Gaucher Disease Therapy Here, IFG was evaluated in vivo in a neuronopathic GCase deficient mouse model [17] for its effect on mutant GCase activity, substrate levels, and phenotypic improvement. Results Treatment of 4L;C* mice with IFG The in vivo effects of IFG were tested using 4L;C* mice that develop neurological signs, including a duck-like waddling gait at ,30 days, and then die from progressive CNS disease by ,48 days. Three to five days prior birth, IFG was added to the drinking water of pregnant dames in a dose calculated to provide ,20 mg/ kg/d based on measured water intake (see methods). At postnatal day 7 (P7), one cohort was maintained on 20 mg/kg/d IFG and a second cohort on 600 mg/kg/d (Fig. 1A). The body weights (BW) of the mice were recorded from P7 to terminal stage. The 4L;C* mice receiving 20 mg/kg/d IFG showed normal increases of BW to ,35 days and then declined to ,70% of WT levels at terminal stage (Fig. 2A). The trend of BW change was similar to that observed with untreated 4L;C* mice. These treated 4L;C* mice developed the characteristic duck-walk gait at 40-44 days and their life span was 54 days on average or about 6–10 days longer than untreated mice (Fig. 2B). The 4L;C* mice receiving 600 mg/kg/d showed slow decreases in BW after 50 days (Fig. 2A). They did not develop duck-walking, but showed spastic-like gait starting 47–50 days (Fig. 1B). The average life span was 63 days or about 15–18 days longer than controls, or ,34% increase in lifespan (Fig. 2B). The untreated and 20 mg/kg/d IFG treated 4L;C+/2 mice showed comparable BW attainments to WT and exhibited a normal phenotype during the entire study period. In comparison, 4L;C+/2 mice treated with 600 mg/kg/d IFG showed slightly lower body weight (data not shown). The untreated 4L;C* mice are infertile and male 4L;C* mice treated with 20 or 600 mg/kg/d IFG produced only a single litter. Additional regimes of IFG treatment were tested. The 4L;C* mice were treated with IFG in a 3-day-on/4-day-off trial. These mice received IFG starting 3-days prior birth at 20 mg/kg/d as above. Then, IFG was stopped from P3 to P7 (4-days off) and then it was given at 20 mg/kg/d for the next 3 days (3-day on). The cycle was continued until the end stage. The mice on this 3-day- on/4-day-off schedule showed no differences of phenotype, onset of signs, or life span (55 days) compared to the mice receiving 20 mg/kg/d of uninterrupted treatment. If IFG treatment was started on postnatal day 25 at 600 mg/kg/d, there was less of an Figure 1. Treatment and phenotypes. (A) IFG treatment regime. IFG was given to pregnant females 3 to 5 days prior birth at 20 mg/kg/d. The first cohort was continued on 20 mg/kg/d for entire course. The dose for the second cohort was increased to 600 mg/kg/d at postnatal 7days. (B) Phenotypes of IFG treated 4L;C* mice. The mice with 20 mg/kg/d IFG showed delayed duck-walk gait (arrow) as seen in the untreated 4L;C* mice. The mice on 600 mg/kg/d IFG showed spastic walk. doi:10.1371/journal.pone.0019037.g001 PLoS ONE | www.plosone.org 2 April 2011 | Volume 6 | Issue 4 | e19037