title: Novel RP1 mutations and a recurrent BBS1 variant explain the co-existence of two distinct retinal phenotypes in the same pedigree.
abstract: BACKGROUND
  Molecular diagnosis of Inherited Retinal Dystrophies (IRD) has long been challenging due to the extensive clinical and genetic heterogeneity present in this group of disorders. Here, we describe the clinical application of an integrated next-generation sequencing approach to determine the underlying genetic defects in a Spanish family with a provisional clinical diagnosis of autosomal recessive Retinitis Pigmentosa (arRP).
  
  
  RESULTS
  Exome sequencing of the index patient resulted in the identification of the homozygous BBS1 p.M390R mutation. Sanger sequencing of additional members of the family showed lack of co-segregation of the p.M390R variant in some individuals. Clinical reanalysis indicated co-ocurrence of two different phenotypes in the same family: Bardet-Biedl syndrome in the individual harboring the BBS1 mutation and non-syndromic arRP in extended family members. To identify possible causative mutations underlying arRP, we conducted disease-targeted gene sequencing using a panel of 26 IRD genes. The in-house custom panel was validated using 18 DNA samples known to harbor mutations in relevant genes. All variants were redetected, indicating a high mutation detection rate. This approach allowed the identification of two novel heterozygous null mutations in RP1 (c.4582_4585delATCA; p.I1528Vfs*10 and c.5962dupA; p.I1988Nfs*3) which co-segregated with the disease in arRP patients. Additionally, a mutational screening in 96 patients of our cohort with genetically unresolved IRD revealed the presence of the c.5962dupA mutation in one unrelated family.
  
  
  CONCLUSIONS
  The combination of molecular findings for RP1 and BBS1 genes through exome and gene panel sequencing enabled us to explain the co-existence of two different retinal phenotypes in a family. The identification of two novel variants in RP1 suggests that the use of panels containing the prevalent genes of a particular population, together with an optimized data analysis pipeline, is an efficient and cost-effective approach that can be reliably implemented into the routine diagnostic process of diverse inherited retinal disorders. Moreover, the identification of these novel variants in two unrelated families supports the relatively high prevalence of RP1 mutations in Spanish population and the role of private mutations for commonly mutated genes, while extending the mutational spectrum of RP1.
authors.affiliation: Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. cristina.mendez.exts@juntadeandalucia.es.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain. cristina.mendez.exts@juntadeandalucia.es.
authors.forename: Cristina
authors.initials: C
authors.lastname: Méndez-Vidal
authors.affiliation: Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. nereidai.bravo.exts@juntadeandalucia.es.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain. nereidai.bravo.exts@juntadeandalucia.es.
authors.forename: Nereida
authors.initials: N
authors.lastname: Bravo-Gil
authors.affiliation: Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. maria.gonzalez.exts@juntadeandalucia.es.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain. maria.gonzalez.exts@juntadeandalucia.es.
authors.forename: María
authors.initials: M
authors.lastname: González-Del Pozo
authors.affiliation: Genomics and Bioinformatics Platform of Andalusia (GBPA), Seville, Spain. alicia.vela.boza@juntadeandalucia.es.
authors.forename: Alicia
authors.initials: A
authors.lastname: Vela-Boza
authors.affiliation: Genomics and Bioinformatics Platform of Andalusia (GBPA), Seville, Spain. jdopazo@cipf.es.|Computational Genomics Department, Centro de Investigación Príncipe Felipe (CIPF), Valencia, Spain. jdopazo@cipf.es.
authors.forename: Joaquín
authors.initials: J
authors.lastname: Dopazo
authors.affiliation: Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. salud.borrego.sspa@juntadeandalucia.es.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain. salud.borrego.sspa@juntadeandalucia.es.
authors.forename: Salud
authors.initials: S
authors.lastname: Borrego
authors.affiliation: Department of Genetics, Reproduction and Fetal Medicine, Institute of Biomedicine of Seville, University Hospital Virgen del Rocío/CSIC/University of Seville, Avenida Manuel Siurot s/n, 41013, Seville, Spain. guillermo.antinolo.sspa@juntadeandalucia.es.|Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Seville, Spain. guillermo.antinolo.sspa@juntadeandalucia.es.|Genomics and Bioinformatics Platform of Andalusia (GBPA), Seville, Spain. guillermo.antinolo.sspa@juntadeandalucia.es.
authors.forename: Guillermo
authors.initials: G
authors.lastname: Antiñolo
mesh_terms: D020788:Bardet-Biedl Syndrome / Q000235:genetics; D001483:Base Sequence; D016022:Case-Control Studies; D004252:DNA Mutational Analysis; D005136:Eye Proteins / Q000235:genetics*; D005808:Genes, Recessive; D056726:Genetic Association Studies; D006801:Humans; D018895:Microsatellite Repeats; D008869:Microtubule-Associated Proteins / Q000235:genetics*; D020125:Mutation, Missense; D010375:Pedigree; D010641:Phenotype; D012160:Retina / Q000473:pathology*; D012174:Retinitis Pigmentosa / Q000235:genetics*
chemical_list: C464790:Bbs1 protein, human; D005136:Eye Proteins; D008869:Microtubule-Associated Proteins; C120042:RP1 protein, human