Subretinal Gene Therapy of Mice With Bardet-Biedl Syndrome Type 1

Compartmentalization and polarized protein trafficking are essential for many cellular functions. The photoreceptor outer segment (OS) is a sensory compartment specialized for phototransduction, and it shares many features with primary cilia. As expected, mutations disrupting protein trafficking to cilia often disrupt protein trafficking to the OS and cause photoreceptor degeneration. Bardet-Biedl syndrome (BBS) is one of the ciliopathies associated with defective ciliary trafficking and photoreceptor degeneration. However, precise roles of BBS proteins in photoreceptor cells and the underlying mechanisms of photoreceptor degeneration in BBS are not well understood. Here, we show that accumulation of non-OS proteins in the OS underlies photoreceptor degeneration in BBS. Using a newly developed BBS mouse model [Leucine zipper transcription factor-like 1 (Lztfl1)/Bbs17 mutant], isolated OSs, and quantitative proteomics, we determined 138 proteins that are enriched more than threefold in BBS mutant OS. In contrast, only eight proteins showed a more than threefold reduction. We found striking accumulation of Stx3 and Stxbp1/Munc18-1 and loss of polarized localization of Prom1 within the Lztfl1 and Bbs1 mutant OS. Ultrastructural analysis revealed that large vesicles are formed in the BBS OS, disrupting the lamellar structure of the OS. Our findings suggest that accumulation (and consequent sequestration) of non-OS proteins in the OS is likely the primary cause of photoreceptor degeneration in BBS. Our data also suggest that a major function of BBS proteins in photoreceptors is to transport proteins from the OS to the cell body or to prevent entry of non-OS proteins into the OS.photoreceptor degeneration | trafficking | primary cilia | outer segment | retinitis pigmentosa

show abstract

“…ERG was conducted on 7-10-wk-old Lztfl1 mutant mice (−/−; n = 10) and their wild-type littermates (+/−; n = 8), as described earlier (44).…”

Section: Methodsmentioning

confidence: 99%

Accumulation of non-outer segment proteins in the outer segment underlies photoreceptor degeneration in Bardet–Biedl syndrome

Datta

Allamargot

Hudson

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

136

128

View full text Add to dashboard Cite

show abstract

“…Topical delivery of the missing BBS gene, e.g. by subretinal injection of BBS-containing adenovirus construct, rescued rhodopsin mislocalization and preserved the function of the eyes in experimental mice [Simons et al, 2011;Seo et al, 2013]. There were also some attempts to prevent apoptosis of photoreceptor cells by various pharmacological compounds [Mockel et al, 2012].…”

Section: Involved In Intraflagellar Transportmentioning

confidence: 99%

Bardet-Biedl Syndrome

Suspitsin

Imyanitov²

2016

Mol Syndromol

114

122

View full text Add to dashboard Cite

Bardet-Biedl syndrome (BBS) is a rare autosomal recessive genetic disorder. It is characterized by heterogeneous clinical manifestations including primary features of the disease (rod-cone dystrophy, polydactyly, obesity, genital abnormalities, renal defects, and learning difficulties) and secondary BBS characteristics (developmental delay, speech deficit, brachydactyly or syndactyly, dental defects, ataxia or poor coordination, olfactory deficit, diabetes mellitus, congenital heart disease, etc.); most of these symptoms may not be present at birth but appear and progressively worsen during the first and second decades of life. At least 20 BBS genes have already been identified, and all of them are involved in primary cilia functioning. Genetic diagnosis of BBS is complicated due to lack of gene-specific disease symptoms; however, it is gradually becoming more accessible with the invention of multigene sequencing technologies. Clinical management of BBS is largely limited to a symptomatic treatment. Mouse experiments demonstrate that the most debilitating complication of BBS, blindness, can be rescued by topical gene therapy. There is a published case report describing the delay of BBS symptoms by nutritional compensation of the disease-related biochemical deficiencies. Progress in DNA testing technologies is likely to rapidly resolve all limitations in BBS diagnosis; however, much slower improvement is expected with regard to BBS treatment.

show abstract

“…Preliminary gene therapy experiments in Bbs1 mice have given promising results, with improved rhodopsin trafficking, reduced photoreceptor degeneration and improved ERG. 235 Similarly, Bbs4 mutant mice have been successfully treated with gene therapy to restore rhodopsin localization, OS structure and prevention of photoreceptor degeneration. 236 While treating BBS has its difficulties (particularly in ensuring that the correct stoichiometry of the BBSome complex is restored), retinal gene therapy remains a promising therapeutic approach that needs further research to assess its clinical efficacy and utility.…”

Section: Future Perspectives and Challengesmentioning

confidence: 99%