Cre-Dependent Human α-Synuclein Expression in ROSA26-αSyn Mice. (A) Cre-dependent expression of α-synuclein variants. Protein extracts (50 μg) derived from distinct brain regions of 10 month-old ROSA26-αSyn119+/+/TH-Cre mice and their ROSA26-αSyn119+/+ littermate controls were probed with the human-specific α-synuclein antibody, Syn204, with actin and TH antibodies as controls. HEK-293T cells expressing human αSyn119 were used as a positive control. Equivalent proteins derived from ROSA26-αSyn-A53T+/-/nestin-Cre mice and their ROSA26-αSyn-A53T+/- littermates were probed with human-specific α-synuclein antibody, LB509, and actin antibody. HEK-293T cells expressing human αSyn-A53T were used as a positive control. (B) Comparison of human αSyn119 expression with endogenous α-synuclein. Proteins (50 μg) derived from distinct brain regions of 10 month-old ROSA26-αSyn119+/-/TH-Cre, ROSA26-αSyn119+/+/TH-Cre, ROSA26-αSyn119+/-/nestin-Cre and their ROSA26-αSyn119+/+ littermate controls were probed with α-synuclein antibody, Syn-1, to detect endogenous mouse (ms) α-synuclein and human αSyn119 expression. (C) Comparison of human A53T α-synuclein expression in ROSA26-αSyn-A53T mice and mouse prion promoter (mo.PrP) A53T-αSyn transgenic mice. Proteins extracted from ventral midbrain tissue of adult ROSA26-αSyn-A53T mice (50 μg) and mo.PrP-A53T mice (5 μg) were probed with LB509 antibody or actin antibody as a loading control. HEK-293T cells expressing human αSyn-A53T were used as a positive control.