Modification: LRRK2: Knock-Out
Disease Relevance: Parkinson's Disease
Strain Name: LEH-Lrrk2tm1sage
Genetic Background: Long Evans Hooded
Availability: Available through Horizon (formerly Sage Labs), Cat #TGRL4620, Live.
Developed in collaboration with the Michael J. Fox Foundation, homozygous Lrrk2 KO rats develop abnormalities in peripheral organs, most notably in the kidney, but also extending to the liver, lung, and spleen. These differences start early and are progressive, although they do not appear to shorten lifespan. Interestingly, these KO rats are partially protected from neurodegeneration in paradigms using intracranial injection of lipopolysaccharide (LPS) or α-synuclein (Daher et al., 2014).
Homozygous rats appear normal early on, with the exception of being larger and heavier than wild-type littermates by one month of age. This difference does not appear to be due to differences in food consumption (Ness et al., 2013; Baptista et al., 2013). In homozygous rats complete knockdown of the protein was observed (Daher et al., 2014).
Abnormalities in peripheral organs develop early. By three to four months of age, the kidneys appear larger and darker due to the presence of a brown pigment and eosinophilic hyaline droplets. As they age, cells in the proximal tubular epithelium develop cytoplasmic vacuolization and lysosomes proliferate in the tubules. Subtle changes in kidney function are detectable as early as one month of age. Urine analysis revealed abnormalities in urine specific gravity, total volume, urine potassium, creatinine, sodium, and chloride. In addition, thickened basement membranes were observed at four, eight, and 12 months of age along with cylindrical structures in the urine called hyaline casts. All together, these data indicate an abnormal kidney phenotype and signs of chronic progressive nephropathy, a renal disease in rats (Ness et al., 2013; Baptista et al., 2013).
The liver, lung, and spleen were also affected. In the liver, hepatocytes showed mild vacuolation along with accumulation of lipid droplets. Some liver function tests were abnormal, including reduced liver transaminases and elevated sorbitol dehydrogenase. In the lung, Type II alveolar cells were noted to have greater numbers of lamellar bodies, secretory organelles that release pulmonary surfactant (Baptista et al., 2013; Miklavc et al., 2014). In the spleen, minor differences in cellular composition were noted at a young age (Ness et al., 2013).
Hematological abnormalities were also present. In general, Lrrk2 KO rats had lower red blood cell counts, lower hemoglobin levels, and lower hematocrit values (Baptista et al., 2013). Circulating levels of some hormones were reduced (e.g., adiponectin, adrenocorticotropic hormone, and prolactin), whereas others were elevated (e.g., galanin, insulin, insulin-like growth factor, and leutinizing hormone). Blood cholesterol (primarily high-density lipoproteins) was increased. Taken together, these changes indicate Lrrk2 deficiency may lead to metabolic hormonal dysregulation (Ness et al., 2013). Notably, lipocalin-2 (NGAL) levels were significantly lower in the both the urine and blood in Lrrk2 KO rats (Ness et al., 2013).
In the brain, stereological counts of tyrosine hydroxylase (TH)-neurons confirmed no difference in dopaminergic neurons in the substantia nigra under basal conditions. Interestingly, Lrrk2 KO rats were resistant to dopaminergic neuron loss elicited by LPS or viral overexpression of α-synuclein. Specifically, when LPS was injected into the substantia nigra pars compacta of wild-type rats, it triggered a 40 percent loss of TH-positive neurons. However, Lrrk2 KO rats exhibited only about 20 percent loss under the same conditions. Likewise, viral overexpression of α-synuclein in the substantia nigra resulted in a 30 percent loss of dopaminergic neurons in wild-type rats at four, eight, and 12 weeks after viral injection. In contrast, no significant neuronal loss was observed in Lrrk2 KO rats. Prominent α-synuclein pathology was observed in both wild-type and KO rats (Daher et al., 2014).
The neuroprotection reported in Lrrk2 KO rats was associated with a decrease in the number of cells staining positive for CD68, a marker of activated microglia, macrophages, and monocytes. Wild-type rats, but not Lrrk2 KO rats, exposed to LPS or α-synuclein overexpression had high levels of CD68-positive cells in the substantia nigra. Many of the CD68-positive cells also expressed iNOS and Lrrrk2 (Daher et al., 2014).
Zinc finger nuclease (ZFN) technology was used to generate a deletion of 10 base pairs in exon 30 of the rat Lrrk2 gene. This resulted in a frameshift and a premature stop codon in the same exon.
When visualized, these models will distributed over a 18 month timeline demarcated at the following intervals: 1mo, 3mo, 6mo, 9mo, 12mo, 15mo, 18mo+.
- Neuronal Loss
- Dopamine Deficiency
- α-synuclein Inclusions
- Motor Impairment
- Mitochondrial Abnormalities
- Cognitive Dysfunction
When challenged with LPS or α-synuclein overexpression, Lrrk2 KO rats show lower levels of pro-inflammatory CD68-positive myeloid cells in the substantia nigra than wild-type rats.
Under basal conditions, the number of TH-positive cells in the substantia nigra was comparable between Lrrk2 KO rats and wild-type rats. When challenged with LPS or α-synuclein overexpression, Lrrk2 KO rats developed significantly less neurodegeneration in the substantia nigra than wild-type rats.
- Daher JP, Volpicelli-Daley LA, Blackburn JP, Moehle MS, West AB. Abrogation of α-synuclein-mediated dopaminergic neurodegeneration in LRRK2-deficient rats. Proc Natl Acad Sci U S A. 2014 Jun 24;111(25):9289-94. Epub 2014 Jun 9 PubMed.
- Ness D, Ren Z, Gardai S, Sharpnack D, Johnson VJ, Brennan RJ, Brigham EF, Olaharski AJ. Leucine-rich repeat kinase 2 (LRRK2)-deficient rats exhibit renal tubule injury and perturbations in metabolic and immunological homeostasis. PLoS One. 2013;8(6):e66164. Print 2013 PubMed.
- Baptista MA, Dave KD, Frasier MA, Sherer TB, Greeley M, Beck MJ, Varsho JS, Parker GA, Moore C, Churchill MJ, Meshul CK, Fiske BK. Loss of leucine-rich repeat kinase 2 (LRRK2) in rats leads to progressive abnormal phenotypes in peripheral organs. PLoS One. 2013;8(11):e80705. Epub 2013 Nov 14 PubMed.
- Miklavc P, Ehinger K, Thompson KE, Hobi N, Shimshek DR, Frick M. Surfactant secretion in LRRK2 knock-out rats: changes in lamellar body morphology and rate of exocytosis. PLoS One. 2014;9(1):e84926. Epub 2014 Jan 21 PubMed.
- Davies P, Hinkle KM, Sukar NN, Sepulveda B, Mesias R, Serrano G, Alessi DR, Beach TG, Benson DL, White CL, Cowell RM, Das SS, West AB, Melrose HL. Comprehensive characterization and optimization of anti-LRRK2 (leucine-rich repeat kinase 2) monoclonal antibodies. Biochem J. 2013 Jul 1;453(1):101-13. PubMed.
- West AB, Cowell RM, Daher JP, Moehle MS, Hinkle KM, Melrose HL, Standaert DG, Volpicelli-Daley LA. Differential LRRK2 expression in the cortex, striatum, and substantia nigra in transgenic and nontransgenic rodents. J Comp Neurol. 2014 Aug 1;522(11):2465-80. Epub 2014 Apr 12 PubMed.