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7.4.2 The Teleost Fate Map
In the 1930s, Jane Oppenheimer (1911–1996) and Jean J. Pasteels (1906–1991)
used Vogt’s technique of labeling cells to produce the first fate maps of killifish and
trout embryos, respectively (Oppenheimer 1935 ; Pasteels 1936 ). These fate maps
were limited by the extensive cell mixing that occurs in early teleost embryos and
by the rapid fading of the dye, which occurred more quickly on teleost embryos than
on amphibians (Oppenheimer 1947 ). Later studies produced a more accurate fate
map of trout by using a different method to mark cell surfaces (Ballard 1973 ). The
zebrafish fate map was made by injection of fluorescent lineage tracing dyes into
individual cells at the late blastula or early gastrula stage (Fig. 7.4) (Kimmel et al.
1990 ; Shih and Fraser 1995 ; Melby et al. 1996 ). Extensive cell movements preclude
making a detailed fate map at earlier stages (Warga and Kimmel 1990 ). In teleost
embryos, cell fates are distributed with the same basic organization with respect to
the yolk cell. Broadly, endodermal tissues arise from blastomeres closest to the yolk
cell, ectodermal tissues arise from blastomeres at the animal pole and mesodermal
tissues arise from the cells in between the yolk and the animal pole (Fig. 7.5b). A
more detailed examination of the data for zebrafish, however, shows that the territo-
ries of the three germ layers overlap significantly. For example, endoderm progeni-
tors are juxtaposed to mesoderm precursors in the region closest to the yolk (Kimmel
et al. 1990 ; Warga and Nusslein-Volhard 1999 ). Because the precursors for the two
germ layers are intermixed, this region is called the mesendoderm. Farther from the
yolk, mesodermal precursors are juxtaposed to presumptive ectodermal cells. The
extensive intermingling of precursors distinguishes the teleost fate map from that of
amphibians. Like the frog fate map, the zebrafish fate map is at single cell resolu-
tion. But the technical limitations of injecting embryos at the blastula stage mean
that the fate map is restricted to cells close to the embryo surface. The fates of more
internal cells have not been determined, although that may change with advances in
fluorescent microscopy that permit the live tracking of every cell (Keller et al. 2008 ).
7.4.3 The Avian Fate Map
Because of the relatively small size of the blastoderm, avian and reptilian embryos
presented a difficult challenge for fate mapping studies. Some early, inconclusive
attempts were made to label reptile blastoderm cells using Vogt’s technique with
vital dyes (Pasteels 1937 ; Chandrasekharan 1966 ). The first maps of the chicken
blastoderm were made by explanting parts of the blastodisc and determining which
tissues formed when they were grown in isolation (Rudnick 1935 ). Today two main
methods are used to fate map chicken embryos. Quail cells are histologically distin-
guishable from chicken cells because they have large nucleoli that act as heritable
lineage tracers when transplanted into chicken embryo hosts (Le Douarin 1969 ).
Quail cells develop normally in chick hosts, and the morphological differences
W. Tseng et al.