OTG mouse not working in Android 4?
Nexus 4 doesn't support OTG as you can read here and see related questions on this site

It is possible if you overcome Kernel and power limitations as explained in Android Advanced: USB OTG on the Nexus 4


  The first problem with getting OTG working on the Nexus 4 is that the kernel does not support it. This has been solved using a modified version of Franco's kernel. The second problem is that the Nexus 4 cannot physically supply the necessary 5 volts. The way around this is to use a Y-cable, and supply the needed voltage from an outside power source such as a wall outlet or external battery pack. Some users have also reported success using a powered USB hub.