Research Models

Parkin KO Rat

Synonyms: Park2 KO, Parkin knockout rat

Species: Rat
Genes: PRKN (parkin)
Modification: PRKN (parkin): Knock-Out
Disease Relevance: Parkinson's Disease
Strain Name: LEH-Park2TM1sage
Genetic Background: Long Evans Hooded
Availability: Available through Horizon Discovery (formerly Sage Labs); TGRL4760; Live.

Summary

This knockout rat model was created at Sage Labs (now Horizon) in collaboration with the Michael J. Fox Foundation. It carries a disrupted Park2 gene, which encodes the E3 ligase parkin. Homozygous rats exhibit only minor behavioral alterations and have no significant degeneration of striatal neurons or loss of dopamine (Dave et al., 2014). However, changes in dopaminergic signaling were detected at an early age (Gemechu et al., 2018), as were changes in mitochondria at striatal synapses (Villeneuve et al., 2018).

The rat Park2 gene was disrupted using zinc finger nuclease (ZFN) technology, in which targeted ZFN RNA was injected into fertilized eggs. The ZFNs were engineered to bind to a recognition site sequence in exon 4 of Park2 and cleave the DNA. When the resulting double strand break was repaired by non-homologous end joining, a deletion of five base pairs was created in the founder rat. This deletion led to a frame shift and the creation of a premature stop codon. Parkin mRNA levels were decreased by about half in the brains of Parkin KO rats. The protein was undetectable by western blot.

Homozygous rats appeared normal at birth. At two months, however, male KO rats exhibited a moderate reduction in stereotypic movements, such as scratching and grooming (Gemechu et al., 2018). A systematic analysis of their behavior at four, six, and eight months of age, did not reveal any other behavioral deficits at any of the ages tested (Dave et al., 2014). Motor functioning, including gait performance on the rotarod, was intact. Similarly, sensory responses, including orientation to an olfactory stimulus, were normal.

The brains of Parkin KO rats are largely intact, although compensatory changes in dopaminergic transmission appear to occur early on. A small, non-significant reduction in dopaminergic neurons was observed in the substantia nigra at eight months of age. There were no differences in striatal dopamine levels at four, six, or eight months compared with wild-type rats. However, the activities of monoamine oxidases (MAOs), which break down dopamine, were reduced in the striata of 2-month-old male KO rats, and the levels of the MAO substrate β-phenylethylamine were increased compared with those of wild-type rats (Gemechu et al., 2018), In addition, levels of trace amine-associated receptor 1, which binds to β-phenylethylamine and regulates dopamine transmission, as well as postsynaptic dopamine D2 receptors, were reduced. Moreover, 2-month-old male KO rats responded more weakly to a low dose of methamphetamine, an indirect agonist of dopamine, than similarly treated wild-type rats.

Levels of the protein tyrosine phosphatase STEP61 are elevated in the striatum of 12-month-old Parkin KO rats compared with wild-type controls. There was no such change in the cortex (Kurup et al., 2015).

Differences in mitochondrial function and protein expression also have been reported. Although oxygen-consumption rates of striatal synaptic mitochondria of 2-month-old KO mice were similar to those of wild-type rats, the proton leak rate was lower and the respiratory control ratio was increased. Moreover, proteomic analysis revealed differentially expressed mitochondrial proteins in the striatal synapses of 3-month-old KO rats compared with those of wild-type animals (Villeneuve et al., 2018).

There was no increase in α-synuclein protein in the striatum or any other brain region.

Modification Details

The rat Park2 gene was disrupted using zinc finger nuclease (ZFN) technology. The targeted ZFN created a DNA strand break in exon 4 of Park2. Repair of this break created a deletion of five base pairs, leading to a frame shift and the creation of a premature stop codon.

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
  • Non-Motor Impairment
  • α-synuclein Inclusions
  • Motor Impairment
  • Neuronal Loss

No Data

  • Neuroinflammation

Neuronal Loss

A small, non-significant reduction in dopaminergic neurons was observed in the substantia nigra at eight months of age.

Dopamine Deficiency

There were no differences in striatal dopamine levels at 4, 6, or 8 months compared with wild-type rats. However, factors involved in dopaminergic transmission, including monoamine oxidase activity, β-phenylethylamine, trace amine-associated receptor 1, and postsynaptic dopamine D2 receptors were altered in the striata of 2-month-old KO rats.

α-synuclein Inclusions

There was no increase in α-synuclein protein in the striatum or any other brain region assessed.

Neuroinflammation

No data.

Mitochondrial Abnormalities

Alterations in mitochondrial function and protein expression were detected in striatal synapses of 2- to 3-month-old KO rats.

Motor Impairment

No behavioral deficits were detected at 4, 6, and 8 months of age. Motor functioning, including performance on the Rotarod, was intact. However, at 2 months, male KO rats made fewer small stereotypic movements, such as scratching and grooming, than wild-type controls.

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. . Characterization of Dopaminergic System in the Striatum of Young Adult Park2-/- Knockout Rats. Sci Rep. 2018 Jan 24;8(1):1517. PubMed.
  3. . Proteomic and functional data sets on synaptic mitochondria from rats with genetic ablation of Parkin. Data Brief. 2018 Oct;20:568-572. Epub 2018 Aug 28 PubMed.
  4. . STEP61 is a substrate of the E3 ligase parkin and is upregulated in Parkinson's disease. Proc Natl Acad Sci U S A. 2015 Jan 27;112(4):1202-7. Epub 2015 Jan 12 PubMed.

External Citations

  1. Horizon Discovery (formerly Sage Labs); TGRL4760

Further Reading

No Available Further Reading