Segmentation in Motion

Andres F. Sarrazin

CONTENTS

  • 8.1 Introduction..................................................................................................183
  • 8.2 Live Imaging to Study Sequential Segmentation in Vertebrates..................184
  • 8.2.1 Cell Dynamics during Somite Border Formation............................184
  • 8.2.2 Real-Time Imaging of the Segmentation Clock...............................186
  • 8.2.3 The Migratory Behavior of the Presomitic Mesoderm Cells...........192
  • 8.3 Live Imaging during Annelid Sequential Segmentation..............................194
  • 8.4 Live Imaging during Arthropod Sequential Segmentation..........................194
  • 8.5 Conclusions...................................................................................................198

References..............................................................................................................199

Introduction

The construction of the enormous variety of animal body plans that are found in nature is mainly based on the combination of cellular behaviors and tissue rearrangements that must be tightly coordinated, both temporally and spatially, with the corresponding gene expression patterning process that organizes the developing embryo. Thus, the study of these biological events in vivo at high resolution emerges as a key aspect that has provided insightful knowledge on developmental morphogenesis.

Over a century ago (1907), the Swiss biologist Julius Ries was one of the first scientists to serially record microscopic images taken at regular time intervals in order to show' his students the cellular dynamics of fertilization and early development of the sea urchin egg in a 2-minute film, a process that normally takes 14 hours (Landecker 2009). The original idea to give movement to static images persists until today, given that the incorporation of the temporal dimension to the study of biological processes confers realism and makes often imperceptible phenomena visible when compared to fixed samples.

Since Ries’s films we can currently visualize single-cell resolution of many biological processes. Given the increasing variety of microscopy imaging techniques that have been developed, together w'ith a broad set of cell labeling methods, direct visualization of single cells wdthin their context in a w'ide range of organisms by time- lapse imaging has become an easier and more reliable way to observe cell behavior during development. At present, the phrase “One look (picture) is w'orth a thousand words” could be easily updated to “One movie is worth a thousand pictures.”

 
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