Fate maps reveal the normal contribution of various regions of an early embryo to larval and adult structures. This chapter describes the mapping of primitive blood in embryos of the frog Xenopus laevis by the technique of lineage tracing with a fluorescent dextran.

The fates of lineage labeled hematopoietic precursor populations in Xenopus embryos are followed by use of in situ hybridization, looking for overlap between lineage labeled cells and in situ probes specific for known cell populations or states of differentiation. By coinjection of do ...

The model genetic organism Drosophila melanogaster has a rudimentary hematopoietic system with two embryonic blood cell types, crystal cells, and plasmatocytes. These distinct lineages provide the animal with an innate immune response and a means to remove apoptotic cells. Genetic ...

We describe here diverse methods used to study the onset of hematopoiesis in the human embryo and fetus. In the first part of this chapter, the criteria for estimating developmental stages in human embryos are discussed. This section also presents in detail a refined method for embedding and free ...

Here, we present a computer-controlled time-lapse system for imaging of cultured hematopoietic cells labeled by the expression of different fluorescent proteins. First, we describe experiments to optimize the visualization of three green fluorescent protein variants (cyan-, ...

The yolk sac is the initial site of hematopoiesis in the mammalian embryo. As the embryo develops, blood vessels form around primitive erythroblasts to connect the yolk sac to the embryo, delivering newly formed blood cells to the embryonic circulation. The limited accessibility of the mamma ...

The hematopoietic stem cells residing in the bone marrow have tremendous proliferative and self-renewing capacity, and until recently these cells were thought to produce only progeny of the blood lineages. We have recently demonstrated that these cells are capable of producing endot ...

Embryonic stem (ES) cells differentiate efficiently in vitro and give rise to many different somatic cell types. Hematopoietic progenitors present within differentiated ES cells (embryoid bodies, EBs) can be identified by replating EB cells into semisolid media with hematopoiet ...

It has long been unclear how the pluripotent hematopoietic stem cell is restricted to the major lineage progenitors including the progenitors for myeloid, T- and B-cells. This is the result of the absence of a methodology capable of determining the developmental potential of individual pro ...

A prerequisite for proper investigation of self-renewal and differentiation of hematopoietic cells is the possibility to obtain large quantities of homogenous primary progenitors under defined conditions, allowing meaningful biochemical and molecular analyses. These ...

T-cell development requires cytokines and intimate contact with stromal cells provided exclusively by the thymus. Consequently, an in vitro model of thymocyte differentiation, fetal thymic organ culture (FTOC), has been developed. FTOC recapitulates the normal development of T- ...

We describe two complementary methods for the study of early thymus organogenesis in the mouse. The first is an in vitro technique for lineage analysis, where a chosen population of cells within the mouse embryo is labeled with a fluorescent cell tracker dye. The embryos are then transferred to who ...

All mature blood cells are derived from hematopoietic progenitors that have been defined by their ability to generate colonies of cells in semisolid media. Investigation of the cellular components of these colonies has confirmed the existence of unilineage, bilineage, and multilin ...

The progress of the last few years in the understanding of hematopoietic cell development during embryogenesis resulted from a combination of experimental approaches used in hematology and developmental biology. This methodology has been particularly powerful for the analys ...

Hematopoietic stem cells (HSCs) constitute a pool of very rare cells able to self-renew, proliferate, and/or differentiate to all the blood cell lineages during the life span. The first murine adult transplantable HSCs appear in the intraembryonic aorta-gonad-mesonephros region at em ...

In vertebrates, the earliest differentiated cell types (hematopoietic and endothelial) arise from mesoderm induced during the process of gastrulation. These cells become organized into the blood islands of the extraembryonic yolk sac and are morphologically apparent by around d 7 ...

In vivo experimental approaches that have been designed to study the ontogeny of the hematopoietic system in higher vertebrates are described in the present chapter. The avian embryo is directly available to manipulations in ovo during gastrulation and organogenesis. This permissi ...

Because zebrafish embryos are transparent, cell behaviors and interactions can be directly imaged noninvasely in live embryos using differential interference contrast-Nomarski light microscopy. We found that the imaging quality can be much improved by coupling differenti ...

The zebrafish (Danio rerio) has emerged as a powerful vertebrate genetic and developmental model that is particularly amenable to the study of hematopoiesis. The zebrafish embryo develops externally and its optical clarity allows the number and morphology of circulating blood cells ...

Xenopus embryos provide a model for studying the earliest stages in the development of the vertebrate hematopoietic system. This chapter provides detailed procedures describing the production of hematopoietic chimeras in Xenopus embryos and the analysis of these chimeras using ...