Chapter 6 Cell Lineage Analysis in Mammalian Embryogenesis

Abstract

This chapter describes different approaches to lineage analysis in mouse embryo and discusses their limitations. It emphasizes newly developed techniques that provide new directions for lineage studies in mammalian embryogenesis. Cell lineage studies are a fundamental component of the comprehensive analysis of any developmental system. Such studies define the fate of cells in the living embryo from egg until birth, identify when and where cells are set aside or allocated to different cell lineages, and determine the progenitor cell number as cells become allocated. Lineage studies delineate the basic developmental decisions that occur during embryogenesis and provide the background for further investigation of mechanisms underlying these decisions. The complementary relationship between cell lineage analysis and the molecular genetics of development is illustrated by recent research in Caenorhabditis elegans and Drosophila , where mutations in genes controlling lineage development are characterized and the wild-type genes cloned. There are important advances in all the three main techniques for lineage analysis in mammalian embryos. Development of ubiquitous in situ genetic markers has greatly enhanced the power of chimera analysis, such that this technique is currently by far the most powerful for later lineage analysis from cells marked in preimplantation stages. Injection of exogenous tracers has elucidated lineage relationships in the intact preimplantation embryo and the precision of marking has also allowed generation of short-term fate maps of the postimplantation embryo.