Greetings,

As suggested by Matthias, the short answer is "yes", you certainly can make a gene interaction network. A longer answer would be to ask "What kind of interaction?". You mention you have expression values, so one kind of network you might look at is a co-expression network - where the edges represent the correlation between two genes based on their expression values. You could also use something like the stringApp or IntActApp to create a protein-protein interaction network based on the genes you have, and then map your expression values onto the nodes.

-- scooter