Dynamic expression of Notch-dependent neurogenic markers in the chick embryonic nervous system.

Leslie Ratiã©,Vã©Ronique David,Michelle Ware,Valã©Rie Dupã©,Hã©Lã¨Ne Jagline

doi:10.3389/fnana.2014.00158

Abstract

The establishment of a functional nervous system requires a highly orchestrated process of neural proliferation and differentiation. The evolutionary conserved Notch signaling pathway is a key regulator of this process, regulating basic helix-loop-helix (bHLH) transcriptional repressors and proneural genes. However, little is known about downstream Notch targets and subsequently genes required for neuronal specification. In this report, the expression pattern of Transgelin 3 (Tagln3), Chromogranin A (Chga) and Contactin 2 (Cntn2) was described in detail during early chick embryogenesis. Expression of these genes was largely restricted to the nervous system including the early axon scaffold populations, cranial ganglia and spinal motor neurons. Their temporal and spatial expression were compared with the neuronal markers Nescient Helix-Loop-Helix 1 (Nhlh1), Stathmin 2 (Stmn2) and HuC/D. We show that Tagln3 is an early marker for post-mitotic neurons whereas Chga and Cntn2 are expressed in mature neurons. We demonstrate that inhibition of Notch signaling during spinal cord neurogenesis enhances expression of these markers. This data demonstrates that Tagln3, Chga and Cntn2 represent strong new candidates to contribute to the sequential progression of vertebrate neurogenesis.

Highlights

The central and peripheral nervous system of vertebrates arises from tissue with various embryological origins
KINETIC EXPRESSION STUDY OF Nescient Helix-Loop-Helix 1 (Nhlh1), Transgelin 3 (Tagln3), Chromogranin A (Chga), Contactin 2 (Cntn2) AND Stathmin 2 (Stmn2) DURING EARLY NEUROGENESIS IN THE CHICK EMBRYO The developmental expression patterns of Tagln3, Chga and Cntn2 were analyzed by whole-mount in situ hybridization between HH8 and HH22
The expression was compared with Nhlh1, an early pan-neuronal marker and Stmn2, a well-known marker of terminally differentiated neurons (Groves et al, 1995; Murdoch et al, 1999)

Summary

Introduction

The central and peripheral nervous system of vertebrates arises from tissue with various embryological origins. During early development neurons develop from the neuroepithelium in specific regions of the brain and spinal cord within the central nervous system. The peripheral nervous system arises from placodal ectoderm as well as from the migratory neural crest cells (NCCs). Despite their different origins, differentiation of neurons throughout the embryo is regulated by multiple genes, which are co-ordinately involved (Cordes, 2001). Notch signaling is the common pathway known to play a key role in the timing of neural progenitor cell differentiation in most, if not all, metazoans (reviewed in Dyer, 2003; Ishibashi, 2004; Louvi and Artavanis-Tsakonas, 2006). Upon activation of Notch signaling, the Notch intracellular domain (NICD)-recombination signal sequence binding protein K (RBPJ)

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