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New COL6A6 variant detected by whole-exome sequencing is linked to break points in intron 4 and 3'-UTR, deleting exon 5 of RHO, and causing adRP.

de Sousa Dias M, Hernan I, Delás B, Pascual B, Borràs E, Gamundi MJ, Mañé B, Fernández-San José P, Ayuso C, Carballo M - Mol. Vis. (2015)

Bottom Line: We also performed WES in affected and unaffected members of four families with adRP in whom a disease-causing mutation was previously not found.Moreover, NGS and WES were inefficient for detecting the complete deletion of exon 5 in the RHO gene in one family with adRP.Carriers of this deletion showed variable clinical status, and two of these carriers had not previously been diagnosed with RP.

View Article: PubMed Central - PubMed

Affiliation: Molecular Genetics Unit, Hospital of Terrassa, Barcelona, Spain.

ABSTRACT

Purpose: This study aimed to test a newly devised cost-effective multiplex PCR assay for the molecular diagnosis of autosomal dominant retinitis pigmentosa (adRP), as well as the use of whole-exome sequencing (WES) to detect disease-causing mutations in adRP.

Methods: Genomic DNA was extracted from peripheral blood lymphocytes of index patients with adRP and their affected and unaffected family members. We used a newly devised multiplex PCR assay capable of amplifying the genetic loci of RHO, PRPH2, RP1, PRPF3, PRPF8, PRPF31, IMPDH1, NRL, CRX, KLHL7, and NR2E3 to molecularly diagnose 18 index patients with adRP. We also performed WES in affected and unaffected members of four families with adRP in whom a disease-causing mutation was previously not found.

Results: We identified five previously reported mutations (p.Arg677X in the RP1 gene, p.Asp133Val and p.Arg195Leu in the PRPH2 gene, and p.Pro171Leu and p.Pro215Leu in the RHO gene) and one novel mutation (p.Val345Gly in the RHO gene) representing 33% detection of causative mutations in our adRP cohort. Comparative WES analysis showed a new variant (p.Gly103Arg in the COL6A6 gene) that segregated with the disease in one family with adRP. As this variant was linked with the RHO locus, we sequenced the complete RHO gene, which revealed a deletion in intron 4 that encompassed all of exon 5 and 28 bp of the 3'-untranslated region (UTR).

Conclusions: The novel multiplex PCR assay with next-generation sequencing (NGS) proved effective for detecting most of the adRP-causing mutations. A WES approach led to identification of a deletion in RHO through detection of a new linked variant in COL6A6. No pathogenic variants were identified in the remaining three families. Moreover, NGS and WES were inefficient for detecting the complete deletion of exon 5 in the RHO gene in one family with adRP. Carriers of this deletion showed variable clinical status, and two of these carriers had not previously been diagnosed with RP.

No MeSH data available.


Related in: MedlinePlus

In the upper two panels, an OCT image of a 5-mm horizontal scan shows a distinct and continuous IS/OS line, correlating with the 20/20 visual acuity in the right eye of patient IV:2 from family RPT65. In the lower two panels, intraretinal cysts in the intermediate retina and abnormally structured IS/OS line correlate with the mother’s (II:1) poorer visual acuity in the right eye (20/30).
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f4: In the upper two panels, an OCT image of a 5-mm horizontal scan shows a distinct and continuous IS/OS line, correlating with the 20/20 visual acuity in the right eye of patient IV:2 from family RPT65. In the lower two panels, intraretinal cysts in the intermediate retina and abnormally structured IS/OS line correlate with the mother’s (II:1) poorer visual acuity in the right eye (20/30).

Mentions: Table 4 and Table 5 show the clinical features of the families RPT100 (Figure 1) and RT65 (Figure 2), who carried novel rhodopsin mutations found in our survey. Initially, we knew only the II:1 branch of the RPT65 family, who had been ophthalmologically examined and followed for years in our hospital (Table 5). They showed early onset of symptoms, including the appearance of night blindness during their early 20s. Fundus examination showed bone spicules, attenuated blood vessels, and optic disc pallor that worsened with age. Visual field testing revealed important visual field constriction in the patients’ 20s, with normal function of the foveal photoreceptors allowing good central vision up until the end-stage of the disease (Figure 3 and Figure 4). Affected family members who were previously diagnosed with RP (descendants of II:1) experienced a slow rate of vision loss and had a more pericentral pattern of degeneration and pigment deposition.


New COL6A6 variant detected by whole-exome sequencing is linked to break points in intron 4 and 3'-UTR, deleting exon 5 of RHO, and causing adRP.

de Sousa Dias M, Hernan I, Delás B, Pascual B, Borràs E, Gamundi MJ, Mañé B, Fernández-San José P, Ayuso C, Carballo M - Mol. Vis. (2015)

In the upper two panels, an OCT image of a 5-mm horizontal scan shows a distinct and continuous IS/OS line, correlating with the 20/20 visual acuity in the right eye of patient IV:2 from family RPT65. In the lower two panels, intraretinal cysts in the intermediate retina and abnormally structured IS/OS line correlate with the mother’s (II:1) poorer visual acuity in the right eye (20/30).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4539015&req=5

f4: In the upper two panels, an OCT image of a 5-mm horizontal scan shows a distinct and continuous IS/OS line, correlating with the 20/20 visual acuity in the right eye of patient IV:2 from family RPT65. In the lower two panels, intraretinal cysts in the intermediate retina and abnormally structured IS/OS line correlate with the mother’s (II:1) poorer visual acuity in the right eye (20/30).
Mentions: Table 4 and Table 5 show the clinical features of the families RPT100 (Figure 1) and RT65 (Figure 2), who carried novel rhodopsin mutations found in our survey. Initially, we knew only the II:1 branch of the RPT65 family, who had been ophthalmologically examined and followed for years in our hospital (Table 5). They showed early onset of symptoms, including the appearance of night blindness during their early 20s. Fundus examination showed bone spicules, attenuated blood vessels, and optic disc pallor that worsened with age. Visual field testing revealed important visual field constriction in the patients’ 20s, with normal function of the foveal photoreceptors allowing good central vision up until the end-stage of the disease (Figure 3 and Figure 4). Affected family members who were previously diagnosed with RP (descendants of II:1) experienced a slow rate of vision loss and had a more pericentral pattern of degeneration and pigment deposition.

Bottom Line: We also performed WES in affected and unaffected members of four families with adRP in whom a disease-causing mutation was previously not found.Moreover, NGS and WES were inefficient for detecting the complete deletion of exon 5 in the RHO gene in one family with adRP.Carriers of this deletion showed variable clinical status, and two of these carriers had not previously been diagnosed with RP.

View Article: PubMed Central - PubMed

Affiliation: Molecular Genetics Unit, Hospital of Terrassa, Barcelona, Spain.

ABSTRACT

Purpose: This study aimed to test a newly devised cost-effective multiplex PCR assay for the molecular diagnosis of autosomal dominant retinitis pigmentosa (adRP), as well as the use of whole-exome sequencing (WES) to detect disease-causing mutations in adRP.

Methods: Genomic DNA was extracted from peripheral blood lymphocytes of index patients with adRP and their affected and unaffected family members. We used a newly devised multiplex PCR assay capable of amplifying the genetic loci of RHO, PRPH2, RP1, PRPF3, PRPF8, PRPF31, IMPDH1, NRL, CRX, KLHL7, and NR2E3 to molecularly diagnose 18 index patients with adRP. We also performed WES in affected and unaffected members of four families with adRP in whom a disease-causing mutation was previously not found.

Results: We identified five previously reported mutations (p.Arg677X in the RP1 gene, p.Asp133Val and p.Arg195Leu in the PRPH2 gene, and p.Pro171Leu and p.Pro215Leu in the RHO gene) and one novel mutation (p.Val345Gly in the RHO gene) representing 33% detection of causative mutations in our adRP cohort. Comparative WES analysis showed a new variant (p.Gly103Arg in the COL6A6 gene) that segregated with the disease in one family with adRP. As this variant was linked with the RHO locus, we sequenced the complete RHO gene, which revealed a deletion in intron 4 that encompassed all of exon 5 and 28 bp of the 3'-untranslated region (UTR).

Conclusions: The novel multiplex PCR assay with next-generation sequencing (NGS) proved effective for detecting most of the adRP-causing mutations. A WES approach led to identification of a deletion in RHO through detection of a new linked variant in COL6A6. No pathogenic variants were identified in the remaining three families. Moreover, NGS and WES were inefficient for detecting the complete deletion of exon 5 in the RHO gene in one family with adRP. Carriers of this deletion showed variable clinical status, and two of these carriers had not previously been diagnosed with RP.

No MeSH data available.


Related in: MedlinePlus