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Updated: Jun 10, 2026
In Vivo Modeling of the Morbid Human Genome using Danio rerio
Published on: August 24, 2013
Characterization of the AP-1 μ1A and μ1B adaptins in zebrafish (Danio rerio)
Daniela Zizioli1, Elena Forlanelli, Michela Guarienti
1Department of Biomedical Sciences and Biotechnology, Unit of Biochemistry and Unit of Biology (GB), University of Brescia, Brescia, Italy.
Abstract:
Protein transport between the trans-Golgi network and endosomes is mediated by transport vesicles formed by the adaptor-protein complex AP-1, consisting of the adaptins γ1, β1, μ1, σ1. Mammalia express μ1A ubiquitously and isoform μ1B in polarized epithelia. Mouse γ1 or μ1A 'knock out's revealed that AP-1 is indispensable for embryonic development. We isolated μ1A and μ1B from Danio rerio. Analysis of μ1A and μ1B expression revealed tissue-specific expression for either one during embryogenesis and in adult tissues in contrast to their expression in mammalia. μ1B transcript was detected in organs of endodermal derivation and "knock-down" experiments gave rise to embryos defective in formation of intestine, liver, and pronephric ducts. Development ceased at 7-8 dpf. μ1B is not expressed in murine liver, indicating loss of μ1B expression and establishment of alternative sorting mechanisms during mammalian development.
Insights
The adaptor-protein complex AP-1 is vital for protein transport. In zebrafish, distinct expression of AP-1 isoforms (μ1A and μ1B) is crucial for organ development, unlike in mammals.
Area of Science:
- Cell Biology
- Developmental Biology
- Molecular Biology
Background:
- Protein transport between the trans-Golgi network and endosomes relies on adaptor-protein complex AP-1.
- AP-1 comprises adaptins γ1, β1, μ1, and σ1.
- Mammals express μ1A ubiquitously and μ1B in polarized epithelia; AP-1 is essential for mammalian embryonic development.
Purpose of the Study:
- To investigate the expression and function of AP-1 adaptins (μ1A and μ1B) in Danio rerio (zebrafish).
- To compare zebrafish AP-1 expression patterns with those in mammals.
- To elucidate the role of μ1B in zebrafish organogenesis.
Main Methods:
- Isolation of μ1A and μ1B adaptins from Danio rerio.
- Analysis of μ1A and μ1B expression patterns during zebrafish embryogenesis and in adult tissues.
- Zebrafish "knock-down" experiments to assess functional consequences of μ1B depletion.
Main Results:
- Zebrafish exhibit tissue-specific expression of μ1A and μ1B, contrasting with mammalian ubiquitous μ1A expression.
- μ1B transcripts were detected in endodermal organs.
- "Knock-down" of μ1B resulted in defective formation of the intestine, liver, and pronephric ducts, leading to developmental arrest at 7-8 days post-fertilization.
Conclusions:
- Zebrafish μ1A and μ1B adaptins play distinct, crucial roles in organ development.
- The tissue-specific expression of μ1B in zebrafish suggests a divergence from mammalian protein sorting mechanisms.
- The loss of μ1B expression in mammalian liver indicates the evolution of alternative sorting pathways during mammalian development.
