What versions can I have for setting up SQL Server Transactional replication
Yes, you can have several versions of SQL Server involved in a replication set up.  You are limited (generally speaking) to the least common denominator of functuality.  That may be just fine for you, but it is something to consider.

SQL Server 2xxx Express can only be a subscriber in a replication landscape. So as long as data only needs to move to the Express database you can use replication.

Microsoft has documented this for SQL Server 2008 R2 at: http://msdn.microsoft.com/en-us/library/ms143241(v=sql.105).aspx