CSN1S1
Chr 4casein alpha s1
Also known as: CASA, CSN1
The protein is a major milk protein with an important role in the capacity of milk to transport calcium phosphate. Mutations cause autosomal recessive congenital lactase deficiency, which presents in infancy with severe diarrhea, dehydration, and failure to thrive when exposed to lactose-containing milk. The gene shows very low constraint to loss-of-function variants, consistent with its specialized role in milk composition rather than essential cellular functions.
Population Genetics & Constraint
gnomAD v4 — loss-of-function & missense intolerance
Highly tolerant — LoF variants common in population
Mild missense constraint
The highest-scoring mechanism for this gene is dominant-negative.
Note: In-silico variant effect predictors (SIFT, PolyPhen, REVEL, CADD) may underestimate pathogenicity of missense variants in genes with GOF or DN mechanisms. Consider functional evidence and clinical context.
Predictions from Badonyi M, Marsh JA. PLoS ONE. 2024;19(8):e0307312.
ClinVar Variant Classifications
0 submitted variants in ClinVar
Protein Context — Lollipop Plot
CSN1S1 · protein map & ClinVar variants
Showing all ClinVar variants across the protein. Search a specific variant to highlight its position.
3D Protein StructureAlphaFold
External Resources
Links to major genomics databases and tools
Clinical Trials
Active and recruiting trials from ClinicalTrials.gov
No active trials found for this gene.
Search ClinicalTrials.gov →External Resources
Links to major genomics databases and tools