Development, Vol 118, Issue 3 967-975, Copyright © 1993 by Company of Biologists

JOURNAL ARTICLES

Modulated expression of a surface epitope on migrating germ cells of Manduca sexta embryos

J. B. Nardi

In embryos of the moth Manduca sexta, the first cells that immunolabel with a monoclonal antibody to a surface epitope are the primordial germ cells. With this specific immunolabel, the migratory pathways of all primordial germ cells can be readily observed in whole mounts of embryos. The germ cells begin their migration by dispersing from an aggregate that lies on the midline of the embryonic germ band. Concurrently with segmentation of the embryo several hours later, germ cells segregate to several abdominal segments. With the advent of neurulation, germ cells again segregate, this time laterally within the segments. Shortly thereafter germ cells begin moving toward the lateral margins of abdominal segments. Simultaneously, two longitudinal strips of mesodermal cells along the lateral margins in each of four abdominal segments (3-6) begin expressing the surface epitope. The four initially noncontiguous strips on each side of the embryo fuse during the next several hours and form a single immunolabeled strip that stretches over four abdominal segments. Upon contacting these two lateral strips of mesodermal cells, germ cells begin moving bidirectionally along the anteroposterior embryonic axis toward the fifth abdominal segment where gonads will complete their morphogenesis. The immunolabel is asymmetrically distributed on the surfaces of germ cells during the early stages of migration and only during the later stages of migration after neurulation does the epitope adopt a more uniform distribution on the cells' surfaces.