The Journal of Neuroscience, May 1, 2000, 20(9):3244-3253
Intrinsic Bias and Lineage Restriction in the Phenotype
Determination of Dopamine and Neuropeptide Y Amacrine Cells
Sally A.
Moody1,
Ida
Chow2, and
Sen
Huang1
1 Department of Anatomy and Cell Biology, George
Washington University Medical Center, Institute for Biomedical
Sciences, Washington, DC 20037, and 2 Department of
Biology, American University, Washington, DC 20016
Blastomere lineages are differentially biased to produce different
neurotransmitter subtypes of amacrine cells (Huang and Moody, 1995,
1997). To elucidate when this bias is acquired, we examined amacrine
lineages at different early developmental times. Our experiments
demonstrate that the bias to express dopamine and neuropeptide Y
amacrine fates involves several steps before the formation of the
definitive optic cup. At cleavage stages, a retinal progenitor that
contributes large numbers of cells is already biased to produce its
normal repertoire of dopamine amacrine cells, as revealed by
transplantation to a new location, whereas the amacrine fate of a
progenitor that contributes fewer cells is modified by its new
position. At neural plate stages, not all retinal progenitors are
multipotent. Nearly one-half populate only the inner nuclear
layer and are enriched in amacrine cells. During early optic vesicle
stages, an appropriate mitotic tree is required for dopamine and
neuropeptide Y, but not serotonin, amacrine cell clusters to form.
Thus, the acquisition of amacrine fate bias involves intrinsic maternal
factors at cleavage, fate restriction in the neural plate, and
specified mitotic patterns in the optic vesicle. At each of these steps
only a subset of the embryonic retinal progenitors contributing to
amacrine subtypes is biased; the remaining progenitors maintain
multipotency. Thus, from the earliest embryonic stages, progenitors of
the retina are a dynamic mosaic. This is the first experimental
demonstration of amacrine fate decisions that occur during early
embryonic periods in advance of the events described in the later,
committed retina.
Key words:
serotonin; cell fate determination; neural plate; eye
fields; Xenopus; retina
Copyright © 2000 Society for Neuroscience 0270-6474/00/2093244-10$05.00/0