CRYBB2 rs121912524: What Your Genotype Means
The rs121912524 variant is a rare genetic change located within the CRYBB2 gene. It is primarily associated with the development of autosomal dominant congenital cataracts, a condition characterized by clouding of the eye's lens present from birth.
What each genotype means
Typical Lens Transparency
You carry two copies of the common reference allele for the CRYBB2 gene. This genotype is not associated with dominant congenital cerulean or sutural cataracts. Your risk of early-onset inherited lens opacities related to this specific crystallin alteration remains at baseline.
Carried by more than 99.99% of individuals across all major global populations.
Cerulean Cataract Risk
You have one copy of the rare nonsense variant in the CRYBB2 gene (traditionally identified as p.Trp151Ter or c.453G>A / c.452G>A on the complementary strand). In published medical genetics literature, this alteration is linked to autosomal dominant congenital cataracts, including cerulean ('blue dot') and sutural opacities of the eye lens. Because it acts in a dominant pattern, carrying a single altered allele has been shown to cause developmental lens opacities that often present in infancy or childhood.
Extremely rare; observed at a frequency of less than 0.001% (less than 1 in 100,000 individuals) in gnomAD and diverse reference cohorts.
Cerulean Cataract Risk
You carry two copies of the premature stop-codon variant in CRYBB2. Because this variant follows an autosomal dominant inheritance pattern for congenital and juvenile cataracts, disruption of normal crystallin dimerization occurs even with one copy. Having two copies is exceptionally rare in clinical databases and is expected to lead to congenital lens opacification.
Virtually absent in general population databases; documented primarily as an ultra-rare finding within individual affected pedigrees.
Understanding the Variant and Its Location
The variant rs121912524 is a specific change in the DNA sequence of the CRYBB2 gene, which is located on chromosome 22. In genetics, a variant like this represents a single point of difference in the genetic code compared to the most common sequence found in the human population. This particular variant is classified as a nonsense mutation, meaning it introduces a premature stop signal during the process of protein synthesis. This premature stop signal can lead to the production of a truncated, or shortened, version of the beta-crystallin B2 protein. Because the lens of the eye relies on the precise structure and concentration of crystallin proteins to remain transparent, alterations in these proteins can disrupt the internal environment of the lens, potentially leading to the formation of opacities known as cataracts.
The Role of the CRYBB2 Gene
The CRYBB2 gene provides instructions for making a protein called beta-crystallin B2. Crystallins are a group of water-soluble proteins that are highly concentrated in the lens of the eye. Their primary function is to maintain the transparency and refractive power of the lens, allowing light to pass through clearly to the retina. Beta-crystallins, including the B2 subtype, work together with other crystallin proteins to form stable, organized structures that prevent the lens from becoming cloudy. When the CRYBB2 gene is mutated, the resulting protein may be unstable, prone to clumping, or unable to interact correctly with other lens proteins. This disruption in protein homeostasis is a well-documented mechanism that can lead to the development of various types of congenital cataracts, where the lens loses its clarity during development.
Research and Evidence Strength
Research into CRYBB2 variants, including rs121912524, has primarily been conducted through family-based studies investigating the genetic causes of inherited cataracts. Scientific literature has consistently identified various mutations in this gene as causative factors for autosomal dominant congenital cataracts. The evidence for these associations is considered strong within the context of the specific families studied, as the variants often cosegregate with the disease phenotype—meaning all affected family members carry the variant, while unaffected members do not. However, because these variants are extremely rare, large-scale population-wide studies are limited. While the link between specific CRYBB2 mutations and cataract formation is well-established in clinical genetics, the clinical presentation can vary significantly between different families, even when the same gene is involved.
What This Information Means for You
If you have received information regarding this variant, it is important to understand that this is a rare genetic finding. Genetic variants associated with congenital cataracts are typically identified in a clinical setting when a family history of eye conditions is present. This information is not a diagnosis and cannot predict the exact severity or type of cataract that might occur. If you or a family member have concerns about vision or eye health, the most appropriate step is to consult with an ophthalmologist or a clinical geneticist. These professionals can provide a comprehensive eye examination and, if necessary, discuss genetic counseling to help interpret what these findings mean for your specific health situation. Never use genetic data to make medical decisions without professional guidance.
How common is this variant?
The rs121912524 variant is extremely rare, with a reported frequency of less than 0.00001 in the gnomAD database, indicating it is not a common polymorphism in the general population.
Frequently asked questions
What are congenital cataracts?
Congenital cataracts are clouding of the lens of the eye that is present at birth or develops shortly after. They can be caused by genetic factors, infections during pregnancy, or metabolic conditions.
Is this variant a diagnosis for cataracts?
No, identifying a genetic variant is not a clinical diagnosis. A diagnosis of cataracts must be made by an eye care professional through a physical examination of the lens.
Can I prevent cataracts if I have this variant?
Cataracts associated with genetic variants are typically developmental. You should discuss any concerns about eye health and potential monitoring with an ophthalmologist.
Why is this variant called a nonsense mutation?
A nonsense mutation is a genetic change that creates a premature stop codon in the DNA sequence. This causes the cell to stop building the protein early, resulting in a shortened or incomplete protein.
Sources & further reading
Educational information only, last refreshed 10/17/2026. Not medical advice — these associations describe population statistics, not individual predictions.
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