**Core Concept**
The question is testing the student's knowledge of the genetic basis of congenital cataracts, specifically the involvement of alpha-crystallin mutations. Alpha-crystallins are small heat shock proteins that play a crucial role in maintaining lens transparency and stability. Mutations in the genes encoding alpha-crystallins can lead to congenital cataracts, a condition characterized by the opacification of the lens in the eye.

**Why the Correct Answer is Right**
The correct answer is D. CRYAA, which encodes alpha-A crystallin, the major component of the alpha-crystallin family in the lens. Mutations in CRYAA have been implicated in a significant proportion of congenital cataracts, particularly those involving the anterior subcapsular region of the lens. The alpha-crystallin protein plays a critical role in maintaining lens transparency by binding to and stabilizing denatured proteins, thereby preventing the formation of protein aggregates that can lead to cataract formation.

**Why Each Wrong Option is Incorrect**
**Option A:** GLC3A is associated with primary congenital glaucoma, not congenital cataract. While both conditions are congenital eye disorders, they have distinct genetic and pathological mechanisms.
**Option B:** PAX6 is a key transcription factor involved in eye development, and mutations in PAX6 can lead to aniridia and other ocular abnormalities. However, PAX6 is not directly implicated in alpha-crystallin mutations or congenital cataracts.
**Option C:** PITX2 is a transcription factor involved in the development of the anterior segment of the eye, and mutations in PITX2 can lead to Axenfeld-Rieger syndrome, a disorder characterized by glaucoma, anterior segment dysgenesis, and other ocular features.

**Clinical Pearl / High-Yield Fact**
A key clinical correlation to remember is that mutations in CRYAA can also lead to age-related cataracts, particularly in the context of other systemic disorders such as diabetes or Down syndrome.

**✓ Correct Answer: D. CRYAA.**