**Core Concept**
Melanocytes, Langerhans cells, and Merkel cells are distinct cell types found in the skin, each with unique functions. However, they share a common feature related to their origin and function.

**Why the Correct Answer is Right**
These cells all express the adhesion molecule **E-cadherin**, which plays a crucial role in maintaining cell-to-cell adhesion and tissue integrity. E-cadherin is a transmembrane glycoprotein that mediates cell-to-cell adhesion via homophilic interactions. This is particularly important in the epidermis, where these cells reside, as it helps maintain the skin's barrier function. Additionally, the expression of E-cadherin is essential for the proper migration and organization of these cells during development and wound healing.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not accurately describe a common feature of melanocytes, Langerhans cells, and Merkel cells.
* **Option B:** This option is incorrect because while melanocytes do produce melanin, this is not a feature shared by Langerhans cells and Merkel cells.
* **Option C:** This option is incorrect because while Merkel cells are mechanoreceptors, this is not a feature shared by melanocytes and Langerhans cells.

**Clinical Pearl / High-Yield Fact**
E-cadherin expression is crucial for maintaining tissue integrity, and its dysfunction has been implicated in various skin disorders, including epidermolysis bullosa and skin cancer.

**Correct Answer: A. Expression of E-cadherin is a common feature of melanocytes, Langerhans cells, and Merkel cells.**