Introduction

The neurodegenerative disease is a global concern, the tremendous population have affected by this disease. Treatment to this condition is considered as a financial burden¹. Only Alzheimer’s patient number is around 46 million globally. And this number expected to go beyond 132.5 million by 2050². The number of pathogenic condition ruinous to neurodegeneration and progression of such condition result into disability and death of patient. These ruinous condition involve Parkinson’s disease, Frontotemporal dementia, Alzheimer’s and ALS i.e., amyotrophic lateral sclerosis.  Most of patient with neurodegenerative disorder have no direct link with genetic cause. But there are some genetic risk factors that influences these conditions³. The animal models are used to study the pathophysiology of disease and their treatment. But issues with these models are they are not exactly similar to that of human diseases. The pathological symptoms they were showing rightly but there is missing the chain of complete step by step occurrence of pathophysiologic changes. However, developing new animal models allow brief understanding of disease at cellular and molecular level. Mouse as animal model gave weak estimation to drug efficacy. This is not the limitation to animal models. Instead of this give scope to discover more animal models using different rodent and non-rodent. The demonstration of human cellular model of neuron degeneration are having disadvantages like missing of maturation process, missing of neuronal circuit and absence of cellular, neuronal components, absence of glia cells⁴. Using naturally found animals as an animal model was discovered 100 years ago and now there is great improvement in health science ^{5, 6}. More than 100 of diseases that found in dogs and cats having likeness to humans⁷. The cancer etiologies are also similar to humans that are described by their genetic characteristics and environment⁸. Some reports suggest that pathophysiology of human and disease etiology are similar to dogs and cats. This facilitates knowing possible preventive majors, identifying risk factors and understanding disease etiology⁹. Duration of life of canine and feline are short compared to humans hence it does not cover full history, etiology of disease in their short life cycle.

In the veterinary clinical sector the animals are often managed with drug therapies which are likeness to humans. In present days veterinary sciences applied their scope to veterinary neurology and their practice. That facilitates brief study of clinical characterization of diseases. This review gives a detailed idea about animals in neurological study⁸.

Figure 1: Human brain showing different brain regions and diseases that are associated with it.  Click here to view figure

Barriers to use animal models in neurological research

Other than the edge over the experimental animals have some disadvantages⁶. Though there are some anatomical and physiological similarities found in animals there are some differences also exist like their effects on drug metabolism, drug action, and its toxicity. Anesthesia is required to study and examine the animals. The anesthetics affect the blood flow to the cerebral region, and O₂  requirement. This is necessary in oxygen dependent MRI. Immobility required for neuroimaging. There is species- species diversity observed in case of disease¹⁰. In the past year the translational science in experimental animals gives knowledge about human subjects in clinical trials, but it has limitations in statistical results and lacks standard medical therapy. The animal models are considered to be expensive and approved through ethical regulations¹¹. These factors do not prohibit the use of animals for neurological research purposes. Instead, these problems give rise to search for more advanced methods to avoid such conflict and improve research work by using animal models. This would add value to preclinical research.

Impulsive neurological disease conditions in experimental animal models

Epilepsy

This is one of the common and widespread diseases. This commonly occurs 0.6 to 1 percent in dogs and in humans, its prevalence is 1 to 3 percent ^{12, 13}. Induction of an epilepsy in animal models like canine, allows brief observation about symptoms, etiology that is exactly the same with humans. The strokes, injury to the brain, tumors that mainly cause brain region are the main cause of the disease ^{14, 15, 16, 17}. “A robust body of seven literature” have mentioned the disease’s occurrence, history, pharmacological changes and many more things that are exactly like human beings and dog species. This also represents that there is ECG data and genetic traits of disease are similar with humans. The diseased dog and the human with the same disease show similar behavioral and general problems ^{18, 19}. However, very little info is known about neuropathy, and salient features of neuron death, BBB and glial cell activation. In case of humans as well as experimental animal models, epilepsy is characterized by long term disability, early death, negative effect on social life, unusual behavior ^{20, 21}. About more than 50 % of dog species had 1 -2 status epilepticus during their life period ¹⁶. This is the most severe disease in humans and dogs with mortality cases about 25%. Whereas in refractory seizure 33% mortality case in both. Hence the dog model is the most preferred animal model to study epilepsy and their therapeutic measure²².

Stroke

According to the global burden of disease study 2010, stroke is the general reason for death and 3^rd common factor for disability worldwide²³. In dog breed stroke experimentally induced and it is used as an experimental model for stroke. Dogs have anatomical and functional similarity of brain with humans like they possess gray and white matter, and their distribution and occurrence are similar to human brain. The cerebral fluid and anatomical features of cerebra is likeness to humans. This allows studying both disease induction and therapeutic measure in a wide descriptive way²⁴. The cerebrovascular accidents are increasing in case of dogs. The common occurrence of CVA is found to resemble that of human CVA, because of this it is the best animal model to evaluate drug efficacy and toxicity. Ischemic stroke is common in both humans and dogs, it can be observed through MRI. Hemorrhagic stroke is rare in both. The parameters that are assessed by using the canine model are-oxidative metabolism, recent radio tracing agents, blood flow to cerebral area, stroke pathology and preventive pharmacological measure etc²⁵. In the age of 8-10 dogs often experience strokes, this is similar in old age humans. The risk factors included are high B.P, long term kidney related diseases, atherosclerosis, DM. The national institute of health stroke provided the various evaluation instruments that can be applied in dog model²⁵.

Cognitive impairment and AD

In animals and in humans the increasing age is the major risk factor for causing Alzheimer’s disorder. Another reason for AD is development of dementia and chronic conditions that led to AD. Cognitive dysfunction syndrome is a neurodegenerative disease condition that affects not only humans but also in animals such as cats and dogs. It occurs in sequence like progression of memory loss then impairment in daily activity, change in behavioral pattern. The characteristic features of AD are plaque formation, neuron fibril tangles occurrence, hippocampus neurodegeneration. Amyloid beta is the major fibrillary tangles in AD, which has a principal component known as tau protein. This protein is found in various neuron related disorders ²⁶. Hence based on tau protein occurrence and amyloid the animal models are tested to study AD.

Parkinson disease

This disease cause due to the injury to Nigrostriatal pathway. To study the history, etiology, and treatment therapy there are number of animal models available. The pros and cons of animal models are making choices to decide specific animal model for study. There are present animal models that used to assess PD drug action, safety and another model that are used for inducing disease called neurotoxic murine; they cause injury to the nigrostriatal dopaminergic area. This model is important to learn about structure, etiology and functioning of the Nigrostriatal pathway. The animal model for PD must involve dopamine neuron system as well as non dopamine neuron system, additionally central, motor and peripheral system. The age related risk factor should be expressed through models. But disadvantage is that none on recent animal model would able to show these features. Besides this problem the animal models are very helpful to understand PD and its pathophysiology²⁷.

Optic nerve diseases

This disease condition is a highly ruinous condition in ophthalmology that causes degradation of retinal ganglion cells, Loss of vision and lastly blindness occur to patients. Animal models are necessary to evaluate drug efficacy in treating this disease. This provides thorough information about the potential of new agents and their mechanism. Additionally help to understand the cause of axon nerve dies.  The number of animal species can be used to study ophthalmic disease. The monkey’s eye anatomy and physiology are similar to a human’s eye. Monkeys have the same anatomical structure to the retinal and optic nerve. Limitation of using this model is that it is very expensive, difficult to handle; it requires an experienced person to deal with this, housing monkeys in laboratories requires a large area etc.  Hence because of this limitation the mice and rats preferred to study optic nerve related diseases. Rats are inexpensive, easy to handle and their eyes and optic nerve are accessible. Optic nerve and retina structure have some differences with human’s eye. They do not possess maculae, this is only found in monkeys hence it is used to study drug inducing macular degeneration. Animal models for optic related neurodegenerative diseases are- glaucoma, optic neuritis, anterior ischemic optic neuropathy²⁸.

Multiple sclerosis

This is the inflammatory disease of CNS that further deteriorates characteristics of neurodegenerative disorder such as axonal damage, synaptic damage, nerve cell damage etc. Effective therapies that prevent such damages are still missing²⁹. The characteristic feature of this disease is there is wide plaque formation of white matter demyelination which correlates with oligodendrocyte degradation, gliosis and axonal degeneration. The content found in inflammatory infiltrate T- lymphocytes and macrophages³⁰. The stimulated astrocytes and microglia cells are involved in lesion initiation, progression and resolution by secreting inflammatory mediators, Growth factor GF. The gray matter demyelination and white matter damage these both factors add value to causing multiple sclerosis³¹.

Figure 2: Representation of normal neuron Vs multiple sclerosis neuron. Click here to view figure

Huntington’s disease

This neurodegenerative disorder is complex in nature with their symptoms, motor activity, and cognitive function. The animal model in this disorder serves as a medium that explains disease conditions and mechanism of drugs and also evaluates newer drugs.  This is basically a human condition hence researchers cannot expect that animal models would cover all the symptoms and pathology of this disease³². Huntington’s disease is caused by gene mutation i.e., expanded CAG repeat in HTT gene. This is a single gene disorder and occurs rarely. When researchers are able to know HD causes then it is helpful to treat other such diseases that are rarely found³³. 

Table 1: Different animal models are used to study the neurodegenerative diseases.

Troubles that are associated during selection of the model for disease in rodents 

The models that are based on genetic changes are not showing proper expression of genetic variants and it makes it difficult to understand pathology and therapy. This type of model is very tedious to know the proper mechanism of a drug and not able to conduct gene specific therapy. One cannot predict the cellular & molecular level changes that occur during the period of neurodegeneration.

Innate limitations are the factors that are used to develop animal models. In transgenic and AAV related animal models the overexpression of protein is overcome by developing knock-in animals. Beside this, such a type of model is time consuming and shows moderate phenotyping. Some methods that give valuable reading by analysis such as automated behavioral analysis, in-vivo image, comics approaches, specific cellular and molecular defects. These readings are most relevant in humans. 

Due to the short life span of rodents, they are not able to give full pathological events with characteristic features of neurodegeneration. This is the big disadvantage of this animal model. There are innate differences found in the development and working of rodents and mankind. Hence special attention should be given while assessing the cognitive impairment, emotional factor, language like characteristics in human disease condition ⁵².

While deciding a model to study disease conditions one should definitely know the thorough information about differences between human and rodent genome. Such as RNA binding proteins that play a crucial role in disease conditions. In mouse models this RNA based processing is not fully understandable.  Another limitation is that there are species related amino acid changes.

Inbred animals do not possess genetic diversity.  There are new methods that cover this problem are collaborative cross and diversity outbreeds animal set of mouse ^{53, 54}. The gene editing system i.e., CRISPR-Cas9 is the virus mediated expression of genes that help to understand mutations and genetic background of different breeds ⁵⁵.

Future expectation regarding animal models on neurodegenerative diseases

By knowing present model pros and cons there is scope to develop a newer animal model by eliminating the cons of the previous one. This would be beneficial in better understanding of various neurodegenerative disorders and their treating therapies. First point that might be taken into consideration while developing an advanced model is that it should be easily predictable in humans and have the same etiology of disease that happens in humans. Some drugs are showing the same efficacy on man and rodents also. So this is a great achievement in modeling the animal. There are a number of animal models present recently but still there is a need to modify them and give an advanced look to previous one by understanding disease pathology.

The two animal models that are very useful in understanding pathophysiology and treatment of AD are APP and tau animal models, the cons of this model are, they are not fully representing the diseases that cause to humans. But still they have the positive side that the APP animal model gives exact regulation of amyloid beta accumulation and hence it is fruitful to assess the factors that contribute to stop aggregation of tau and thus prevent future consequences. While designing the new model one thing kept in mind that which factors that expressing well and that completely likeness to humans. And which factors that do not represent the criteria to overcome these things. Many researchers are working on development of superior animal models in neurodegenerative disorders that are mostly based on genetic characteristics and some genetic factors that contribute for initiation of neurological related disorders. The phenotype similarities in models are suitable to compare directly with humans and easy to predict the exact cause of disease. Best and effective animal model development ,simply means , it should be economic, it should provide better evaluation ,easy to test all the parameters, overcome the previous  hindrance and present a brief etiology of disease and provide a drug mechanism of action.

Conclusion

The conclusion of this paper is to give a brief idea about neurodegenerative health conditions and the diseases that are associated due to neurodegeneration. For understanding the disease thoroughly the animal models are the best thing which provide etiology of disease with drug mechanisms. The paper shortly summaries the animal models for various neurodegenerative disorders with brief insights on the diseases.  Many models have been developed to understand the disease conditions but still there are some lacuna’s present. So there is a need to overcome these lacuna’s and modify the recent models that are future outcome of this paper.

Acknowledgement

Authors are thankful to Dr. Sanjay J. Kshirsagar, principal MET Institute of Pharmacy, Bhujbal knowledge city for the support, motivation and facilities.

Conflict of Interest

There is no conflict of interest.

Funding Sources

There is no funding source.

References

1. Mohamed E. A. H., Lim C. P., Ebrika O. S., Asmawi M. Z., Sadikun A., & Yam M. F. Toxicity evaluation of a standardized 50% ethanol extract of Orthosiphon stamineus. Journal of ethnopharmacology, 2011; 133(2), 358-363.
2. Retinasamy T., Shaikh M. F., Kumari Y., & Othman I. Ethanolic Extract of Orthosiphon stamineus Improves Memory in Scopolamine-Induced Amnesia Model. Frontiers in pharmacology, 2019; 1216.
3. Dawson T. M., Golde T. E., & Lagier-Tourenne, C. Animal models of neurodegenerative diseases. Nature neuroscience, 2018; 21(10), 1370-1379.
4. Liu C., Oikonomopoulos A., Sayed N., & Wu J. C. Modeling human diseases with induced pluripotent stem cells: from 2D to 3D and beyond. Development, 2018; 145(5), dev156166.
5. Krogh A. The progress of physiology. Science, 1929; 70(1809), 200-204.
6. Androutsopoulos J. Languaging when contexts collapse: Audience design in social networking. Discourse, Context & Media, 2014; 4, 62-73.
7. Starkey M. P., Scase T. J., Mellersh C. S., & Murphy S. Dogs really are man’s best friend—canine genomics has applications in veterinary and human medicine!. Briefings in Functional Genomics, 2005; 4(2), 112-128.
8. LeBlanc A. K., Mazcko C., Brown D. E., Koehler J. W., Miller A. D., Miller C. R., & Gilbert M. R. Creation of an NCI comparative brain tumor consortium: informing the translation of new knowledge from canine to human brain tumor patients. Neuro-oncology,  2016; 18(9), 1209-1218.
9. Parker H. G., Shearin  A. L., & Ostrander E. A. Man’s best friend becomes biology’s best in show: genome analyses in the domestic dog. Annual review of genetics, 2010; 44, 309-336.
10. Connolly N. P., Shetty A. C., Stokum J. A., Hoeschele I., Siegel M. B., Miller C. R., & Woodworth, G. F. Cross-species transcriptional analysis reveals conserved and host-specific neoplastic processes in mammalian glioma. Scientific reports, 2018; 8(1), 1-15.
11. Baneux  P. J., Martin  M. E., Allen  M. J., & Hallman T. M. Issues related to institutional animal care and use committees and clinical trials using privately owned animals. ILAR journal, 2014; 55(1), 200-209.
12. Kearsley‐Fleet L., O’neill D. G., Volk H. A., Church D. B., & Brodbelt D. C. Prevalence and risk factors for canine epilepsy of unknown origin in the UK. Veterinary Record, 2013; 172(13), 338-338.
13. Wu J., Lai T., Han H., Liu J., Wang S., & Lyu J. Global, regional and national disability‐adjusted life years due to HIV from 1990 to 2019: findings from the Global Burden of Disease Study 2019. Tropical Medicine & International Health, 2021; 26(6), 610-620.
14. Blades Golubovic S., & Rossmeisl Jr J. H. Status epilepticus in dogs and cats, part 1: etiopathogenesis, epidemiology, and diagnosis. Journal of Veterinary Emergency and Critical Care, 2017; 27(3), 278-287.
15. Ekenstedt K. J., Patterson E. E., & Mickelson J. R. Canine epilepsy genetics. Mammalian genome, 2012; 23(1), 28-39.
16. Blades Golubovic S., & Rossmeisl Jr J. H. Status epilepticus in dogs and cats, part 2: treatment, monitoring, and prognosis. Journal of veterinary emergency and critical care, 2017; 27(3), 288-300.
17. Grone B. P., & Baraban S. C. Animal models in epilepsy research: legacies and new directions. Nature neuroscience, 2015; 18(3), 339-343.
18. Packer R. M., McGreevy P. D., Salvin H. E., Valenzuela M. J., Chaplin C. M., & Volk, H. A. Cognitive dysfunction in naturally occurring canine idiopathic epilepsy. PLoS One, 2018; 13(2), e0192182.
19. Watson F., Rusbridge C., Packer R. M., Casey R. A., Heath S., & Volk HA. A review of treatment options for behavioral manifestations of clinical anxiety as a comorbidity in dogs with idiopathic epilepsy. The Veterinary Journal, 2018; 238, 1-9.
20. Matiasek K., Pumarola i Batlle M., Rosati M., Fernández-Flores F., Fischer, A., Wagner, E., & Volk H. A. (2015). International veterinary epilepsy task force recommendations for systematic sampling and processing of brains from epileptic dogs and cats. BMC Veterinary Research, 2015; 11(1), 1-28.
21. Tröscher A. R., Klang A., French M., Quemada-Garrido L., Kneissl S. M., Bien C. G., & Bauer J. Selective limbic blood–brain barrier breakdown in a feline model of limbic encephalitis with LGI1 antibodies. Frontiers in immunology, 2017; 8, 1364.
22. Patterson E. E., Leppik I. E., Coles L. D., Podell M., Vite C. H., Bush W., & Cloyd J. C. Canine status epilepticus treated with fosphenytoin: a proof of principle study. Epilepsia, 2015; 56(6), 882-887.
23. Berendt  M.,  Farquhar R. G., Mandigers P. J., Pakozdy A., Bhatti S. F., De Risio L.,  & Volk H. A. International veterinary epilepsy task force consensus report on epilepsy definition, classification and terminology in companion animals. BMC veterinary research,2015; 11(1), 1-11.
24. Casals J. B., Pieri N. C., Feitosa M. L., Ercolin A., Roballo K., Barreto R. S., & Ambrósio C. E. The use of animal models for stroke research: a review. Comparative medicine, 2011; 61(4), 305-313.
25. Garosi L.S., & McConnell J. F. Ischaemic stroke in dogs and humans: a comparative review. Journal of Small Animal Practice, 2005; 46(11), 521-529.
26. Holtzman D. M., Carrillo M. C., Hendrix J. A., Bain L. J., Catafau A. M., Gault L. M., & Hutton, M. Tau: From research to clinical development. Alzheimer’s & Dementia, 2016; 12(10), 1033-1039.
27. Tieu K. A guide to neurotoxic animal models of Parkinson’s disease. Cold Spring Harbor perspectives in medicine, 2011;  1(1), a009316.
28. Levkovitch-Verbin H. (2004). Animal models of optic nerve diseases. Eye, 2004; 18(11), 1066-1074.
29. Kipp  M.,  Nyamoya S., Hochstrasser T., & Amor S. Multiple sclerosis animal models: a clinical and histopathological perspective. Brain pathology, 2017; 27(2), 123-137.
30. Lucchinetti C., Brück, W., Parisi J., Scheithauer B., Rodriguez, M., & Lassmann H. Heterogeneity of multiple sclerosis lesions: implications for the pathogenesis of demyelination. Annals of Neurology: Official Journal of the American Neurological Association and the Child Neurology Society, 2000; 47(6), 707-717.
31. Comi G. Is it clinically relevant to repair focal multiple sclerosis lesions?. Journal of the neurological sciences, 2008; 265(1-2), 17-20.
32. Morton A. J., & Howland D. S. Large genetic animal models of Huntington’s disease. Journal of Huntington’s disease, 2013;  2(1), 3-19.
33. MacDonald M. E., Ambrose C. M., Duyao M. P., Myers R. H., Lin C., Srinidhi, L., & Harper P. S. A novel gene containing a trinucleotide repeat that is expanded and unstable on Huntington’s disease chromosomes. Cell, 1993; 72(6), 971-983.
34. Schwarting  R. K. W., & Huston J. P. The unilateral 6-hydroxydopamine lesion model in behavioral brain research. Analysis of functional deficits, recovery and treatments. Progress in neurobiology, 1996;  50(2-3), 275-331.
35. Blesa J., Phani, S., Jackson-Lewis V., & Przedborski S. Classic and new animal models of Parkinson’s disease. Journal of Biomedicine and Biotechnology, 2012.
36. Roeling T. A. P., Docter G. J., Voorn P., Melchers B. P. C., Wolters  E. C., & Groenewegen  H. J. Effects of unilateral 6-hydroxydopamine lesions on neuropeptide immunoreactivity in the basal ganglia of the common marmoset, Callithrix jacchus, a quantitative immunohistochemical analysis. Journal of chemical neuroanatomy, 1995; 9(3), 155-164.
37. Langston J. W., Ballard P., Tetrud J. W., & Irwin I. (1983). Chronic Parkinsonism in humans due to a product of meperidine-analog synthesis. Science, 1983; 219(4587), 979-980.
38. Zigmond M. J., Berger T. W., Grace A. A., & Stricker E. M. Compensatory responses to nigrostriatal bundle injury. Molecular and Chemical Neuropathology, 1989; 10(3), 185-200.
39. Przedborski S., & Ischiropoulos H. Reactive oxygen and nitrogen species: weapons of neuronal destruction in models of Parkinson’s disease. Antioxidants & redox signaling, 2005; 7(5-6), 685-693.
40. Dauer W., & Przedborski  S. (2003). Parkinson’s disease: mechanisms and models. Neuron,2003;  39(6), 889-909.
41. Ramaswamy S., McBride J. L., & Kordower J. H. Animal models of Huntington’s disease. Ilar Journal, 2007; 48(4), 356-373.
42. Gold R., Linington C., & Lassmann H. Understanding pathogenesis and therapy of multiple sclerosis via animal models: 70 years of merits and culprits in experimental autoimmune encephalomyelitis research. Brain, 2006; 129(8), 1953-1971.
43. Bjelobaba I., Begovic‐Kupresanin V., Pekovic S., & Lavrnja I. Animal models of multiple sclerosis: Focus on experimental autoimmune encephalomyelitis. Journal of neuroscience research, 2018; 96(6), 1021-1042.
44. Woodruff R. H., & Franklin R. J. Demyelination and remyelination of the caudal cerebellar peduncle of adult rats following stereotaxic injections of lysolecithin, ethidium bromide, and complement/anti‐galactocerebroside: A comparative study. Glia, 1999; 25(3), 216-228.
45. Saida T., Saida K., Silberberg D. H., & Brown M. J. Experimental allergic neuritis induced by galactocerebroside. Annals of Neurology: Official Journal of the American Neurological Association and the Child Neurology Society, 1981; 9(S1), 87-101.
46. Bjelobaba I., Savic D., & Lavrnja I. Multiple sclerosis and neuroinflammation: the overview of current and prospective therapies. Current pharmaceutical design, 2017; 23(5), 693-730.
47. Lassmann H., & Bradl M. Multiple sclerosis: experimental models and reality. Acta neuropathologica, 2017; 133(2), 223-244.
48. Dal Canto M. C., Melvold R. W., Kim B. S., & Miller S. D. Two models of multiple sclerosis: experimental allergic encephalomyelitis (EAE) and Theiler’s murine encephalomyelitis virus (TMEV) infection. A pathological and immunological comparison. Microscopy research and technique, 1995; 32(3), 215-229.
49. Ashe K. H., & Zahs K. R. (2010). Probing the biology of Alzheimer’s disease in mice. Neuron,  2010; 66(5), 631-645.
50. LaFerla F. M., & Green  K. N. Animal models of Alzheimer disease. Cold Spring Harbor perspectives in medicine, 2012; 2(11), a006320
51. Strang K. H., Croft C. L., Sorrentino Z. A., Chakrabarty P., Golde T. E., & Giasson B. I. Distinct differences in prion-like seeding and aggregation between Tau protein variants provide mechanistic insights into tauopathies. Journal of Biological Chemistry, 2018; 293(7), 2408-2421.
52. Ahmed R. M., Irish, M., van Eersel J., Ittner A., Ke Y. D., Volkerling A., & Ittner L. M. Mouse models of frontotemporal dementia: a comparison of phenotypes with clinical symptomatology. Neuroscience & Biobehavioral Reviews, 2017; 74, 126-138.
53. Lutz C. Mouse models of ALS: Past, present and future. Brain Research, 2018; 1693, 1-10.
54. Onos K. D., Rizzo S. J. S., Howell G. R., & Sasner M. Toward more predictive genetic mouse models of Alzheimer’s disease. Brain research bulletin, 2016; 122, 1-11.
55. Liu E. T., Bolcun‐Filas E., Grass  D. S., Lutz C., Murray S., Shultz L., & Rosenthal N. Of mice and CRISPR: The post‐CRISPR future of the mouse as a model system for the human condition. EMBO reports, 2017; 18(2), 187-193.