The genetic spectrum of polycystic kidney disease in children

SUMMARY OBJECTIVE: Autosomal dominant polycystic kidney disease is an inherited kidney disorder with mutations in polycystin-1 or polycystin-2. Autosomal recessive polycystic kidney disease is a severe form of polycystic kidney disease that is characterized by enlarged kidneys and congenital hepatic fibrosis. Mutations at PKHD1 are responsible for all typical forms of autosomal recessive polycystic kidney disease. METHODS: We evaluated the children diagnosed with polycystic kidney disease between October 2020 and May 2022. The diagnosis was established by family history, ultrasound findings, and/or genetic analysis. The demographic, clinical, and laboratory findings were evaluated retrospectively. RESULTS: There were 28 children (male/female: 11:17) evaluated in this study. Genetic analysis was performed in all patients (polycystin-1 variants in 13, polycystin-2 variants in 7, and no variants in 8 patients). A total of 18 variants in polycystin-1 and polycystin-2 were identified and 9 (50%) of them were not reported before. A total of eight novel variants were identified as definite pathogenic or likely pathogenic mutations. There was no variant detected in the PKDH1 gene. CONCLUSION: Our results highlighted molecular features of Turkish children with polycystic kidney disease and demonstrated novel variations that can be utilized in clinical diagnosis and prognosis.

Identification of novel variants in retinitis pigmentosa genes by whole-exome sequencing

SUMMARY OBJECTIVE: Retinitis pigmentosa is an inherited degenerative disorder causing severe retinal dystrophy and visual impairment, mainly with onset in the first or second decades. The next-generation sequencing has become an efficient tool to identify disease-causing mutations in retinitis pigmentosa. The aim of this retrospective study was to investigate novel gene variants and evaluate the utility of whole-exome sequencing in patients with retinitis pigmentosa. METHODS: The medical records of 20 patients with retinitis pigmentosa at Eskişehir City Hospital between September 2019 and February 2022 were analyzed retrospectively. Peripheral venous blood was obtained, followed by the extraction of genomic DNAs. The medical and ophthalmic histories were collected, and ophthalmological examinations were performed. Whole-exome sequencing was performed to determine the genetic etiology of the patients. RESULTS: The proportion of genetically solved cases was 75% (15/20) in the patients with retinitis pigmentosa. Molecular genetic testing identified 13 biallelic and 4 monoallelic mutations in known retinitis pigmentosa genes, including 11 novel variants. According to in silico prediction tools, nine variants were predicted as pathogenic or possibly pathogenic. We identified six previously reported mutations to be associated with retinitis pigmentosa. The age of onset of the patients ranged from 3 to 19, with a mean age of onset of 11.6. All patients had a loss of central vision. CONCLUSION: As the first study of the application of whole-exome sequencing among patients with retinitis pigmentosa in a Turkish cohort, our results may contribute to the characterization of the spectrum of variants related to retinitis pigmentosa in the Turkish population. Future population-based studies will enable us to reveal the detailed genetic epidemiology of retinitis pigmentosa.

Novel NR2F1 variant identified by whole-exome sequencing in a patient with Bosch–Boonstra–Schaaf optic atrophy syndrome

Bosch–Boonstra–Schaaf optic atrophy syndrome (BBSOAS) is an extremely rare autosomal dominant disorder characterized by intellectual disability, developmental delay, seizures, hypotonia, hearing loss, and optic nerve atrophy. This syndrome is caused by loss-of-function variants in the nuclear receptor subfamily 2 group F member 1 ( NR2F1 ) gene. To date, approximately 80 patients have been reported with BBSOAS. Here, we describe a 3-year-old infant with delayed development, intellectual disability, strabismus, nystagmus, and optic atrophy with well-characterized features associated with BBSOAS. Whole-exome sequencing revealed a novel heterozygous missense mutation (NM_005654.6:c.437G>A, p.Cys146Tyr) in the NR2F1 gene. This missense variant is predicted to be deleterious by the protein prediction tools (SIFT, PolyPhen-2, and MutationTaster). To the best of our knowledge, this is the first patient with BBSOAS reported from Turkey.