Nuclear derivatives and axonal projections originating from rhombomere 4 in the mouse hindbrain

Maria Di Bonito,Michèle Studer,Luis Puelles

doi:10.1007/s00429-017-1416-0

Abstract

The r4-derived territory is located in the pontine region of the brainstem, forming a wedge-shaped slice that broadens from the choroidal roof to the ventral midline. R4-derived neuronal populations migrate radially inside and tangentially outside this rhombomere, forming nuclei of the sensorimotor auditory, vestibular, trigeminal and reticular systems. R4-derived fibre tracts contribute to the lateral lemniscus, the trigeminothalamic tracts, the medial tegmental tract and the medial forebrain bundle, which variously project to the midbrain, thalamus, hypothalamus and telencephalon. Other tracts such as the trigeminocerebellar and vestibulocerebellar tracts reach the cerebellum, while the medial and lateral vestibulospinal tracts, and the reticulospinal and trigeminal oro-spinal tracts extend into the spinal cord. Many r4-derived fibres are crossed; they decussate to the contralateral side traversing the midline through the cerebellar, collicular and intercollicular commissures, as well as the supraoptic decussation. Moreover, some fibres enter into the posterior and anterior commissures and some terminals reach the septum. Overall, this study provides an overview of all r4 neuronal populations and axonal tracts from their embryonic origin to the adult final location and target.

Highlights

Hindbrain neurons process and relay sensory information, control vital functions and contribute to motor coordination
Going beyond the preliminary data recorded by Di Bonito et al (2015) and Di Bonito et al (2013a, b), we mapped in detail the anatomical fate of tangentially and radially migrated r4-derived neuronal populations from embryogenesis to adult, analysing the r4-originated fibre tracts
The classic columns have a plurisegmental origin; it is believed that the subtle molecular differences that distinguish segmental modules one from another causes the columns to be structurally and functionally heterogeneous lengthwise

Summary

Introduction

Hindbrain neurons process and relay sensory information, control vital functions and contribute to motor coordination. The caudal medullary hindbrain has instead a hidden rhombomeric organization, which is molecularly detectable using Hox gene markers, but is not distinct morphologically as visible transverse bulges This domain was divided into five cryptorhombomeres (r7–r11) (Cambronero and Puelles 2000; Puelles et al 2013), which display typical anteroposterior (3′–5′) spatial colinearity of Hox gene expression; the rostral expression limits of the paralogue Hox groups 4–8 sequentially coincide with the experimentally fatemapped limits of r7–r11 (Marin et al 2008; Tomas-Roca et al 2016). The cryptically delimited isthmus (r0) and r1 are patterned under the influence of the isthmic organizer, which induces across their dorsal aspect the cerebellum

Methods

Results

Conclusion