Molecular analysis of neurogenic placode development in a basal ray‐finned fish

Abstract

Summary: Neurogenic placodes are transient, thickened patches of embryonic vertebrate head ectoderm that give rise to the paired peripheral sense organs and most neurons in cranial sensory ganglia. We present the first analysis of gene expression during neurogenic placode development in a basal actinopterygian (rayfinned fish), the North American paddlefish (Polyodon spathula). Pax3 expression in the profundal placode confirms its homology with the ophthalmic trigeminal placode of amniotes. We report the conservation of expression of Pax2 and Pax8 in the otic and/or epibranchial placodes, Phox2b in epibranchial placode-derived neurons, Sox3 during epibranchial and lateral line placode development, and NeuroD in developing cranial sensory ganglia. We identify Sox3 as a novel marker for developing fields of electrosensory ampullary organs and for ampullary organs themselves. Sox3 is also the first molecular marker for actinopterygian ampullary organs. This is consistent with, though does not prove, a lateral line placode origin for actinopterygian ampullary organs. genesis 49:278-294, 2011. V V C 2011 Wiley-Liss, Inc.

Insights into electrosensory organ development, physiology and evolution from a lateral line-enriched transcriptome

“…Sox3 is 5.2-fold lateral line-enriched (Supplementary file 1); as noted above, we previously reported its expression in paddlefish ampullary organs and neuromasts (Modrell et al, 2011b). Sox1 is 8.6-fold lateral line-enriched (Supplementary file 1) and expressed in ampullary organs from their eruption (Figure 2M–P).…”

“…These were: the homeodomain transcription factor genes Six1 and Six2 (Modrell et al, 2011a); the HMG-domain SoxB1 class transcription factor gene Sox3 (Modrell et al, 2011b); and the basic helix-loop-helix (bHLH) transcription factor gene Atoh1 , whose lateral line organ expression at stages 40–45 was noted, in passing, in a study on cerebellum development (Butts et al, 2014). …”

Evolution of electrosensory ampullary organs: conservation of Eya4 expression during lateral line development in jawed vertebrates

“…The expression of Sox2 in axolotls is currently unknown; however, in paddlefish, Sox2 is expressed in both neuromasts and ampullary organs (M.S.M., unpublished data). Recently, we also identified the related SoxB1-group family member Sox3 as a marker for both neuromasts and ampullary organs in the paddlefish (Modrell et al 2011b). …”

“…Phylogenetic analyses were performed under a Bayesian-coalescence framework, implemented in BEAST v1.6.1 (Drummond and Rambaut 2007). The analysis was performed as previously described (Modrell et al 2011b). …”

From Sequence to Spike to Spark: Evo-devo-neuroethology of Electric Communication in Mormyrid Fishes

“…The cells within each ridge then begin to differentiate, forming neuromast mechanoreceptor primordia within their central zone and ampullary electroreceptor primordia within their lateral zone, each originating from different cell lineages (Northcutt et al, 1994). All of the placodes express several genes that appear to constitute a regulatory network for the specifi cation of different groups of placodes and their sensory cells (Baker & Bonner-Fraser, 2001;Freitas et al, 2006;Gibbs & Northcutt, 2004;Metscher et al, 1997;Modrell et al, 2011aModrell et al, , 2011bO ' Neill et al, 2007;Schlosser, 2002).…”