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Molecular Cloning and Characterization of the Zebrafish (Danio rerio) Telomerase Catalytic Subunit (Telomerase Reverse Transcriptase, TERT)

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Abstract

Telomerase is an enzyme composed of a catalytic subunit (TERT) and RNA template (TR), which specifically elongates telomeres and prevents cellular senescence. Although telomerase cannot be detected in most human somatic tissues, including the nervous system, it can be detected in teleost tissues. To facilitate the investigation of telomerase function in the teleost visual system, the coding sequence of zebrafish TERT is revealed and cloned. Immunoblot, immunohistochemistry, reverse transcription polymerase chain reaction (RT-PCR), and telomeric repeats amplification protocol (TRAP) assay are used to assess the expression of telomerase at mRNA, protein, and functional levels in zebrafish retina. Based on the amino acid sequence of mouse TERT, a full-length telomerase reverse transcriptase cDNA of zebrafish has been isolated and cloned. The deduced protein sequence contains 1,091 amino acid residues and a predicted molecular mass of 126 kDa. Multiple alignment shows that the protein sequence contains the conserved motifs and residues found in TERT of other species. RT-PCR and TRAP assay has detected TERT mRNA expression and telomerase activity, respectively, in all tissues examined, including the retina and the brain. The presence of telomerase activity indicates that a fully functional form of telomerase can be found in the retina. Immunohistochemistry reveals that most neurons in zebrafish retina express TERT in the cell nucleus. The presence of telomerase in different tissues may be associated with the indeterminate growth of teleost. However, teleost retinal neurons are post-mitotic and do not further divide under normal situation. The expression of telomerase activity and TERT in retina implies that telomerase has functions other than the elongation of telomere. These findings could provide new insights on telomerase function in the nervous system.

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Acknowledgments

The authors would like to thank Ms. Tania Wan for her technical assistance in the study. This work was supported by a CRCG grant from the University of Hong Kong and grants from the Regional Grants Council of Hong Kong.

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Authors and Affiliations

  1. Department of Anatomy, Faculty of Medicine, The University of Hong Kong, 21 Sassoon Road, Pokfulam, Hong Kong SAR, China

    Benson Wui-Man Lau, George Sai-Wah Tsao, Kwok-Fai So & Henry Ka-Fun Yip

  2. Department of Zoology, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

    Anderson On-Lam Wong

  3. Research Centre of Heart, Brain, Hormone and Health Aging, Faculty of Medicine, The University of Hong Kong, Pokfulam, Hong Kong SAR, China

    Kwok-Fai So & Henry Ka-Fun Yip

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  1. Benson Wui-Man Lau
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  2. Anderson On-Lam Wong
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Correspondence to Henry Ka-Fun Yip.

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Lau, B.WM., Wong, A.OL., Tsao, G.SW. et al. Molecular Cloning and Characterization of the Zebrafish (Danio rerio) Telomerase Catalytic Subunit (Telomerase Reverse Transcriptase, TERT). J Mol Neurosci 34, 63–75 (2008). https://doi.org/10.1007/s12031-007-0072-x

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