TOTIPOTENTIALITY: HISTORY, CHARACTERISTICS AND IMPORTANCE - BIOLOGY - 2024

The totipotency or totipotency is the ability, ability and potential possessed by each of embryonic cells to produce the total cells of an individual. The term derives from the Latin word totipotentia, which means ability for all things and / or ability to become or give rise to a complete organism.

The totipotent cells that are best defined or studied are the zygote and spores. Some authors use the term stem cells and totipotent cells as a synonym, but however there is no consensus in this regard.

Totipotential cells. Taken and edited from: Jucomo.

Stem cells, according to some authors, are groups of undifferentiated cells that can become different groups or types of specialized cells. They can be unipotent, multipotent and also totipotent. Only the latter are capable of giving rise to a complete individual.

History

The father of totipotentiality is the German biologist and philosopher Hans Adolf Eduard Driesch. This scientist revolutionized the understanding of embryology thanks to his experiments with sea urchins.

In 1891 Driesch conducted experiments with two-celled (two-cell) embryos of the sea urchin Echinus microtuberculatus (now known as Psammechinus microtuberculatus) challenging the accepted hypotheses of the time about embryonic development.

Their results showed that the cells of an early embryo (zygote) when they are separated, either mechanically or naturally, could continue to develop until forming normal larvae, concluding that these cells are totipotent in their early stages of development.

This was in contrast to the results of Wilhelm Roux (pioneer of experimental embryology), who had worked with two-celled frog eggs. Roux found that killing one of the two cells developed malformed embryos, concluding that embryonic cells have predetermined destinations.

Later in 1910, the American chemist, zoologist and physiologist Jesse Francis McClendon would verify that Driesch's results could be replicated in frogs, chickens, other hedgehogs and even mammals.

characteristics

Totipotentiality is characterized by the potential of some cells to give rise to a complete individual. These are capable of becoming any type of cell in the body and also in other extra-embryonic tissue.

Totipotent cells are formed in organisms of both sexual and asexual reproduction, they are zygotes or spores. They can be a zygote in the seed of a phanerogam (plant), in an egg of any animal, or in a uterus of a mammal (such as humans, elephants or mice).

This potential in most cases has a short life span during development. In the human body they have a limited time, approximately 4 days after fertilization. In other organisms such as plants, marine sponges, annelid worms, starfish and mice they have different duration.

Totipotentiality in different groups of organisms

In plants and fungi that reproduce by spores, it is said that these cells that do not need fertilization are of the totipotent type, since the zygote of these organisms has the capacity to produce all the types of cells required to develop a complete individual.

Numerous development, growth, and tissue culture studies in plants have repeatedly shown that many plant cells are totipotent. An example of this are the cultures of small tissues or stem cuts that, when placed in growth media, are capable of giving rise to or regenerating a completely new individual.

Invertebrates

As it has already been mentioned before, the first study that demonstrated the existence of totipotent embryonic cells was carried out with sea urchins (echinoderms). Since then many studies have been carried out to replicate Driesch's experiment and in all of them the result is the same (the existence of totipotentiality).

Another case in echinoderms, but this time with starfish and starfish, is the ability of some species of these to regenerate a complete organism from a section or part of an arm (without portions of the central disk). This regenerative capacity is due to the presence of adult totipotent stem cells.

Linckia guildingi starfish, organism regenerated from an arm of other organisms. Taken and edited from: Emőke Dénes.

Poriferous (sponge) tissue studies reveal that these primitive organisms have large numbers of totipotent cells. This allows them to produce or obtain any type of cell they need and sometimes also to be able to regenerate a complete organism from a small body portion.

Vertebrates

In vertebrates, totipotentiality studies are described in embryonic development; that is, the embryonic cells of vertebrates such as fish, reptiles, birds and mammals have a totipotent behavior similar to that of Driesch's hedgehogs.

Regardless of the type of reproduction (cross-fertilization, self-fertilization and also parthenogenesis) the cells present between the zygote and the morula (first segmentations of the zygote) have the capacity to produce all types of cells and to organize them into a coherent bauplan (a complete organism).

Cell types according to their totipotent capacity

A good part of the scientific community classifies totipotent cells according to their origin and potentiality. According to their origin they are classified into embryonic, fetal and adult, while according to their potentiality they are classified into the following groups.

Totipotent

Those that give rise to a complete individual.

Pluripotent

They can form cells that will give rise to any embryonic lineage, but they do not give rise to a complete organism.

Multipotent

Those that can only give rise to cells of the same lineage or embryonic layer.

Unipotent

Specialized cells that have the ability to differentiate into a single cell type.

Importance

Studies with totipotent cells (in the broad sense of the classification according to their potential) allow us to see them as a possible cure for many diseases, tissue regeneration, cell therapies and even potential sources for the cloning of plants, animals and the human being himself. which has been the subject of much ethical debate.

Studies of congenital diseases and cancer are approached by expert scientists in totipotent cells, due to the cell development and multiplication present in some of these diseases.

Analyzes and studies of the first zygotic divisions (of totipotent cells) have provided much insight into the activation and inactivation of genes and also about the involvement of proteins that make this process possible.

Other scientific advances related to studies of the first embryonic or zygotic divisions are malformations and / or birth defects caused by abnormal early cell divisions and differentiation.

References

1. Mother cells. Totipotentiality. Recovered from biologia.edu.ar.
2. ML Condic (2014). Totipotency: What It Is and What It Is Not. Stem Cells and Development.
3. Cell potency. Recovered from en.wikipedia.org.
4. Y. Cortés Rivera. RI Hernández, P. San Martín del Angel, E. Zarza Meza, R. Cuervo
5. González (2016). Regenerative potential of the starfish Linckia guildinguii. Hydrobiological.
6. M. Kearl (2012). The Potency of the First Two Cleavage Cells in Echinoderm Development. Experimental Production of Partial and Double Formations »(1891-1892), by Hans Driesch. Embryo Project Encyclopedia. Recovered from embryo.asu.edu.
7. Types of Stem Cells. Latin American Stem Cell Society. Recovered from solcema.com.
8. JFMcClendon (1910). The Development of Isolated Blastomeres of the Frog's Egg. » American Journal of Anatomy.