Glucagon receptor inactivation leads to α-cell hyperplasia in zebrafish

Mingyu Li; E Danielle Dean; Liyuan Zhao; Wendell E Nicholson; Alvin C Powers; Wenbiao Chen

doi:10.1530/JOE-15-0284

Glucagon receptor inactivation leads to α-cell hyperplasia in zebrafish

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

Authors

Mingyu Li¹, E Danielle Dean¹, Liyuan Zhao², Wendell E Nicholson¹, Alvin C Powers³, Wenbiao Chen⁴

Affiliations

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.

Publication types

Research Support, N.I.H., Extramural
Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

Animals
Animals, Genetically Modified
Cell Proliferation / genetics
Cloning, Molecular
Embryo, Nonmammalian
Gene Expression Regulation, Developmental
Gene Silencing*
Glucagon-Secreting Cells / metabolism
Glucagon-Secreting Cells / pathology*
Hyperplasia / genetics
Receptors, Glucagon / genetics*
Receptors, Glucagon / metabolism
Zebrafish

Substances

Receptors, Glucagon

Abstract

Publication types

MeSH terms

Substances

Grants and funding