We describe the developmental expression in grasshopper (Schistocerca americana) and molecular characterization in grasshopper and fruit fly (Drosophila melanogaster) of
Lachesin, a novel
immunoglobulin superfamily
protein.
Lachesin is expressed on the surfaces of differentiating neuronal cells from the onset of neurogenesis in both the central and peripheral nervous systems.
Lachesin expression begins in some cells of the neurogenic ectoderm immediately after engrailed expression begins in the posterior cells of each future segment. All neurogenic cells express
Lachesin early, but only those cells that become neuroblasts continue to express
Lachesin. Ectodermal cells in the neurogenic region that adopt non-neuronal fates lose
Lachesin at the time that they diverge from a potentially neurogenic pathway. Neuroblasts,
ganglion mother cells and neurons all express
Lachesin early in their lives, but expression becomes restricted to a subset of neurons as development progresses. Sensory neurons express
Lachesin as they delaminate from the body wall ectoderm.
Lachesin is also present on growing axons of the CNS and PNS and becomes restricted to a subset of axons later in development. This expression is unique among known insect neurogenic genes and suggests a role for
Lachesin in early neuronal differentiation and axon outgrowth. Grasshopper
Lachesin is a 38 x 10(3) M(r)
protein linked to cell membranes through a
glycosyl phosphatidylinositol anchor. We have cloned the
Lachesin gene from both grasshopper and fly. The
proteins are highly conserved (70% identical) between the two species.
Lachesin is similar to Drosophila amalgam, bovine OBCAM and the human
poliovirus receptor, putting it into a subgroup of the
immunoglobulin superfamily containing one V- and two C2-type immunoglobulin domains.
Lachesin is also similar to several other vertebrate
immunoglobulin superfamily
proteins (TAG-1, F11, L1 and NgCAM) known to function in neurite outgrowth and other cell surface recognition events.