Main Difference – Totipotent vs Pluripotent
Totipotent and pluripotent are two types of potencies exhibited by stem cells in the body. Both totipotent and pluripotent stem cells are found in the early stages of development. Totipotent stem cells are found in both spore and zygote. They are the first stage of differentiation. Totipotent stem cells give rise to pluripotent stem cells in the embryo. Since embryonic stem cells are commonly used for research, they can be used to regenerate organs in vitro. The main difference between totipotent and pluripotent is that totipotent stem cells are capable of differentiating into all types of body cells whereas pluripotent stem cells are capable of differentiating into any of the three germ layers of the embryo.
This article looks at,
1. What is Totipotent
– Definition, Differentiation, Uses, Examples
2. What is Pluripotent
– Definition, Differentiation, Uses, Examples
3. What is the difference between Totipotent and Pluripotent
What is Totipotent
A stem cell which is capable of giving rise to any kind of differentiated cells in a particular organism is considered as totipotent. That means these cells contain the highest potential of differentiation. Zygote and spore are two examples of totipotent cells. But some differentiated cells are also capable of returning to totipotency state.
In humans, the zygote is formed after the fertilization of the ovum by the sperm. Zygote is divided by mitosis, generating identical cells which later become totipotent. Zygote forms the morula, which is further divided to form the blastocyte. After the implantation of blastocyte in the endometrium, the differentiation process begins. This stage is referred to as the embryonic stage, and it has separated two cell masses called outer trophoblast and inner cell mass. Hence, the trophoblast and the inner cell mass are differentiated from the totipotent cells in the morula. Then, inner cell mass becomes pluripotent by differentiating into three germ layers: endoderm, mesoderm, or ectoderm. These three germ layers give rise to different types of specialized cells in the body by becoming multipotent. Therefore, the totipotent stem cells in humans are capable of differentiating into any type of a body cell; there are more than 200 distinct types of human body cells.
Figure 1: Differentiation of totipotent embryonic stem cells
What is Pluripotent
A stem cell that is capable of differentiating into any of the three germ layers is considered as pluripotent. The three germ layers are endoderm, ectoderm, and mesoderm. Each of these three germ layers is then differentiated into different organs and tissues by becoming multipotent. Multipotent cells are capable of differentiating into several types of cells which are functionally related to each other. Endoderm gives rise to the interior stomach lining, gastrointestinal tract, and lungs. Ectoderm gives rise to epidermal tissues and the nervous system. Mesoderm gives rise to bones, muscles, and blood. However, some cells like embryonic cells and induced pluripotent stem cells (iPS) are completely pluripotent. The iPS are reprogrammed from adult stem cells by genetically modifying the cell in order to behave like embryonic stem cells. They can be used to regenerate organs in vitro. Some are partially pluripotent, though they are capable of forming three germ layers. Regeneration of organs using iPS is shown in figure 2.
Figure 2: Regeneration of organs from iPS
Difference Between Totipotent and Pluripotent
Definition
Totipotent: Stem cells which are capable of differentiating into all types of body cells are totipotent.
Pluripotent: Stem cells which are capable of differentiating into any of the three germ layers are pluripotent.
Differentiation
Totipotent: Totipotent stem cells are capable of differentiating into more than 200 functionally distinct types of body cells in humans.
Pluripotent: Pluripotent stem cells are differentiated into three germ layers in the embryo.
Potential of Differentiation
Totipotent: The potential of differentiation is optimal in totipotent stem cells.
Pluripotent: The potential of differentiation of pluripotent stem cells is low compared to totipotent stem cells.
Examples
Totipotent: The zygote and spore are totipotent.
Pluripotent: Embryonic stem cells and iPS are pluripotent.
Sequence
Totipotent: Totipotent stem cells are derived early.
Pluripotent: The development of totipotent stem cells is followed by the development of pluripotent stem cells.
Uses in Research
Totipotent: Totipotent stem cells are less achievable compared to embryonic stem cells. Hence, they are less used in research.
Pluripotent: Pluripotent stem cells like embryonic cells are easy to obtain. Hence, their uses in research are high. The iPS are a type of stem cells in adults, which are genetically reprogrammed to become embryonic stem cells.
Conclusion
Both totipotent and pluripotent stem cells are found in the early development stages of the body. After the fertilization of the ovum by a sperm, the zygote is divided by mitosis, producing a cell mass, which is known as the morula with identical copies of cells. Morula is considered to be totipotent, containing the ability to differentiate into all functional types of body cells. The totipotent cells of the morula are differentiated into the embryo, containing blastomere. Embryonic stem cells, which have the ability to differentiate into three germ layers in humans, are considered to be pluripotent. The three germ layers, endoderm, ectoderm and meseoderm are responsible for the differentiation of all organs and tissues in the body. Therefore, cells in the three germ layers are considered as multipotent, each giving rise to functionally related types of body cells. However, the main difference between totipotent and pluripotent is the potential of differentiation to produce cells in the body.
Reference:
1. Condic, Maureen L. “Totipotency: What It Is and What It Is Not.” Stem Cells and Development. Mary Ann Liebert, Inc., 15 Apr. 2014. Web. 29 Mar. 2017.
2. Bhartiya, Deepa, Punam Nagvenkar, and Kalpana Sriraman AndAmbreen Shaikh. “An Overview of Pluripotent Stem Cells.” An Overview of Pluripotent Stem Cells | InTechOpen. InTech, 28 Aug. 2013. Web. 29 Mar. 2017.
Image Courtesy:
1. “422 Feature Stem Cell new” By OpenStax College – Anatomy & Physiology, Connexions Web site. (CC BY 3.0) via Commons Wikimedia
2. “Ips cells” By GcG (wpja user) (Public Domain) via Commons Wikimedia
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