Key result
Transfer of cytoplasm from wild-type eggs into af mutant Xenopus eggs partially rescued contraction of the cleavage furrow, identifying a high molecular weight protein complex required for cytokinesis.
A high molecular weight protein complex from wild-type Xenopus eggs can partially rescue cleavage furrow contraction in cytokinesis-defective af mutant eggs.
Hypothesis-generating in Xenopus; leaves open relevance to mammalian cardiomyocyte division or cardiac repair.
The abnormal furrow (af) gene was identified through a maternal effect mutation that causes a defect in cell division in Xenopus embryos. In eggs obtained from mutant females (af eggs), polar body formation and cytokinesis are completely inhibited while nuclear division continues uninterrupted. Cleavage furrows are recognized as unpigmented narrow bands on the egg surface but they do not contract. Transfer of cytoplasm from wild-type eggs into af eggs partially rescues contraction of the cleavage furrow. The factor responsible for contraction promoting activity was present in wild-type eggs throughout the first cell division cycle and induced contraction in a dose dependent manner. The factor was characterized as a high molecular weight protein complex that was associated with particulate fraction in the extract. The recovery of contraction was associated with accumulation of filamentous actin and WGA-binding sites within the cleavage furrow of the af eggs which were normally not enriched for these components. Formation and contraction of a filamentous actin ring during cortical wound healing in af eggs was indistinguishable from that of wild-type eggs. From these results, the af gene product may be specifically required for reorganization of the actin filaments and WGA-binding sites in the cleavage furrow and contraction through these structures during cytokinesis.
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Katsu et al. (1998) studied abnormal furrow (af) mutation. Cytoplasmic extract from wild-type eggs vs. Untreated af eggs or control extracts was evaluated on Contraction of the first cleavage furrow. Transfer of cytoplasm from wild-type eggs into af mutant Xenopus eggs partially rescued contraction of the cleavage furrow, identifying a high molecular weight protein complex required for cytokinesis.
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