akula, Wen-Hann Tan, Anne Fulton
Centrioles are structures in microtubules and are the key components of many cellular processes, including cell division, signaling, and motility. Centrioles are essential for ciliogenesis. Pathogenic variants in centriole biogenesis genes have been reported in primary microcephaly and other disorders without the hallmark clinical features of ciliopathies. Pathogenic variants in the genes encoding PLK4 kinase (master regulator of centriole duplication) and its substrate TUBGCP6 result in microcephaly and retinopathy. Different levels of impaired PLK4 activity result in different cilia phenotypes, providing a mechanism by which microcephaly disorders can occur with or without ciliopathic features (5).
Centrosome Abnormalities and Polyploidy in Murine Mammary Carcinomas with Different Degrees of Hormone Responsiveness
Published in Cancer Investigation, 2020
Melina Bilinski, Claudia Lanari, Victoria T. Fabris
Centrosomes are organelles formed by two centrioles surrounded by pericentriolar material (PCM) principally composed by γ-tubulin and pericentrin. Mammalian cells normally have one or two centrosomes depending on the phase of the cell cycle. Centrioles duplicate only once during the G1-S transition to form the poles of the mitotic spindle that nucleate the microtubules to which the chromosomes will attach during mitosis (reviewed in (9)).
Related Knowledge Centers
- Cell Biology
- Centrosome
- Drosophila Melanogaster
- Eukaryote
- Microtubule
- Spermatozoon
- Tubulin
- Organelle
- Cell
- Pericentriolar Material