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J Endocrinol. 2015 Nov;227(2):93-103. doi: 10.1530/JOE-15-0284.

Glucagon receptor inactivation leads to α-cell hyperplasia in zebrafish.

Author information

1
Departments of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Light Hall, Room 711, 2215 Garland Avenue, Nashville, Tennessee 37232, USADivision of DiabetesEndocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USAThird Institute of OceanographyState Oceanic Administration, Xiamen 361005, ChinaVeterans Affairs Tennessee Valley Healthcare SystemNashville, Tennessee 37212, USA.
2
Departments of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Light Hall, Room 711, 2215 Garland Avenue, Nashville, Tennessee 37232, USADivision of DiabetesEndocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USAThird Institute of OceanographyState Oceanic Administration, Xiamen 361005, ChinaVeterans Affairs Tennessee Valley Healthcare SystemNashville, Tennessee 37212, USA Departments of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Light Hall, Room 711, 2215 Garland Avenue, Nashville, Tennessee 37232, USADivision of DiabetesEndocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USAThird Institute of OceanographyState Oceanic Administration, Xiamen 361005, ChinaVeterans Affairs Tennessee Valley Healthcare SystemNashville, Tennessee 37212, USA.
3
Departments of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Light Hall, Room 711, 2215 Garland Avenue, Nashville, Tennessee 37232, USADivision of DiabetesEndocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USAThird Institute of OceanographyState Oceanic Administration, Xiamen 361005, ChinaVeterans Affairs Tennessee Valley Healthcare SystemNashville, Tennessee 37212, USA Departments of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Light Hall, Room 711, 2215 Garland Avenue, Nashville, Tennessee 37232, USADivision of DiabetesEndocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USAThird Institute of OceanographyState Oceanic Administration, Xiamen 361005, ChinaVeterans Affairs Tennessee Valley Healthcare SystemNashville, Tennessee 37212, USA Departments of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Light Hall, Room 711, 2215 Garland Avenue, Nashville, Tennessee 37232, USADivision of DiabetesEndocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USAThird Institute of OceanographyState Oceanic Administration, Xiamen 361005, ChinaVeterans Affairs Tennessee Valley Healthcare SystemNashville, Tennessee 37212, USA.
4
Departments of Molecular Physiology and BiophysicsVanderbilt University School of Medicine, Light Hall, Room 711, 2215 Garland Avenue, Nashville, Tennessee 37232, USADivision of DiabetesEndocrinology, and Metabolism, Department of Medicine, Vanderbilt University, Nashville, Tennessee 37232, USAThird Institute of OceanographyState Oceanic Administration, Xiamen 361005, ChinaVeterans Affairs Tennessee Valley Healthcare SystemNashville, Tennessee 37212, USA wenbiao.chen@vanderbilt.edu.

Abstract

Glucagon antagonism is a potential treatment for diabetes. One potential side effect is α-cell hyperplasia, which has been noted in several approaches to antagonize glucagon action. To investigate the molecular mechanism of the α-cell hyperplasia and to identify the responsible factor, we created a zebrafish model in which glucagon receptor (gcgr) signaling has been interrupted. The genetically and chemically tractable zebrafish, which provides a robust discovery platform, has two gcgr genes (gcgra and gcgrb) in its genome. Sequence, phylogenetic, and synteny analyses suggest that these are co-orthologs of the human GCGR. Similar to its mammalian counterparts, gcgra and gcgrb are mainly expressed in the liver. We inactivated the zebrafish gcgra and gcgrb using transcription activator-like effector nuclease (TALEN) first individually and then both genes, and assessed the number of α-cells using an α-cell reporter line, Tg(gcga:GFP). Compared to WT fish at 7 days postfertilization, there were more α-cells in gcgra-/-, gcgrb-/-, and gcgra-/-;gcgrb-/- fish and there was an increased rate of α-cell proliferation in the gcgra-/-;gcgrb-/- fish. Glucagon levels were higher but free glucose levels were lower in gcgra-/-, gcgrb-/-, and gcgra-/-;gcgrb-/- fish, similar to Gcgr-/- mice. These results indicate that the compensatory α-cell hyperplasia in response to interruption of glucagon signaling is conserved in zebrafish. The robust α-cell hyperplasia in gcgra-/-;gcgrb-/- larvae provides a platform to screen for chemical and genetic suppressors, and ultimately to identify the stimulus of α-cell hyperplasia and its signaling mechanism.

KEYWORDS:

cell growth control; fish; glucagon; mutations; whole animal physiology

PMID:
26446275
PMCID:
PMC4598637
DOI:
10.1530/JOE-15-0284
[Indexed for MEDLINE]
Free PMC Article

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