Related Experiment Video
Updated: Jun 7, 2026
07:01
Manipulation of Gene Function in Mexican Cavefish
Published on: April 22, 2019
Pineal-specific agouti protein regulates teleost background adaptation.
Chao Zhang1, Youngsup Song, Darren A Thompson
1Department of Molecular Physiology and Biophysics, The Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
Summary
Teleost fish use background adaptation for camouflage. A unique agouti gene (agrp2) in the pineal gland regulates this process, controlling pigment changes in response to background color.
Area of Science:
- Neuroendocrinology
- Comparative Physiology
- Genetics
Background:
- Teleost fish utilize background adaptation as a key camouflage strategy against predators.
- This process involves retinal light sensing and hormonal regulation of melanocytes via melanocyte-stimulating hormone and melanin-concentrating hormone.
- The specific role of the agouti gene family in this adaptation remained largely uncharacterized.
Purpose of the Study:
- To investigate the role of the teleost-specific agouti gene, agrp2, in background adaptation.
- To identify the neuroendocrine pathways involved in regulating pigmentation in response to environmental background.
- To elucidate the function of the pineal gland in mediating background adaptation.
Main Methods:
- Expression analysis of the agrp2 gene in teleost pineal tissue.
- Assessment of hypothalamic pmch and pmchl mRNA levels in response to white background exposure.
- Analysis of melanosome contraction in dermal melanocytes.
- Phenotypic characterization of mutants with defects in pineal development (floating head) and vision (nrc).
Main Results:
- The agouti gene, agrp2, is uniquely expressed in the teleost pineal gland.
- agrp2 is essential for the up-regulation of hypothalamic pmch and pmchl mRNA and melanosome contraction on a white background.
- Mutants with defective pineal development (floating head) showed impaired MCH mRNA up-regulation, while blind mutants (nrc) responded normally.
- These findings highlight a critical role for the pineal gland in background adaptation.
Conclusions:
- The pineal gland plays a significant role in mediating background adaptation in teleosts.
- The teleost-specific agouti gene, agrp2, has a novel physiological function in regulating pigmentation.
- A neuroendocrine axis involving the pineal gland and MCH signaling regulates pigment changes based on environmental background.
Related Concept Videos
01:02The Pineal Gland
The pineal gland, a diminutive endocrine structure named for its pinecone-shaped appearance, is situated atop the third ventricle within the diencephalon region of the forebrain. This gland, composed of secretory cells known as pinealocytes arranged in compact cords and clusters around dense particles of calcium salts, plays a pivotal role in hormonal regulation.
The primary secretion of the pineal gland is the hormone melatonin, derived from serotonin. The concentration of melatonin in the...
The primary secretion of the pineal gland is the hormone melatonin, derived from serotonin. The concentration of melatonin in the...
01:39Epistasis
In addition to multiple alleles at the same locus influencing traits, numerous genes or alleles at different locations may interact and influence phenotypes in a phenomenon called epistasis. For example, rabbit fur can be black or brown depending on whether the animal is homozygous dominant or heterozygous at a TYRP1 locus. However, if the rabbit is also homozygous recessive at a locus on the tyrosinase gene (TYR), it will have an unshaded coat that appears white, regardless of its TYRP1...
02:27Background and Environment Affect Phenotype
Although the genetic makeup of an organism plays a major role in determining the phenotype, there are also several environmental factors, such as temperature, oxygen availability, presence of mutagens, that can alter an organism’s phenotype.
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
An example of how genetic background affects phenotype can be seen in horses. The Extension gene in horses is responsible for their coat color. A wild-type gene (EE) produces black pigment in the coat, while a mutant gene (ee) produces red pigment. A...
02:45Biological Clocks and Seasonal Responses
The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. The period of light-exposure is called the photoperiod.
01:09Epistasis Analysis
Although Mendel chose seven unrelated traits in peas to study gene segregation, most traits involve multiple gene interactions that create a spectrum of phenotypes. When the interaction of various genes or alleles at different locations influences a phenotype, this is called epistasis. Epistasis often involves one gene masking or interfering with the expression of another (antagonistic epistasis). Epistasis often occurs when different genes are part of the same biochemical pathway. The...