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Variable expression of myoglobin among the hemoglobinless Antarctic icefishes.

ABSTRACT: The important intracellular oxygen-binding protein, myoglobin (Mb), is thought to be absent from oxidative muscle tissues of the family of hemoglobinless Antarctic icefishes, Channichthyidae. Within this family of fishes, which is endemic to the Southern Ocean surrounding Antarctica, there exist 15 known species and 11 genera. To date, we have examined eight species of icefish (representing seven genera) using immunoblot analyses. Results indicate that Mb is present in heart ventricles from five of these species of icefish. Mb is absent from heart auricle and oxidative skeletal muscle of all species. We have identified a 0.9-kb mRNA in Mb-expressing species that hybridizes with a Mb cDNA probe from the closely related red-blooded Antarctic nototheniid fish, Notothenia coriiceps. In confirmation that the 0.9-kb mRNA encodes Mb, we report the full-length Mb cDNA sequence of the ocellated icefish, Chionodraco rastrospinosus. Of the eight icefish species examined, three lack Mb polypeptide in heart ventricle, although one of these expresses the Mb mRNA. All species of icefish retain the Mb gene in their genomic DNA. Based on phylogeny of the icefishes, loss of Mb expression has occurred independently at least three times and by at least two distinct molecular mechanisms during speciation of the family.

SUBMITTER: Sidell BD

PROVIDER: S-EPMC20385 | biostudies-literature | 1997 Apr

REPOSITORIES: biostudies-literature

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Variable expression of myoglobin among the hemoglobinless Antarctic icefishes.

Sidell B D BD Vayda M E ME Small D J DJ Moylan T J TJ Londraville R L RL Yuan M L ML Rodnick K J KJ Eppley Z A ZA Costello L L

Proceedings of the National Academy of Sciences of the United States of America 19970401 7

The important intracellular oxygen-binding protein, myoglobin (Mb), is thought to be absent from oxidative muscle tissues of the family of hemoglobinless Antarctic icefishes, Channichthyidae. Within this family of fishes, which is endemic to the Southern Ocean surrounding Antarctica, there exist 15 known species and 11 genera. To date, we have examined eight species of icefish (representing seven genera) using immunoblot analyses. Results indicate that Mb is present in heart ventricles from five ...[more]

PMID: 9096409

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Project description:BackgroundThe metabolic phenotype of stem cells is increasingly recognized as a hallmark of their pluripotency with mitochondrial and oxygen-related metabolism playing a not completely defined role in this context. In a previous study, we reported the ectopic expression of myoglobin (MB) in bone marrow-derived hematopoietic stem/progenitor cells. Here, we have extended the analysis to mesenchymal stem cells (MSCs) isolated from different tissues.MethodsMSCs were isolated from human placental membrane, mammary adipose tissue and dental pulp and subjected to RT-PCR, Western blotting and mass spectrometry to investigate the expression of MB. A combination of metabolic flux analysis and cyto-imaging was used to profile the metabolic phenotype and the mitochondria dynamics in the different MSCs.ResultsAs for the hematopoietic stem/progenitor cells, the expression of Mb was largely driven by an alternative transcript with the protein occurring both in the monomer and in the dimer forms as confirmed by mass spectrometry analysis. Comparing the metabolic fluxes between neonatal placental membrane-derived and adult mammary adipose tissue-derived MSCs, we showed a significantly more active bioenergetics profile in the former that correlated with a larger co-localization of myoglobin with the mitochondrial compartment. Differences in the structure of the mitochondrial network as well as in the expression of factors controlling the organelle dynamics were also observed between neonatal and adult mesenchymal stem cells. Finally, the expression of myoglobin was found to be strongly reduced following osteogenic differentiation of dental pulp-derived MSCs, while it was upregulated following reprogramming of human fibroblasts to induce pluripotent stem cells.ConclusionsEctopic expression of myoglobin in tissues other than muscle raises the question of understanding its function therein. Properties in addition to the canonical oxygen storage/delivery have been uncovered. Finding of Mb expressed via an alternative gene transcript in the context of different stem cells with metabolic phenotypes, its loss during differentiation and recovery in iPSCs suggest a hitherto unappreciated role of Mb in controlling the balance between aerobic metabolism and pluripotency. Understanding how Mb contributes through modulation of the mitochondrial physiology to the stem cell biology paves the way to novel perspectives in regenerative medicine as well as in cancer stem cell therapy.

Dataset Information

Variable expression of myoglobin among the hemoglobinless Antarctic icefishes.

Publications

Variable expression of myoglobin among the hemoglobinless Antarctic icefishes.

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