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Splice-site mutations identified in PDE6A responsible for retinitis pigmentosa in consanguineous Pakistani families.

Khan SY, Ali S, Naeem MA, Khan SN, Husnain T, Butt NH, Qazi ZA, Akram J, Riazuddin S, Ayyagari R, Hejtmancik JF, Riazuddin SA - Mol. Vis. (2015)

Bottom Line: An ophthalmic clinical examination consisting of fundus photography and electroretinography confirmed the diagnosis of RP.Haplotype analyses identified the region; however, the region did not segregate with the disease phenotype in the family.Taken together with our previously published work, our data suggest that mutations in PDE6A account for about 2% of the total genetic load of RP in our cohort and possibly in the Pakistani population as well.

View Article: PubMed Central - PubMed

Affiliation: The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore MD.

ABSTRACT

Purpose: This study was conducted to localize and identify causal mutations associated with autosomal recessive retinitis pigmentosa (RP) in consanguineous familial cases of Pakistani origin.

Methods: Ophthalmic examinations that included funduscopy and electroretinography (ERG) were performed to confirm the affectation status. Blood samples were collected from all participating individuals, and genomic DNA was extracted. A genome-wide scan was performed, and two-point logarithm of odds (LOD) scores were calculated. Sanger sequencing was performed to identify the causative variants. Subsequently, we performed whole exome sequencing to rule out the possibility of a second causal variant within the linkage interval. Sequence conservation was performed with alignment analyses of PDE6A orthologs, and in silico splicing analysis was completed with Human Splicing Finder version 2.4.1.

Results: A large multigenerational consanguineous family diagnosed with early-onset RP was ascertained. An ophthalmic clinical examination consisting of fundus photography and electroretinography confirmed the diagnosis of RP. A genome-wide scan was performed, and suggestive two-point LOD scores were observed with markers on chromosome 5q. Haplotype analyses identified the region; however, the region did not segregate with the disease phenotype in the family. Subsequently, we performed a second genome-wide scan that excluded the entire genome except the chromosome 5q region harboring PDE6A. Next-generation whole exome sequencing identified a splice acceptor site mutation in intron 16: c.2028-1G>A, which was completely conserved in PDE6A orthologs and was absent in ethnically matched 350 control chromosomes, the 1000 Genomes database, and the NHLBI Exome Sequencing Project. Subsequently, we investigated our entire cohort of RP familial cases and identified a second family who harbored a splice acceptor site mutation in intron 10: c.1408-2A>G. In silico analysis suggested that these mutations will result in the elimination of wild-type splice acceptor sites that would result in either skipping of the respective exon or the creation of a new cryptic splice acceptor site; both possibilities would result in retinal photoreceptor cells that lack PDE6A wild-type protein.

Conclusions: we report two splice acceptor site variations in PDE6A in consanguineous Pakistani families who manifested cardinal symptoms of RP. Taken together with our previously published work, our data suggest that mutations in PDE6A account for about 2% of the total genetic load of RP in our cohort and possibly in the Pakistani population as well.

No MeSH data available.


Related in: MedlinePlus

Electroretinography recordings of family PKRP133. Scotopic −25 dB, scotopic 0 dB response, and photopic 0 dB 30Hz flicker response of A) OD and B) OS of individual 21; C) OD and D) OS of individual 30; E) OD and F) OS of individual 33 (examined at the age of 22 years); G) OD and H) OS of individual 33 (examined at the age of 24 years); I) OD and J) OS of unaffected individual 41. Affected individuals 21 and 30 manifest typical retinitis pigmentosa (RP) changes on electroretinography (ERG), including loss of the rod and cone responses, while the ERG readings of unaffected individuals 33 and 41 show normal rod and cone responses. OD=oculus dexter (right eye); OS=oculus sinister (left eye).
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f3: Electroretinography recordings of family PKRP133. Scotopic −25 dB, scotopic 0 dB response, and photopic 0 dB 30Hz flicker response of A) OD and B) OS of individual 21; C) OD and D) OS of individual 30; E) OD and F) OS of individual 33 (examined at the age of 22 years); G) OD and H) OS of individual 33 (examined at the age of 24 years); I) OD and J) OS of unaffected individual 41. Affected individuals 21 and 30 manifest typical retinitis pigmentosa (RP) changes on electroretinography (ERG), including loss of the rod and cone responses, while the ERG readings of unaffected individuals 33 and 41 show normal rod and cone responses. OD=oculus dexter (right eye); OS=oculus sinister (left eye).

Mentions: PKRP133 was recruited from the Punjab province of Pakistan. A total of 23 individuals including five affected individuals were enrolled in the study (Figure 1). Medical records and clinical reports of earlier examinations by the family physician suggested retinal dystrophy with early most likely congenital onset. Interviews with family elders revealed the initial presenting symptoms of night blindness and decreased visual acuity experienced by affected individuals in early childhood. We performed a detailed ophthalmic examination of selected individuals. Visual acuity in affected individuals 21 and 30 was limited, progressing to only counting fingers in affected individual 21 (Table 1). The fundus examination of affected individual 21 shows severe bone spicule-like pigmentation in the mid-periphery and periphery of the retina along with milder macular involvement, arteriolar attenuation, and disc pallor (Figure 2A). The fundus examination of affected individual 30 shows only milder macular involvement, arteriolar attenuation, and disc pallor, and no bone spicule-like pigmentation was observed in the mid-periphery and periphery of the retina (Figure 2B). The affected individuals had reduced ERG responses with delayed implicit time (Figure 3A–D). Photophobia or nystagmus was not observed in any affected or unaffected family member.


Splice-site mutations identified in PDE6A responsible for retinitis pigmentosa in consanguineous Pakistani families.

Khan SY, Ali S, Naeem MA, Khan SN, Husnain T, Butt NH, Qazi ZA, Akram J, Riazuddin S, Ayyagari R, Hejtmancik JF, Riazuddin SA - Mol. Vis. (2015)

Electroretinography recordings of family PKRP133. Scotopic −25 dB, scotopic 0 dB response, and photopic 0 dB 30Hz flicker response of A) OD and B) OS of individual 21; C) OD and D) OS of individual 30; E) OD and F) OS of individual 33 (examined at the age of 22 years); G) OD and H) OS of individual 33 (examined at the age of 24 years); I) OD and J) OS of unaffected individual 41. Affected individuals 21 and 30 manifest typical retinitis pigmentosa (RP) changes on electroretinography (ERG), including loss of the rod and cone responses, while the ERG readings of unaffected individuals 33 and 41 show normal rod and cone responses. OD=oculus dexter (right eye); OS=oculus sinister (left eye).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4539017&req=5

f3: Electroretinography recordings of family PKRP133. Scotopic −25 dB, scotopic 0 dB response, and photopic 0 dB 30Hz flicker response of A) OD and B) OS of individual 21; C) OD and D) OS of individual 30; E) OD and F) OS of individual 33 (examined at the age of 22 years); G) OD and H) OS of individual 33 (examined at the age of 24 years); I) OD and J) OS of unaffected individual 41. Affected individuals 21 and 30 manifest typical retinitis pigmentosa (RP) changes on electroretinography (ERG), including loss of the rod and cone responses, while the ERG readings of unaffected individuals 33 and 41 show normal rod and cone responses. OD=oculus dexter (right eye); OS=oculus sinister (left eye).
Mentions: PKRP133 was recruited from the Punjab province of Pakistan. A total of 23 individuals including five affected individuals were enrolled in the study (Figure 1). Medical records and clinical reports of earlier examinations by the family physician suggested retinal dystrophy with early most likely congenital onset. Interviews with family elders revealed the initial presenting symptoms of night blindness and decreased visual acuity experienced by affected individuals in early childhood. We performed a detailed ophthalmic examination of selected individuals. Visual acuity in affected individuals 21 and 30 was limited, progressing to only counting fingers in affected individual 21 (Table 1). The fundus examination of affected individual 21 shows severe bone spicule-like pigmentation in the mid-periphery and periphery of the retina along with milder macular involvement, arteriolar attenuation, and disc pallor (Figure 2A). The fundus examination of affected individual 30 shows only milder macular involvement, arteriolar attenuation, and disc pallor, and no bone spicule-like pigmentation was observed in the mid-periphery and periphery of the retina (Figure 2B). The affected individuals had reduced ERG responses with delayed implicit time (Figure 3A–D). Photophobia or nystagmus was not observed in any affected or unaffected family member.

Bottom Line: An ophthalmic clinical examination consisting of fundus photography and electroretinography confirmed the diagnosis of RP.Haplotype analyses identified the region; however, the region did not segregate with the disease phenotype in the family.Taken together with our previously published work, our data suggest that mutations in PDE6A account for about 2% of the total genetic load of RP in our cohort and possibly in the Pakistani population as well.

View Article: PubMed Central - PubMed

Affiliation: The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore MD.

ABSTRACT

Purpose: This study was conducted to localize and identify causal mutations associated with autosomal recessive retinitis pigmentosa (RP) in consanguineous familial cases of Pakistani origin.

Methods: Ophthalmic examinations that included funduscopy and electroretinography (ERG) were performed to confirm the affectation status. Blood samples were collected from all participating individuals, and genomic DNA was extracted. A genome-wide scan was performed, and two-point logarithm of odds (LOD) scores were calculated. Sanger sequencing was performed to identify the causative variants. Subsequently, we performed whole exome sequencing to rule out the possibility of a second causal variant within the linkage interval. Sequence conservation was performed with alignment analyses of PDE6A orthologs, and in silico splicing analysis was completed with Human Splicing Finder version 2.4.1.

Results: A large multigenerational consanguineous family diagnosed with early-onset RP was ascertained. An ophthalmic clinical examination consisting of fundus photography and electroretinography confirmed the diagnosis of RP. A genome-wide scan was performed, and suggestive two-point LOD scores were observed with markers on chromosome 5q. Haplotype analyses identified the region; however, the region did not segregate with the disease phenotype in the family. Subsequently, we performed a second genome-wide scan that excluded the entire genome except the chromosome 5q region harboring PDE6A. Next-generation whole exome sequencing identified a splice acceptor site mutation in intron 16: c.2028-1G>A, which was completely conserved in PDE6A orthologs and was absent in ethnically matched 350 control chromosomes, the 1000 Genomes database, and the NHLBI Exome Sequencing Project. Subsequently, we investigated our entire cohort of RP familial cases and identified a second family who harbored a splice acceptor site mutation in intron 10: c.1408-2A>G. In silico analysis suggested that these mutations will result in the elimination of wild-type splice acceptor sites that would result in either skipping of the respective exon or the creation of a new cryptic splice acceptor site; both possibilities would result in retinal photoreceptor cells that lack PDE6A wild-type protein.

Conclusions: we report two splice acceptor site variations in PDE6A in consanguineous Pakistani families who manifested cardinal symptoms of RP. Taken together with our previously published work, our data suggest that mutations in PDE6A account for about 2% of the total genetic load of RP in our cohort and possibly in the Pakistani population as well.

No MeSH data available.


Related in: MedlinePlus