NTRS - NASA Technical Reports Server

Back to Results
Leech segmental repeats develop normally in the absence of signals from either anterior or posterior segmentsWe have investigated whether the development of segmental repeats is autonomous in the embryo of the leech Helobdella robusta. The segmental tissues of the germinal band arise from progeny of five stem cells called teloblasts. Asymmetric divisions of the teloblasts form chains of segment founder cells (called primary blast cells) that divide in a stereotypical manner to produce differentiated descendants. Using two distinct techniques, we have looked for potential interactions between neighboring blast cell clones along the anterior-posterior axis. In one technique, we prevented the birth of primary blast cells by injection of DNase I into the teloblast, thereby depriving the last blast cell produced before the ablation of its normal posterior neighbors. We also ablated single blast cells with a laser microbeam, which allowed us to assess potential signals acting on either more anterior or more posterior primary blast cell clones. Our results suggest that interactions along the anterior-posterior axis between neighboring primary blast cell clones are not required for development of normal segmental organization within the blast cell clone. We also examined the possibility that blast cells receive redundant signals from both anterior and posterior neighboring clones and that either is sufficient for normal development. Using double blast cell laser ablations to isolate a primary blast cell clone by removal of both its anterior and its posterior neighbor, we found that the isolated clone still develops normally. These results reveal that the fundamental segmental repeat in the leech embryo, the primary blast cell clone, can develop normally in the apparent absence of signals from adjacent repeats along the anterior-posterior axis.
Document ID
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Seaver, E. C.
(Institute of Cellular and Molecular Biology, University of Texas at Austin 78712, United States)
Shankland, M.
Date Acquired
August 22, 2013
Publication Date
August 15, 2000
Publication Information
Publication: Developmental biology
Volume: 224
Issue: 2
ISSN: 0012-1606
Subject Category
Life Sciences (General)
Funding Number(s)
Distribution Limits
NASA Discipline Evolutionary Biology
Non-NASA Center

Available Downloads

There are no available downloads for this record.
No Preview Available