Junhui Sun1,2, Zhongwei Zhou1, Chen Weng1, Chaojun Wang3, Jiao Chen1, Xue Feng1, Ping Yu1, Ming Qi4,5,6,7,8. 1. Department of Cell Biology and Medical Genetics, School of Medicine, Zhejiang University, Research Building A713, Yuhangtang Road 866, Hangzhou, China. 2. Zhejiang California International Nanosystems Institute, Zhjiang University, Hangzhou, China. 3. Department of Urology, The First Affiliated Hospital of Zhejiang University, Hangzhou, China. 4. Department of Cell Biology and Medical Genetics, School of Medicine, Zhejiang University, Research Building A713, Yuhangtang Road 866, Hangzhou, China. ming_qi@urmc.rochester.edu. 5. Zhejiang California International Nanosystems Institute, Zhjiang University, Hangzhou, China. ming_qi@urmc.rochester.edu. 6. Center for Genetic and Genomic Medicine First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China. ming_qi@urmc.rochester.edu. 7. Department of Pathology and Laboratory of Medicine, University of Rochester Medical Centre, Rochester, NY, USA. ming_qi@urmc.rochester.edu. 8. DIAN Diagnostics, Hangzhou, China. ming_qi@urmc.rochester.edu.
Abstract
BACKGROUND: Lowe syndrome is an X-linked multisystem disorder affecting eyes, nervous system, and kidney. The main causes are mutations in the OCRL gene that encodes a member of the inositol polyphosphate-5-phosphatase protein family. In this study, we aimed to gain new insights into the consequences of a novel OCRL intronic variant on pre-mRNA splicing as a main cause of Lowe syndrome in a boy. METHODS: After clinical diagnosis of the patient with Lowe syndrome, genetic testing was used to detect the presence of the OCRL variants. In silico analysis, human splicing finder and PyMol were used to predict this variant effect. Then, we analyzed the variant transcript by using a minigene construct in addition to in silico analysis. RESULTS: A hemizygous novel splicing variant in the intron 10 splice donor site of OCRL (c.939 + 3A > C) was identified in a boy with Lowe syndrome. We detected that the splice junction variant leads to aberrant OCRL mRNA splicing which results in the formation of an alternative transcript in which 29 nucleotides of exon 10 were skipped. The findings obtained from the exon-trapping assay were identical to those of in silico analysis. Hence, the truncated OCRL protein may lacked the last 597 native amino acids. CONCLUSIONS: The minigene assays detected the same transcript abnormality to in silico assay and were reliable in revealing the pathogenicity of the intronic variant we have used previously. Overall, this study provides new insights about Lowe syndrome and further reveals the molecular pathogenicity mechanism of the intronic variant disease.
BACKGROUND:Lowe syndrome is an X-linked multisystem disorder affecting eyes, nervous system, and kidney. The main causes are mutations in the OCRL gene that encodes a member of the inositol polyphosphate-5-phosphatase protein family. In this study, we aimed to gain new insights into the consequences of a novel OCRL intronic variant on pre-mRNA splicing as a main cause of Lowe syndrome in a boy. METHODS: After clinical diagnosis of the patient with Lowe syndrome, genetic testing was used to detect the presence of the OCRL variants. In silico analysis, human splicing finder and PyMol were used to predict this variant effect. Then, we analyzed the variant transcript by using a minigene construct in addition to in silico analysis. RESULTS: A hemizygous novel splicing variant in the intron 10 splice donor site of OCRL (c.939 + 3A > C) was identified in a boy with Lowe syndrome. We detected that the splice junction variant leads to aberrant OCRL mRNA splicing which results in the formation of an alternative transcript in which 29 nucleotides of exon 10 were skipped. The findings obtained from the exon-trapping assay were identical to those of in silico analysis. Hence, the truncated OCRL protein may lacked the last 597 native amino acids. CONCLUSIONS: The minigene assays detected the same transcript abnormality to in silico assay and were reliable in revealing the pathogenicity of the intronic variant we have used previously. Overall, this study provides new insights about Lowe syndrome and further reveals the molecular pathogenicity mechanism of the intronic variant disease.
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