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.

Let me give you an example: Sox - 4 is important for very early B - cell differentiation , while TCF - 1 / LEF - 1 play a crucial role in early thymocyte development 
The answer to this example can be: TCF - 1
Here is why: The gene, TCF - 1 has been tagged as protein since it plays a crucial role in early thymocyte development.

OK. solve this:
Transgenic expression of the human Vitamin D receptor (hVDR) in the duodenum of VDR-null mice attenuates the age-dependent decline in calcium absorption.
Answer:
human Vitamin D receptor