Spindle assembly checkpoint genes reveal distinct as well as overlapping expression that implicates MDF-2/Mad2 in postembryonic seam cell proliferation in Caenorhabditis elegans.
BACKGROUND
The spindle assembly checkpoint (SAC) delays anaphase onset by inhibiting the activity of the anaphase promoting complex/cyclosome (APC/C) until all of the kinetochores have properly attached to the spindle. The importance of SAC genes for genome stability is well established; however, the roles these genes play, during postembryonic development of a multicellular organism, remain largely unexplored.


RESULTS
We have used GFP fusions of 5' upstream intergenic regulatory sequences to assay spatiotemporal expression patterns of eight conserved genes implicated in the spindle assembly checkpoint function in Caenorhabditis elegans. We have shown that regulatory sequences for all of the SAC genes drive ubiquitous GFP expression during early embryonic development. However, postembryonic spatial analysis revealed distinct, tissue-specific expression of SAC genes with striking co-expression in seam cells, as well as in the gut. Additionally, we show that the absence of MDF-2/Mad2 (one of the checkpoint genes) leads to aberrant number and alignment of seam cell nuclei, defects mainly attributed to abnormal postembryonic cell proliferation. Furthermore, we show that these defects are completely rescued by fzy-1(h1983)/CDC20, suggesting that regulation of the APC/CCDC20 by the SAC component MDF-2 is important for proper postembryonic cell proliferation.


CONCLUSIONS
Our results indicate that SAC genes display different tissue-specific expression patterns during postembryonic development in C. elegans with significant co-expression in hypodermal seam cells and gut cells, suggesting that these genes have distinct as well as overlapping roles in postembryonic development that may or may not be related to their established roles in mitosis. Furthermore, we provide evidence, by monitoring seam cell lineage, that one of the checkpoint genes is required for proper postembryonic cell proliferation. Importantly, our research provides the first evidence that postembryonic cell division is more sensitive to SAC loss, in particular MDF-2 loss, than embryonic cell division.
Tarailo-Graovac
Maja
M
Department of Molecular Biology and Biochemistry, Simon Fraser University, Burnaby, British Columbia, V5A 1S6, Canada.
Wang
Jun
J
Chu
Jeffrey S C
JS
Tu
Domena
D
Baillie
David L
DL
Chen
Nansheng
N
D020121:5' Untranslated Regions / Q000235:genetics; D000818:Animals; D017173:Caenorhabditis elegans / Q000196:embryology / Q000254:growth & development; D029742:Caenorhabditis elegans Proteins / Q000235:genetics / Q000378:metabolism*; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D049109:Cell Proliferation; D047108:Embryonic Development / Q000235:genetics; D020869:Gene Expression Profiling; D018816:Genes, cdc / Q000502:physiology*; D005818:Genetic Engineering; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D009024:Morphogenesis / Q000235:genetics; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism*
D020121:5' Untranslated Regions; D029742:Caenorhabditis elegans Proteins; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; C577505:FZY-1 protein, C elegans; C412840:MDF-2 protein, C elegans; D049452:Green Fluorescent Proteins