Collaborative Resources for
Learning Developmental Biology
Collaborative Resources for Learning Developmental Biology
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Sea urchin small micromeres
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Joseph Campanale
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Additional Author(s): Amro Hamdoun

Published on SDB CoRe: Jun 21 2012

Tools & Techniques: Embryo Manipulation; Microscopy
Early Embryogenesis: Cleavage; Blastula
The Germline: Germline/Soma Divide
Ecological Developmental Biology: Environ & Molecular Change
Organism: Sea Urchin
Stage of Development: Embryo

Object Description

Featured from left to right are living 28-cell, 60-cell, early blastula and blastula stage embryos of the purple sea urchin, Strongylocentrotus purpuratus, treated with calcein-AM. To protect growing embryos from toxic molecules, cells have proteins called ABC (ATP-binding cassette) transporters that recognize toxic molecules and transport them out of the cell. Calcein is seen as a “toxin” by ABC transporters and is actively removed from most cells of the sea urchin embryo. The plasma membrane of micromeres is reorganized shortly after their birth, resulting in fewer ABC transporters on the cell membrane and thus a reduced capacity to export toxic molecules. The four micromeres of the 28-cell embryo therefore accumulate more fluorescent calcein than other cells in the embryo. The micromeres divide to form the small micromeres (which give rise to the germline) and the large micromeres in the 60-cell embryo. The small micromeres’ membranes retain lower ABC transporter activity through blastulation. The reduction of protective efflux activity in these cells could have implications for the formation and development of the germline by rendering these cells vulnerable to toxic molecules.


Campanale, J. P. and Hamdoun, A. Programmed reduction of ABC transporter activity in sea urchin germline progenitors. Development, 2012, 139:783-792

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