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The epithelial sodium channel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

ABSTRACT: Epithelial sodium channel (ENaC) is a Na(+)-selective, aldosterone-stimulated ion channel involved in sodium transport homeostasis. ENaC is rate-limiting for Na(+) absorption in the epithelia of osmoregulatory organs of tetrapods. Although the ENaC/degenerin gene family is proposed to be present in metazoans, no orthologues or paralogues for ENaC have been found in the genome databases of teleosts. We studied full-length cDNA cloning and tissue distributions of ENaC?, ? and ? subunits in the Australian lungfish, Neoceratodus forsteri, which is the closest living relative of tetrapods. Neoceratodus ENaC (nENaC) comprised three subunits: nENaC?, ? and ? proteins. The nENaC?, ? and ? subunits are closely related to amphibian ENaC?, ? and ? subunits, respectively. Three ENaC subunit mRNAs were highly expressed in the gills, kidney and rectum. Amiloride-sensitive sodium current was recorded from Xenopus oocytes injected with the nENaC??? subunit complementary RNAs under a two-electrode voltage clamp. nENaC? immunoreactivity was observed in the apical cell membrane of the gills, kidney and rectum. Thus, nENaC may play a role in regulating sodium transport of the lungfish, which has a renin-angiotensin-aldosterone system. This is interesting because there may have been an ENaC sodium absorption system controlled by aldosterone before the conquest of land by vertebrates.

SUBMITTER: Uchiyama M

PROVIDER: S-EPMC3497098 | biostudies-literature | 2012 Dec

REPOSITORIES: biostudies-literature

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The epithelial sodium channel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

Uchiyama Minoru M Maejima Sho S Yoshie Sumio S Kubo Yoshihiro Y Konno Norifumi N Joss Jean M P JM

Proceedings. Biological sciences 20121010 1748

Epithelial sodium channel (ENaC) is a Na(+)-selective, aldosterone-stimulated ion channel involved in sodium transport homeostasis. ENaC is rate-limiting for Na(+) absorption in the epithelia of osmoregulatory organs of tetrapods. Although the ENaC/degenerin gene family is proposed to be present in metazoans, no orthologues or paralogues for ENaC have been found in the genome databases of teleosts. We studied full-length cDNA cloning and tissue distributions of ENaCα, β and γ subunits in the Aus ...[more]

PMID: 23055064

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Project description:The Australian lungfish is a unique living representative of an ancient dipnoan lineage, listed as 'vulnerable' to extinction under Australia's Environment Protection and Biodiversity Conservation Act 1999. Historical accounts indicate this species occurred naturally in two adjacent river systems in Australia, the Burnett and Mary. Current day populations in other rivers are thought to have arisen by translocation from these source populations. Early genetic work detected very little variation and so had limited power to answer questions relevant for management including how genetic variation is partitioned within and among sub-populations. In this study, we use newly developed microsatellite markers to examine samples from the Burnett and Mary Rivers, as well as from two populations thought to be of translocated origin, Brisbane and North Pine. We test whether there is significant genetic structure among and within river drainages; assign putatively translocated populations to potential source populations; and estimate effective population sizes. Eleven polymorphic microsatellite loci genotyped in 218 individuals gave an average within-population heterozygosity of 0.39 which is low relative to other threatened taxa and for freshwater fishes in general. Based on FST values (average over loci = 0.11) and STRUCTURE analyses, we identify three distinct populations in the natural range, one in the Burnett and two distinct populations in the Mary. These analyses also support the hypothesis that the Mary River is the likely source of translocated populations in the Brisbane and North Pine rivers, which agrees with historical published records of a translocation event giving rise to these populations. We were unable to obtain bounded estimates of effective population size, as we have too few genotype combinations, although point estimates were low, ranging from 29 - 129. We recommend that, in order to preserve any local adaptation in the three distinct populations that they be managed separately.

Dataset Information

The epithelial sodium channel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

Publications

The epithelial sodium channel in the Australian lungfish, Neoceratodus forsteri (Osteichthyes: Dipnoi).

Similar Datasets

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