REVERE – Police are investigating circumstances that led a 44-year old Winthrop man to jump in front of an out-bound Blue Line train as it pulled into Revere Beach station at 11 a.m. Friday.According to a rider on the train who would not identify herself, the man appeared poised to jump in front of the train as it pulled into the station. As the train slowed, the rider said the man altered his posture “to a calm stance” and then as the train approached the platform leaped in front of it. Police investigated along the stretch of the platform and track and police tape covered the entrance from Ocean Avenue down to the tracks.MBTA Spokesman Joe Pesaturo said Blue Line service was interrupted due to the incident forcing commuters to be bused between Orient Heights and Wonderland in both directions. Service was fully functioning again by about 12:30 p.m.In other Blue Line news, Wonderland Station will be closed this weekend to perform necessary signal work along the Blue Line, creating the need for a a diversion between Wonderland and Airport stations.Beginning at the start of service on Saturday and continuing through the end of service on Sunday, Wonderland Station to Wood Island Station will be closed. Blue Line service will be replaced with free shuttle bus service making all stops from Airport Station to Wonderland Station. Please allow an additional 15-20 minutes to your commuting time. For more information, call Customer Service Center at 617- 222-3200 or visit www.mbta.com