Research Models

Pink1 KO Rat

Synonyms: Pink1 knockout rat, PARK6 KO rat

Species: Rat
Genes: PINK1
Modification: PINK1: Knock-Out
Disease Relevance: Parkinson's Disease
Strain Name: LEH-Pink1tm1Sage-/-
Genetic Background: Long Evans Hooded
Availability: Available through Horizon Discovery (formerly Sage Labs), Cat# TGRL4690; Live.

Summary

This knockout rat model was created at Sage Labs (now Horizon) in collaboration with the Michael J. Fox Foundation. The model carries a deletion of the Pink1 (PTEN-induced putative kinase 1) gene, which encodes a serine/threonine protein kinase. Homozygous Pink1 KO rats show both motor impairments and dopaminergic cell loss (Dave et al., 2014).

Homozygous rats appear normal at birth. Their behavior has been assessed systematically at four, six, and eight months of age (Dave et al., 2014). Notably, Pink1 KO rats show abnormalities in gait, coordination, and strength. Deficits in coordination were reported as early as five weeks, with KO rats having increased foot slips on the tapered balance beam compared with wild-type animals (Horizon Cat. #TGRL4690, Jan 2019). At four months of age, KO rats exhibited abnormal paw positioning and a shorter stride than wild-type rats. By eight months, Pink1 KOs had three- to fivefold more foot slips (both fore-and hind limb) on the balance beam (Dave et al., 2014), and took longer to traverse a tapered beam (Grant et al., 2015). KO rats at this age also took more hind limb steps in the cylinder test, displaying a shuffling-like gait (Grant et al. 2015). However, Dave et al. reported they performed normally on the accelerating Rotarod at four, six, and eight months of age (Dave et al., 2014).

In terms of strength, both homozygous and heterozygous KO rats traveled less distance in an open field after a hind limb fatigue challenge than wild-type rats at seven weeks of age (Horizon Cat. #TGRL4690, Jan 2019). At five months, 30 percent were dragging their hind limbs (Horizon Cat. #TGRL4690, Jan 2019) and by eight months the percentage rose to 87 (Dave et al., 2014). In addition, at eight months the KO rats showed reduced overall muscle tone, less rearing behavior, and a 70 percent decrease in open-field mobility. Grip strength was impaired as early as four months of age. The rats did not exhibit convulsions or tremors. Nor did they exhibit grooming deficits or differences in startle response or body temperature. However, abnormalities in oromotor behaviors, including vocalization, licking, and biting, were detected at 2 months (Grant et al. 2015). There was no increase in mortality up to eight months of age.

Pink1 KOs were heavier than wild-type counterparts at four, six, and eight months of age. 

The effects of knocking out Pink1 on striatal dopamine remain uncertain. Dave et al. found Pink1 KO rats had more dopamine in the striatum than wild-type rats. Levels were elevated two- to threefold at eight months of age (Dave et al., 2014). However, Kelm-Nelson et al. reported a slight decrease at the same age, which correlated with slower traversals of the tapered balance beam (Kelm-Nelson et al., 2018). The authors speculate the inconsistent results may be due to differences in animal husbandry and/or experimental procedures. Dave et al. also found striatal serotonin levels were up two- to threefold. There were no significant differences in the turnover of either transmitter (Dave et al., 2014). Quantitative autoradiography revealed subtle changes in the density of dopaminergic receptor subtypes in the striatum. At six months of age, KO rats had a 26 percent increase in the D2 receptor and a 19 percent increase in the D3 receptor. Densities of the D1 receptor and the dopamine transporter were unchanged (Sun et al., 2013).

Dave et al. also reported that Pink1 KOs exhibited age-related decreases in the number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra (Dave et al., 2014). Specifically, compared with wild-type, there was a 25 percent reduction at six months and a reduction of more than 50 percent at eight months. Despite the robust and progressive loss of dopaminergic neurons in the substantia nigra, TH-positive cells in the striatum were intact at all ages tested. Consistent with these findings, Villeneuve et al. reported a loss of TH-positive neurons in the substantia nigra pars compacta at nine months (Villeneuve et al., 2016a). In contrast, Grant et al. found no alterations in TH levels in either the substantia nigra or striatum at eight months, but observed TH reductions in the locus coeruleus which correlated with vocal loudness, tongue force, and chewing rate (Grant et al., 2015, Cullen et al., 2018). Moreover, Kelm-Nelson et al. reported increased levels of norepinephrine in the substantia nigra, and reduced levels of this transmitter in the locus coeruleus, which positively correlated with the number of complex calls (Kelm-Nelson et al., 2018).

In addition, although Dave et al. reported no overt differences in brain α-synuclein staining compared with wild-type rats (Dave et al., 2014), others have found insoluble, proteinase K-resistant aggregates that stained positive for α-synuclein, thioflavin S, and ubiquitin in tissue sections from several brain regions. Aggregates were detected as early as four months of age and increased in number up to 12 months (Creed and Goldberg, 2019). In 8-month-old KO rats, aggregates were found in the periaqueductal gray, substantia nigra pars compacta, locus coeruleus, and nucleus ambiguous, which projects to muscles involved in vocalization and swallowing (Grant et al., 2015). In the periaqueductal gray, where aggregates were particularly dense, the expression of α-synuclein remained unchanged, but mRNA levels of Atp13a2, a lysosomal ATPase, were reduced (Kelm-Nelson et al., 2016). At 12 months, inclusions were reported in the cortex, thalamus, striatum, and ventral midbrain (Creed and Goldberg, 2019). Also, an analysis of cortical homogenates at this age revealed an increase in the ratio of α-synuclein in synaptic vesicle-enriched fractions versus cytosolic fractions.

Metabolomic and proteomic analyses of mitochondria-associated factors in the brain revealed differences between Pink1 KO rats and wild-type controls as early as 10 days of age (Villeneuve et al., 2016a, Villeneuve et al., 2016b, Stauch et al., 2016). Several alterations suggested mitochondrial dysfunction, such as a reduction of mitochondrial complex I subunits, particularly in the striatum of 4-month-old rats. In addition, respiration driven by complex I was reduced in mitochondria isolated from striatal synapses of 3-month-olds, while that driven by complex II was increased, possibly as a compensatory mechanism. In 9-month-old rats, the oxygen consumption ratios of striatal mitochondria were actually elevated.

Modification Details

The rat Pink1 gene was disrupted using zinc finger nuclease (ZFN) technology, in which targeted ZFN RNA was injected into fertilized rat oocytes. The ZFNs were engineered to bind to a recognition site in exon 4 of Pink1 and cleave the DNA. When the resulting double strand break was repaired by non-homologous end joining, a deletion of 26 base pairs was created. This deletion lead to a frameshift and the creation of a premature stop codon. Pink1 mRNA is virtually undetectable in homozygous rats.

Phenotype Characterization

When visualized, these models will distributed over a 18 month timeline demarcated at the following intervals: 1mo, 3mo, 6mo, 9mo, 12mo, 15mo, 18mo+.

Absent

  • Dopamine Deficiency

No Data

  • Non-Motor Impairment
  • Neuroinflammation

Neuronal Loss

Age-related decrease in tyrosine hydroxylase (TH)-positive dopaminergic neurons in the substantia nigra. Twenty-five and 50 percent reduction at 6 months and 8 months, respectively. No change in TH-positive cells in the striatum.

Dopamine Deficiency

One study found striatal dopamine levels were increased two- to threefold in Pink1 KO rats compared with wild-type levels at 8 months of age, whereas another reported a slight decrease at this age.

α-synuclein Inclusions

Alpha-synuclein aggregates were found as early as 4 months of age and increased in number up to 12 months. Areas affected include the periaqueductal gray, substantia nigra pars compacta, locus coeruleus, nucleus ambiguous, cortex, thalamus, and striatum.

Neuroinflammation

No data.

Mitochondrial Abnormalities

Alterations in mitochondrial metabolites and mitochondrial protein expression were reported as early as 4 months of age in cortex and striatum. Oxygen consumption rates were elevated in striatal mitochondria isolated from 9-month-old rats.

Motor Impairment

Abnormalities in gait, coordination, and strength. As early as 5 weeks of age, KOs had increased foot slips on the tapered balance beam, at 7 weeks they showed hind limb fatigue, which progressed to hind limb dragging, and by 2 months they exhibited alterations in oromotor behaviors.

Non-Motor Impairment

No data.

Last Updated: 11 Feb 2019

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References

Paper Citations

  1. . Phenotypic characterization of recessive gene knockout rat models of Parkinson's disease. Neurobiol Dis. 2014 Oct;70:190-203. Epub 2014 Jun 24 PubMed.
  2. . Evidence for early and progressive ultrasonic vocalization and oromotor deficits in a PINK1 gene knockout rat model of Parkinson's disease. J Neurosci Res. 2015 Nov;93(11):1713-27. Epub 2015 Jul 31 PubMed.
  3. . Quantitative Analysis of Catecholamines in the Pink1 -/- Rat Model of Early-onset Parkinson's Disease. Neuroscience. 2018 May 21;379:126-141. Epub 2018 Feb 27 PubMed.
  4. . Regulation of dopamine presynaptic markers and receptors in the striatum of DJ-1 and Pink1 knockout rats. Neurosci Lett. 2013 Oct 21; PubMed.
  5. . Early Expression of Parkinson's Disease-Related Mitochondrial Abnormalities in PINK1 Knockout Rats. Mol Neurobiol. 2014 Nov 25; PubMed.
  6. . Pink1 -/- Rats Show Early-Onset Swallowing Deficits and Correlative Brainstem Pathology. Dysphagia. 2018 Apr 30; PubMed.
  7. . Analysis of α-Synuclein Pathology in PINK1 Knockout Rat Brains. Front Neurosci. 2018;12:1034. Epub 2019 Jan 9 PubMed.
  8. . Atp13a2 expression in the periaqueductal gray is decreased in the Pink1 -/- rat model of Parkinson disease. Neurosci Lett. 2016 May 16;621:75-82. Epub 2016 Apr 4 PubMed.
  9. . Neonatal mitochondrial abnormalities due to PINK1 deficiency: Proteomics reveals early changes relevant to Parkinson׳s disease. Data Brief. 2016 Mar;6:428-32. Epub 2015 Dec 17 PubMed.
  10. . Loss of Pink1 modulates synaptic mitochondrial bioenergetics in the rat striatum prior to motor symptoms: concomitant complex I respiratory defects and increased complex II-mediated respiration. Proteomics Clin Appl. 2016 Dec;10(12):1205-1217. Epub 2016 Sep 21 PubMed.

External Citations

  1. Horizon Cat. #TGRL4690
  2. Horizon Discovery (formerly Sage Labs), Cat# TGRL4690

Further Reading

Papers

  1. . Exercise Effects on Early Vocal Ultrasonic Communication Dysfunction in a PINK1 Knockout Model of Parkinson's Disease. J Parkinsons Dis. 2015;5(4):749-63. PubMed.
  2. . SWATH-MS proteome profiling data comparison of DJ-1, Parkin, and PINK1 knockout rat striatal mitochondria. Data Brief. 2016 Dec;9:589-593. Epub 2016 Sep 23 PubMed.