Related Experiment Video
Updated: Jun 17, 2026
07:34
The Power of Simplicity: Sea Urchin Embryos as in Vivo Developmental Models for Studying Complex Cell-to-cell Signaling Network Interactions
Published on: February 16, 2017
Indirect development, transdifferentiation and the macroregulatory evolution of metazoans
1Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182-4614, USA. arenas@sciences.sdsu.edu
Summary
Metazoans primarily use a biphasic life cycle with larval dedifferentiation, not just set-aside cells. This developmental plasticity in larvae is key to indirect development and evolution.
Area of Science:
- Developmental Biology
- Evolutionary Biology
- Genetics
Background:
- Metazoan life cycles often involve distinct larval and adult stages.
- The origin of indirect development and its relationship to direct development remain debated.
- Cellular plasticity and its role in development and evolution are key areas of research.
Purpose of the Study:
- To propose a biphasic life cycle with partial dedifferentiation as the mainstream metazoan developmental mode.
- To highlight developmental plasticity of differentiated cells as central to indirect development.
- To explore the evolutionary origins and implications of developmental plasticity.
Main Methods:
- Comparative analysis of metazoan life cycles and developmental strategies.
- Review of cellular and molecular mechanisms underlying developmental plasticity.
- Examination of genetic data, including Hox gene function and histone variants.
Main Results:
- Many differentiated larval cells can dedifferentiate and contribute to adult tissues, challenging the 'set-aside' cell model.
- Transcriptional pluripotency, potentially facilitated by H2A.Z, has premetazoan origins.
- Developmental plasticity may drive the evolution of polyphenism and influence larval gut formation and Hox gene function.
Conclusions:
- A biphasic life cycle with partial larval dedifferentiation is proposed as the dominant metazoan developmental strategy.
- Developmental plasticity of differentiated cells is a fundamental aspect of indirect development and evolution.
- The ancestral function of the Hox cluster may have been in gonad formation rather than anteroposterior patterning.
Related Concept Videos
01:28Forced Transdifferentiation
Transdifferentiation, also known as lineage reprogramming, was first discovered by Selman and Kafatos in 1974 in silkmoths. They observed that the moths’ cuticle-producing cells transformed into salt-producing cells. Many such cases of natural transdifferentiation occur in organisms. In humans, pancreatic alpha cells can become beta cells. In newts, the loss of the eye’s lens causes the pigmented epithelial cells to transdifferentiate into the lens cells.
Artificial transdifferentiation occurs...
Artificial transdifferentiation occurs...
00:57Cellular Differentiation
How does a complex organism such as a human develop from a single cell? It all starts from a single fertilized egg which gives rise to a vast array of cell types, such as nerve cells, muscle cells, and epithelial cells that characterize the adult? Throughout development and adulthood, cellular differentiation leads cells to assume their final morphology and physiology. Differentiation is the process by which unspecialized cells become specialized to carry out distinct functions.
A zygote is a...
A zygote is a...
01:24Evolution of New Traits in Microbes
Microorganisms evolve rapidly due to their large population sizes and short generation times, often exhibiting measurable changes within days under laboratory conditions. Natural selection acts on standing genetic variation, enabling the retention and amplification of beneficial traits that confer fitness advantages in changing environments.Adaptive Pigment Regulation in RhodobacterIn Rhodobacter, a genus of purple non-sulfur bacteria, light-harvesting pigments such as bacteriochlorophyll and...
02:02Cis-regulatory Sequences
Cis-regulatory sequences are short fragments of non-coding DNA that are present on the same chromosomes as the genes that they regulate. These fragments serve as binding sites for transcriptional regulators, proteins that are responsible for controlling gene transcription and differential gene expression across cell types in eukaryotes. Cis-regulatory sequences can be close to the gene of interest or thousands of bases away in the DNA sequence; however, those sequences that are further away are...
01:56Gastrulation
Gastrulation establishes the three primary tissues of an embryo: the ectoderm, mesoderm, and endoderm. This developmental process relies on a series of intricate cellular movements, which in humans transforms a flat, “bilaminar disc” composed of two cell sheets into a three-tiered structure. In the resulting embryo, the endoderm serves as the bottom layer, and stacked directly above it is the intermediate mesoderm, and then the uppermost ectoderm. Respectively, these tissue strata will form...
02:23Master Transcription Regulators
Master transcription regulators are regulatory proteins that are predominantly responsible for regulating the expression of multiple genes. Often these genes work in concert to drive a complex process. Activation of a master transcription regulator can lead to a cascade of transcriptional activation necessary for that outcome. These regulators can directly bind to the regulatory sequences of the various genes involved, or they can indirectly regulate transcription by binding to regulatory...