Species: Mouse
Genes: LRRK2
Modification: LRRK2: Transgenic
Disease Relevance: Parkinson's Disease
Strain Name: FVB/N-Tg(LRRK2)1Cjli/J
Genetic Background: BAC injected into fertilized FVB zygotes. Founder mice bred with FVB/N inbred mice for many generations, and then with FVB/NJ inbred mice.
Availability: Available through The Jackson Laboratory, Stock# 009610, Cryopreserved.

Summary

These transgenic mice, referred to here as WT-OX, overexpress human wild-type LRRK2 using a bacterial artificial chromosome (BAC) (Li et al., 2009). The BAC encodes the entire gene with 29 kb upstream and 42 kb downstream. Expression is controlled by endogenous regulatory elements. Transgene expression is observed at approximately five-to 10-fold above the level of endogenous mouse Lrrk2 in the brain (Li et al., 2009); overexpression is also observed in the spleen (Bliederhaeuser et al., 2016). Of note, whereas in the striata of wild-type mice LRRK2 localizes to the striosomal area, in WT-OX mice it spreads into the matrix area (Mandemakers et al., 2012).

Behaviorally, hemizygous WT-OX mice appear largely similar to non-Tg mice, though some exceptions have been uncovered. Motor behavior was assessed in 12-month-old WT-OX mice using the open-field test. WT-OX mice were hyperactive, with distance travelled, speed, and overall ambulatory activity all being significantly higher than in non-Tg mice. In addition, the ratio of central to peripheral area entries was higher in WT-OX mice, which some investigators consider to represent decreased anxiety-like behavior. The number of rears at 12 months of age did not significantly differ from controls in the open-field test (Chen and Wu, 2022), nor at 10 months of age in the cylinder test (Li et al., 2009).

The Cat-Walk system was used to detect gait impairments in 12-month-old mice (Chen and Wu, 2022). Relative to non-Tg mice, WT-OX mice had a significantly increased swing velocity and stride length and a significantly decreased stance duration (how long the mouse’s paw is in contact with the glass floor). Other gait parameters—cadence, swing duration, and weight distribution of paws (based of support)—did not differ between WT-OX and non-Tg mice.

Gene expression in striatal tissue, as determined by genome-wide microarrays in 4-month-old mice, was largely similar between the non-Tg and WT-OX groups. Only one gene, Hjurp, which encodes a protein involved in chromosome segregation, was identified as upregulated in WT-OX mice. In contrast to mRNA, miRNA microarray analysis revealed 64 dysregulated miRNAs in WT-OX versus non-Tg mice (Dorval et al., 2014).

Neurite lengths of primary hippocampal neurons and primary nigral tyrosine hydroxylase-positive neurons from WT-OX mice are reduced compared with non-Tg neurons (Lin et al., 2020). Other cytoskeletal perturbations have also been observed. For instance, phosphorylation of the S3 residue of cofilin, an enzyme that modulates actin filament turnover, is reduced in the brains of developing (postnatal day 2-15) WT-OX mice compared to non-Tg mice (Parisiadou et al., 2014).

Dopamine levels in the striatum were evaluated by PET imaging with [18F]FDOPA. Uptake of the tracer was significantly higher in WT-OX compared with non-Tg mice (Chen and Wu, 2022).

Transmission electron microscopy of the substantia nigra pars compacta was used to assess mitochondrial and lysosomal morphology in 12-month-old mice. WT-OX mice exhibited a healthy morphology of mitochondria as well as dense, spherical, membrane-enclosed lysosomes. Moreover, in the brain, levels of proteins involved in mitochondrial fission (Drp1 and Fis1) and autophagy (LC3 and p62) did not differ from non-Tg mice (Chen and Wu, 2022). In contrast, chaperone-mediated autophagy was significantly reduced in cultured ventral midbrain dopaminergic neurons from WT-OX mice compared with non-Tg neurons, perhaps through inhibition of LAMP-2A multimerization. Moreover, colocalization of LAMP-2 with α-syn was increased in cultured neurons from WT-OX mice compared with neurons from control mice (Orenstein et al., 2013).

Immune cells may also be perturbed in WT-OX mice. One study observed a trend towards an increased ratio of Ly6Chigh:Ly6Clow monocytes in WT-OX versus non-Tg mice (Bliederhaeuser et al., 2016), supporting the idea that LRRK2 may be involved in regulating immune cell maturation.

In a study by The Jackson Laboratory, this WT-OX mouse line was found to carry the retinal degeneration 1 mutation (Pde6brd1), and thus it is recommended that this strain not be used to study retinal disorders (Chang et al., 2013).

Related Strains
The WT-OX strain was generated to serve as a control for the strain FVB/N-Tg(LRRK2*R1441G)135Cjli/J (Li et al., 2009).

Modification Details

A 188 kb human BAC containing the entire human LRRK2 gene, including 29 kb upstream and 42 kb downstream regions.

Phenotype Characterization

Q&A with Model Creator

Q&A with Ruey-Meei Wu.

What would you say are the unique advantages of this model? The unique advantages of this model are hyperactivity, altered gait behavior, and dopaminergic system alterations.

What do you think this model is best used for? It appears to be well-suited for investigations related to the following areas:
1. Study of hyperactivity and motor behavior
2. Dopaminergic system research
3. Gait abnormalities and motor coordination
4. Exploration of anxiety-like behavior

What caveats are associated with this model?
1. Model-Specific Characteristics: The observed behaviors and biological features are specific to the WT-OX mice model. This means that findings may not be directly generalizable to other mouse strains or species. Researchers should be cautious about extrapolating results to different genetic backgrounds or experimental conditions.
2. Behavioral Variability:
Behavioral phenotypes can be influenced by various factors, including environmental conditions, housing, and the specific testing protocols. It's essential to consider the potential impact of these factors on the observed behaviors and to replicate findings across different experimental setups.
3. Complexity of Behavioral Assessments: Behavioral tests, such as the open-field test and gait analysis, are complex and multifaceted. While they provide valuable information, the interpretation of behaviors should be done cautiously, considering the various factors that can influence test outcomes.
4. Interpretation of Dopamine Levels: The increase in dopamine uptake observed in the striatum may suggest alterations in the dopaminergic system. However, the specific mechanisms underlying this change and its relevance to human conditions may require further investigation.
5. Specificity of Gait Abnormalities: Gait abnormalities observed in WT-OX mice may be indicative of motor dysfunction, but the specific causes and implications need to be carefully explored. Gait analysis is complex, and alterations may be attributed to various factors, including neurological, musculoskeletal, or sensory issues.

Anything else useful or particular about this model you think our readers would like to know?
1. Applicability to Neurodegenerative Studies: Given the observed alterations in dopamine levels, researchers interested in neurodegenerative disorders, particularly those involving dopaminergic pathways, may find this model relevant for their investigations.
2. Potential for Pharmacological Studies: The hyperactivity and altered motor behavior in WT-OX mice could make the model suitable for pharmacological studies aimed at testing the effects of compounds targeting neurotransmitter systems or pathways associated with motor control.
3. Integration of In Vivo Imaging Techniques: The use of PET imaging with [18F]FDOPA to assess dopamine levels provides a non-invasive in vivo imaging approach. Researchers interested in imaging techniques for longitudinal studies may find this aspect of the model advantageous.
4. Inclusion of Age-Related Assessments: The information provided focuses on assessments at 12 months of age. Including assessments at different ages can help researchers understand the age-related progression or stability of the observed behaviors and neurobiological features.
5. Relevance to Anxiety Research: The potential decrease in anxiety-like behavior, as suggested by the higher ratio of central to peripheral area entries in the open-field test, could make the WT-OX mice model applicable to studies investigating anxiety-related neural circuits and behaviors.
6. Consideration of Sex Differences: Researchers should consider the potential influence of sex differences on the observed phenotypes. Conducting studies with both male and female mice, and analyzing results separately, can provide insights into potential sex-specific effects.

COMMENTS / QUESTIONS

1. • Benjamin Wolozin
     Boston University School of Medicine
   • Posted: 16 Jun 2009
   • Paper: Mutant LRRK2(R1441G) BAC transgenic mice recapitulate cardinal features of Parkinson's disease.

   LRRK2 R1441C Mice Recapitulate PD Motor Deficits
   The recent article by C.J. Li’s group reports on the first transgenic LRRK2 mouse model. The LRRK2 mouse uses a BAC system to express WT or R1441C LRRK2, which is a mutation in the GTPase domain of LRRK2. The benefit of the BAC system is that it permits use of the LRRK2 promoter, which allows for an expression pattern that is elevated but exhibits a distribution that recapitulates the pattern of endogenous LRRK2. The mouse is notable in several respects. The most important observation is that the mouse exhibits age-dependent motor deficits that are responsive to L-DOPA, which is a classic phenotype observed in patients with Parkinson disease and shows that the motor deficits derive from dysfunction of dopaminergic neurons. The nature of the dysfunction, though, is not entirely clear. The group reports a modest decrease in dopamine release from the neurons. This phenotype is reminiscent of phenotypes observed for parkin and PINK1 mice, and might be a preliminary indication that deficits in dopamine release are a common feature of genes associated with PD. A second encouraging observation is that mice show signs that are commonly associated with neuronal degeneration. The researchers observe tyrosine hydroxylase positive spheroids, and increased tau phosphorylation, shown with the AT8 antibody.

   These degenerative phenotypes are interesting for what they do and do not show. On the positive side, the morphologic changes are consistent with a hypothesis that there is degeneration of dopaminergic neurons. Spheroids are a common, non-specific sign of neurodegeneration. Tau phosphorylation is also an early sign of neuronal degeneration, or at least neuronal stress. From my perspective, the evidence of dopaminergic degeneration is quite believable because it is consistent with what we observe in our C. elegans model, which has been in review for over a year and hopefully will be out soon. The presence of phospho-tau reactivity is also interesting because neurofibrillary tangles are observed in some cases of LRRK2-associated parkinsonism, and because polymorphisms in tau are strongly associated with Parkinson disease, being the second strongest result observed in multiple GWAS studies after those in α-synuclein. On the negative side, the manuscript is striking for the absence of any mention of loss of dopamine neurons or the presence of α-synuclein inclusions or Lewy body pathology. This might mean that expressing mutant LRRK2 alone is insufficient to recapitulate Parkinson disease and one needs to also have the human proteins present, such as α-synuclein and tau. Alternatively, this might reflect the vagaries of transgenic models, and some other models might show α-synuclein pathology (although I am not aware of any reports of α-synuclein pathology in the other mouse models that are in development). Nevertheless, the presence of a L-DOPA responsive transgenic mouse model derived from a genetic mutation associated with Parkinson disease represents an important advance for the field.

   View all comments by Benjamin Wolozin

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References

Paper Citations

1. Li Y, Liu W, Oo TF, Wang L, Tang Y, Jackson-Lewis V, Zhou C, Geghman K, Bogdanov M, Przedborski S, Beal MF, Burke RE, Li C. Mutant LRRK2(R1441G) BAC transgenic mice recapitulate cardinal features of Parkinson's disease. Nat Neurosci. 2009 Jul;12(7):826-8. PubMed.
2. Bliederhaeuser C, Zondler L, Grozdanov V, Ruf WP, Brenner D, Melrose HL, Bauer P, Ludolph AC, Gillardon F, Kassubek J, Weishaupt JH, Danzer KM. LRRK2 contributes to monocyte dysregulation in Parkinson's disease. Acta Neuropathol Commun. 2016 Nov 24;4(1):123. PubMed.
3. Mandemakers W, Snellinx A, O'Neill MJ, de Strooper B. LRRK2 expression is enriched in the striosomal compartment of mouse striatum. Neurobiol Dis. 2012 Dec;48(3):582-93. Epub 2012 Jul 29 PubMed.
4. Chen ML, Wu RM. Homozygous mutation of the LRRK2 ROC domain as a novel genetic model of parkinsonism. J Biomed Sci. 2022 Aug 14;29(1):60. PubMed.
5. Dorval V, Mandemakers W, Jolivette F, Coudert L, Mazroui R, De Strooper B, Hébert SS. Gene and MicroRNA transcriptome analysis of Parkinson's related LRRK2 mouse models. PLoS One. 2014;9(1):e85510. Epub 2014 Jan 10 PubMed.
6. Lin CH, Lin HY, Fang JM, Chen CC. A dual inhibitor targeting HMG-CoA reductase and histone deacetylase mitigates neurite degeneration in LRRK2-G2019S parkinsonism. Aging (Albany NY). 2020 Nov 24;12(24):25581-25598. PubMed.
7. Parisiadou L, Yu J, Sgobio C, Xie C, Liu G, Sun L, Gu XL, Lin X, Crowley NA, Lovinger DM, Cai H. LRRK2 regulates synaptogenesis and dopamine receptor activation through modulation of PKA activity. Nat Neurosci. 2014 Mar;17(3):367-76. Epub 2014 Jan 26 PubMed.
8. Orenstein SJ, Kuo SH, Tasset I, Arias E, Koga H, Fernandez-Carasa I, Cortes E, Honig LS, Dauer W, Consiglio A, Raya A, Sulzer D, Cuervo AM. Interplay of LRRK2 with chaperone-mediated autophagy. Nat Neurosci. 2013 Apr;16(4):394-406. Epub 2013 Mar 3 PubMed.
9. Chang B, Hurd R, Wang J, Nishina P. Survey of common eye diseases in laboratory mouse strains. Invest Ophthalmol Vis Sci. 2013 Jul 24;54(7):4974-81. PubMed.

External Citations

1. FVB/N-Tg(LRRK2*R1441G)135Cjli/J
2. The Jackson Laboratory, Stock# 009610

Further Reading