Cell specialization or cell differentiation is a process of converting generic cells in the body into specialized cells. The specialized cells can perform a certain function within the body. The cell specialization occurs in two stages of a multicellular organism. During the embryonic development, cell specialization occurs mainly due to cell signaling of cytoplasmic determinants. During adult development, the stem cells become specialized to various types of stem cells mainly due to the regulation of gene expression. Cell specialization in both development stages is described in this article.
Key Areas Covered
1. What is Cell Specialization
– Definition, Features, Function
2. How Do Cells Become Specialized
– Embryonic Development, Adult Development
Key Terms: Adult Stem Cells, Cell Specialization, Cytoplasmic Determinants, Embryonic Stem Cells, Epigenetic Control, Signaling Cascades
What is Cell Specialization
Cell specialization refers to the differentiation of cells based on their location of the tissue during their development. Within a multicellular organism, cell specialization occurs in numerous times during tissue repair and during normal cell turnover. Moreover, within the embryo, the cells are specialized into various types for developing a multicellular organism. The cell specialization is shown in figure 1.
Figure 1: Cell Specialization
The cell specialization changes the size of the cell, shape, metabolic activity, membrane potential, and the responsiveness to signals.
How Do Cells Become Specialized
Different types of cell specialization can be observed in different developmental stages of life.
Cell Specialization During Embryonic Development
The zygote is the conceptus of fertilization, and it is composed of a single cell. It divides into many cells through mitosis, forming the blastomere. The cells in the blastomere are totipotent, and they are capable of differentiating into any type of cells in the body as well as the in the placenta. The cells of the eight-cell stage are known as embryonic stem cells. The embryonic stem cells are pluripotent, and they are capable of differentiating into any types of cells in the body of an animal. The pluripotent cells in plants are known as meristematic cells. These embryonic stem cells are differentiated into the three germ layers of the body: endoderm, ectoderm, and mesoderm. The cells in the germ layers are multipotent, and they are capable of differentiating into corresponding tissues of the body developed from each of the three germ layers. The embryonic development is shown in figure 1.
Figure 1: Embryonic Development
The cell division that occurs during the embryonic development is a type of asymmetric cell division. Asymmetric cell division gives rise to the daughter cells with distinct development fates. The two main reasons for the asymmetric cell division are cytoplasmic determinants and different cell signaling cascades. Cytoplasmic determinants are regulatory molecules of the parent cell. In signaling cascades, a particular cell induces its neighboring cells to develop into its type by transmitting signaling molecules into them.
Cell Specialization During Adult Development
Multicellular organisms have different types of cells that are specialized to perform a particular function in the body. The cells that perform a certain function are arranged into tissues. Therefore, a particular tissue consists of cells with a defined function. The unspecialized cells in the adult body are known as adult stem cells. The differentiation of hematopoietic stem cells into specialized cell types in the blood is shown in figure 3.
Figure 3: Hematopoietic Stem Cell Differentiation
The main mechanism of producing specialized cells from stem cells is the regulation of gene expression through epigenetic mechanisms. Hence, the type of the cell is determined at the level of gene expression. Moreover, the pattern of gene expression has to be maintained over generations. The differential gene expression is achieved by histone modifications and different levels of DNA methylation. Generally, the patterns of DNA methylation in embryonic stem cells and pluripotent adult stem cells are the same. But, it is different in the specialized somatic cells. Adult stem cells are pluripotent, and their pluripotency is maintained by transcription factors known as OCT4, SOX2, and NANGO.
Conclusion
Cell specialization is the differentiation of cells to perform a certain function of the body of multicellular organisms. Different types of cell specialization occur during embryonic development and adult development. During embryonic development, the cells in the blastomere are differentiated into cells with different potency through cell signaling and cytoplasmic determinants. During adult development, the cell specialization occurs through the regulation of gene expression.
Reference:
1.“Cellular Differentiation.” Wikipedia, Wikimedia Foundation, 17 Mar. 2018, Available here.
2.“Breakthrough in Understanding How Stem Cells Become Specialized.” SBP, Available here.
Image Courtesy:
1. “Figure 2. Résultats de différenciation de cellules souches en une des trois différentes catégories de cellules qui se sous-divisent en types de cellules spécifiques avec des rôles précis7” By Ryongraf (CC BY-SA 4.0) via Commons Wikimedia
2. “Stemcelldifferentiaion” By US gov (Public Domain) via Commons Wikimedia
3.”422 Feature Stem Cell new” By OpenStax College – Anatomy & Physiology, Connexions Web site, Jun 19, 2013 (CC BY 3.0) via Commons Wikimedia
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