Research Models

DJ-1 KO Rat

Synonyms: DJ-1 knockout rat

Species: Rat
Genes: PARK7 (DJ1)
Modification: PARK7 (DJ1): Knock-Out
Disease Relevance: Parkinson's Disease
Strain Name: LEH-Park7tm1sage
Genetic Background: Long Evans Hooded
Availability: Available through Horizon Discovery (formerly Sage Labs). Cat #TGRL4830; Live.

Summary

This knockout rat model was created at Sage Labs (now Horizon Discovery) in collaboration with the Michael J. Fox Foundation. The rat carries a disrupted Park7 gene, which encodes the protein DJ-1. Homozygous DJ-1 KO rats develop motor impairments (e.g., gait, strength) and loss of dopaminergic neurons in the substantia nigra; however, levels of striatal dopamine are high (Dave et al., 2014).

The Park7 gene was disrupted using zinc finger nuclease (ZFN) technology, in which targeted ZFN RNA was injected into fertilized eggs. ZFNs were engineered to bind to a recognition sequence in exon 5 of Park7 and cleave DNA. When the resulting break was repaired by non- homologous end joining, the result was a nine base pair deletion and a one base pair insertion. The resulting frame shift produced a premature stop codon. DJ-1 mRNA was dramatically reduced in homozygous rats. Likewise, DJ-1 protein was undetectable by Western blot.

Homozygous rats appeared normal at birth. There was no increase in mortality up to eight months of age. Behavior has been assessed systematically at four, six, and eight months of age. Notably, DJ-1 KO rats show abnormalities in gait and strength, but motor coordination appears largely intact.

Impairments in gait appear as early as four months of age, with abnormal paw positioning and a shorter stride than wild-type rats. Reduced overall muscle tone was evident by eight months of age, with notable lack of strength in the hind-limb extensor, leading to the appearance of dragging hind limbs. In terms of ambulatory behavior, KO rats reared less frequently, but travelled equivalent distances to wild-type counterparts.

Motor coordination remained largely intact. They performed normally on the accelerating Rotarod at all ages. On tests using a tapered balance beam, the number of foot slips was comparable to wild-type rats. They did not exhibit tremors or any grooming deficits.

Interestingly, DJ-1 KO rats had more dopamine in the striatum than wild-type rats. Levels were elevated two- to threefold at eight months of age. Similarly, striatal serotonin levels were up two- to threefold. There were no significant differences in the overall rate of turnover for either transmitter (Dave et al., 2014). Quantitative autoradiography revealed a higher density of dopaminergic receptors in the striatum. At eight months of age, DJ-1 KOs had higher densities of all three receptor subtypes (D1, D2, and D3). The density of the dopamine transporter was unchanged (Sun et al., 2013).

Despite higher dopamine levels in the striatum, DJ-1 KOs exhibited age-related decreases in the number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra. Specifically, compared to wild-type, there was a 25 percent reduction at six months and a more than 50 percent reduction at eight months. TH-immunoreactivity was unaffected in the ventral tegmental area and the striatum.

Staining for α-synuclein revealed no increase in the striatum or in any other brain region assessed.

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
  • α-synuclein Inclusions

No Data

  • Neuroinflammation
  • Mitochondrial Abnormalities
  • Cognitive Dysfunction

Dopamine Deficiency

Striatal dopamine level was increased 2-3 fold in KO rats compared to wild-type levels at eight months of age.

α-synuclein Inclusions

Staining for α-synuclein revealed no increase in the striatum or in any other brain region assessed.

Neuronal Loss

Age-related decrease in tyrosine hydroxylase (TH)-positive dopaminergic neurons in the substantia nigra. 25 and 50 percent reduction at six months and eight months, respectively. No change in TH-immunoreactivity in the ventral tegmental area or striatum.

Neuroinflammation

No data.

Motor Impairment

Abnormalities in gait and strength. As early as four months of age, KOs have abnormal paw positioning and a shorter stride. Overall decrease in muscle tone, particularly in the hind-limb extensor, leading to dragging hind limbs in some animals.

Mitochondrial Abnormalities

No data.

Cognitive Dysfunction

No data.

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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. . Regulation of dopamine presynaptic markers and receptors in the striatum of DJ-1 and Pink1 knockout rats. Neurosci Lett. 2013 Oct 21; PubMed.

External Citations

  1. Horizon Discovery (formerly Sage Labs). Cat #TGRL4830

Further Reading

No Available Further Reading