Role of reverse phenotyping in interpretation of next generation sequencing data and a review of INPP5E related disorders.

INTRODUCTION: 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. METHODS AND 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. DISCUSSION: 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.

Mutations in PRDM5 in brittle cornea syndrome identify a pathway regulating extracellular matrix development and maintenance.

Extreme corneal fragility and thinning, which have a high risk of catastrophic spontaneous rupture, are the cardinal features of brittle cornea syndrome (BCS), an autosomal-recessive generalized connective tissue disorder. Enucleation is frequently the only management option for this condition, resulting in blindness and psychosocial distress. Even when the cornea remains grossly intact, visual function could also be impaired by a high degree of myopia and keratoconus. Deafness is another common feature and results in combined sensory deprivation. Using autozygosity mapping, we identified mutations in PRDM5 in families with BCS. We demonstrate that regulation of expression of extracellular matrix components, particularly fibrillar collagens, by PRDM5 is a key molecular mechanism that underlies corneal fragility in BCS and controls normal corneal development and maintenance. ZNF469, encoding a zinc finger protein of hitherto undefined function, has been identified as a quantitative trait locus for central corneal thickness, and mutations in this gene have been demonstrated in Tunisian Jewish and Palestinian kindreds with BCS. We show that ZNF469 and PRDM5, two genes that when mutated cause BCS, participate in the same regulatory pathway.

Standards in consent for cataract surgery.

Consent forms for cataract surgery performed at Burnley General Hospital (BGH) and Blackburn Royal Infirmary (BRI) from October 4 to December 7, 2004, were prospectively reviewed to ensure that the East Lancashire Hospital's National Health Service (NHS) Trust Policy on consent to treatment and Department of Health (DoH) guidelines were being followed when seeking consent for cataract surgery. A set of 22 criteria derived as standards were formulated from the reference guide published by the DoH and from the East Lancashire trust policy document for consent to treatment. Each consent form was measured against these standards. Cases were randomly selected between BRI and BGH prospectively. All consent forms completed by physicians involved in formulating the standards were excluded. The review showed the NHS Trust Policy and DoH guidelines were largely followed when seeking consent for cataract surgery. However, certain areas were found to be deficient. If a health professional fails to obtain proper consent and the patient suffers harm as a result of treatment, it may be a factor in a claim of negligence against that health professional. Subsequent recommendations may include simple solutions that can be implemented to improve clinical practice when obtaining informed consent.