Serially homologous engrailed stripes are generated via different cell lineages in the germ band of amphipod crustaceans (Malacostraca, Peracarida).

Abstract

A monoclonal antibody (mAb 4D9) was used to analyze engrailed expression in amphipod embryos. As in other arthropods, engrailed is expressed in iterated transverse stripes in the germ band. In the anterior region these stripes are generated without a recognizable division pattern, and their appearance and formation show some irregularities. In the posterior region of the germ band, engrailed expression is correlated with a stereotyped cell division pattern resulting in a highly ordered formation and array of stripes. The engrailed positive cells mark the anterior border of genealogical units, which therefore can be compared with parasegments in Drosophila. Expression starts in the mandibular segment and proceeds first anteriorly and subsequently in a posterior direction. Initial stripes are one cell wide. The widening of stripes is caused by both division of engrailed positive cells and recruitment of new cells that did not previously express engrailed. The widening process is related to segment formation as the intersegmental furrows are established behind the engrailed expressing cells, which are restricted to the posterior portion of the forming segments. A comparison of the modes of engrailed expression in different segments suggests that initial engrailed expression is independent of a certain cell lineage or division pattern. The comparison of the development of the early engrailed stripes in different insects and crustaceans reveals some similarities which show that early engrailed expression is not necessarily clonally inherited.