Tubes are the building blocks of many internal organs in multicellular organisms, and defects in tube morphogenesis cause devastating diseases. To understand the molecular mechanisms of tube formation, our previous screen in C. elegans has identified hundreds of molecules required for tubulogenesis in intestine and/or excretory canals. Here in this study, we are aiming to identify genes involved in the formation and the size and shape regulation of a different tubular organ - the spermatheca - through a genome-wide RNAi screen.
The hermaphrodite spermatheca is composed of 24 epithelial cells organized into an accordion-like stretchable tube that contains sperm. Its ability to expand during the passage of oocytes demonstrates unique resilience and flexibility of a tubular epithelium. The spermatheca develops post-embryonically starting from late L3/early L4 stages, providing the following advantages for a tube morphogenesis screen: (1) it can be specifically targeted with conditional RNAi for those embryonic and larval lethal genes, conveniently bypassing their functions in growth regulation, signaling, transcriptional regulation, and cell fate determination; (2) it will help to recover non-lethal genes, whose knockdown may hardly affect the development of intestine and excretory canals; (3) its specific features may allow us to identify molecules involved specifically in tube resilience and flexibility, the characteristic existing in a number of human internal organs too.
The screen is designed to target non-lethal genes using standard RNAi condition and essential genes using conditional RNAi initiated after completion of embryogenesis on the C. elegans strains expressing distinct fluorescent markers that outline the structure of the spermatheca, such as LET-413, AJM-1 and ERM-1. Worms subjected to RNAi knockdown are first evaluated for morphological defects in gonad system under a dissecting fluorescence microscope followed by detailed characterization on spermathecal phenotypes by a confocal microscope. We are expecting to identify specific genes affecting spermatheca structure, size and shape etc. Here some preliminary results of our tube morphogenesis screen on the hermaphrodite spermatheca will be presented.