- The cranial nerve responsible for innervating the muscles involved in facial expression is the Facial nerve (VII).
- This nerve controls the majority of the muscles that allow us to produce facial expressions such as smiling, frowning, blinking, and other movements of the face.

Here is a brief explanation of the options:
- Trigeminal nerve (V): Primarily responsible for sensation in the face and motor functions such as biting and chewing, but not facial expressions.
- Facial nerve (VII): This is the correct answer. It innervates the muscles responsible for facial expression.
- Glossopharyngeal nerve (IX): Involved in taste sensation and some functions related to swallowing, but not facial expression.
- Accessory nerve (XI): Primarily controls certain muscles of the neck and shoulder, such as the sternocleidomastoid and trapezius, not facial muscles.

Therefore, the Facial nerve (VII) is uniquely responsible for the motor control of facial expression muscles.

Reference: Gray's Anatomy, 41st Edition, Volume 1, Chapter 16 - The Face and Parotid Region