Cell type

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A cell type is a classification used to identify cells that share morphological or phenotypical features. [1] A multicellular organism may contain cells of a number of widely differing and specialized cell types, such as muscle cells and skin cells, that differ both in appearance and function yet have identical genomic sequences. Cells may have the same genotype, but belong to different cell types due to the differential regulation of the genes they contain. Classification of a specific cell type is often done through the use of microscopy (such as those from the cluster of differentiation family that are commonly used for this purpose in immunology). Recent developments in single cell RNA sequencing facilitated classification of cell types based on shared gene expression patterns. This has led to the discovery of many new cell types in e.g. mouse cortex, hippocampus, [2] dorsal root ganglion [3] and spinal cord. [4]

Contents

Animals have evolved a greater diversity of cell types in a multicellular body (100–150 different cell types), compared with 10–20 in plants, fungi, and protists. [5] The exact number of cell types is, however, undefined, and the Cell Ontology, as of 2021, lists over 2,300 different cell types. [6]

Multicellular organisms

All higher multicellular organisms contain cells specialised for different functions. Most distinct cell types arise from a single totipotent cell that differentiates into hundreds of different cell types during the course of development. Differentiation of cells is driven by different environmental cues (such as cell–cell interaction) and intrinsic differences (such as those caused by the uneven distribution of molecules during division). Multicellular organisms are composed of cells that fall into two fundamental types: germ cells and somatic cells. During development, somatic cells will become more specialized and form the three primary germ layers: ectoderm, mesoderm, and endoderm. After formation of the three germ layers, cells will continue to specialize until they reach a terminally differentiated state that is much more resistant to changes in cell type than its progenitors.

The simplest organism considered to have well defined cell types are some volvoceans, such as Volvox carteri , in which each organism is composed of distinct and interdependent cell populations, some somatic and some reproductive. [7]

Conceptual definition

Even though the concept of cell type is widely used, specialists still discuss the exact definition of what constitutes a cell type. [8]

Humans

A list of cell types in the human body may include several hundred distinct types depending on the source. [9] [10]

A 2006 peer-reviewed article by Vickaryous and Hall listed 411 distinct human cell types. [11]

See also

Related Research Articles

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Developmental biology is the study of the process by which animals and plants grow and develop. Developmental biology also encompasses the biology of regeneration, asexual reproduction, metamorphosis, and the growth and differentiation of stem cells in the adult organism.

<span class="mw-page-title-main">Mutation</span> Alteration in the nucleotide sequence of a genome

In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, mitosis, or meiosis or other types of damage to DNA, which then may undergo error-prone repair, cause an error during other forms of repair, or cause an error during replication. Mutations may also result from insertion or deletion of segments of DNA due to mobile genetic elements.

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<span class="mw-page-title-main">Cellular differentiation</span> Developmental biology

Cellular differentiation is the process in which a stem cell changes from one type to a differentiated one. Usually, the cell changes to a more specialized type. Differentiation happens multiple times during the development of a multicellular organism as it changes from a simple zygote to a complex system of tissues and cell types. Differentiation continues in adulthood as adult stem cells divide and create fully differentiated daughter cells during tissue repair and during normal cell turnover. Some differentiation occurs in response to antigen exposure. Differentiation dramatically changes a cell's size, shape, membrane potential, metabolic activity, and responsiveness to signals. These changes are largely due to highly controlled modifications in gene expression and are the study of epigenetics. With a few exceptions, cellular differentiation almost never involves a change in the DNA sequence itself. However, metabolic composition does get altered quite dramatically where stem cells are characterized by abundant metabolites with highly unsaturated structures whose levels decrease upon differentiation. Thus, different cells can have very different physical characteristics despite having the same genome.

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<span class="mw-page-title-main">Multicellular organism</span> Organism that consists of more than one cell

A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni- and partially multicellular, like slime molds and social amoebae such as the genus Dictyostelium.

<span class="mw-page-title-main">Germ cell</span> Gamete-producing cell

A germ cell is any cell that gives rise to the gametes of an organism that reproduces sexually. In many animals, the germ cells originate in the primitive streak and migrate via the gut of an embryo to the developing gonads. There, they undergo meiosis, followed by cellular differentiation into mature gametes, either eggs or sperm. Unlike animals, plants do not have germ cells designated in early development. Instead, germ cells can arise from somatic cells in the adult, such as the floral meristem of flowering plants.

<span class="mw-page-title-main">Germline</span> Population of a multicellular organisms cells that pass on their genetic material to the progeny

In biology and genetics, the germline is the population of a multicellular organism's cells that pass on their genetic material to the progeny (offspring). In other words, they are the cells that form the egg, sperm and the fertilised egg. They are usually differentiated to perform this function and segregated in a specific place away from other bodily cells.

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Embryomics is the identification, characterization and study of the diverse cell types which arise during embryogenesis, especially as this relates to the location and developmental history of cells in the embryo. Cell type may be determined according to several criteria: location in the developing embryo, gene expression as indicated by protein and nucleic acid markers and surface antigens, and also position on the embryogenic tree.

<span class="mw-page-title-main">Cell potency</span> Ability of a cell to differentiate into other cell types

Cell potency is a cell's ability to differentiate into other cell types. The more cell types a cell can differentiate into, the greater its potency. Potency is also described as the gene activation potential within a cell, which like a continuum, begins with totipotency to designate a cell with the most differentiation potential, pluripotency, multipotency, oligopotency, and finally unipotency.

Vasa is an RNA binding protein with an ATP-dependent RNA helicase that is a member of the DEAD box family of proteins. The vasa gene is essential for germ cell development and was first identified in Drosophila melanogaster, but has since been found to be conserved in a variety of vertebrates and invertebrates including humans. The Vasa protein is found primarily in germ cells in embryos and adults, where it is involved in germ cell determination and function, as well as in multipotent stem cells, where its exact function is unknown.

<i>Volvox carteri</i> Species of alga

Volvox carteri is a species of colonial green algae in the order Volvocales. The V. carteri life cycle includes a sexual phase and an asexual phase. V. carteri forms small spherical colonies, or coenobia, of 2000–6000 Chlamydomonas-type somatic cells and 12–16 large, potentially immortal reproductive cells called gonidia. While vegetative, male and female colonies are indistinguishable; however, in the sexual phase, females produce 35-45 eggs and males produce up to 50 sperm packets with 64 or 128 sperm each.

Unique molecular identifiers (UMIs), or molecular barcodes (MBC) are short sequences or molecular "tags" added to DNA fragments in some next generation sequencing library preparation protocols to identify the input DNA molecule. These tags are added before PCR amplification, and can be used to reduce errors and quantitative bias introduced by the amplification.

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Germ-Soma Differentiation is the process by which organisms develop distinct germline and somatic cells. The development of cell differentiation has been one of the critical aspects of the evolution of multicellularity and sexual reproduction in organisms. Multicellularity has evolved upwards of 25 times, and due to this there is great possibility that multiple factors have shaped the differentiation of cells. There are three general types of cells: germ cells, somatic cells, and stem cells. Germ cells lead to the production of gametes, while somatic cells perform all other functions within the body. Within the broad category of somatic cells, there is further specialization as cells become specified to certain tissues and functions. In addition, stem cell are undifferentiated cells which can develop into a specialized cell and are the earliest type of cell in a cell lineage. Due to the differentiation in function, somatic cells are found ony in multicellular organisms, as in unicellular ones the purposes of somatic and germ cells are consolidated in one cell.

References

  1. ↑ Zeng, Hongkui (2022). "What is a cell type and how to define it?". Cell. 185 (15): 2739–2755. doi:10.1016/j.cell.2022.06.031. ISSN   0092-8674. PMC   9342916 . PMID   35868277.
  2. ↑ Zeisel A, Muñoz-Manchado AB, Codeluppi S, Lönnerberg P, La Manno G, Juréus A, Marques S, Munguba H, He L, Betsholtz C, Rolny C, Castelo-Branco G, Hjerling-Leffler J, Linnarsson S (March 2015). "Brain structure. Cell types in the mouse cortex and hippocampus revealed by single-cell RNA-seq". Science. 347 (6226): 1138–42. doi: 10.1126/science.aaa1934 . PMID   25700174. S2CID   29506785.
  3. ↑ Usoskin D, Furlan A, Islam S, Abdo H, Lönnerberg P, Lou D, Hjerling-Leffler J, Haeggström J, Kharchenko O, Kharchenko PV, Linnarsson S, Ernfors P (January 2015). "Unbiased classification of sensory neuron types by large-scale single-cell RNA sequencing". Nature Neuroscience. 18 (1): 145–53. doi:10.1038/nn.3881. PMID   25420068. S2CID   205437148.
  4. ↑ Häring M, Zeisel A, Hochgerner H, Rinwa P, Jakobsson JE, Lönnerberg P, La Manno G, Sharma N, Borgius L, Kiehn O, Lagerström MC, Linnarsson S, Ernfors P (June 2018). "Neuronal atlas of the dorsal horn defines its architecture and links sensory input to transcriptional cell types". Nature Neuroscience. 21 (6): 869–880. doi:10.1038/s41593-018-0141-1. PMID   29686262. S2CID   5057143.
  5. ↑ Margulis L; Chapman MJ (2009). Kingdoms and Domains: An Illustrated Guide to the Phyla of Life on Earth (4th ed.). Amsterdam: Academic Press/Elsevier. p. 116.
  6. ↑ Osumi-Sutherland, David; Xu, Chuan; Keays, Maria; Kharchenko, Peter V.; Regev, Aviv; Lein, Ed; Teichmann, Sarah A. (2021-06-28). "Cell type ontologies of the Human Cell Atlas". Nature Cell Biology. 23 (11): 1129–1135. arXiv: 2106.14443 . doi:10.1038/s41556-021-00787-7. PMID   34750578. S2CID   235658396.
  7. ↑ Gilbert, Scott F. (1997). Developmental biology (5th ed.). Sunderland (Mass.): Sinauer. p. 17. ISBN   978-0-87893-244-3.
  8. ↑ "What Is Your Conceptual Definition of "Cell Type" in the Context of a Mature Organism?". Cell Systems. 4 (3): 255–259. 22 March 2017. doi: 10.1016/j.cels.2017.03.006 . ISSN   2405-4712. PMID   28334573.
  9. ↑ Alberts B, Johnson A, Lewis J, Morgan D, Raff M, Roberts K, Walter P. Molecular Biology of the Cell (Sixth ed.). p. 1217.
  10. ↑ "COPE database".
  11. ↑ Vickaryous, Matthew K.; Hall, Brian K. (August 2006). "Human cell type diversity, evolution, development, and classification with special reference to cells derived from the neural crest". Biological Reviews. 81 (3): 425–455. doi:10.1017/S1464793106007068. ISSN   1464-7931. PMID   16790079. S2CID   41969112.

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