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Targeted next generation sequencing identifies novel mutations in RP1 as a relatively common cause of autosomal recessive rod-cone dystrophy.

El Shamieh S, Boulanger-Scemama E, Lancelot ME, Antonio A, Démontant V, Condroyer C, Letexier M, Saraiva JP, Mohand-Saïd S, Sahel JA, Audo I, Zeitz C - Biomed Res Int (2015)

Bottom Line: Eight of the mutations were novel, and all cosegregated with severe arRCD phenotype, found associated with additional macular changes.Among the identified mutations, 4 belong to a region, previously associated with arRCD, and 5 others in a region previously associated with adRCD.These results point out for the necessity of sequencing RP1 when genetically investigating sporadic and arRCD.

View Article: PubMed Central - PubMed

Affiliation: INSERM, U968, 75012 Paris, France ; Sorbonne Universités, UPMC University, Paris 06, UMR_S 968, Institut de la Vision, 75012 Paris, France ; CNRS, UMR_7210, 75012 Paris, France.

ABSTRACT
We report ophthalmic and genetic findings in families with autosomal recessive rod-cone dystrophy (arRCD) and RP1 mutations. Detailed ophthalmic examination was performed in 242 sporadic and arRCD subjects. Genomic DNA was investigated using our customized next generation sequencing panel targeting up to 123 genes implicated in inherited retinal disorders. Stringent filtering coupled with Sanger sequencing and followed by cosegregation analysis was performed to confirm biallelism and the implication of the most likely disease causing variants. Sequencing identified 9 RP1 mutations in 7 index cases. Eight of the mutations were novel, and all cosegregated with severe arRCD phenotype, found associated with additional macular changes. Among the identified mutations, 4 belong to a region, previously associated with arRCD, and 5 others in a region previously associated with adRCD. Our prevalence studies showed that RP1 mutations account for up to 2.5% of arRCD. These results point out for the necessity of sequencing RP1 when genetically investigating sporadic and arRCD. It further highlights the interest of unbiased sequencing technique, which allows investigating the implication of the same gene in different modes of inheritance. Finally, it reports that different regions of RP1 can also lead to arRCD.

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Related in: MedlinePlus

Schematic presentation of RP1 disease causing mutations. Disease causing mutations were represented based on the classification by Chen and coworkers [13]. Mutations responsible for recessive arRCD were shown in the upper half, whereas mutations causing adRCD were shown in the lower half. p.Gly402Alafs*7, p.Lys443Asnfs*12, p.Arg1364Valfs*8, and p.Ser1529Argfs*9 belong to class III. Although p.Ser574Cysfs*7, p.Ser676Ilefs*22, p.Arg793Glufs*55, and p.Asp799* are class II mutations, these variants do not cause adRCD but arRCD instead. Amino acid modifications shown in red and blue represent novel frameshift or nonsense mutations and the recurrent p.Ser542* mutation respectively. Protein localization of p.Ser542* was highlighted in blue as it marked a recurrent mutation. adRCD: autosomal dominant: rod-cone dystrophy, arRCD: autosomal recessive rod-cone dystrophy, BIF: drosophila melanogaster bifocal.
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fig4: Schematic presentation of RP1 disease causing mutations. Disease causing mutations were represented based on the classification by Chen and coworkers [13]. Mutations responsible for recessive arRCD were shown in the upper half, whereas mutations causing adRCD were shown in the lower half. p.Gly402Alafs*7, p.Lys443Asnfs*12, p.Arg1364Valfs*8, and p.Ser1529Argfs*9 belong to class III. Although p.Ser574Cysfs*7, p.Ser676Ilefs*22, p.Arg793Glufs*55, and p.Asp799* are class II mutations, these variants do not cause adRCD but arRCD instead. Amino acid modifications shown in red and blue represent novel frameshift or nonsense mutations and the recurrent p.Ser542* mutation respectively. Protein localization of p.Ser542* was highlighted in blue as it marked a recurrent mutation. adRCD: autosomal dominant: rod-cone dystrophy, arRCD: autosomal recessive rod-cone dystrophy, BIF: drosophila melanogaster bifocal.

Mentions: Based on Chen et al. [13], RP1 truncating mutations leading to arRCD or adRCD can be divided into four distinct groups. Class I is composed of truncating mutations located in exons 2 and 3. These variants are sensitive to NMD and thus are considered as true loss-of-function alleles (Figure 4) [13]. Class II involves truncating mutations that are located in a spot between codons 500 and 1053 in exon 4 [13], the so called “RP1 hot spot.” The “hot spot” variants tend to be insensitive to NMD process and thus result in a protein with a potential dominant negative effect leading to adRCD (Figure 4) [13]. Class III includes truncating mutations insensible to NMD located between codons 264 and 499 and between codons 1054 to 1751 in exon 4. These truncating proteins result in a loss of function leading to arRCD (Figure 4) [13]. Finally, class IV includes protein-truncating mutations near the 3′ end of the fourth exon (Figure 4) [13]. Most likely, the resulting proteins display only a minor loss of their C-terminal portion, preserving the majority of functional domains and keeping a residual activity. According to the classification of Chen et al. [13], p.Gly402Alafs*7, p.Lys443Asnfs*12, p.Arg1364Valfs*8, and p.Ser1529Argfs*9 belong to class III (Figure 4).


Targeted next generation sequencing identifies novel mutations in RP1 as a relatively common cause of autosomal recessive rod-cone dystrophy.

El Shamieh S, Boulanger-Scemama E, Lancelot ME, Antonio A, Démontant V, Condroyer C, Letexier M, Saraiva JP, Mohand-Saïd S, Sahel JA, Audo I, Zeitz C - Biomed Res Int (2015)

Schematic presentation of RP1 disease causing mutations. Disease causing mutations were represented based on the classification by Chen and coworkers [13]. Mutations responsible for recessive arRCD were shown in the upper half, whereas mutations causing adRCD were shown in the lower half. p.Gly402Alafs*7, p.Lys443Asnfs*12, p.Arg1364Valfs*8, and p.Ser1529Argfs*9 belong to class III. Although p.Ser574Cysfs*7, p.Ser676Ilefs*22, p.Arg793Glufs*55, and p.Asp799* are class II mutations, these variants do not cause adRCD but arRCD instead. Amino acid modifications shown in red and blue represent novel frameshift or nonsense mutations and the recurrent p.Ser542* mutation respectively. Protein localization of p.Ser542* was highlighted in blue as it marked a recurrent mutation. adRCD: autosomal dominant: rod-cone dystrophy, arRCD: autosomal recessive rod-cone dystrophy, BIF: drosophila melanogaster bifocal.
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig4: Schematic presentation of RP1 disease causing mutations. Disease causing mutations were represented based on the classification by Chen and coworkers [13]. Mutations responsible for recessive arRCD were shown in the upper half, whereas mutations causing adRCD were shown in the lower half. p.Gly402Alafs*7, p.Lys443Asnfs*12, p.Arg1364Valfs*8, and p.Ser1529Argfs*9 belong to class III. Although p.Ser574Cysfs*7, p.Ser676Ilefs*22, p.Arg793Glufs*55, and p.Asp799* are class II mutations, these variants do not cause adRCD but arRCD instead. Amino acid modifications shown in red and blue represent novel frameshift or nonsense mutations and the recurrent p.Ser542* mutation respectively. Protein localization of p.Ser542* was highlighted in blue as it marked a recurrent mutation. adRCD: autosomal dominant: rod-cone dystrophy, arRCD: autosomal recessive rod-cone dystrophy, BIF: drosophila melanogaster bifocal.
Mentions: Based on Chen et al. [13], RP1 truncating mutations leading to arRCD or adRCD can be divided into four distinct groups. Class I is composed of truncating mutations located in exons 2 and 3. These variants are sensitive to NMD and thus are considered as true loss-of-function alleles (Figure 4) [13]. Class II involves truncating mutations that are located in a spot between codons 500 and 1053 in exon 4 [13], the so called “RP1 hot spot.” The “hot spot” variants tend to be insensitive to NMD process and thus result in a protein with a potential dominant negative effect leading to adRCD (Figure 4) [13]. Class III includes truncating mutations insensible to NMD located between codons 264 and 499 and between codons 1054 to 1751 in exon 4. These truncating proteins result in a loss of function leading to arRCD (Figure 4) [13]. Finally, class IV includes protein-truncating mutations near the 3′ end of the fourth exon (Figure 4) [13]. Most likely, the resulting proteins display only a minor loss of their C-terminal portion, preserving the majority of functional domains and keeping a residual activity. According to the classification of Chen et al. [13], p.Gly402Alafs*7, p.Lys443Asnfs*12, p.Arg1364Valfs*8, and p.Ser1529Argfs*9 belong to class III (Figure 4).

Bottom Line: Eight of the mutations were novel, and all cosegregated with severe arRCD phenotype, found associated with additional macular changes.Among the identified mutations, 4 belong to a region, previously associated with arRCD, and 5 others in a region previously associated with adRCD.These results point out for the necessity of sequencing RP1 when genetically investigating sporadic and arRCD.

View Article: PubMed Central - PubMed

Affiliation: INSERM, U968, 75012 Paris, France ; Sorbonne Universités, UPMC University, Paris 06, UMR_S 968, Institut de la Vision, 75012 Paris, France ; CNRS, UMR_7210, 75012 Paris, France.

ABSTRACT
We report ophthalmic and genetic findings in families with autosomal recessive rod-cone dystrophy (arRCD) and RP1 mutations. Detailed ophthalmic examination was performed in 242 sporadic and arRCD subjects. Genomic DNA was investigated using our customized next generation sequencing panel targeting up to 123 genes implicated in inherited retinal disorders. Stringent filtering coupled with Sanger sequencing and followed by cosegregation analysis was performed to confirm biallelism and the implication of the most likely disease causing variants. Sequencing identified 9 RP1 mutations in 7 index cases. Eight of the mutations were novel, and all cosegregated with severe arRCD phenotype, found associated with additional macular changes. Among the identified mutations, 4 belong to a region, previously associated with arRCD, and 5 others in a region previously associated with adRCD. Our prevalence studies showed that RP1 mutations account for up to 2.5% of arRCD. These results point out for the necessity of sequencing RP1 when genetically investigating sporadic and arRCD. It further highlights the interest of unbiased sequencing technique, which allows investigating the implication of the same gene in different modes of inheritance. Finally, it reports that different regions of RP1 can also lead to arRCD.

Show MeSH
Related in: MedlinePlus