Concatamer arrays were previously suggested to be a sensitive tool for detecting gene expression for genes with low levels of transcription. We confirmed the sensitivity of this approach when we generated a pmdf 2,GFP stable line using MosSCI. This stable line had very www.selleckchem.com/products/DAPT-GSI-IX.html low GFP signal intensity and required long exposure times for the expression to be observed. The 5 DNA sequences selected as containing putative promoters of the SAC genes displayed common early embryonic activities in the majority, if not all, of the rapidly dividing embryonic cells. This finding is consis tent with the known roles of the checkpoint genes in cell division. We expected this result because of the fact that 556 of the 959 somatic cells present in adult her maphrodite are generated during embryogenesis.

Furthermore, our observations of early embryonic expression is supported by published analyses which used antibodies against some of the SAC gene products. Thus, it is likely that these transcrip tional fusions recapitulate endogenous SAC gene pro moter activities. Importantly, this common ubiquitous expression of SAC genes during early embryogenesis, suggests that expression of mdf 1, the only one located within an operon, has to be driven by the internal promoter. Thus, the mdf 1 containing operon is likely a hybrid operon. czw 1 was also included in our study, however, analysis of two different constructs did not reveal any detectable GFP expression. It is possible that expression of the analyzed transgenes was either too low for visible detection, germline speci fic, conditional, or that regulatory elements of this gene are located in regions not included by our putative pro moter selection criteria.

In contrast to expression in embryos, postembryonic expression of SAC genes in C. elegans is more localized. During the four larval stages in a hermaphrodite, the 53 undifferentiated somatic blast cells generate an addi tional 403 somatic nuclei. The somatic blast cell divisions generate somatic gonad, muscle, coelomocytes, nerves, hypodermis and intestine. If all of the checkpoint genes played the same role in postembryonic development, one would expect to observe the same expression patterns for the SAC genes. However, our analysis revealed that checkpoint promoters generally dictate differential postembryonic expression patterns. For example, it is very interesting that mdf 1internal and the rod 1 promoters drive GFP expression exclusively in intestine after embryogenesis, while the hcp 1 promoter drives GFP expression in multiple tissues. These findings suggest distinct, yet overlapping, roles of the GSK-3 checkpoint genes in postembryonic development and provide an excellent resource for further research.