The size regulation of an organism’s body and cells is a fundamental biological process, which involves signalling pathways. In C. elegans, BMP (Bone Morphogenetic Proteins) signalling, a pathway controlling developmental processes in many species, is known regulating worm body volume, length and hypodermal ploidy. These size parameters are often used to monitor BMP level (intensity of BMP signaling activity), in the studies about body size control through BMP signals. The reliability of the conventional BMP level indicators is doubted, as BMP- related research expands broader and deeper and identifies more BMP mutants. The conventional indicators may not be sensitive enough to distinguish among BMP mutants. In addition, the ploidy measurement can be affected by the staining process and...[ Read more ]

The size regulation of an organism’s body and cells is a fundamental biological process, which involves signalling pathways. In C. elegans, BMP (Bone Morphogenetic Proteins) signalling, a pathway controlling developmental processes in many species, is known regulating worm body volume, length and hypodermal ploidy. These size parameters are often used to monitor BMP level (intensity of BMP signaling activity), in the studies about body size control through BMP signals. The reliability of the conventional BMP level indicators is doubted, as BMP- related research expands broader and deeper and identifies more BMP mutants. The conventional indicators may not be sensitive enough to distinguish among BMP mutants. In addition, the ploidy measurement can be affected by the staining process and conditions. Therefore, we seek alternative BMP level indicators which are more sensitive and reliable than the conventional ones. Three alternative BMP level indicators are identified in the study, which are the volume and length of Int2 cell (a polyploid intestinal cell), and worm body aspect ratio. Int2 cell volume is the most sensitive among the tested BMP level indicators, but its sensitivity is not outstanding among others. Moreover, all the tested BMP indicators responds non-linearly to BMP levels. This implies that the reliability of both conventional and alternative BMP level indicators is comparable. However, these indicators still help people determine if the BMP level of worms is higher or lower than WT worms. To improve and find more alternatives of BMP indicators, it is suggested to develop different types of BMP level indicators, such as transcriptional reporters (fluorescence tag expression driven by the promoter of the genes known to be regulated by BMP signalling). Using multiple indicators to monitor BMP level should also be considered.