ZOOHCC - 601: Developmental Biology (Theory)
Unit 1: Introduction
Basic concepts of Cell-cell interaction
Cell-cell interaction is a fundamental process in developmental biology that involves communication and coordination between adjacent cells during embryonic development. It is essential for the proper formation and function of tissues and organs in multicellular organisms. Here are some basic concepts of cell-cell interaction in developmental biology:
Stable cell-cell interactions
Stable cell-cell interactions refer to long-lasting and persistent connections between cells that are required for the proper functioning of tissues and organs. These interactions are typically mediated by adhesion molecules and extracellular matrix components, which allow cells to stick together and form stable structures.
Stable cell-cell interactions are crucial for the maintenance of tissue architecture and function. For example, the stable interaction between epithelial cells in the skin forms a barrier that protects the body from environmental stresses, while the stable interactions between muscle cells in the heart allow for coordinated contraction and efficient pumping of blood.
Unstable or transient cell-cell interactions occur when cells interact for short periods of time and then dissociate. These interactions are often mediated by signaling molecules and are involved in processes such as cell migration and immune cell recognition.
Example of stable cell interection
An example of stable cell-cell interactions is the interaction between endothelial cells and smooth muscle cells in blood vessels. Endothelial cells form the inner lining of blood vessels and provide a barrier between the blood and the surrounding tissues. Smooth muscle cells, located in the middle layer of blood vessels, provide structural support and regulate vessel diameter.
During blood vessel formation and maintenance, endothelial cells and smooth muscle cells interact through stable adhesive interactions mediated by specific adhesion molecules and extracellular matrix components. This interaction is critical for proper blood vessel function, as disruption of the endothelial-smooth muscle cell interaction can lead to diseases such as atherosclerosis and hypertension.
Another example of stable cell-cell interactions is the interaction between neurons and glial cells in the nervous system. Neurons are the functional units of the nervous system, while glial cells provide support and insulation. During development, neurons and glial cells interact through adhesive interactions and signaling pathways, which are essential for proper nervous system development and function. Disruption of these stable interactions can lead to neurological disorders such as multiple sclerosis and Alzheimer's disease.
Different types of stable cell interection
There are several different types of stable cell-cell interactions, which vary depending on the type of cells involved and the specific molecules that mediate the interaction. Here are some examples:
Adhesion-mediated interactions: This type of interaction occurs when cells stick together through specialized adhesion molecules on their surfaces. These molecules can be either homophilic (binding to the same type of molecule on another cell) or heterophilic (binding to a different type of molecule on another cell). Examples of adhesion molecules include cadherins, integrins, and selectins.
Extracellular matrix-mediated interactions: Cells can interact with the extracellular matrix (ECM) that surrounds them through receptors on their surfaces. This type of interaction is essential for cell migration and differentiation. ECM molecules such as collagen and fibronectin can interact with integrin receptors on the cell surface.
Tight junction-mediated interactions: Tight junctions are specialized cell-cell junctions that form a barrier between cells and prevent the diffusion of molecules between them. This type of interaction is crucial for the proper functioning of epithelial and endothelial tissues, where tight junctions form a physical barrier to control the movement of substances across the tissue.
Gap junction-mediated interactions: Gap junctions are channels between adjacent cells that allow for the direct transfer of ions and small molecules. This type of interaction is essential for coordinating the behavior of cells within a tissue.
Synapse-mediated interactions: Synapses are specialized junctions between neurons or between neurons and other cells, such as muscle cells. These interactions involve the release of chemical messengers called neurotransmitters, which allow cells to communicate and coordinate their activity.
Transient interactions
Transient interactions refer to short-lived connections between cells that occur for a limited time and then dissociate. These interactions can be mediated by various mechanisms, such as signaling molecules or mechanical forces, and can be important for a variety of biological processes, such as cell migration, immune cell recognition, and neuronal communication.
Examples of transient interactions
Signaling interactions: Cells can communicate with each other through the release of signaling molecules, such as growth factors or cytokines. These interactions are often transient, with the signaling molecule binding to its receptor on the target cell for a limited time before dissociating.
Immune cell recognition: Immune cells such as T cells and B cells recognize and respond to foreign antigens through transient interactions with antigen-presenting cells, such as dendritic cells. These interactions are mediated by specialized receptors on the immune cells and can lead to the activation of the immune response.
Neuronal communication: Neurons communicate with each other through transient interactions at specialized junctions called synapses. These interactions involve the release of neurotransmitters, which bind to receptors on the target cell and trigger a response.
Cell migration: During development and wound healing, cells can migrate to new locations through transient interactions with the extracellular matrix and neighboring cells. These interactions are often mediated by specialized adhesion molecules and can be influenced by signaling molecules such as chemokines.
transient interactions play important roles in many biological processes, but their transient nature means that they can be easily regulated and fine-tuned to achieve specific outcomes.
Pathological implications
Disruptions in transient interactions can have pathological implications and contribute to various diseases. Here are some examples:
Cancer metastasis: Cancer cells can spread to other parts of the body through transient interactions with the extracellular matrix and neighboring cells. These interactions can be mediated by adhesion molecules and signaling pathways, and disruptions in these interactions can lead to uncontrolled cell migration and invasion, resulting in the formation of metastatic tumors.
Autoimmune diseases: In autoimmune diseases, the immune system mistakenly attacks the body's own cells and tissues. This can occur due to disruptions in transient interactions between immune cells and self-antigens, which can lead to the activation of autoreactive immune cells.
Neurodegenerative diseases: Neurodegenerative diseases such as Alzheimer's and Parkinson's are characterized by the progressive loss of neurons and synapses. Disruptions in transient interactions between neurons and glial cells, or between neurons and their targets, can contribute to this degeneration.
Inflammatory diseases: Inflammatory diseases such as rheumatoid arthritis and inflammatory bowel disease can occur due to disruptions in transient interactions between immune cells and tissues, leading to chronic inflammation and tissue damage.
Disruptions in transient interactions can contribute to a wide range of pathological conditions, and understanding the underlying mechanisms can provide insights into the development of new therapeutic strategies.
