F-Spondin/spon1b Expression Patterns in Developing and Adult Zebrafish 1 1 1 1 2 Veronica Akle , Emmanuel Guelin , Lili Yu , Helena Brassard-Giordano , Barbara E. Slack , 1 Irina V. Zhdanova * 1 Department of Anatomy & Neurobiology, Boston University School of Medicine, Boston, Massachusetts, United States of America, 2 Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America Abstract F-spondin, an extracellular matrix protein, is an important player in embryonic morphogenesis and CNS development, but its presence and role later in life remains largely unknown. We generated a transgenic zebrafish in which GFP is expressed under the control of the F-spondin (spon1b) promoter, and used it in combination with complementary techniques to undertake a detailed characterization of the expression patterns of F-spondin in developing and adult brain and periphery. We found that F-spondin is often associated with structures forming long neuronal tracts, including retinal ganglion cells, the olfactory bulb, the habenula, and the nucleus of the medial longitudinal fasciculus (nMLF). F-spondin expression coincides with zones of adult neurogenesis and is abundant in CSF-contacting secretory neurons, especially those in the hypothalamus. Use of this new transgenic model also revealed F-spondin expression patterns in the peripheral CNS, notably in enteric neurons, and in peripheral tissues involved in active patterning or proliferation in adults, including the endoskeleton of zebrafish fins and the continuously regenerating pharyngeal teeth. Moreover, patterning of the regenerating caudal fin following fin amputation in adult zebrafish was associated with F-spondin expression in the blastema, a proliferative region critical for tissue reconstitution. Together, these findings suggest major roles for F-spondin in the CNS and periphery of the developing and adult vertebrate. Citation: Akle V, Guelin E, Yu L, Brassard-Giordano H, Slack BE, et al. (2012) F-Spondin/spon1b Expression Patterns in Developing and Adult Zebrafish. PLoS ONE 7(6): e37593. doi:10.1371/journal.pone.0037593 Editor: Filippo Del Bene, Institut Curie, France Received February 17, 2012; Accepted April 26, 2012; Published June 29, 2012 Copyright: 2012 Akle et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: The work was supported by a grant from the Chaikin-Wile Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Abbreviations: A, Anterior hypothalamic nucleus; APP, Amyloid precursor protein; BNSM, Bed nucleus of stria medullaris; BrdU, 5-Bromo-2-deoxyuridine; DAB-1, Disabled-1; Cans, Ansulate commissure; Cant, Anterior commissure; CC, Cerebellar crest; CCe, Cerebellar corpus; Cgus, Gustatory commissure; cHb, Caudal habenula; Chor, Horizontal commissure; CM, Mammillary corpus; Cp, Central posterior thalamic nucleus; Cpost, Posterior commissure; Ctec, Tectal commissure; D, Dorsal pallium; Dd, Dorsal nucleus of dorsal telencephalon; dHb, Dorsal habenula; Dl, Lateral nucleus of dorsal telencephalon; dlHb, Dorsolateral habenula; Dm, Medial nucleus of dorsal telencephalon; dmHb, Dorsomedial habenula; dmHbi, Inferior nucleus of dorsomedial habenula; DOT, Dorsal optic tract; DON, Descending octaval nucleus; Dp, Posterior zone of dorsal telencephalic area; ECM, Extracellular matrix; EG, Granular eminence; fp, Floor plate; FR, Fasciculus retroflexus; Fv, Ventral funiculus; GL, Glomerular layer of olfactory bulbs; H, Hypothalamus; Hb, Habenula; Hc, Caudal hypothalamus; Hd, Dorsal hypothalamus; Hv, Ventral zone of periventricular hypothalamus; IAF, Internal arcuate fibers; ICL, Inner cell layer of olfactory bulbs; LLF, Lateral longitudinal fasciculus; LOT, Lateral olfactory tract; LX, Vagal lobe; Me, Medula oblongata; MLF, Medial longitudinal fasciculus; mn, Motor neuron; MOT, Medial olfactory tract; NI, Nucleus isthmi; Nin, Interpeduncular nucleus; nMLF, Nucleus of medial longitudinal fasciculus; no, Notochord; NPR, Nucleus of the posterior recess; NXm, Motor nucleus of vagus; OB, Olfactory bulb; on, Optic nerve; PGm, Medial preglomerular nucleus; PGl, Lateral preglomerular nucleus; PGZ, Periventricular grey zone; PNT, Posterior tuberal nucleus; Ppa, Parvocellular preoptic area, anterior; Ppp, Posterior preoptic area; PVO, Paraventricular organ; PM, Magnocellular preoptic nucleus; PTN, Posterior tuberal nucleus; PPd, Periventricular pretectal nucleus, dorsal part; PPv, Periventricular pretectal nucleus, ventral part; Pur, Purkinje cell layer; PVO, Paraventricular nucleus; SAC, Stratum album centrale; SCO, Subcommissural organ; SFGS, Stratum fiibrosum et griseum superficiale; SGC, Stratum griseum centrale; SGN, Secondary gustatory nucleus; sm Stria medullaris, ; SM, Stratum marginale; SO, Stratum opticum; SPV, Stratum periventriculare; SR, Superior raphe; RGC, Retinal ganglion cells; RF, Reticular formation; RV, Rhomboencephalic ventricle; Tel, Telencephalon; TeO, Optic tectum; TPp, Posterior tuberculum; TL, Torus longitudinalis; TTB, Tectobulbar tract; URL, Upper rhombic lip; Val, Valvula cerebellis; Vl, Ventrolateral nucleus of the thalamus; VOT, Ventrolateral optic tract; Vv, Ventral nucleus of ventral telencephalic area; vHb, Ventral nucleus of habenula; vNIn, Ventral interpeduncular nucleus; Te, Telencephalon * E-mail: zhdanova@bu.edu Introduction The extracellular matrix (ECM) is an essential component of many tissues, providing for structural support and guidance, and affecting signaling and homeostasis [1]. A small family of ECM proteins, called spondins, is evolutionarily well conserved and includes f-spondin, mindin and subcommissural organ (SCO)- spondin [2]. F-spondin was found to be an important player in embryonic morphogenesis in such diverse species as C. elegans and rat [3,4]. It is also expressed in adult tissues and might play diverse roles in the central nervous system (CNS) and the periphery [2,5–8]. The F-spondin molecule consists of about 800 amino acids, and contains an N-terminal domain homologous to the amino terminus of reelin, a spondin domain and six C-terminal thrombospondin repeats [4]. This structure allows F-spondin to affect different processes through binding to the ECM or membrane receptors. For example, during development, the two proteolytic fragments of F-spondin were found to play opposing though complementary roles in guiding the growth of commissural neurons between the floor plate cells and the basement membrane [9]. Thus, whereas the C-terminal fragment binds to the ECM, promoting neuronal outgrowth along the basement membrane PLoS ONE | www.plosone.org 1 June 2012 | Volume 7 | Issue 6 | e37593