Gene Expression Patterns 7 (2007) 274–281 www.elsevier.com/locate/modgep 1567-133X/$ - see front matter  2006 Elsevier B.V. All rights reserved. doi:10.1016/j.modgep.2006.09.004 Localization of anosmin-1a and anosmin-1b in the inner ear and neuromasts of zebraWsh Sylvain Ernest a,b , Stéphanie Guadagnini c , Marie-Christine Prévost c , Nadia Soussi-Yanicostas d,e,¤ a INSERM, U784, Paris, F-75005, France b Ecole Normale Supérieure, Paris, F-75005, France c Institut Pasteur, Microscopie électronique (Plate-forme), Paris, F-75015, France d INSERM, U616, Equipe Avenir, Paris, F-75651, France e Université Pierre et Marie Curie, Laboratoire du développement normal et pathologique du cerveau, Paris, F-75651, France Received 1 August 2006; received in revised form 5 September 2006; accepted 6 September 2006 Available online 10 September 2006 Abstract Anosmin-1, encoded by the KAL-1 gene, is the protein defective in the X-linked form of Kallmann syndrome. This human develop- mental disorder is characterized by defects in cell migration and axon target selection. Anosmin-1 is an extracellular matrix protein that plays a role, in vitro, in processes such as cell adhesion, neurite outgrowth, axon guidance, and axon branching. The zebraWsh possesses two orthologues of the KAL-1 gene: kal1a and kal1b, which encode anosmin-1a and anosmin-1b, respectively. Previous in situ hybridiza- tion studies have shown that kal1a and kal1b mRNAs are expressed in undetermined cells of the inner ear but not in neuromast cells. Using speciWc antibodies against anosmin-1a and anosmin-1b, we report here that both proteins are expressed in sensory hair cells of the inner ear cristae ampullaris and the lateral line neuromasts. Accumulation of these proteins was observed mainly at the level of the hair bundle and also at the cell membrane. In neuromast hair cells, immunogold scanning electronmicroscopy demonstrated that anosmin-1a and anosmin-1b were present at the surface of the stereociliary bundle. In addition, anosmin-1a, but not anosmin-1b, was detected on the track of the ampullary nerve. This is the Wrst report of anosmin-1 expression in sensory hair cells of the inner ear and lateral line, and along the ampullary nerve track.  2006 Elsevier B.V. All rights reserved. Keywords: ZebraWsh; Kallmann syndrome; Kal1a; Kal1b; Anosmin-1a; Anosmin-1b; Neuromast; Inner ear; Hair cells; Kinocilia; Stereocilia; Lateral line; Crista; Anosmia; Hypogonadism; Anti-anosmin-1a; Anti-anosmin-1b; Scanning electron microscopy 1. Results and discussion Kallmann syndrome is a human developmental disorder in which cell migration and axon target selection are aVected (De Morsier, 1954; Kallmann et al., 1994; Maestre de San Juan, 1856; Naftolin et al., 1971; Quinton et al., 2001). In this disease, the olfactory neuron axons and the gonadotropin-releasing hormone (GnRH) synthesizing neurons do not reach their targets in the brain (Schwanzel- Fukuda et al., 1989), thus leading to anosmia and gonado- tropic hypogonadism. KAL-1 encodes anosmin-1, an extra- cellular matrix protein that displays cell adhesion, neurite outgrowth, axon guidance, and axon branch-promoting activities in vitro (Hardelin et al., 1999; Soussi-Yanicostas et al., 1996, 1998, 2002). In zebraWsh (Danio rerio), two orthologues of the KAL-1 gene have been identiWed: kal1a and kal1b (Ardouin et al., 2000), which encode anosmin-1a and anosmin-1b, respectively. Expression patterns of kal1a and kal1b, as determined by in situ hybridization (Ardouin et al., 2000), are largely non-overlapping. kal1a and/or kal1b are transcribed in the olfactory system, the inner ear, the lateral line primor- dium, the retina, areas of the central nervous system, and * Corresponding author. Tel.: +33 142162676; fax: +33 145709990. E-mail address: soussi@chups.jussieu.fr (N. Soussi-Yanicostas).