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The First Nationwide Survey and Genetic Analyses of Bardet-Biedl Syndrome in Japan.

Hirano M, Satake W, Ihara K, Tsuge I, Kondo S, Saida K, Betsui H, Okubo K, Sakamoto H, Ueno S, Ikuno Y, Ishihara R, Iwahashi H, Ohishi M, Mano T, Yamashita T, Suzuki Y, Nakamura Y, Kusunoki S, Toda T - PLoS ONE (2015)

Bottom Line: The latter mutation that resided far from the authentic splicing site was associated with skipping of exon 8.We also found 3 previously reported mutations in the BBS2 (p.R413X and p.R480X) and BBS7 (p.C243Y) genes in 2 patients.Our results indicate that BBS in Japan is genetically heterogeneous and at least partly shares genetic features with BBS in other countries.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Sakai Hospital Kinki University Faculty of Medicine, Sakai, Japan; Department of Neurology, Kinki University Faculty of Medicine, Osakasayama, Japan.

ABSTRACT
Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder characterized by central obesity, mental impairment, rod-cone dystrophy, polydactyly, hypogonadism in males, and renal abnormalities. The causative genes have been identified as BBS1-19. In Western countries, this disease is often reported, but remains undiagnosed in many patients until later in life, while only a few patients with no mutations identified have been reported in Japan. We thus conducted the first nationwide survey of BBS in Japan by sending questionnaires to 2,166 clinical departments with board-certified specialists and found 7 patients with clinically definite BBS. We performed exome analyses combined with analyses of mRNA and protein in these patients. We identified 2 novel mutations in the BBS5 gene (p.R89X and IVS7-27 T>G) in 2 sibling patients. The latter mutation that resided far from the authentic splicing site was associated with skipping of exon 8. We also found 3 previously reported mutations in the BBS2 (p.R413X and p.R480X) and BBS7 (p.C243Y) genes in 2 patients. To our knowledge, a nationwide survey of BBS has not been reported in any other country. In addition, this is the first study to identify genetic alterations in Japanese patients with BBS. Our results indicate that BBS in Japan is genetically heterogeneous and at least partly shares genetic features with BBS in other countries.

No MeSH data available.


Related in: MedlinePlus

Novel mutations in Patients 1 (P1) and 2 (P2).(A) Genomic DNA sequencing of exon 5 in the BBS5 gene showed a C>T transition at the codon 89, resulting in arginine to stop (p.R89X). (B) RT-PCR revealed that an extra band with a shorter fragment in P1, P2, and their father (Fa), but not in normal control (C) or their mother (Mo). NC indicates no cDNA contained. (C) Sequencing of RT-PCR fragments showed that the shorter fragment lacked exon 8 with normal sequences in exon 5, while the normal-size fragment included exon 8, but had p.R89X mutation in exon 5. (D) Genomic DNA sequencing in exon 8 and surrounding introns in the BBS5 gene showed IVS7-27 T>G mutation in the patients.
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pone.0136317.g001: Novel mutations in Patients 1 (P1) and 2 (P2).(A) Genomic DNA sequencing of exon 5 in the BBS5 gene showed a C>T transition at the codon 89, resulting in arginine to stop (p.R89X). (B) RT-PCR revealed that an extra band with a shorter fragment in P1, P2, and their father (Fa), but not in normal control (C) or their mother (Mo). NC indicates no cDNA contained. (C) Sequencing of RT-PCR fragments showed that the shorter fragment lacked exon 8 with normal sequences in exon 5, while the normal-size fragment included exon 8, but had p.R89X mutation in exon 5. (D) Genomic DNA sequencing in exon 8 and surrounding introns in the BBS5 gene showed IVS7-27 T>G mutation in the patients.

Mentions: Exome analyses of 2 siblings, Patients 1 and 2, revealed that they were heterozygous for a novel mutation, p.R89X (c.C265T), in the BBS5 gene (Fig 1A). No apparently pathological mutation was additionally detected in this gene, although BBS is thought to be an autosomal recessive disease usually associated with alterations in both alleles. We then examined BBS5 mRNA to find a whole-exon deletion that exome analyses could not detect. Our RT-PCR analyses of fibroblasts and lymphocytes from patients, their parents, and a control showed that the patients and their father had a shorter transcript in addition to an apparently normal-size transcript, while the control and the mother had an apparently single normal-size transcript (Fig 1B). The shorter transcript lacked exon 8 (Fig 1C). Unexpectedly, sequencing of exon 8 and conjunctive introns 7 and 8 (more than 100 bases upstream and downstream of exon 8) in the genomic DNA revealed an only heterozygous IVS7-27 T>G mutation (Fig 1D), suggesting that this mutation is attributed to skipping of exon 8. DNA analyses of the patients’ parents revealed that the father was heterozygous for only IVS7-27 T>G mutation, consistent with the result that the father had the transcript lacking exon 8, and the mother was heterozygous for only p.R89X mutation (not shown). The results of long-range RT-PCR of the patients’ DNA showed that the apparently normal-size transcript exclusively contained p.R89X mutation, while the transcript lacking exon 8 did not contain this nonsense mutation, indicating that the patients had only mutant transcripts encoding truncated proteins. These mutations were not present in our in-house 300 controls or in the 1000 genome database.


The First Nationwide Survey and Genetic Analyses of Bardet-Biedl Syndrome in Japan.

Hirano M, Satake W, Ihara K, Tsuge I, Kondo S, Saida K, Betsui H, Okubo K, Sakamoto H, Ueno S, Ikuno Y, Ishihara R, Iwahashi H, Ohishi M, Mano T, Yamashita T, Suzuki Y, Nakamura Y, Kusunoki S, Toda T - PLoS ONE (2015)

Novel mutations in Patients 1 (P1) and 2 (P2).(A) Genomic DNA sequencing of exon 5 in the BBS5 gene showed a C>T transition at the codon 89, resulting in arginine to stop (p.R89X). (B) RT-PCR revealed that an extra band with a shorter fragment in P1, P2, and their father (Fa), but not in normal control (C) or their mother (Mo). NC indicates no cDNA contained. (C) Sequencing of RT-PCR fragments showed that the shorter fragment lacked exon 8 with normal sequences in exon 5, while the normal-size fragment included exon 8, but had p.R89X mutation in exon 5. (D) Genomic DNA sequencing in exon 8 and surrounding introns in the BBS5 gene showed IVS7-27 T>G mutation in the patients.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4556711&req=5

pone.0136317.g001: Novel mutations in Patients 1 (P1) and 2 (P2).(A) Genomic DNA sequencing of exon 5 in the BBS5 gene showed a C>T transition at the codon 89, resulting in arginine to stop (p.R89X). (B) RT-PCR revealed that an extra band with a shorter fragment in P1, P2, and their father (Fa), but not in normal control (C) or their mother (Mo). NC indicates no cDNA contained. (C) Sequencing of RT-PCR fragments showed that the shorter fragment lacked exon 8 with normal sequences in exon 5, while the normal-size fragment included exon 8, but had p.R89X mutation in exon 5. (D) Genomic DNA sequencing in exon 8 and surrounding introns in the BBS5 gene showed IVS7-27 T>G mutation in the patients.
Mentions: Exome analyses of 2 siblings, Patients 1 and 2, revealed that they were heterozygous for a novel mutation, p.R89X (c.C265T), in the BBS5 gene (Fig 1A). No apparently pathological mutation was additionally detected in this gene, although BBS is thought to be an autosomal recessive disease usually associated with alterations in both alleles. We then examined BBS5 mRNA to find a whole-exon deletion that exome analyses could not detect. Our RT-PCR analyses of fibroblasts and lymphocytes from patients, their parents, and a control showed that the patients and their father had a shorter transcript in addition to an apparently normal-size transcript, while the control and the mother had an apparently single normal-size transcript (Fig 1B). The shorter transcript lacked exon 8 (Fig 1C). Unexpectedly, sequencing of exon 8 and conjunctive introns 7 and 8 (more than 100 bases upstream and downstream of exon 8) in the genomic DNA revealed an only heterozygous IVS7-27 T>G mutation (Fig 1D), suggesting that this mutation is attributed to skipping of exon 8. DNA analyses of the patients’ parents revealed that the father was heterozygous for only IVS7-27 T>G mutation, consistent with the result that the father had the transcript lacking exon 8, and the mother was heterozygous for only p.R89X mutation (not shown). The results of long-range RT-PCR of the patients’ DNA showed that the apparently normal-size transcript exclusively contained p.R89X mutation, while the transcript lacking exon 8 did not contain this nonsense mutation, indicating that the patients had only mutant transcripts encoding truncated proteins. These mutations were not present in our in-house 300 controls or in the 1000 genome database.

Bottom Line: The latter mutation that resided far from the authentic splicing site was associated with skipping of exon 8.We also found 3 previously reported mutations in the BBS2 (p.R413X and p.R480X) and BBS7 (p.C243Y) genes in 2 patients.Our results indicate that BBS in Japan is genetically heterogeneous and at least partly shares genetic features with BBS in other countries.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Sakai Hospital Kinki University Faculty of Medicine, Sakai, Japan; Department of Neurology, Kinki University Faculty of Medicine, Osakasayama, Japan.

ABSTRACT
Bardet-Biedl syndrome (BBS) is an autosomal recessive disorder characterized by central obesity, mental impairment, rod-cone dystrophy, polydactyly, hypogonadism in males, and renal abnormalities. The causative genes have been identified as BBS1-19. In Western countries, this disease is often reported, but remains undiagnosed in many patients until later in life, while only a few patients with no mutations identified have been reported in Japan. We thus conducted the first nationwide survey of BBS in Japan by sending questionnaires to 2,166 clinical departments with board-certified specialists and found 7 patients with clinically definite BBS. We performed exome analyses combined with analyses of mRNA and protein in these patients. We identified 2 novel mutations in the BBS5 gene (p.R89X and IVS7-27 T>G) in 2 sibling patients. The latter mutation that resided far from the authentic splicing site was associated with skipping of exon 8. We also found 3 previously reported mutations in the BBS2 (p.R413X and p.R480X) and BBS7 (p.C243Y) genes in 2 patients. To our knowledge, a nationwide survey of BBS has not been reported in any other country. In addition, this is the first study to identify genetic alterations in Japanese patients with BBS. Our results indicate that BBS in Japan is genetically heterogeneous and at least partly shares genetic features with BBS in other countries.

No MeSH data available.


Related in: MedlinePlus