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Development and initial characterization of a novel ghrelin receptor CRISPR/Cas9 knockout wistar rat model

International Journal of Obesity volume 43, pages 344–354 (2019)Cite this article

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Abstract

Background/objectives

Ghrelin, a stomach-derived hormone implicated in numerous behaviors including feeding, reward, stress, and addictive behaviors, acts by binding to the growth hormone secretagogue receptor (GHSR). Here, we present the development, verification, and initial characterization of a novel GHSR knockout (KO) Wistar rat model created with CRISPR genome editing.

Methods

Using CRISPR/Cas9, we developed a GHSR KO in a Wistar background. Loss of GHSR mRNA expression was histologically verified using RNAscope in wild-type (WT; n = 2) and KO (n = 2) rats. We tested the effects of intraperitoneal acyl-ghrelin administration on food consumption and plasma growth hormone (GH) concentrations in WT (n = 8) and KO (n = 8) rats. We also analyzed locomotion, food consumption, and body fat composition in these animals. Body weight was monitored from early development to adulthood.

Results

The RNAscope analysis revealed an abundance of GHSR mRNA expression in the hypothalamus, midbrain, and hippocampus in WTs, and no observed probe binding in KOs. Ghrelin administration increased plasma GH levels (p = 0.0067) and food consumption (p = 0.0448) in WT rats but not KOs. KO rats consumed less food overall at basal conditions and weighed significantly less compared with WTs throughout development (p = 0.0001). Compared with WTs, KOs presented higher concentrations of brown adipose tissue (BAT; p = 0.0322).

Conclusions

We have verified GHSR deletion in our KO model using histological, physiological, neuroendocrinological, and behavioral measures. Our findings indicate that GHSR deletion in rats is not only associated with a lack of response to ghrelin, but also associated with decreases in daily food consumption and body growth, and increases in BAT. This GHSR KO Wistar rat model provides a novel tool for studying the role of the ghrelin system in obesity and in a wide range of medical and neuropsychiatric disorders.

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Acknowledgements

This work was supported by the National Institute on Drug Abuse Intramural Research Program (L.J.Z., B.J.T., C.T.R., Y.J.Z., Z.B.Y., E.L.G., G.F.K., L.F.V., B.K.H., L.L), the National Institute on Alcohol Abuse and Alcoholism Division of Intramural Clinical and Biological Research (L.J.Z., Y.J.Z., M.H., L.L.), and the National Institute of Mental Health Intramural Research Program (J.P.).

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Authors and Affiliations

  1. Section on Clinical Psychoneuroendocrinology and Neuropsychopharmacology, National Institute on Alcohol Abuse and Alcoholism Division of Intramural Clinical and Biological Research and National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Bethesda, MD, USA

    L. J. Zallar & L. Leggio

  2. Neurobiology of Addiction Section, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, USA

    L. J. Zallar, B. J. Tunstall, G. F. Koob & L. F. Vendruscolo

  3. Genetic Engineering and Viral Vector Core, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, USA

    C. T. Richie & Y. J. Zhang

  4. National Institute on Alcohol Abuse and Alcoholism Division of Intramural Clinical and Biological Research, Rockville, MD, USA

    Y. J. Zhang

  5. Neuropsychopharmacology Section, Molecular Targets and Medications Discover Branch, National Institute on Drug Abuse Intramural Research Program, National Institutes of Health, Baltimore, MD, USA

    Z. B. You & E. L. Gardner

  6. Center for Social and Affective Neuroscience, IKE, Linköping University, Linköping, Sweden

    M. Heilig

  7. Transgenic Core Facility, National Institute of Mental Health Intramural Research Program, Bethesda, MD, USA

    J. Pickel

  8. Molecular Mechanisms of Cellular Stress and Inflammation Unit, National Institute on Drug Abuse Intramural Research Program, Baltimore, MD, USA

    B. K. Harvey

  9. Center for Alcohol and Addiction Studies, Department of Behavioral and Social Sciences, Brown University, Providence, RI, USA

    L. Leggio

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  1. L. J. Zallar
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Correspondence to L. Leggio.

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Zallar, L.J., Tunstall, B.J., Richie, C.T. et al. Development and initial characterization of a novel ghrelin receptor CRISPR/Cas9 knockout wistar rat model. Int J Obes 43, 344–354 (2019). https://doi.org/10.1038/s41366-018-0013-5

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