The sensory rays of C. elegans were adopted as a model to investigate the regulation of morphogenesis. One of the genes required in sensory ray morphogenesis, ram-1, was identified to be a cuticle collagen with a longer than average C-terminal non-collagenous domain. The male-specific expression profile of ram-1 and other ram genes, as well as the suppression of the ram-2(bx32) phenotype by the ram-1(RNAi) and the ram-4(RNAi), have supported the notion that the three male-specific cuticle collagens, RAM-1, RAM-2 and RAM-4, form the same cuticle sub-structure that maintains the sensory ray morphology....[ Read more ]

The sensory rays of C. elegans were adopted as a model to investigate the regulation of morphogenesis. One of the genes required in sensory ray morphogenesis, ram-1, was identified to be a cuticle collagen with a longer than average C-terminal non-collagenous domain. The male-specific expression profile of ram-1 and other ram genes, as well as the suppression of the ram-2(bx32) phenotype by the ram-1(RNAi) and the ram-4(RNAi), have supported the notion that the three male-specific cuticle collagens, RAM-1, RAM-2 and RAM-4, form the same cuticle sub-structure that maintains the sensory ray morphology.

Nematode cuticle is a layer of extracellular matrix comprising mainly of cuticle collagens. C. elegans has more than 170 of them. Since their amino acid sequences are highly similar, their uniqueness might be conferred by subtle amino acid differences. Mutant rescue assay substantiates this hypothesis as RAM-4-like collagens, DPY-13 and COL-125, could not substitute RAM-4. The key determinant of this specific function resides on the segment Y of the N-terminal non-collagenous (N-NC) domain with a motif of variable sequence at conserved position. This region potentially confers uniqueness on the cuticle collagens. In combination to the interference of different RAM collagen N-NC domains in wild-type animal and the cytoplasmic aggregation of the RAM-4::GFP fusion protein, I hypothesize that the N-NC domain is used for initiating collagen chain association and mediating collagen chain selection. Since there are only few literatures studying the cuticle collagens using a biochemical approach, I have explored multiple different biochemical assays to evaluate the hypothesis. Among them, the FPLC analysis has shown the requirement of the N-NC domain for large complex formation. The in vitro co-precipitation demonstrated the physical association between the RAM-4 N-NC domain and the N-NC domains of RAM-1, RAM-2 and RAM-4 itself. Both assays offer a platform for in depth investigation to the N-NC domain function in collagen chain association and selection.