The leech hunchback protein is expressed in the epithelium and CNS but not in the segmental precursor lineages

Abstract

We are interested in identifying the regulatory genes involved in segmental pattern formation in annelids. The Drosophila segmentation gene hunchback (hb) is critical for the proper anteroposterior development of the fly embryo, but its function outside the diptera is currently unknown. Here, the protein expression pattern of Leech Zinc Finger II (LZF2), a leech orthologue of hb is characterized. In early embryogenesis, LZF2 protein is expressed in a subset of micromeres and is later expressed in the micromere-derived epithelium of the provisional epithelium and prostomium. LZF2 protein is detected in the ventral nerve cord during organogenesis, first in interganglionic muscle cells and later in subsets of neurons in each neuromere of the CNS. The location of immunoreactive cells during development and the similarity of the expression pattern of LZF2 to the expression of the Caenhorhabditis elegans hb homologue hbl-1 suggests that LZF2 plays a role in the morphogenetic movements of leech gastrulation and later in CNS specification but not in anteroposterior pattern formation.

Ahedgehoghomolog regulates gut formation in leech(Helobdella)

“…Subject to the caveats necessary for any negative result, the apparent dissociation of en and hh gene expression during leech segmentation is consistent with other studies suggesting that the segmentation processes in Helobdella and Drosophila are not homologous at the molecular level (Iwasa et al, 2000;Pilon and Weisblat, 1997;Savage and Shankland, 1996;Seaver and Shankland, 2000;Seaver and Shankland, 2001;Shain et al, 1998;Song et al, 2002). (De Robertis, 1997;Dewel, 2000;Collins and Valentine, 2001;Valentine and Collins, 2000), but it seems unlikely to us that the ancestral bilaterian had these particular features, in which case the ancestral hh gene could not have functioned in any of those roles.…”

Expression of hunchback protein in a subset of ectodermal teloblasts of the oligochaete annelid Tubifex

“…In contrast, there is no detectable hb expression in either teloblasts and blast cells in leech embryos or in the posterior growth zone in polychaete embryos. This suggests it is unlikely that hb is involved in the AP patterning and segmentation in these species in a manner comparable to that of hb in flies (Iwasa et al 2000;Werbrock et al 2001).…”

“…The hb expression patterns during annelid embryogenesis have been examined in two species, the polychaete Capitella capitata and the hirudinidan Helobdella triserialis (Iwasa et al 2000;Werbrock et al 2001). In both species, hb is expressed first in early cleavage blastomeres, next in the provisional micromere-derived epithelium, and then in the central nervous system.…”

“…Using a cross-species antibody (designated anti-LZF2) raised against the LZF2 protein in leech (Iwasa et al 2000), we examined the distribution patterns of hb protein in embryos of an oligochaete Tubifex through gastrulation. We found that not only early cleavage blastomeres and epithelial cells exhibit hb protein in their nuclei, but a subset of ectodermal teloblasts also express hb protein during Tubifex embryogenesis.…”

Turning back the clock on neural progenitors

“…Hunchback homologues have been described in the CNS of C. elegans as well as in the leech. (21)(22)(23) To date there is no published data to suggest that the function of any hunchback-like genes in mammals parallels that of Drosophila Hunchback in neuroblasts. However, it is known that, in mammals, the Ikaros family of Hunchback-related transcription factors are expressed predominantly in embryonic CNS.…”