**Core Concept:** Intercellular connections are essential for maintaining tissue and organ integrity, allowing communication between cells, and facilitating various physiological processes. Key proteins involved in these connections are adhesion molecules, specifically those in the cadherin family.

**Why the Correct Answer is Right:** The correct answer, **Option D**: **E-cadherin**, is a member of the cadherin family of adhesion molecules involved in calcium-dependent cell-cell adhesion. E-cadherin is primarily expressed in epithelia, where it contributes to tissue architecture, cell differentiation, and maintaining tissue homeostasis.

**Why Each Wrong Option is Incorrect:**

A. **N-cadherin**: Although also part of the cadherin family, N-cadherin is mainly expressed in neurons and smooth muscle cells, not in epithelia.

B. **Ig-cadherin**: This option is incorrect because Ig-cadherin (Immunoglobulin-like cadherin) is not predominantly expressed in epithelia but rather in hematopoietic cells and immune cells.

C. **Desmoglein**: Desmoglein is part of the desmocollin and desmoglein family, not the cadherin family. It is involved in desmosomal adhesion, not epithelial adhesion.

**Clinical Pearl:** Understanding the specific cadherins (E-cadherin, N-cadherin, and P-cadherin) and their distribution within various tissues is crucial for understanding tissue homeostasis, differentiation, and pathological processes that involve cell adhesion and tissue disruption, such as cancer invasion and metastasis.

**Correct Answer:** **E-cadherin**.