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Independent validation of experimental results requires timely and unrestricted access to animal models and reagents

  • Cassandra R. Diegel,

    Affiliation Program in Skeletal Disease and Tumor Microenvironment and Center for Cancer and Cell Biology, Van Andel Institute, Grand Rapids, Michigan, United States of America

  • Steven Hann,

    Affiliation Orthopedic Research Labs, Boston Children’s Hospital and Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America

  • Ugur M. Ayturk,

    Affiliations Orthopedic Research Labs, Boston Children’s Hospital and Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America, Musculoskeletal Integrity Program, Hospital for Special Surgery Research Institute, New York, New York, United States of America

  • Jennifer C. W. Hu,

    Affiliation Orthopedic Research Labs, Boston Children’s Hospital and Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America

  • Kyung-Eun Lim,

    Affiliation Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America

  • Casey J. Droscha,

    Affiliation Program in Skeletal Disease and Tumor Microenvironment and Center for Cancer and Cell Biology, Van Andel Institute, Grand Rapids, Michigan, United States of America

  • Zachary B. Madaj,

    Affiliation Bioinformatics and Biostatistics Core, Van Andel Institute, Grand Rapids, Michigan, United States of America

  • Gabrielle E. Foxa,

    Affiliation Program in Skeletal Disease and Tumor Microenvironment and Center for Cancer and Cell Biology, Van Andel Institute, Grand Rapids, Michigan, United States of America

  • Isaac Izaguirre,

    Affiliation Program in Skeletal Disease and Tumor Microenvironment and Center for Cancer and Cell Biology, Van Andel Institute, Grand Rapids, Michigan, United States of America

  • VAI Vivarium and Transgenics Core ,

    Members of the VAI Vivarium and Transgenics Core are listed in the Acknowledgments

    Affiliation Vivarium and Transgenics Core, Van Andel Institute, Grand Rapids, Michigan, United States of America

  • Alexander G. Robling,

    Affiliation Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, Indiana, United States of America

  • Matthew L. Warman,

    Affiliation Orthopedic Research Labs, Boston Children’s Hospital and Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America

  • Bart O. Williams

    bart.williams@vai.org

    Affiliation Program in Skeletal Disease and Tumor Microenvironment and Center for Cancer and Cell Biology, Van Andel Institute, Grand Rapids, Michigan, United States of America

Independent validation of experimental results requires timely and unrestricted access to animal models and reagents

  • Cassandra R. Diegel, 
  • Steven Hann, 
  • Ugur M. Ayturk, 
  • Jennifer C. W. Hu, 
  • Kyung-Eun Lim, 
  • Casey J. Droscha, 
  • Zachary B. Madaj, 
  • Gabrielle E. Foxa, 
  • Isaac Izaguirre, 
  • VAI Vivarium and Transgenics Core
PLOS
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We used CRISPR/Cas9 gene editing to create mice that are lacking Bglap and Bglap2, which encode osteocalcin [1]. We did not find evidence of increased bone mass, elevated blood glucose levels, or reduced male fertility in our mice [1], which contrasts to what Dr. Karsenty has reported [24]. Another group of investigators, working independently of us, created a third Bglap and Bglap2 mouse knockout strain and also failed to substantiate Dr. Karsenty’s results [5]. Furthermore, the osteocalcin-null rat model did not develop obesity, insulin resistance, or glucose intolerance, which conflicts with Dr. Karsenty’s mice [6].

We are pleased that after 24 years Dr. Karsenty has finally made available through JAX the osteocalcin knockout strain he published in 1996. Dr. Karsenty could have donated these mice to JAX, to serve as easy to obtain positive and negative controls for interested investigators, much sooner. Of note, he only submitted these mice to JAX in October 2019, two months after we posted our paper on bioRxiv, and they became available only as cryopreserved stocks the day after our paper was published in PLOS Genetics. Specific to the multiple claimed roles of osteocalcin, we urge Dr. Karsenty to also donate his conditional (i.e., floxed) osteocalcin knockout strain since he used that strain as an important independent control in other experiments [4]. These strains along with our knockout mice, which we shipped to JAX on June 17, 2020 after lifting of COVID-19-related shipping restrictions, should enable other independent investigators to study the endogenous role of osteocalcin in vivo.

Contrary to what Dr. Karsenty has written, we recognize bone as an endocrine organ as we clearly indicate in our Authors’ Summary [1]. We make no claims regarding whether or not osteocalcin is a hormone. We cannot comment on the protein’s effect when given exogenously, since we did not inject osteocalcin into mice in our study. However, we [1], and others [57], found no evidence that supports an endogenous hormonal role for osteocalcin. Should Dr. Karsenty make available batches of his biologically-active osteocalcin without restriction, interested parties could avoid the potential confounder of reagent quality [8] and assess objectively whether osteocalcin has a hormonal role when administered exogenously.

This is not the first time that some of us (CRD, AGR, MLW, and BOW) published data that did not support findings published by Dr. Karsenty. Dr. Karsenty reported that LRP5 controls bone mass by inhibiting serotonin synthesis in the duodenum [9,10]. We found no evidence for this mechanism [11,12]. Of interest, another group studying a larger cohort of patients with the same LRP5 mutation that Dr. Karsenty reported in his original paper [9] could not replicate his findings regarding circulating levels of serotonin [13]. We donated the mice we created for our paper [11] to JAX (Stock numbers 026269, 012668, 012669, 012670, 012671, 012672). The mice created by Dr. Karsenty and used in his experiments still have not been supplied to JAX to our knowledge.

We recognize the importance of fostering integrity in research [14]. This is why we have consistently donated mice we created to JAX for public distribution. We look forward to other investigators using our and Dr. Karsenty’s mice to determine the endogenous role of osteocalcin, meeting the standards of transparency, rigor, and reproducibility upon which the scientific and medical communities rely.

Acknowledgments

Key members of the VARI Vivarium and Transgenics Core include Bryn Eagleson, Adam Rapp, Nicholas Getz, Audra Guikema, Tristan Kempston, Tina Schumaker, and Malista Powers.

References

  1. 1. Diegel CR, Hann S, Ayturk UM, Hu JCW, Lim KE, et al. (2020) An osteocalcin-deficient mouse strain without endocrine abnormalities. PLoS Genet 16: e1008361. pmid:32463812
  2. 2. Ducy P, Desbois C, Boyce B, Pinero G, Story B, et al. (1996) Increased bone formation in osteocalcin-deficient mice. Nature 382: 448–452. pmid:8684484
  3. 3. Lee NK, Sowa H, Hinoi E, Ferron M, Ahn JD, et al. (2007) Endocrine regulation of energy metabolism by the skeleton. Cell 130: 456–469. pmid:17693256
  4. 4. Oury F, Sumara G, Sumara O, Ferron M, Chang H, et al. (2011) Endocrine regulation of male fertility by the skeleton. Cell 144: 796–809. pmid:21333348
  5. 5. Moriishi T, Ozasa R, Ishimoto T, Nakano T, Hasegawa T, et al. (2020) Osteocalcin is necessary for the alignment of apatite crystallites, but not glucose metabolism, testosterone synthesis, or muscle mass. PLoS Genet 16: e1008586. pmid:32463816
  6. 6. Lambert LJ, Challa AK, Niu A, Zhou L, Tucholski J, et al. (2016) Increased trabecular bone and improved biomechanics in an osteocalcin-null rat model created by CRISPR/Cas9 technology. Dis Model Mech 9: 1169–1179. pmid:27483347
  7. 7. Fowlkes JL, Clay Bunn R, Kalaitzoglou E, Ray P, Popescu I, et al. (2020) Postnatal loss of the insulin receptor in osteoprogenitor cells does not impart a metabolic phenotype. Sci Rep 10: 8842. pmid:32483283
  8. 8. von Herrath M, Pagni PP, Grove K, Christoffersson G, Tang-Christensen M, et al. (2019) Case Reports of Pre-clinical Replication Studies in Metabolism and Diabetes. Cell Metab 29: 795–802. pmid:30879984
  9. 9. Yadav VK, Ryu JH, Suda N, Tanaka KF, Gingrich JA, et al. (2008) Lrp5 controls bone formation by inhibiting serotonin synthesis in the duodenum. Cell 135: 825–837. pmid:19041748
  10. 10. Kode A, Obri A, Paone R, Kousteni S, Ducy P, et al. (2014) Lrp5 regulation of bone mass and serotonin synthesis in the gut. Nat Med 20: 1228–1229. pmid:25375916
  11. 11. Cui Y, Niziolek PJ, MacDonald BT, Zylstra CR, Alenina N, et al. (2011) Lrp5 functions in bone to regulate bone mass. Nat Med 17: 684–691. pmid:21602802
  12. 12. Cui Y, Niziolek PJ, MacDonald BT, Alenina N, Matthes S, et al. (2014) Reply to Lrp5 regulation of bone mass and gut serotonin synthesis. Nat Med 20: 1229–1230. pmid:25375917
  13. 13. Lee GS, Simpson C, Sun BH, Yao C, Foer D, et al. (2014) Measurement of plasma, serum, and platelet serotonin in individuals with high bone mass and mutations in LRP5. J Bone Miner Res 29: 976–981. pmid:24038240
  14. 14. National Academies of Sciences Engineering and Medicine (U.S.). Committee on Responsible Science, Committee on Science Engineering Medicine and Public Policy (U.S.) (2017) Fostering integrity in research. 1 online resource (1 PDF file (xv, 307 pages)) p.