Abstract. Eleven aquaporins are identified in mammals. They all have highly conserved two asparagine-proline-alanine (NPA) boxes that are important for the formation of the water permeating pore. Recently we identified two new proteins in mammals distantly related to aquaporins (AQPs) with poorly conserved NPA boxes. Similarly poorly conserved AQP-like proteins were found in several genome projects of multicellular organisms. They may be subgrouped as the AQP superfamily or superaquaporins. Their function is still unknown. AQP11 knockout mice suffer from polycystic kidneys and neonatal fatality. The identification of superaquaporins will provide new insights into the role of AQPs in organogenesis.

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Gene duplication is a major genetic event that can produce multiple protein isoforms. Comparative sequence and functional analysis of related gene products can provide insights into protein family evolution. To characterize the Caenorhabditis elegans troponin I family, we analyzed gene structures, tissue expression patterns and RNAi phenotypes of four troponin I isoforms. Tissue expression patterns were determined using lacZ/gfp/rfp reporter gene assays. The tni-1 , tni-2 / unc-27 and tni-3 genes, each encoding a troponin I isoform, are uniquely expressed in body wall, vulval and anal muscles but at different levels; tni-4 was expressed solely in the pharynx. Expressing tni-1 and -2 gene RNAi caused motility defects similar to unc-27 ( e155 ) mutant, a tni-2 null allele. The tni-3 RNAi expression produced egg laying defects while the tni-4 RNAi caused arrest at gastrulation. Overlay analyses were used to assay interactions between the troponin I and two troponin C isoforms. The three body wall troponin I isoforms interacted with body wall and pharyngeal troponin C isoforms; TNI-4 interacted only with pharyngeal troponin C. Our results suggest the body wall genes have evolved following duplication of the pharynx gene and provide important data about gene duplication and functional differentiation of nematode troponin I isoforms.

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