Mesencephalic basolateral domain specification is dependent on Sonic Hedgehog.

Jesus E Martinez-Lopez,Juan A Moreno-Bravo,Juan A Moreno-Bravo,M Pilar Madrigal,M Pilar Madrigal,Eduardo Puelles,Eduardo Puelles,Salvador Martinez

doi:10.3389/fnana.2015.00012

Jesus E Martinez-Lopez, Juan A Moreno-Bravo + Show 6 more

Open Access

https://doi.org/10.3389/fnana.2015.00012

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Abstract

In the study of central nervous system morphogenesis, the identification of new molecular markers allows us to identify domains along the antero-posterior and dorso-ventral (DV) axes. In the past years, the alar and basal plates of the midbrain have been divided into different domains. The precise location of the alar-basal boundary is still under discussion. We have identified Barhl1, Nhlh1 and Six3 as appropriate molecular markers to the adjacent domains of this transition. The description of their expression patterns and the contribution to the different mesencephalic populations corroborated their role in the specification of these domains. We studied the influence of Sonic Hedgehog on these markers and therefore on the specification of these territories. The lack of this morphogen produced severe alterations in the expression pattern of Barhl1 and Nhlh1 with consequent misspecification of the basolateral (BL) domain. Six3 expression was apparently unaffected, however its distribution changed leading to altered basal domains. In this study we confirmed the localization of the alar-basal boundary dorsal to the BL domain and demonstrated that the development of the BL domain highly depends on Shh.

Highlights

The midbrain, located between the forebrain and the hindbrain, is subdivided, along the antero-posterior axis, into two mesomeres (m1–m2) (Hidalgo-Sánchez et al, 2005; Moreno-Bravo et al, 2012; Puelles et al, 2012)
The alar plate is compartmentalized in alar dorsal (AD), alar lateral (AL) and alar ventrolateral (AVL) domains, whereas the basal plate is divided into basolateral (BL), basal intermediate (BI) and basal medial (BM) domains (Nakatani et al, 2007; Kala et al, 2009; Moreno-Bravo et al, 2012; Puelles et al, 2012; see Figure 1A)
ROLE OF SHH IN THE DEVELOPMENT OF dorso-ventral axis (DV) MESENCEPHALIC DOMAINS With the aim to better characterize the different domains of the basal midbrain, we studied the expression pattern of Barhl1, Nhlh1 and Six3

Summary

Introduction

The midbrain, located between the forebrain and the hindbrain, is subdivided, along the antero-posterior axis, into two mesomeres (m1–m2) (Hidalgo-Sánchez et al, 2005; Moreno-Bravo et al, 2012; Puelles et al, 2012). This triggers differentiation programs that specify different neuronal populations along the DV axis (Basler et al, 1993; Dickinson et al, 1995; Lee and Jessell, 1999; Patten and Placzek, 2000; Chizhikov and Millen, 2005; Placzek and Briscoe, 2005; Ingham and Placzek, 2006; Szabó et al, 2009a,b) In the midbrain this DV organization is referred to as tectum (dorsal) and tegmentum (ventral), which acquire their alar and basal characteristics under the influence of roof and floor plate organizers respectively. The fact that this domain generates different neuronal subtypes highlights the complexity of this area

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