Growth hormone receptors in zebrafish (Danio rerio): Adult and embryonic expression patterns Cecilia M. Di Prinzio a , Pablo E. Botta a , Elías H. Barriga b , Eduardo A. Ríos b , Ariel E. Reyes b,c , Silvia E. Arranz a, * a Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET/UNR), Area Biología, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Suipacha 531, S2002LRK Rosario, Argentina b Laboratorio de Biología del Desarrollo, Departamento de Biología, Facultad de Ciencias Biológicas, Universidad Andrés Bello, Av. República 217, Piso 3, Santiago, Chile c Laboratorio de Biología del Desarrollo, Facultad de Ciencias de la Salud, Universidad Diego Portales, Santiago, Chile article info Article history: Received 14 September 2009 Received in revised form 4 March 2010 Accepted 7 March 2010 Available online xxxx Keywords: Zebrafish Growth hormone receptor Growth hormone Development Alternative transcripts In situ hybridization Yolk cell abstract Growth hormone receptor (GHR) is a critical regulator of growth and metabolism. Although two GHRs have been characterized in many fish species, their functional characteristics, mechanisms of regulation and roles in embryonic development remain unclear. The zebrafish (Danio rerio) is an excellent model organism to study both developmental and physiological processes. In the present work, we character- ized the complete cDNA sequences of zebrafish GHRs, ghra and ghrb, and their gene structures. We stud- ied the expression of both receptors in adult tissues, and during embryonic development and larval stages by means of RT-PCR and whole-mount in situ hybridization. We determined that both transcripts are maternal ones, with specific expression patterns during development. Both GHR transcripts are mainly expressed in the notochord, myotomes, anterior structures and in the yolk cell. Interestingly, their expression became undetectable at 96 h post-fertilization. Unlike other reports in fish, ghrs expression could not be detected in brain when adult tissues were used, and we detected ghrb but not ghra tran- scripts in muscle. In addition, we determined alternative transcript sequences for ghra with specific domain deletions, and alternative transcripts for ghrb that generate a premature stop codon and codify for truncated isoforms. These isoforms lack intracellular regions necessary for the activation of signal transducers and activators of transcription (STAT) family transcription factors 5. Ó 2010 Elsevier B.V. All rights reserved. Growth hormone (GH) belongs to the GH/prolactin (PRL)/ somatolactin (SL) family. It is a pleiotropic hormone, implicated in many physiological functions besides growth, such as energy mobilization, gonadal development, appetite, osmoregulation, so- cial behavior (revised in Canosa et al. (2007)) and immunity in fish (Yada et al., 2001). The actions of GH are initiated by its binding to the growth hormone receptor (GHR), localized on the cell mem- brane of target tissues and this could be by means of a trimeric complex, as it has been seen in tetrapods. This complex is formed by a homodimeric receptor (two disulfide linked GHR subunits) and a GH molecule (van den Eijnden et al., 2006). Binding of growth hormone to its receptor results in activation of tyrosine ki- nases that initiate a cascade of events resulting in the rapid tyro- sine phosphorylation of several proteins and the induction of early-response genes (Herrington and Carter-Su, 2001; Zhu et al., 2001). Signaling takes place through the activation of the STAT family of transcription factors, which translocate to the nucleus where they modify the transcription of specific genes (Zhu et al., 2001). The presence of GHR in fish has been demonstrated mainly in the liver and also in other organs such as the brain (Perez-San- chez et al., 1991), gonads (Gomez et al., 1999), gill, intestine and kidney (Sakamoto and Hirano, 1991) and in whole embryos and embryonic tissues (Fuentes et al., 2008; Ozaki et al., 2006b). GHR is a single transmembrane receptor which belongs to the cytokine class I receptor superfamily. It has some conserved characteristics: an extracellular domain with conserved cysteines residues, a li- gand-binding region WSXWS (Y/FGEFS in GHRs) and an intracellu- lar signal transduction region, conformed by Box 1 and Box 2 domains and conserved cytoplasmic tyrosine residues (Kopchick and Andry, 2000). Although GHRs have been characterized in many different fish species, such as Carassius auratus (Lee et al., 2001), Acanthopagrus schlegeli (Tse et al., 2003), Sparus aurata (Calduch- Giner et al., 2003; Saera-Vila et al., 2005), Anguilla japonica (Ozaki et al., 2006a), Silurus meridionalis (Jiao et al., 2006), Oncorhynchus masou (Fukada et al., 2004) and Oreochromis niloticus (Ma et al., 2007) among others, their functional characteristics, mechanisms of regulation and their roles in larval growth and embryonic 1567-133X/$ - see front matter Ó 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.gep.2010.03.001 * Corresponding author. Tel.: +54 341 4350596; fax: +54 341 4804601. E-mail address: arranz@ibr.gov.ar (S.E. Arranz). Gene Expression Patterns xxx (2010) xxx–xxx Contents lists available at ScienceDirect Gene Expression Patterns journal homepage: www.elsevier.com/locate/gep ARTICLE IN PRESS Please cite this article in press as: Di Prinzio, C.M., et al. Growth hormone receptors in zebrafish (Danio rerio): Adult and embryonic expression patterns. Gene Expr. Patterns (2010), doi:10.1016/j.gep.2010.03.001