Extensive molecular differences between anterior- and posterior-half-sclerotomes underlie somite polarity and spinal nerve segmentation.

Daniel St Hughes,David Tannahill,Roger J Keynes

doi:10.1186/1471-213x-9-30

Daniel St Hughes, David Tannahill + Show 1 more

Open Access

https://doi.org/10.1186/1471-213x-9-30

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Abstract

BackgroundThe polarization of somite-derived sclerotomes into anterior and posterior halves underlies vertebral morphogenesis and spinal nerve segmentation. To characterize the full extent of molecular differences that underlie this polarity, we have undertaken a systematic comparison of gene expression between the two sclerotome halves in the mouse embryo.ResultsSeveral hundred genes are differentially-expressed between the two sclerotome halves, showing that a marked degree of molecular heterogeneity underpins the development of somite polarity.ConclusionWe have identified a set of genes that warrant further investigation as regulators of somite polarity and vertebral morphogenesis, as well as repellents of spinal axon growth. Moreover the results indicate that, unlike the posterior half-sclerotome, the central region of the anterior-half-sclerotome does not contribute bone and cartilage to the vertebral column, being associated instead with the development of the segmented spinal nerves.

Highlights

The polarization of somite-derived sclerotomes into anterior and posterior halves underlies vertebral morphogenesis and spinal nerve segmentation
Pilot experiments indicated that ~300 pg of total ribonucleic acid (RNA) could be isolated per sclerotome half
The pooling strategy was used for two reasons: first, to avoid inefficient amplification of sub-nanogram quantities of RNA, and second, to minimize the variation in gene expression that might be caused by position-specific and somite-stage-specific differences in the samples

Summary

Introduction

The polarization of somite-derived sclerotomes into anterior and posterior halves underlies vertebral morphogenesis and spinal nerve segmentation. The subdivision of embryonic tissues into serial repeatunits, or segments, is a fundamental patterning process in early vertebrate development, and is most prominent in the formation of the mesodermal somites. Somite formation is dependent on a molecular 'clock' within the PSM that generates periodic expression of genes including the notch, wnt and fibroblast growth factor (FGF) signalling pathways [3,4,5]. These cyclical gene expression patterns are superimposed on a regressing, longitudinal gradient of FGF expression along the A-P axis that results in the coordinated maturation of groups of PSM cells into each successive somite. Somite polarity is determined within (page number not for citation purposes)

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