In addition, the PrP2 expression area included glial cells which was confirmed by the presence ofsox10-GFPcells within the PrP2 positive area (Figure 3GI)

In addition, the PrP2 expression area included glial cells which was confirmed by the presence ofsox10-GFPcells within the PrP2 positive area (Figure 3GI). In conclusion, we describe the presence of PrP2 protein Triptolide (PG490) within the precursors cells (primordium) as well as in the sensory organs of the PLL. lateral Triptolide (PG490) line is altered inPrP2morphants, including nerve axonal outgrowth and primordium migration defects. Reduced neuromast deposition was observed inPrP2morphants as well as inPrP2/mutants. Rosette formation defects were observed inPrP2morphants, strongly suggesting an abnormal primordium organization and reflecting loss of cell cohesion during migration of the primordium. In addition, the adherens junction proteins, E-cadherin and -catenin, were mis-localized after reduction of PrP2 expression and thus contribute to the primordium disorganization. Consequently, hair cell differentiation and number were affected and this resulted in reduced functional neuromasts. At later developmental stages, myelination of the posterior lateral line nerve was altered. Altogether, our study reports an essential role of PrP2 in collective migration process of the primordium and in neuromast formation, further implicating a role for prion protein in cell adhesion. == Introduction == Prion protein, PrPC, is a conserved GPI-anchored protein that can undergo conformational changes to a -sheet enriched form called PrPSc, which is involved in the etiology of transmissible spongiform encephalopathy (TSE). The misfolded form PrPScis well known for its ability to recruit and template the misfolding of normal cellular PrPC, initiating the pathological development of the disease and TSE[1][3]. Furthermore, increasing data demonstrate the involvement of PrPCin mediating A oligomer toxicity in Alzheimer’s disease models[4],[5]. A oligomers affect the localization of PrPCat the cell surface through a high affinity interaction. In addition, lack of PrPCrescues memory impairment and loss of synaptic markers[1],[5],[6],[7]. Moreover prion and amyloid precursor protein have a conserved interaction, demonstrated functionally in zebrafish and at the biochemical level in humans[8]. PrPCis involved in many cellular processes such as neuritic outgrowth[9], adhesion and neuronal activity[1]. PrPCdisruption leads to an increased sensitivity to toxins or hypoxia that results in neuronal death, reflecting a neuroprotective role for PrPC[10],[11]. Mouse knockout models for the prion genePrnpdisplay normal development, metabolism and lifespan, and present with a resistance to PrPScinfection[12],[13]. In the zebrafish model, thePrnpgene is duplicated and the expression of the two paralagous genesPrP1andPrP2are dissociated both spatially and temporally: (i) PrP1 is expressed during early embryonic stages in the whole embryo and is down regulated before the pharyngula stage[14]; and (ii) PrP2 expression coincides with the onset of somitogenesis and is expressed in the central nervous system and cranial ganglia. In comparison with the mammalianPrnpgene,PrP2represents the closest ortholog[15]. While mousePrnpgene knockout does not affect any major developmental or physiological process,PrP1inactivation in zebrafish results in a dramatic phenotype with cellular movement defects and early embryonic lethality[8],[14],[16]. Such severe phenotypes have been Rabbit Polyclonal to HSP105 linked to the loss of blastomere cell adhesion and in particular to the decreased stability of adherens junctions.PrP2inactivation leads to nervous system malformations that affect the anterior part of the neural tube, essentially the telencephalic, midbrain and hindbrain regions[14],[17]. However, discrepancies have been observed followingPrP2gene inactivation using gene targeting, as mutant embryos or larvae show no developmental abnormalities but Triptolide (PG490) impaired NMDA receptor regulation[18]. Whether thePrP2gene is required in nervous Triptolide (PG490) system development is still in debate and morpholino-mediated inactivation has to be carefully evaluated. To clarify the role of PrP2, we took advantage of the well-characterized mechano-sensory system, the zebrafish posterior lateral line (PLL). The PLL ganglion displays a strong expression of PrP2 as early as 30 hours post-fertilization (hpf) and at later developmental stagesPrP2mRNA is observed in the differentiated sensory organs, including in the neuromasts and in its differentiated hair cells[14],[19]. The PLL provides a powerfulin vivomodel to study multiple cellular processes such as cell migration, axonal outgrowth and differentiation process. PLL development relies on the migration of the primordium, a cohesive group of cells that is organized and polarized throughout the migration process. Sensory organs called neuromasts are organized in a stereotype pattern along the PLL at the body surface. Hair cells positioned at the center of each neuromast register and measure water movements and are homologs of mammalian inner ear hair cells[20]. In the present study, using morpholino knockdown, we performed partial gene inactivation and.