Thioredoxin domain-containing protein 3 (TXNDC3), also known as spermatid-specific thioredoxin-2 (Sptrx-2), is a protein that in humans is encoded by the NME8 gene (also known as the TXNDC3 gene) on chromosome 7. Function This gene encodes a protein with an N-terminal thioredoxin domain and three C-terminal nucleoside diphosphate kinase (NDK) domains, but the NDK domains are thought to be catalytically inactive. The sea urchin ortholog of this gene encodes a component of sperm outer dynein arms, and the protein is implicated in ciliary function. Clinical significance Mutations in the TXNDC3 gene are associated with primary ciliary dyskinesia. References Further reading External links GeneReviews/NCBI/NIH/UW entry on Primary Ciliary Dyskinesia