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 9 base pair deletion and a 1 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. Although one study found no difference in KO and wild-type rat weights (Dave et al., 2014), another reported KO male rats were heavier (Yang et al., 2018).

Behavior has been assessed systematically at four, six, and eight months of age (Dave et al., 2014). Notably, DJ-1 KO rats show abnormalities in gait and strength, as well as in vocalizations and tongue movement.

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.

Impairments in gait appear as early as four to six weeks of age, when hind limb dragging, ultimately affecting approximately 30 percent of animals, first emerges (Horizon Discovery, Cat # TGRL4830, Jan 2019). At four months, abnormal paw positioning and a shorter stride than wild-type rats was reported (Dave et al., 2014). Reduced overall muscle tone was evident by eight months of age, with notable lack of strength in the hind-limb extensor. In addition, KO rats reared less frequently. Although Dave et al. observed no reduction in the distance traveled in an open-field test at four, six, and eight months of age, Horizon reported open-field mobility impairment in five of 15 rats at eight months of age (Horizon Discovery, Cat # TGRL4830, Jan 2019).

Motor coordination remained largely intact. They performed normally on the accelerating Rotarod at all ages. They did not exhibit tremors or any grooming deficits. On tests using a tapered balance beam, Yang et al. reported that male KO rats were slower than controls, but had fewer foot slips (Yang et al., 2018), while Dave et al. reported comparable performances (Dave et al., 2014).

Male DJ-1 KO rats produced longer and more frequent ultrasonic vocalizations than wild-type rats, and the average intensity of their calls decreased with age compared to controls (Yang et al., 2018). In addition, they had a decreased ability to regulate tongue force during a licking task as early as two months of age.

Interestingly, DJ-1 KO rats had more dopamine in the striatum than wild-type rats. Levels were elevated 2- to 3-fold at 8 months of age. Similarly, striatal serotonin levels were up 2- to 3-fold. 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 and locus coeruleus. Specifically, compared with wild-type, there was a 25 percent reduction in the substantia nigra at 6 months and a more than 50 percent reduction at eight months. In the locus coeruleus, the loss reached nearly 50 percent at eight months (Yang et al., 2018). 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

  • Non-Motor Impairment
  • Neuroinflammation
  • Mitochondrial Abnormalities

Neuronal Loss

Age-related decreases in tyrosine hydroxylase (TH)-positive dopaminergic neurons were reported in the substantia nigra and locus coeruleus reaching approximately 50 percent by 8 months of age. No change was found in TH-immunoreactivity in the ventral tegmental area or striatum.

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.

Neuroinflammation

No data.

Mitochondrial Abnormalities

No data.

Motor Impairment

Abnormalities in gait and strength, vocalizations, and tongue movements were observed. Some animals began dragging their hindlimbs as early as 4-6 weeks. By 4 months, the rats exhibited abnormal paw positioning and a shorter stride. Males showed impaired licking, longer and more frequent ultrasonic vocalizations, and an accelerated decrease in average call intensity with age.

Non-Motor Impairment

No data.

Last Updated: 08 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 oromotor and limb motor dysfunction in the DJ1 -/- model of Parkinson disease. Behav Brain Res. 2018 Feb 26;339:47-56. Epub 2017 Nov 3 PubMed.
  3. . 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, Cat # TGRL4830
  2. Horizon Discovery (formerly Sage Labs), Cat #TGRL4830

Further Reading

No Available Further Reading