title: Analysis of three μ1-AP1 subunits during zebrafish development.
abstract: BACKGROUND
  The family of AP-1 complexes mediates protein sorting in the late secretory pathway and it is essential for the development of mammals. The ubiquitously expressed AP-1A complex consists of four adaptins γ1, β1, μ1A, and σ1A. AP-1A mediates protein transport between the trans-Golgi network and early endosomes. The polarized epithelia AP-1B complex contains the μ1B-adaptin. AP-1B mediates specific transport of proteins from basolateral recycling endosomes to the basolateral plasma membrane of polarized epithelial cells.
  
  
  RESULTS
  Analysis of the zebrafish genome revealed the existence of three μ1-adaptin genes, encoding μ1A, μ1B, and the novel isoform μ1C, which is not found in mammals. μ1C shows 80% sequence identity with μ1A and μ1B. The μ1C expression pattern largely overlaps with that of μ1A, while μ1B is expressed in epithelial cells. By knocking-down the synthesis of μ1A, μ1B and μ1C with antisense morpholino techniques we demonstrate that each of these μ1 adaptins is essential for zebrafish development, with μ1A and μ1C being involved in central nervous system development and μ1B in kidney, gut and liver formation.
  
  
  CONCLUSIONS
  Zebrafish is unique in expressing three AP-1 complexes: AP-1A, AP-1B, and AP-1C. Our results demonstrate that they are not redundant and that each of them has specific functions, which cannot be fulfilled by one of the other isoforms. Each of the μ1 adaptins appears to mediate specific molecular mechanisms essential for early developmental processes, which depends on specific intracellular vesicular protein sorting pathways.
authors.affiliation: Unit of Experimental Oncology and Immunology, Department of Molecular and Translational Medicine University of Brescia, Italy.
authors.forename: Giuseppina
authors.initials: G
authors.lastname: Gariano
authors.forename: Michela
authors.initials: M
authors.lastname: Guarienti
authors.forename: Roberto
authors.initials: R
authors.lastname: Bresciani
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Borsani
authors.forename: Giulia
authors.initials: G
authors.lastname: Carola
authors.forename: Eugenio
authors.initials: E
authors.lastname: Monti
authors.forename: Roberta
authors.initials: R
authors.lastname: Giuliani
authors.forename: Rita
authors.initials: R
authors.lastname: Rezzani
authors.forename: Francesca
authors.initials: F
authors.lastname: Bonomini
authors.forename: Augusto
authors.initials: A
authors.lastname: Preti
authors.forename: Peter
authors.initials: P
authors.lastname: Schu
authors.forename: Daniela
authors.initials: D
authors.lastname: Zizioli
mesh_terms: D000165:Acridine Orange; D033961:Adaptor Protein Complex 1 / Q000235:genetics / Q000378:metabolism; D033966:Adaptor Protein Complex beta Subunits / Q000235:genetics / Q000378:metabolism; D033983:Adaptor Protein Complex mu Subunits / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D017931:DNA Primers / Q000235:genetics; D047108:Embryonic Development / Q000235:genetics*; D055785:Gene Knockdown Techniques; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D060172:Morpholinos / Q000235:genetics; D010802:Phylogeny; D021122:Protein Subunits / Q000235:genetics; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D016415:Sequence Alignment; D017421:Sequence Analysis; D015027:Zebrafish / Q000196:embryology* / Q000378:metabolism; D021601:trans-Golgi Network / Q000378:metabolism*
chemical_list: C439126:AP1B1 protein, human; D033961:Adaptor Protein Complex 1; D033966:Adaptor Protein Complex beta Subunits; D033983:Adaptor Protein Complex mu Subunits; D017931:DNA Primers; D060172:Morpholinos; D021122:Protein Subunits; D000165:Acridine Orange
keywords: adaptin; central nervous system; development; kidney; vesicular transport; zebrafish