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A Chinese family with Oguchi's disease due to compound heterozygosity including a novel deletion in the arrestin gene.

Huang L, Li W, Tang W, Zhu X, Ou-Yang P, Lu G - Mol. Vis. (2012)

Bottom Line: No mutations were found in the GRK1 gene.A heterozygous nonsense Arg193stop (R193X) mutation was found in the SAG gene in the patient and the unaffected mother.No pathogenic SAG mutations were found in the unaffected father. qPCRs showed a heterozygous deletion encompassing exon 2 of the SAG gene in the patient and the unaffected father.

View Article: PubMed Central - PubMed

Affiliation: Institute of Reproductive and Stem Cell Engineering, Central South University, Changsha, PR China.

ABSTRACT

Purpose: Oguchi's disease is a rare autosomal recessive disease and known to be caused by mutations in the rhodopsin kinase (GRK1) gene or the arrestin (SAG) gene. SAG contains 16 exons and encodes a protein with 405 amino acids. This study was to identify the underlying genetic defects in a non-consanguineous Chinese family with Oguchi's disease.

Methods: Ophthalmologic examinations including fundus photography and electroretinography (ERG) were performed on all family members. All exons of the GRK1 gene and the SAG gene were amplified with PCR and directly sequenced. Quantitative real-time PCR (qPCR) was performed to screen heterozygous deletions/duplications in the SAG gene. Long-range PCR and direct sequencing were further performed to define the breakpoints.

Results: The patient had characteristic clinical features of Oguchi's disease, including night blindness, normal vision fields, typical fundus appearance with the Mizuo-Nakamura phenomenon, nearly undetectable rod b waves in the scotopic 0.01 ERGs, and nearly "negative" scotopic 3.0 ERGs. No mutations were found in the GRK1 gene. A heterozygous nonsense Arg193stop (R193X) mutation was found in the SAG gene in the patient and the unaffected mother. No pathogenic SAG mutations were found in the unaffected father. qPCRs showed a heterozygous deletion encompassing exon 2 of the SAG gene in the patient and the unaffected father. Long-range PCR and direct sequencing verified the deletion and revealed the breakpoints of the deletion, skipping a 3,224-bp fragment of the SAG gene. The deletion was not detected in 96 unrelated healthy controls. This deletion was predicted to eliminate the exon 2 and the AUG initiate codon in the mature SAG mRNA and cause no production of the SAG protein or low-level production of a non-functional truncated protein lacking 134 amino acids in the NH(2) terminus.

Conclusions: Compound heterozygosity of a nonsense R193X mutation and a heterozygous deletion of 3,224 bp encompassing exon 2 in the SAG gene is the cause of Oguchi's disease in this Chinese family. qPCR analysis should be performed if there is a negative result of the mutation screening of the SAG gene in patients with Oguchi's disease.

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Related in: MedlinePlus

Relative quantity (RQ) value and standard deviation calculated from the data of quantitative real-time PCRs for detecting possible heterozygous deletions/duplications in the SAG exons in the patient and her father. An RQ value of about 1.0, 0.5, or 1.5 indicates the diploid genotype, heterozygous deletion, or heterozygous duplication, respectively. A: Identification of a heterozygous deletion encompassing the SAG exon 2 in the patient and her father. B: Validation and fine-mapping the deletion using the primers of In1, In2–1, In2–2, In2–3, In2–4, and In2–5 located in intron 1 and intron 2. The heterozygous deletion involved In2–1, In2–2, and In2–3. Data were based on two independent experiments. E, Exon; In, Intron. The error bar represents the standard deviation.
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f4: Relative quantity (RQ) value and standard deviation calculated from the data of quantitative real-time PCRs for detecting possible heterozygous deletions/duplications in the SAG exons in the patient and her father. An RQ value of about 1.0, 0.5, or 1.5 indicates the diploid genotype, heterozygous deletion, or heterozygous duplication, respectively. A: Identification of a heterozygous deletion encompassing the SAG exon 2 in the patient and her father. B: Validation and fine-mapping the deletion using the primers of In1, In2–1, In2–2, In2–3, In2–4, and In2–5 located in intron 1 and intron 2. The heterozygous deletion involved In2–1, In2–2, and In2–3. Data were based on two independent experiments. E, Exon; In, Intron. The error bar represents the standard deviation.

Mentions: The existence of four heterozygous nucleotide changes in the patient suggested that exon 7, exon 8, exon 9, and exon 16 were deletion-negative. qPCR analysis of the other 12 exons of the SAG gene was performed and revealed a heterozygous deletion of the SAG exon 2 in the patient and her unaffected father (Figure 4A). Fine mapping of the exon 2 deletion with qPCR analysis using the primers including In1, In2–1, In2–2, In2–3, In2–4, and In2–5 revealed the heterozygous deletion involving In2–1, In2–2, and In2–3 in the patient and her father (Figure 4B, Figure 5A).


A Chinese family with Oguchi's disease due to compound heterozygosity including a novel deletion in the arrestin gene.

Huang L, Li W, Tang W, Zhu X, Ou-Yang P, Lu G - Mol. Vis. (2012)

Relative quantity (RQ) value and standard deviation calculated from the data of quantitative real-time PCRs for detecting possible heterozygous deletions/duplications in the SAG exons in the patient and her father. An RQ value of about 1.0, 0.5, or 1.5 indicates the diploid genotype, heterozygous deletion, or heterozygous duplication, respectively. A: Identification of a heterozygous deletion encompassing the SAG exon 2 in the patient and her father. B: Validation and fine-mapping the deletion using the primers of In1, In2–1, In2–2, In2–3, In2–4, and In2–5 located in intron 1 and intron 2. The heterozygous deletion involved In2–1, In2–2, and In2–3. Data were based on two independent experiments. E, Exon; In, Intron. The error bar represents the standard deviation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3298420&req=5

f4: Relative quantity (RQ) value and standard deviation calculated from the data of quantitative real-time PCRs for detecting possible heterozygous deletions/duplications in the SAG exons in the patient and her father. An RQ value of about 1.0, 0.5, or 1.5 indicates the diploid genotype, heterozygous deletion, or heterozygous duplication, respectively. A: Identification of a heterozygous deletion encompassing the SAG exon 2 in the patient and her father. B: Validation and fine-mapping the deletion using the primers of In1, In2–1, In2–2, In2–3, In2–4, and In2–5 located in intron 1 and intron 2. The heterozygous deletion involved In2–1, In2–2, and In2–3. Data were based on two independent experiments. E, Exon; In, Intron. The error bar represents the standard deviation.
Mentions: The existence of four heterozygous nucleotide changes in the patient suggested that exon 7, exon 8, exon 9, and exon 16 were deletion-negative. qPCR analysis of the other 12 exons of the SAG gene was performed and revealed a heterozygous deletion of the SAG exon 2 in the patient and her unaffected father (Figure 4A). Fine mapping of the exon 2 deletion with qPCR analysis using the primers including In1, In2–1, In2–2, In2–3, In2–4, and In2–5 revealed the heterozygous deletion involving In2–1, In2–2, and In2–3 in the patient and her father (Figure 4B, Figure 5A).

Bottom Line: No mutations were found in the GRK1 gene.A heterozygous nonsense Arg193stop (R193X) mutation was found in the SAG gene in the patient and the unaffected mother.No pathogenic SAG mutations were found in the unaffected father. qPCRs showed a heterozygous deletion encompassing exon 2 of the SAG gene in the patient and the unaffected father.

View Article: PubMed Central - PubMed

Affiliation: Institute of Reproductive and Stem Cell Engineering, Central South University, Changsha, PR China.

ABSTRACT

Purpose: Oguchi's disease is a rare autosomal recessive disease and known to be caused by mutations in the rhodopsin kinase (GRK1) gene or the arrestin (SAG) gene. SAG contains 16 exons and encodes a protein with 405 amino acids. This study was to identify the underlying genetic defects in a non-consanguineous Chinese family with Oguchi's disease.

Methods: Ophthalmologic examinations including fundus photography and electroretinography (ERG) were performed on all family members. All exons of the GRK1 gene and the SAG gene were amplified with PCR and directly sequenced. Quantitative real-time PCR (qPCR) was performed to screen heterozygous deletions/duplications in the SAG gene. Long-range PCR and direct sequencing were further performed to define the breakpoints.

Results: The patient had characteristic clinical features of Oguchi's disease, including night blindness, normal vision fields, typical fundus appearance with the Mizuo-Nakamura phenomenon, nearly undetectable rod b waves in the scotopic 0.01 ERGs, and nearly "negative" scotopic 3.0 ERGs. No mutations were found in the GRK1 gene. A heterozygous nonsense Arg193stop (R193X) mutation was found in the SAG gene in the patient and the unaffected mother. No pathogenic SAG mutations were found in the unaffected father. qPCRs showed a heterozygous deletion encompassing exon 2 of the SAG gene in the patient and the unaffected father. Long-range PCR and direct sequencing verified the deletion and revealed the breakpoints of the deletion, skipping a 3,224-bp fragment of the SAG gene. The deletion was not detected in 96 unrelated healthy controls. This deletion was predicted to eliminate the exon 2 and the AUG initiate codon in the mature SAG mRNA and cause no production of the SAG protein or low-level production of a non-functional truncated protein lacking 134 amino acids in the NH(2) terminus.

Conclusions: Compound heterozygosity of a nonsense R193X mutation and a heterozygous deletion of 3,224 bp encompassing exon 2 in the SAG gene is the cause of Oguchi's disease in this Chinese family. qPCR analysis should be performed if there is a negative result of the mutation screening of the SAG gene in patients with Oguchi's disease.

Show MeSH
Related in: MedlinePlus