Name: planarian regeneration and body patterning
Uploaded: 2023-04-30T12:10:28.000Z
Duration: 1 min 33 s
Channel: JoVE

K12 Standards

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NC K-12 Science Standard Course of Study

9-12

Biology

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From Molecules to Organisms- Structures and Processes

LS.Bio.2.1

Whole Body Regeneration

Animals across diverse phyla exhibit varying regeneration capacity, including regenerating tissues, organs, or even the entire body from small injury remnants.&#160;
Planaria are flatworms extensively used as model organisms to study regeneration.
They demonstrate extraordinary regenerative abilities owing to a population of adult somatic stem cells, called neoblasts, present throughout their bodies. These cells can divide to produce all types of planarian cells.
After an injury, the wound site first contracts to minimize the surface area, followed by the production of a protective mucosal covering.
The neoblasts then divide throughout the planarian body. This global increase in the neoblast population is followed by a more localized division at the wound site, generating an undifferentiated mass of cells called a blastema.
The blastema then differentiates to form lost tissues and organs. But how do the neoblasts determine which structures need regeneration?
For instance, when a planarian is cut in half transversely, the head needs to regenerate the tail, and the tail needs to regenerate the head. This is regulated by signaling pathways, such as Wnt, that control regeneration polarity.

whole body regeneration

Regeneration is the process of restoring injured or lost tissues, organs, or&#160;body parts. While simpler organisms generally show greater ability to regenerate their whole body, few complex animals show similarly exceptional regeneration. For example, planarian flatworms have a unique regenerative potential making them a popular study organism among biologists to understand the mechanisms of whole body regeneration. Other organisms, such as hydra, also show extreme regeneration potential; even when cut into several pieces, each piece can turn into an individual organism.
Planarian Stem Cells
Planarians are among the few animals that maintain pluripotent stem cells throughout life. First described in the 1800s, these pluripotent stem cells are now called neoblasts. Neoblasts are essential for the regeneration of the endoderm, mesoderm, and ectoderm, thus, facilitating whole body regeneration. These neoblasts are present throughout the planarian body, including the space surrounding the gut. As much as 30 percent of cells in planaria are neoblasts. Thus, a planarian worm can regenerate a whole body even when cut into small pieces.
Regeneration Polarity in Planarians
Regeneration requires the restoration of complex anatomical structures and specific integration of organs within the body through precise control of the organs&#8217; size, location, and identity. When a planarian flatworm is amputated transversely, two fragments are generated &#8212; a fragment containing the head that regenerates a tail; and a tail fragment that regenerates the head. The location along the anterior-posterior axis determines whether the tissue differentiates into the head or tail. The Wnt proteins are a major determinant of this axis, with high Wnt expression in the anterior cells and low Wnt expression in the posterior cells. At the wound site, posterior cells express the Wnt1 gene, which triggers tail regeneration. In contrast, anterior cells express the notum gene, which inhibits the Wnt signaling and facilitates regeneration of the head.

Regeneration is the process of restoring injured or lost tissues, organs, or&#160;body parts. While simpler organisms generally show greater ability to ...

Education

JoVE Core

Cell Biology

Unit 1

Regeneration and Repair

KEY TERMS AND CONCEPTS

planarian regeneration and body patterning

Planarian regeneration shows how a flatworm can rebuild missing body parts and restore the correct body pattern. Regeneration is the process of replacing injured or lost tissues, organs, or body parts. In some simpler organisms, whole-body regeneration is especially strong. Planarians are a key example because biologists study them to understand how this process works.

Other organisms also have extreme regenerative ability. Hydra can regenerate so well that each piece can become a new individual organism. Planarians are unusual because they keep pluripotent stem cells throughout life. These stem cells were first described in the 1800s and are now called neoblasts.

Neoblasts are needed to rebuild the endoderm, mesoderm, and ectoderm, which are the three main tissue layers in the body. They are spread throughout the planarian body, including the area around the gut. In fact, as much as 30 percent of planarian cells are neoblasts. This large stem cell pool helps a planarian worm regenerate a whole body even after being cut into small pieces.

Planarian regeneration also depends on body polarity, which means the body must rebuild structures in the correct direction and position. When a planarian is cut across its body, one fragment with the head grows a tail, and the tail fragment grows a head. Which part forms depends on where the wound is along the anterior-posterior axis, or the head-to-tail axis.

Wnt proteins help control this axis. High Wnt expression is found in anterior cells, while low Wnt expression is found in posterior cells. At the wound site, posterior cells express the Wnt1 gene, which triggers tail regeneration. In contrast, anterior cells express the notum gene, which blocks Wnt signaling and supports head regeneration.

Planarian Regeneration and Body Patterning

planarian-regeneration-and-body-patterning

overview of regeneration and repair

How Tissues Regrow and Heal After Injury

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Planarian regeneration shows how a flatworm can rebuild missing body parts and restore the correct body pattern. Regeneration is the process of replacing injured or lost tissues, organs, or body parts. In some simpler organisms, whole-body regeneration is especially strong. Planarians are a key example because biologists study them to understand how this process works. Other organisms also have extreme regenerative ability. Hydra can regenerate so well that each piece can become a new...

liver regeneration

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stem cell therapy for tissue regeneration

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Stem Cell Repair in Blood and Tissues

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introduction to nuclear reprogramming

Nuclear Reprogramming in Cloning and Stem Cells

Nuclear reprogramming changes the gene expression of one cell type to match another cell type. It often shifts a differentiated cell into a more undifferentiated state. This process is important during development, morphogenesis, tissue regeneration, and malignancy. Cells can also be reprogrammed with laboratory methods. These include nuclear transfer, induced pluripotency, and cell fusion. Scientists use these approaches in molecular medicine, biotechnology, and oncology. A classic early...

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Dolly the sheep was the first successfully cloned mammal. She was born on 5 July 1996 at the Roslin Institute in Scotland, and her name came from the American singer Dolly Parton. Dolly lived for seven years, and she died from respiratory complications. Scientists think her shortened life may have been linked to the age of the DNA used to make her. In cloned cells, the DNA comes from an older individual. Analysis of Dolly’s DNA also showed shorter telomeres than those in other sheep of the...

key terms and concepts

Learn how planarians rebuild lost body parts using neoblast stem cells and Wnt signaling to form the right head or tail after injury.

Planarian Regeneration and Body Patterning | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

LS.Bio.2.2

Tennessee Academic Standards

High School

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Links Among Engineering, Technology, Science, and Society

BIO1.ETS2.3

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From Molecules to Organisms: Structures and Processes

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Planarian Regeneration and Body Patterning

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