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Research article2020Peer reviewedOpen access

Deletion in the Bardet-Biedl syndrome gene TTC8 results in a syndromic retinal degeneration in dogs

Mäkeläinen, Suvi; Hellsand, Minas; Van Der Heiden, Anna Darlene; Andersson, Elina; Thorsson, Elina; Ström Holst, Bodil; Häggström, Jens; Bersås Ljungvall, Ingrid; Mellersh, Cathryn; Hallböök, Finn; Andersson, Göran; Ekesten, Björn; Bergström, Tomas


In golden retriever dogs, a 1 bp deletion in the canine TTC8 gene has been shown to cause progressive retinal atrophy (PRA), the canine equivalent of retinitis pigmentosa. In humans, TTC8 is also implicated in Bardet–Biedl syndrome (BBS). To investigate if the affected dogs only exhibit a non-syndromic PRA or develop a syndromic ciliopathy similar to human BBS, we recruited 10 affected dogs to the study. The progression of PRA for two of the dogs was followed for 2 years, and a rigorous clinical characterization allowed a careful comparison with primary and secondary characteristics of human BBS. In addition to PRA, the dogs showed a spectrum of clinical and morphological signs similar to primary and secondary characteristics of human BBS patients, such as obesity, renal anomalies, sperm defects, and anosmia. We used Oxford Nanopore long-read cDNA sequencing to characterize retinal full-length TTC8 transcripts in affected and non-affected dogs, the results of which suggest that three isoforms are transcribed in the retina, and the 1 bp deletion is a loss-of-function mutation, resulting in a canine form of Bardet–Biedl syndrome with heterogeneous clinical signs.


Bardet–Biedl syndrome (BBS); primary cilia; ciliopathy; BBS8; progressive retinal atrophy (PRA); retinitis pigmentosa

Published in

2020, Volume: 11, number: 9, article number: 1090