Panel‐based whole exome sequencing identifies novel mutations in microphthalmia and anophthalmia patients showing complex Mendelian inheritance patterns

• Published in: Molecular genetics & genomic medicine 2017-11, Vol.5 (6), p.709-719
• Main Authors: Riera, Marina, Wert, Ana, Nieto, Isabel, Pomares, Esther
• Format: Article
• Language: English
• Subjects: Abnormalities; Amino Acid Sequence; Animals; Anophthalmia; Anophthalmos - diagnosis; Anophthalmos - genetics; Base Sequence; Complexity; DNA Mutational Analysis; Eye; Gene sequencing; Genes; Genetic analysis; Genetic screening; Heredity; Heterozygote; Humans; Identification methods; Inheritance Patterns; Microphthalmia; Microphthalmos - diagnosis; Microphthalmos - genetics; Missense mutation; Mosaicism; Mutation; Mutation, Missense; ophthalmology; Original; Otx Transcription Factors - genetics; Otx2 protein; Patients; Pax6 protein; PAX6 Transcription Factor - genetics; Pedigree; Polymorphism, Single Nucleotide; Retinol-Binding Proteins, Plasma - genetics; Sequence Alignment; Whole Exome Sequencing
• ISSN: 2324-9269; 2324-9269
• DOI: 10.1002/mgg3.329

Background Microphthalmia and anophthalmia (MA) are congenital eye abnormalities that show an extremely high clinical and genetic complexity. In this study, we evaluated the implementation of whole exome sequencing (WES) for the genetic analysis of MA patients. This approach was used to investigate three unrelated families in which previous single‐gene analyses failed to identify the molecular cause. Methods A total of 47 genes previously associated with nonsyndromic MA were included in our panel. WES was performed in one affected patient from each family using the AmpliSeqTM Exome technology and the Ion ProtonTM platform. Results A novel heterozygous OTX2 missense mutation was identified in a patient showing bilateral anophthalmia who inherited the variant from a parent who was a carrier, but showed no sign of the condition. We also describe a new PAX6 missense variant in an autosomal‐dominant pedigree affected by mild bilateral microphthalmia showing high intrafamiliar variability, with germline mosaicism determined to be the most plausible molecular cause of the disease. Finally, a heterozygous missense mutation in RBP4 was found to be responsible in an isolated case of bilateral complex microphthalmia. Conclusion This study highlights that panel‐based WES is a reliable and effective strategy for the genetic diagnosis of MA. Furthermore, using this technique, the mutational spectrum of these diseases was broadened, with novel variants identified in each of the OTX2, PAX6, and RBP4 genes. Moreover, we report new cases of reduced penetrance, mosaicism, and variable phenotypic expressivity associated with MA, further demonstrating the heterogeneity of such disorders. We evaluated the implementation of whole exome sequencing (WES) for the genetic analysis of a panel in which all dominant, recessive, and X‐linked MA candidates were included. We identified three novel missense mutations associated with MA, as well as cases of reduced penetrance, mosaicism, and variable phenotypic expressivity associated with the conditions. The analysis not only demonstrates the utility of panel‐based WES for diagnosing the molecular basis of MA, but also provides further evidence of the heterogeneity of these disorders, highlighting the significant challenges associated with genetic counseling.