Corresponding author: Alexey Deykin ( deikin@igb.ac.ru ) Academic editor: Mikhail Korokin
© 2018 Vladislav Kalmykov, Pavel Kusov, Maria Yablonskaia, Evgeniy Korshunov, Diana Korshunova, Marina Kubekina, Yuliya Silaeva, Alexey Deykin, Nikolay Lukyanov.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Kalmykov V, Kusov P, Yablonskaia M, Korshunov E, Korshunova D, Kubekina M, Silaeva Y, Deykin A, Lukyanov N (2018) New personalized genetic mouse model of Lesch-Nyhan syndrome for pharmacology and gene therapy. Research Results in Pharmacology 4(4): 97-104. https://doi.org/10.3897/rrpharmacology.4.32209
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Introduction: Lesch-Nyhan syndrome is a clinical and laboratory disorder caused by X-linked disruption of the purine metabolism. The deletion in the HPRT1 gene leads to the disappearance of valine in the eighth position of the protein amino acid sequence. The disease occurs in males and is accompanied by an excess of uric acid, urate nephropathy and neurologic impairment.
Objective of the Study: Generation of the new personalized genetic mouse model of Lesch-Nyhan syndrome for preclinical study of new approaches to the pharmacological and gene therapy
Materials and Methods: For genomic editing, the sequence was synthesized the sequence of the matrix GACCGGTCCCGTCATGCCGACACGCAGTCCCAGCGTGGTGAGCCAAGGGGACTCCAGCAGAGCCCCACAG was synthesized. For the cultivation of viable mouse embryos after microinjection, KSOM media was used. Amplification and sequencing was performed by the standard methods.
Results: A boy with not previously described hemizygous variant in the HPRT1 gene, was observed in our clinic. The mutation was the deletion of 8Val in the first exon of the HPRT1 gene. To introduce this mutation, we used the CRISPR-Cas9 genomic editing system. The genetic construct for microinjections included a mixture of the vector for the expression of Cas9 and sgRNA (px330), as well as the matrix for homologous recombination (ssODN), in a ratio of 1 part Cas9 to 3 parts of the ssODN matrix. Four of the 12 obtained animals were mosaic transgenes. One of 4 mice mated with a male from the hybrid strain CBA x C57BL/6, and descendants of F2 have already been received from this mating.
Discussion: During the creation of HPRT1 genetically modified mice, we encountered certain difficulties. First, from 615 transplanted embryos, only 12 were able to complete full embryonic development. 9 recipients we observed abortions in the later stages. These data may indicate possible violations of embryonic development in animals carrying a mutant copy of the HPRT1 gene.
Conclusion: In the current study, we present the results of the generation of a genetically modified mouse strain carrying a deletion in the HPRT1 gene. These mice can be effectively used for the preclinical testing of new drugs aimed at the treatment of Lesch-Nyhan syndrome.
transgenic mice, Lesch-Nyhan syndrome, CRISPR-Cas9, personalized medicine, orphane deases, CBAxC57BL/6
The problem of orphan (rare) diseases, despite the low prevalence in the population, is very important for medicine. It is now believed that most of these diseases are incurable. However, hereditary metabolic diseases, as global medical practice shows, are considered one of the most promising directions in the development of therapies. Lesch-Nyhan syndrome (ICD-10: E79.1; OMIM 300322; ORPHA: 510) is an X-linked inborn error of purine metabolism that is caused by mutations in the HPRT1 gene encoding the purine recycling enzyme hypoxanthine-guanine phosphoribosyltransferase (HPRT), which catalyzes the conversion of hypoxanthine to inosine monophosphate and guanine to guanosine monophosphate in the presence of phosphoribosylpyrophosphate (
The intensive development of animal genetic engineering methods allows for a wider consideration of the concept of personalized medicine. Experiments on animal models are becoming an indispensable stage in the preclinical testing of therapeutic strategies. Thus, a personalized model of a genetic disease makes it possible to evaluate the contribution of the detected mutation to the phenotype- to evaluate the potential efficacy of gene therapy.
Despite the fact that Hprt1-deficient mice models do not have a clinical complex characteristic of patients with Lesch-Nyhan syndrome, these models should be used in studies of brain metabolism (
At present, the genome editing technology CRIPSR-Cas9 (
The animals and the conditions of their care have been described previously (
We used the px330 vector (
The matrix was synthesized by the Evrogen Company. The sequence of the matrix was GACCGGTCCCGTCATGCCGACACGCAGTCCCAGCGTGGTGAGCCAAGGGGACTCCAGCAGAGCCCCACAG
Mouse embryo culture. For the cultivation of viable mouse embryos after microinjection, KSOM media was used. The cultivation of the embryos to the blastocyst stage was carried out in mineral oil (Merck, USA) under conditions of absolute humidity at 37°C in 5% CO2.
The DNA isolation from blastocysts was performed according to a previously published protocol (
The DNA isolation from tissue samples was performed according to a standard protocol (
Sample preparation for Sanger sequencing included the amplification of the gene of interest (fragment size 544 b.p.) using the primers presented in Table
Primers used to amplify a fragment of the HPRT1 gene of 544 b.p. in size.
Primer | Sequence |
Forward | TGATTATCTGGGAATCCTCTGG |
Reverse | CATCTAGCCAGACTCCAGGAA |
The restriction analysis of the F0 and F1 generations was performed based on the presence of the BstX1 restriction site in the wild-type HPRT1 matrix and its absence in the mutant gene (Figures
A) – Sequencing results for F0 transgenes; B) – Restriction analysis results for F0 transgenes
A) – Sequencing results for F1 transgenes; B) – Restriction analysis results for F1 transgene
Software. Analysis of the sequencing results was performed using the program Peak Scanner (Thermo Fisher Scientific). Then, to identify matches with the mutant matrix and the wild-type matrix, the program Geneious (Biomatters Limited) was used. The protein models were visualized and aligned in PyMol (Schrödinger, Portland, OR). The analysis of the transgenic animal generation results was performed in Microsoft Excel (USA).
Clinical case. A boy with a classic variant of Lesch-Nyhan syndrome was observed in our clinic. The age of the patient at the time of diagnosis was 9 years. Genetic analysis of the HPRT1 gene was performed by direct automatic sequencing of the entire coding region of the gene, including exon-intron boundaries. The patient had a hemizygous variant in the HPRT1 gene, which has not been previously described (Table
Results of direct automatic sequencing of the entire coding region of the HPRT1 gene, including exon-intron boundaries.
Nucleotide | Effect | Amino acid change |
c.23_25delTCG | Small deletion (exon 1) | p.Val8del |
The BLAST algorithm (NCBI) was used for the comparison of human and murine HPRT1 gene sequences. The alignment shows 98.6% nucleotide sequence homology. The primary structure of the HPRT1 protein and mutation locus was similar enough to be studied in Mus musculus.
Structural models of the HPRT1 protein and its fragments (PDB) were used as templates for the M4T RaptorX structure prediction algorithm to obtain structural models of the mutation site and whole mutated protein with altered conformation (
Models were visualized and aligned in PyMol (Schrödinger, Portland, OR). The cooperativity of HPRT1 homodimer subunits was suggested to be disrupted by the conformational changes observed in the predicted structure of HPRT1. The deleted valine was found to be located in the HPRT1 monomer surface close to the homodimer junction.
Hindered enzymatic soma assembly may be the reason for the biological function loss - the HPRT1 homotetramer appears in its native conformation as a dimer of dimers. The fully functional HPRT1 complex strongly depends on its intermolecular surface structure (Figures
Native conformation of the HPRT1 monomer (left green colored) in contact with predicted mutated rotamer (cyan) built by the RaptorX algorithm.
The alignment of three native monomers with the del8Val HPRT1 predicted model shows that the whole protein is slightly changed, with a rotational conformational distribution along the chain. Accordingly, dislocated charged residues are suggested to be the reason for the dimerization disruption.
To introduce the 8Val deletion in the first exon of the HPRT1 gene, we used the CRISPR-Cas9 genomic editing system with the most successful sgRNA, the PAM site of which was removed at 13 bp from the place of the proposed deletion. For the selection of sgRNA, we used Chop-chop (http://chopchop.cbu.uib.no/) (
Scheme for introducing a deletion at the 8Val position in the first exon of the HPRT1 gene
The genetic construct for microinjections included a mixture of the vector for the expression of Cas9 and sgRNA (px330), as well as the matrix for homologous recombination (ssODN), in a ratio of 1 part Cas9 to 3 parts of the ssODN matrix.
To verify the efficiency of the selected genomic editing system, microinjected embryos were cultured to the blastocyst stage, and then the DNA from these organisms was isolated and amplified. A fragment of the gene of interest was sequenced, as described above. As shown in Figure
The F0 generation of a genetically modified animal model of Lesch-Nyhan syndrome was obtained by the microinjection of a solution of a genetic construct into the pronucleus of a fertilized egg cell and subsequent transplantation into the oviduct of a pseudopregnant recipient (Ittner and Götz 2007,
. The results of the generation of primary genetically modified animals to obtain a model of Lesch-Nyhan syndrome.
Used Recipients | Amount of Transplanted embryos | Amount of recipients giving birth | The amount of newborn mice | Amount of genetically modified animals from newborns |
78 | 615 | 9 | 12 | 4 |
In total, 78 recipients were used, and 615 one- and two-cell embryos were transferred at 3-5 embryos per horn of the uterus. We significantly reduced the number of embryos transferred to an individual recipient compared to standard protocols (
9 recipients, we observed abortions in the later stages (genetic analysis of abortive material was not performed due to the unsuitability of the material). Of the 615 transferred embryos, 12 newborn mice were received. Seven to 14 days after birth, all mice were sampled, the DNA was isolated and sequenced, and restriction analysis was performed on the obtained samples. Four of the 12 obtained animals were mosaic transgenes (Figure
The resulting primary transgenes were assigned numbers 565, 566, 567, and 568. Males 565, 567 and 568 were mated with females of the CBA x C57BL/6 hybrid strain, and female 566 was mated with a male of the CBA x C57BL/6 hybrid strain. A total of 31 descendants of F1 were received from mouse 565, 8 descendants of F1 were received from mouse 566, 21 descendants of F1 were received from mouse 568, and no offspring were produced from mouse 567. All progeny obtained were analyzed using Sanger sequencing and restriction analysis, and one genetically modified F1 animal, female 2296, was identified (Fig.
The results of experiments conducted to obtain F1 animals carrying the mutant HPRT1 gene.
Primary transgene, number | Descendants of F1, amount | Transgenes from these animals |
565 | 31 | 1 |
566 | 8 | 0 |
567 | 0 | 0 |
567 | 21 | 0 |
Mutations in the HPRT1 gene can cause severe neurological and metabolic disorders in humans (
In this paper, we presented the results of the development and production of a new genetically modified mouse line model for Lesch–Nyhan syndrome.
We believe that the proposed model can be successfully used for basic research and preclinical testing of drugs for the treatment of Lesch–Nyhan syndrome.
The authors state no conflict of interest concerning with the present submitted manuscript.
We thank Vasiliy Sukhorukov (Institute of General Pathology and Pathophysiology, Moscow, Russia) for the discussion of the work. This work was carried out using infrastructure of Center for collective use of the Institute of gene Biology, Russian academy of science: “Biology of the living cell and drug biomedical nanotransporters”.
This work is supported by a grant from the Russian Scientific Foundation № 17-75-20249.
Vladislav A. Kalmykov, post-graduate student of Institute of Gene Biology of the Russian Academy of Sciences, e-mail: kalmykov@genebiology.ru ORCID: 0000-0002-9125-8538. Methodology, Formal analysis, Investigation, Review and editing. Visualization
Pavel A. Kusov, post-graduate student of Skolkovo institute of science and technology, Institute of Gene Biology of the Russian Academy of Sciences, e-mail: Pavel.Kusov@skoltech.ru, ORCID: 0000-0001-6383-0077. Methodology, Formal analysis, Investigation, Original draft of paper, Review and editing, Visualization.
Maria I. Yablonskaia, PhD in Medicine, Research and Clinical Institute for Pediatrics named after Academician Yuri Veltischev of the Pirogov Russian National Research Medical University of the Russian Ministry of Health, e-mail: i.yablonsky@mail.ru ORCID: 0000-0002-7233-4048. Conceptualization, Formal analysis, Original draft of paper.
Evgeniy N. Korshunov, post-graduate student of Institute of Gene Biology of the Russian Academy of Sciences, e-mail: korshunov@genebiology.ru. Investigation, Review and editing.
Diana S. Korshunova, post-graduate student of Institute of Gene Biology of the Russian Academy of Sciences, e-mail: korshunova@genebiology.ru. Investigation, Review and editing.
Marina V. Kubekina, post-graduate student of Institute of Gene Biology of the Russian Academy of Sciences, e-mail: kubekina@genebiology.ru, ORCID: 0000-0002-8834-1111. Methodology, Formal analysis, Review and editing of paper.
Yuliya Yu. Silaeva, PhD in Biology, Institute of Gene Biology of the Russian Academy of Sciences, e-mail: silaeva@genebiology.ru, ORCID: 0000-0003-2070-9001. Methodology, Original draft of paper, Review and editing, Visualization
Alexey V. Deykin, PhD in Biology, Institute of Gene Biology of the Russian Academy of Sciences, Institute of General Pathology and Pathophysiology e-mail: deikin@igb.ac.ru, ORCID: 0000-0001-9960-0863. Conceptualization, Methodology, Formal analysis, Investigation, Original draft of paper, review and editing, Supervision
Nikolay E. Lukyanov, MD, Yaroslavl State Medical University, Ministry of Health of Russia, e-mail: lukyanov@ysmu.ru. Investigation, Review and editing.