Rs13225917

rs13225917 represents a relatively rare SNP tested by the 23andMe v3 chip. Due to its rarity, its effects have not and likely won't be determined through GWAS surveys. In HapMap populations, it's most common among Mexicans and Japanese occurring on the dominant European haplotype, and no homozygous A-allele carriers exist in HapMap, OpenSNP or 1000 Genomes, though this might be due to the overall rarity of the rs13225917(A) allele. The mutation causes an aspartate (D) to asparagine (N) change at position 310 (D310N, p.Asp310Asn) in the Tetratricopeptide repeat protein 26 (TTC26), which might (or might not) result in a damaging missense variant. The protein is IFT complex B protein, also known as DYF13 in nematodes, and it has a proposed function-dependent name of IFT56.

TTC26 is thought to play a critical role in ciliogenesis and normal cilia (cellular "hairs") function, as determined by protein similarity, and it is highly conserved between ciliated species studied. In studies on Zebrafish, disabling the gene prevented normal development of photoreceptor sensory and other cilia. The protein is necessary for assembly of full length cilia, although the effect (if any) of rs13225917 on its functioning has not been determined. One publication speculates that this protein may play a role in Inherited Retinal Degeneration and so screening for TTC26 mutations in human ciliopathies could be warranted, but to date there is no evidence supporting rs13225917 as a mutation of any consequence.

TTC26/DYF13 is an intraflagellar transport protein required for transport of motility-related proteins into flagella.

Knockdown of ttc26 disrupts ciliogenesis of the photoreceptor cells and the pronephros in zebrafish.

The tetratricopeptide repeat: a structural motif mediating protein-protein interactions.