Marjan Chapi1, Hamideh Sabbaghi2, Fatemeh Suri2, Elham Alehabib1, Simin Rahimi-Aliabadi1, Faezeh Jamali1, Javad Jamshidi3,4, Babak Emamalizadeh5, Hossein Darvish6,7, Mehraban Mirrahimi8, Hamid Ahmadieh2,8, Narsis Daftarian2,8. 1. a Department of Medical Genetics , School of Medicine, Shahid Beheshti University of Medical Sciences , Tehran , Iran. 2. b Ophthalmic Research Center , Shahid Beheshti University of Medical Sciences , Tehran , Iran. 3. c Department of Psychology , University of New South Wales and Neuroscience Research Australia , Sydney , NSW , Australia. 4. d Noncommunicable Diseases Research Center , Fasa University of Medical Sciences , Fasa , Iran. 5. e Department of Medical Genetics, Faculty of Medicine , Tabriz University of Medical Sciences , Tabriz , Iran. 6. f Cancer Research Center , Semnan University of Medical Sciences , Semnan , Iran. 7. g Department of Medical Genetics , Semnan University of Medical Sciences , Semnan , Iran. 8. h Ocular Tissue Engineering Research Center , Shahid Beheshti University of Medical Sciences , Tehran , Iran.
Abstract
Purpose: Cone-rod dystrophy (CRD) is an inherited retinal dystrophy that is transmitted via different modes of inheritance. Mutations in more than 30 genes have been identified to cause the disease. We aimed to investigate the genetic agents of two unrelated cone-rod dystrophy affected Iranian families with autosomal recessive inheritance patterns. Methods: Whole-exome sequencing (WES) was performed for identification of the disease-causing mutations in the probands of both families. The candidate mutations were further confirmed by Sanger sequencing. Samples from five available members of each family were then sequenced for the mutations present in the probands. Comprehensive ocular examinations for all members of the families carrying the mutations were completed by ophthalmologists. Results: We identified a novel premature stop codon c.310C>T in CRX gene in heterozygote form in two symptomatic and two non-symptomatic members of one family (family-A), and a known CRX mutation c.122G>A in homozygote form in another (family B). c.122G>A has been reported to cause late-onset autosomal dominant form of the disease in previous studies. However, the middle-aged heterozygous carriers of the mutation in this family showed normal phenotype. Conclusion: The CRX gene has been previously linked to the autosomal dominant form of cone-rod dystrophy. We report incomplete penetrance of CRX gene for autosomal dominant form of the disease. Incomplete penetrance of the mutations may be partly caused by the influence of other genes in the complex genetic network underlying retinal regulation.
Purpose: Cone-rod dystrophy (CRD) is an inherited retinal dystrophy that is transmitted via different modes of inheritance. Mutations in more than 30 genes have been identified to cause the disease. We aimed to investigate the genetic agents of two unrelated cone-rod dystrophy affected Iranian families with autosomal recessive inheritance patterns. Methods: Whole-exome sequencing (WES) was performed for identification of the disease-causing mutations in the probands of both families. The candidate mutations were further confirmed by Sanger sequencing. Samples from five available members of each family were then sequenced for the mutations present in the probands. Comprehensive ocular examinations for all members of the families carrying the mutations were completed by ophthalmologists. Results: We identified a novel premature stop codon c.310C>T in CRX gene in heterozygote form in two symptomatic and two non-symptomatic members of one family (family-A), and a known CRX mutation c.122G>A in homozygote form in another (family B). c.122G>A has been reported to cause late-onset autosomal dominant form of the disease in previous studies. However, the middle-aged heterozygous carriers of the mutation in this family showed normal phenotype. Conclusion: The CRX gene has been previously linked to the autosomal dominant form of cone-rod dystrophy. We report incomplete penetrance of CRX gene for autosomal dominant form of the disease. Incomplete penetrance of the mutations may be partly caused by the influence of other genes in the complex genetic network underlying retinal regulation.
Authors: Saoud Al-Khuzaei; Karl A Z Hudspith; Suzanne Broadgate; Morag E Shanks; Penny Clouston; Andrea H Németh; Stephanie Halford; Susan M Downes Journal: BMC Ophthalmol Date: 2021-04-09 Impact factor: 2.209