title: Role of reverse phenotyping in interpretation of next generation sequencing data and a review of INPP5E related disorders.
abstract: BACKGROUND
  Next Generation Sequencing (NGS) is a useful tool in diagnosis of rare disorders but the interpretation of data can be challenging in clinical settings. We present results of extended studies on a family of multiple members with global developmental delay and learning disability, where another research group postulated the underlying cause to be a homozygous RABL6 missense variant.
  
  
  RESULTS
  Using data from the Exome Variant Server, we show that missense RABL6 variants are unlikely to cause early onset rare developmental disorder. Protein structural analysis, cellular functional studies and reverse phenotyping proved that the condition in this family is due to a homozygous INPP5E mutation. An in-depth review of mutational and phenotypic spectrum associated with INPP5E demonstrated that mutations in this gene lead to a range of cilliopathy-phenotypes.
  
  
  CONCLUSIONS
  We use this study as an example to demonstrate the importance of careful clinical evaluation of multiple family members, reverse phenotyping, considering the unknown phenotypic variability of rare diseases, utilizing publically available genomic databases and conducting appropriate bioinformatics and functional studies while interpreting results from NGS in uncertain cases. We emphasize that interpretation of NGS data is an iterative process and its dynamic nature should be explained to patients and families. Our study shows that developmental delay, intellectual disability, hypotonia and ocular motor apraxia are common in INPP5E-related disorders and considerable intra-familial phenotypic variability is possible. We have compiled the INPP5E mutational spectrum and provided novel insights into their molecular mechanisms.
authors.affiliation: Department of Paediatric Neurology, Royal Preston Hospital, Lancashire Teaching Hospitals NHS Foundation Trust, Preston, UK; Faculty of Health and Medicine, Lancaster University, Lancaster, UK.
authors.forename: Christian
authors.initials: C
authors.lastname: de Goede
authors.affiliation: Structural Genomics Consortium, Old Road Campus Research Building, University of Oxford, Oxford, UK.
authors.forename: Wyatt W
authors.initials: WW
authors.lastname: Yue
authors.affiliation: Faculty of Life Sciences, University of Manchester, UK.
authors.forename: Guanhua
authors.initials: G
authors.lastname: Yan
authors.affiliation: Department of Community and Neurodevelopmental Paediatrics, Royal Blackburn Hospital, East Lancashire Hospital NHS Trust, Blackburn, UK.
authors.forename: Shyamala
authors.initials: S
authors.lastname: Ariyaratnam
authors.affiliation: Manchester Centre for Genomic Medicine, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK.
authors.forename: Kate E
authors.initials: KE
authors.lastname: Chandler
authors.affiliation: Manchester Centre for Genomic Medicine, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK.
authors.forename: Laura
authors.initials: L
authors.lastname: Downes
authors.affiliation: Manchester Centre for Genomic Medicine, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK.
authors.forename: Nasaim
authors.initials: N
authors.lastname: Khan
authors.affiliation: Department of Ophthalmology, Royal Blackburn Hospital, East Lancashire Hospital NHS Trust, Blackburn, UK.
authors.forename: Meyyammai
authors.initials: M
authors.lastname: Mohan
authors.affiliation: Faculty of Life Sciences, University of Manchester, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Lowe
authors.affiliation: Manchester Centre for Genomic Medicine, St. Mary's Hospital, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, UK; Manchester Centre for Genomic Medicine, Institute of Human Development, Faculty of Medical and Human Sciences, University of Manchester, Manchester, UK. Electronic address: Siddharth.Banka@manchester.ac.uk.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Banka
mesh_terms: D002658:Developmental Disabilities / Q000235:genetics*; D005260:Female; D059014:High-Throughput Nucleotide Sequencing / Q000379:methods*; D006801:Humans; D008297:Male; D009154:Mutation; D015513:Oncogene Proteins / Q000235:genetics; D010375:Pedigree; D010641:Phenotype; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics*; D020691:rab GTP-Binding Proteins / Q000235:genetics; D000099182:Phosphoinositide 5-Phosphatases
chemical_list: D015513:Oncogene Proteins; D010744:Phosphoric Monoester Hydrolases; D020691:rab GTP-Binding Proteins; D000099182:Phosphoinositide 5-Phosphatases; C000595658:RABL6A protein, human
keywords: C9orf86; INPP5E; Joubert syndrome; MORM syndrome; Next generation sequencing; RABL6; Reverse phenotyping