title: Molecular diagnosis of putative Stargardt Disease probands by exome sequencing.
abstract: BACKGROUND
  The commonest genetic form of juvenile or early adult onset macular degeneration is Stargardt Disease (STGD) caused by recessive mutations in the gene ABCA4. However, high phenotypic and allelic heterogeneity and a small but non-trivial amount of locus heterogeneity currently impede conclusive molecular diagnosis in a significant proportion of cases.
  
  
  METHODS
  We performed whole exome sequencing (WES) of nine putative Stargardt Disease probands and searched for potentially disease-causing genetic variants in previously identified retinal or macular dystrophy genes. Follow-up dideoxy sequencing was performed for confirmation and to screen for mutations in an additional set of affected individuals lacking a definitive molecular diagnosis.
  
  
  RESULTS
  Whole exome sequencing revealed seven likely disease-causing variants across four genes, providing a confident genetic diagnosis in six previously uncharacterized participants. We identified four previously missed mutations in ABCA4 across three individuals. Likely disease-causing mutations in RDS/PRPH2, ELOVL, and CRB1 were also identified.
  
  
  CONCLUSIONS
  Our findings highlight the enormous potential of whole exome sequencing in Stargardt Disease molecular diagnosis and research. WES adequately assayed all coding sequences and canonical splice sites of ABCA4 in this study. Additionally, WES enables the identification of disease-related alleles in other genes. This work highlights the importance of collecting parental genetic material for WES testing as the current knowledge of human genome variation limits the determination of causality between identified variants and disease. While larger sample sizes are required to establish the precision and accuracy of this type of testing, this study supports WES for inherited early onset macular degeneration disorders as an alternative to standard mutation screening techniques.
authors.affiliation: Jules Stein Eye Institute, University of California Los Angeles, 200 Stein Plaza, Los Angeles, CA 90095, USA. strom@jsei.ucla.edu
authors.forename: Samuel P
authors.initials: SP
authors.lastname: Strom
authors.forename: Yong-Qing
authors.initials: YQ
authors.lastname: Gao
authors.forename: Ariadna
authors.initials: A
authors.lastname: Martinez
authors.forename: Carolina
authors.initials: C
authors.lastname: Ortube
authors.forename: Zugen
authors.initials: Z
authors.lastname: Chen
authors.forename: Stanley F
authors.initials: SF
authors.lastname: Nelson
authors.forename: Steven
authors.initials: S
authors.lastname: Nusinowitz
authors.forename: Deborah B
authors.initials: DB
authors.lastname: Farber
authors.forename: Michael B
authors.initials: MB
authors.lastname: Gorin
mesh_terms: D000123:Acetyltransferases / Q000235:genetics*; D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000378:metabolism; D059472:Exome / Q000235:genetics*; D005136:Eye Proteins / Q000235:genetics*; D000081031:Fatty Acid Elongases; D005260:Female; D006801:Humans; D007381:Intermediate Filament Proteins / Q000235:genetics*; D008268:Macular Degeneration / Q000175:diagnosis* / Q000235:genetics; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics*; D008565:Membrane Proteins / Q000235:genetics*; D008875:Middle Aged; D009154:Mutation / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000235:genetics*; D064531:Peripherins; D058499:Retinal Dystrophies / Q000175:diagnosis* / Q000235:genetics; D017422:Sequence Analysis, DNA; D055815:Young Adult
chemical_list: D015415:Biomarkers; C448939:CRB1 protein, human; D005136:Eye Proteins; D007381:Intermediate Filament Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; C578997:PRPH2 protein, human; D064531:Peripherins; D000123:Acetyltransferases; D000081031:Fatty Acid Elongases