SPAG8
Chr 9sperm associated antigen 8
Also known as: BS-84, CILD28, CT142, HSD-1, SMP1, SPAG3, hSMP-1
This gene encodes a microtubule inner protein that is essential for motile cilia beating and plays critical roles in spermatogenesis, including enhancing CREM-mediated gene transcription, regulating cell cycle progression through G2/M phase, and facilitating sperm-zona pellucida binding. Mutations in SPAG8 cause primary ciliary dyskinesia with male infertility, inherited in an autosomal recessive pattern. The gene shows very low constraint against loss-of-function variants, consistent with recessive inheritance where heterozygous carriers are typically unaffected.
Population Genetics & Constraint
gnomAD v4 — loss-of-function & missense intolerance
Highly tolerant — LoF variants common in population
Mild missense constraint
This gene has evidence for multiple mechanisms of pathogenicity (gain-of-function and dominant-negative). Both the Badonyi & Marsh prediction and the broader genomic evidence point to gain-of-function as the predominant mechanism. Different variants in this gene may act through different mechanisms — interpret in context of the specific variant.
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
SPAG8 · 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