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 neccessary for assembly of full length cilia. Studies suggest the protein may play role in Inhertited Retinal Degenration and screening for TTC26 mutations in human ciliopathies.
Looking at this in HapMap is fairly interesting, there is a haplotype spanning the whole gene and not much else. 8.8% of 205 CEU+TSI individuals have African haplotype with every SNP included by HapMap in the gene changed to the minor allele. rs10268763 can be used to differentiate between these two "ancestral" haplotypes, there seems to be a slight bias towards homozygous haplotypes for these variants, possibly due to population structure. 0.7% have single SNP rs10248924 changed from the most common haplotype, and another 0.7% have rs10215341 changed from the two most common ones, which looks like a potential phasing error. Additional 0.2% have three SNP's changed from the most common variant, but this is single individual on this sample. In conclusion, Europeans have one form of this gene with at least one prominent back-mutation while most Sub-Saharan Africans and Kenyans have very different one, with other populations having a varying mix of the two.
[PMID 24596149] TTC26/DYF13 is an intraflagellar transport protein required for transport of motility-related proteins into flagella.
[PMID 22718903] Knockdown of ttc26 disrupts ciliogenesis of the photoreceptor cells and the pronephros in zebrafish.
[PMID 10517866] The tetratricopeptide repeat: a structural motif mediating protein-protein interactions.