You will be given a definition of a task first, then an example. Follow the example to solve a new instance of the task.
In this task, you are given a sentence. You are expected to recognize the name of gene or protein. Although there might be several correct answers, you need to write one of them.

Sox - 4 is important for very early B - cell differentiation , while TCF - 1 / LEF - 1 play a crucial role in early thymocyte development 
Solution: TCF - 1
Why? The gene, TCF - 1 has been tagged as protein since it plays a crucial role in early thymocyte development.

New input: Multiple affinity states of opiate receptor in neuroblastoma x glioma NG108-15 hybrid cells. Opiate agonist association rate is a function of receptor occupancy.
Solution:
opiate receptor