A splice-site mutation in a retina-specific exon of BBS8 causes nonsyndromic retinitis pigmentosa.
Tissue-specific alternative splicing is an important mechanism for providing spatiotemporal protein diversity. Here we show that an in-frame splice mutation in BBS8, one of the genes involved in pleiotropic Bardet-Biedl syndrome (BBS), is sufficient to cause nonsyndromic retinitis pigmentosa (RP). A genome-wide scan of a consanguineous RP pedigree mapped the trait to a 5.6 Mb region; subsequent systematic sequencing of candidate transcripts identified a homozygous splice-site mutation in a previously unknown BBS8 exon. The allele segregated with the disorder, was absent from controls, was completely invariant across evolution, and was predicted to lead to the elimination of a 10 amino acid sequence from the protein. Subsequent studies showed the exon to be expressed exclusively in the retina and enriched significantly in the photoreceptor layer. Importantly, we found this exon to represent the major BBS8 mRNA species in the mammalian photoreceptor, suggesting that the encoded 10 amino acids play a pivotal role in the function of BBS8 in this organ. Understanding the role of this additional sequence might therefore inform the mechanism of retinal degeneration in patients with syndromic BBS or other related ciliopathies.
Riazuddin
S Amer
SA
McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21205, USA.
Iqbal
Muhammad
M
Wang
Yue
Y
Masuda
Tomohiro
T
Chen
Yuhng
Y
Bowne
Sara
S
Sullivan
Lori S
LS
Waseem
Naushin H
NH
Bhattacharya
Shomi
S
Daiger
Stephen P
SP
Zhang
Kang
K
Khan
Shaheen N
SN
Riazuddin
Sheikh
S
Hejtmancik
J Fielding
JF
Sieving
Paul A
PA
Zack
Donald J
DJ
Katsanis
Nicholas
N
D000483:Alleles; D017398:Alternative Splicing; D020788:Bardet-Biedl Syndrome / Q000235:genetics*; D001483:Base Sequence; D003598:Cytoskeletal Proteins; D005091:Exons; D006720:Homozygote; D006801:Humans; D009154:Mutation; D010375:Pedigree; D010641:Phenotype; D011506:Proteins / Q000235:genetics*; D012326:RNA Splicing; D012333:RNA, Messenger / Q000235:genetics; D012160:Retina / Q000378:metabolism; D012162:Retinal Degeneration / Q000235:genetics; D012174:Retinitis Pigmentosa / Q000235:genetics*
D003598:Cytoskeletal Proteins; D011506:Proteins; D012333:RNA, Messenger; C478138:TTC8 protein, human
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