Age- and Sex-Dependent Behavioral and Neurochemical Alterations in hLRRK2-G2019S BAC Mice

Abstract

The G2019S mutation in the leucine-rich repeat kinase 2 (LRRK2) gene is associated with late-onset Parkinson's disease (PD). Although PD affects men and women differently, longitudinal studies examining sex- and age-dependent alterations in mice carrying the G2019S mutation are limited. We examined if behavioral and neurochemical dysfunctions, as well as neurodegeneration, occur in male and female BAC LRRK2-hG2019S (G2019S) mice, compared to their age-matched wild type littermates, at four age ranges. In the open field test, hyperlocomotion was observed in 10-12 month old male and 2-4.5 months old female G2019S mice. In the pole test, motor coordination was impaired in male G2019S mice from 15 months of age and in 20-21 months old female G2019S mice. In the striatum of G2019S male and female mice, the amounts of tyrosine hydroxylase (TH), measured with Western blotting, were unaltered. However, we found a decreased expression of the dopamine transporter in 20-21 month old male G2019S mice. The number of TH-positive neurons in the substantia nigra compacta was unaltered in 20-21 month old male and female G2019S mice. These results identify sex- and age-dependent differences in the occurrence of motor and neurochemical deficits in BAC LRRK2-hG2019S mice, and no degeneration of DA neurons.

Keywords: BAC: bacterial artificial chromosome; DA: dopaminergic; DAT: dopamine transporter; KI: knock-in; LRRK2: leucine-rich repeat kinase 2; PD: Parkinson’s disease; SNc: substantia nigra pars compacta; TH: tyrosine hydroxylase.

Figure 1

Male and female G2019S mice display hyperlocomotion at different ages. Total distance covered in the open field test during 60 min by male (A) and female (B) WT and G2019S mice at the ages indicated above the graphs (m: months). N = 4–23 mice in each group. ** p < 0.001 unpaired Student’s t-test. Circles represent data of male. Squares represent data of female. Colors indicate different ages.

Figure 2

Male and female G2019S mice display fine motor impairment at different ages. Fine motor coordination was assessed with the pole test in male (A) and female (B) mice at four age ranges. Tturn: time taken by the mice to turn downward from the top of a vertical pole; Ttotal: total time to descend the pole. N = 4–14 mice in each group. * p < 0.05; ** p < 0.01; *** p < 0.001 unpaired Student’s t-test. ^## p < 0.01 Mann-Whitney U test.

Figure 3

Old male G2019S mice display decreased DAT amount in the striatum. Western blotting of TH and DAT in the striatum of 10–12 months old and 20–21 months old male (A) and female (B) WT and G2019S mice. N = 4–25 mice in each group. * p < 0.05 unpaired Student’s t-test.

Figure 4

Intact cell counts in the SNc of old WT and G2019S male and female mice. (A) Confocal images showing immunofluorescence for TH in midbrain sections containing the SNc (dotted lines) of 20–21 months old WT and G2019S male and female mice; scale bars: 500 µm. (B) Number of TH-positive neurons in the SNc of 20–21 months old mice. N = 6 WT male mice, N = 4 G2019S male mice, N = 4 WT female mice, and N = 4 G2019S female mice.