MERTK Arginine-844-Cysteine in a Patient with Severe Rod-Cone Dystrophy: Loss of Mutant Protein Function in Transfected Cells
| Autor: | Christina L. McHenry, Andreas Gal, Yuhui Liu, Anita R. Nair, Wei Feng, Debra A. Thompson, Xiaoling Ding, Kecia L. Feathers, Paul A. Sieving, Douglas Vollrath |
|---|---|
| Rok vydání: | 2004 |
| Předmět: |
Retinal degeneration
Adolescent Blotting Western Mutation Missense Biology Arginine Kidney Transfection Cellular and Molecular Neuroscience Exon Mutant protein Proto-Oncogene Proteins Retinitis pigmentosa medicine Humans Missense mutation Cysteine Phosphorylation Polymorphism Single-Stranded Conformational Genetics c-Mer Tyrosine Kinase Reverse Transcriptase Polymerase Chain Reaction Retinal Degeneration Genetic Variation Receptor Protein-Tyrosine Kinases Dystrophy MERTK medicine.disease Molecular biology Sensory Systems Ophthalmology MERTK Gene Gene Expression Regulation Tyrosine Female Photoreceptor Cells Vertebrate |
| Zdroj: | Investigative Ophthalmology & Visual Science. 45:1456-1463 |
| ISSN: | 0146-0404 |
| DOI: | 10.1167/iovs.03-0909 |
| Popis: | PURPOSE. Mutations in the MERTK gene are responsible for retinal degeneration in the Royal College of Surgeons (RCS) rat and are a cause of human autosomal recessive retinitis pigmentosa (RP). This study reports the identification and functional analysis of novel MERTK mutations to provide information regarding whether they are causative of severe rod- cone degeneration in a young patient. METHODS. MERTK missense variants identified by single-strand conformational polymorphism (SSCP) and sequence analysis were introduced into expression constructs and used to transfect HEK293T cells. Recombinant protein expression was assayed with anti-MERTK and anti-phosphotyrosine antibodies. Protein turnover was assayed in pulse-chase studies of 35 S-methionine incorporation. Transcript levels were determined by quantitative RT-PCR. RESULTS. Three MERTK sequence variants were identified in a patient with rod-cone dystrophy: R722X in exon 16 and R865W in exon 19 on the paternal allele and R844C in exon 19 on the maternal allele. The R844C sequence change affects an evolutionarily conserved amino acid residue and was not detected in unaffected individuals. In transfected HEK293Tcells, wild-type (wt) and W865 MERTK were expressed at equivalent levels and present in the plasma membrane, stimulated tyrosine phosphorylation, and induced significant rounding of the cell bodies. In contrast, C844 MERTK was expressed at low levels and did not stimulate tyrosine phosphorylation. In addition, the relative stability of C844 MERTK was significantly less than wt in assays of protein turnover. At age 13, the patient had 20/60 and 20/200 acuities, tunnel vision of 5° centrally, and a far temporal peripheral crescent bilaterally, and ERGs were nondetectable. The fundi showed bull's-eye macular atrophy and widespread RPE thinning. CONCLUSIONS. The present study reports the identification of R844C, the first putative pathogenic MERTK missense mutation that results in severe retinal degeneration with childhood onset when in compound heterozygous form with a R722X allele. The loss of function of C844 MERTK is probably due to decreased protein stability. |
| Databáze: | OpenAIRE |
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