Development, Vol 127, Issue 4 735-744, Copyright © 2000 by Company of Biologists

JOURNAL ARTICLES

Segmentation of the central nervous system in leech

DH Shain, DK Stuart, FZ Huang and DA Weisblat
Department of Molecular and Cell Biology, University of California, Berkeley, CA, 94720-3200, USA.

Central nervous system (CNS) in leech comprises segmentally iterated progeny derived from five embryonic lineages (M, N, O, P and Q). Segmentation of the leech CNS is characterized by the formation of a series of transverse fissures that subdivide initially continuous columns of segmental founder cells in the N lineage into distinct ganglionic primordia. We have examined the relationship between the N lineage cells that separate to form the fissures and lateral ectodermal and mesodermal derivatives by differentially labeling cells with intracellular lineage tracers and antibodies. Although subsets of both lateral ectoderm and muscle fibers contact N lineage cells at or near the time of fissure formation, ablation experiments suggest that these contacts are not required for initiating fissure formation. It appears, therefore, that this aspect of segmentation occurs autonomously within the N lineage. To support this idea, we present evidence that fundamental differences exist between alternating ganglionic precursor cells (nf and ns primary blast cells) within the N lineage. Specifically, ablation of an nf primary blast cell sometimes resulted in the fusion of ipsilateral hemi-ganglia, while ablation of an ns primary blast cell often caused a 'slippage' of blast cells posterior to the lesion. Also, differences in cell behavior were observed in biochemically arrested nf and ns primary blast cells. Collectively, these results lead to a model of segmentation in the leech CNS that is based upon differences in cell adhesion and/or cell motility between the alternating nf and ns primary blast cells. We note that the segmentation processes described here occur well prior to the expression of the leech engrailed-class gene in the N lineage.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?

This article has been cited by other articles:

				S. O. Zhang and D. A. Weisblat Applications of mRNA injections for analyzing cell lineage and asymmetric cell divisions during segmentation in the leech Helobdella robusta Development, May 1, 2005; 132(9): 2103 - 2113. [Abstract] [Full Text] [PDF]

				D. H. Shain, D. K. Stuart, F. Z. Huang, and D. A. Weisblat Cell interactions that affect axonogenesis in the leech Theromyzon rude Development, September 1, 2004; 131(17): 4143 - 4153. [Abstract] [Full Text] [PDF]

				K. A. Hohenstein and D. H. Shain Changes in Gene Expression at the Precursor -> Stem Cell Transition in Leech Stem Cells, July 1, 2004; 22(4): 514 - 521. [Abstract] [Full Text] [PDF]

				D.-H. Kuo and M. Shankland A distinct patterning mechanism of O and P cell fates in the development of the rostral segments of the leech Helobdella robusta: implications for the evolutionary dissociation of developmental pathway and morphological outcome Development, January 1, 2004; 131(1): 105 - 115. [Abstract] [Full Text] [PDF]

				M. H. Song, F. Z. Huang, G. Y. Chang, and D. A. Weisblat Expression and function of an even-skipped homolog in the leech Helobdella robusta Development, August 1, 2002; 129(15): 3681 - 3692. [Abstract] [Full Text] [PDF]

				E. Seaver and M Shankland Establishment of segment polarity in the ectoderm of the leech Helobdella Development, January 5, 2001; 128(9): 1629 - 1641. [Abstract] [PDF]