Rescue of KO mouse neonatal lethality by PEG-CBS administration. A) Kaplan-Meier survival curves of KO mice that were injected subcutaneously 3 times weekly with 7.5 mg/kg of 40MA (blue) or 20NHS (red) PEG-CBS vs. similarly treated PBS-injected KO mice (black). Mice were maintained on betaine water until weaning (d 21). P < 0.00001, PBS vs. 40MA/20NHS PEG-CBS–injected mice; P = 0.49, 40MA vs. 20NHS. B) Kaplan-Meier survival curves of surviving KO mice followed beyond the initial 5-wk treatment up to 17 wk of age. The KO mice, which received 20NHS PEG-CBS during the first 5 wk and survived, were divided into 2 groups: the first cohort continued with the similar treatment up to 17 wk of age (continuous, solid red line); the second cohort was left untreated beyond the initial 5-wk treatment (initial 5 wk only, dashed red line). PBS-injected KO mice (black solid line) are shown for comparative purposes. P < 0.00001, PBS vs. 20NHS (CONT/5 W); P = 0.19, 20NHS CONT vs. 20NHS 5W.