Identification of novel mutations by targeted exome sequencing and the genotype-phenotype assessment of patients with achromatopsia.
BACKGROUND
Achromatopsia (ACHM) is a severe congenital autosomal recessive retinal disorder caused by loss of cone photoreceptors. Here, we aimed to determine the underlying genetic lesions and phenotypic correlations in two Chinese families with ACHM.


METHODS
Medical history and clinical evaluation were obtained from both families. Targeted exome sequencing (TES) was performed on 201 disease-causing genes of inherited retinal dystrophies to screen for ACHM causative mutations in the two probands.


RESULTS
The compound heterozygous mutations in CNGA3 (c.1074G > A, p.W358X; c.1706G > A, p.R569H) were identified in the first proband, and a novel homozygous mutation (c.968C > A, p.A323D) was detected in the other pedigree. The proposed topological model of the CNGA3 polypeptide suggested that the missense mutations primarily affected the transmembrane helix 5 and the cGMP-binding domain, respectively. Crystal structure modeling of the cyclic nucleotide-gated cation channel α-3 (CNGA3) protein encoded by the CNGA3 gene revealed an abnormal combined structure generated by R569H.


CONCLUSIONS
We firstly used the TES approach to identify genetic alterations in patients with ACHM. We uncovered three mutations in CNGA3, including one novel mutation. Our results not only expand the genotypic spectrum for CNGA3 mutations, but also demonstrate that the TES approach is a valuable tool for molecular diagnosis.
The Eye Hospital of Wenzhou Medical University, The State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health, Wenzhou, 325027, China. lifenfen2@qq.com.
Fen-Fen
FF
Li
The Eye Hospital of Wenzhou Medical University, The State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health, Wenzhou, 325027, China. hxf@mail.eye.ac.cn.
Xiu-Feng
XF
Huang
The Eye Hospital of Wenzhou Medical University, The State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health, Wenzhou, 325027, China. cj@mail.eye.ac.cn.
Jie
J
Chen
The Eye Hospital of Wenzhou Medical University, The State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health, Wenzhou, 325027, China. yxd@mail.eye.ac.cn.
Xu-Dong
XD
Yu
The Eye Hospital of Wenzhou Medical University, The State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health, Wenzhou, 325027, China. zmqlyllh@126.com.
Mei-Qin
MQ
Zheng
The Eye Hospital of Wenzhou Medical University, The State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health, Wenzhou, 325027, China. lufan@mail.eye.ac.cn.
Fan
F
Lu
The Eye Hospital of Wenzhou Medical University, The State Key Laboratory Cultivation Base and Key Laboratory of Vision Science, Ministry of Health, Wenzhou, 325027, China. jinzb@mail.eye.ac.cn.
Zi-Bing
ZB
Jin
Department of Ophthalmology, Eye and ENT Hospital of Fudan University, 83 Fen Yang Road, Shanghai, 200031, People's Republic of China. dekang.gan@fdeent.org.
De-Kang
DK
Gan
D000328:Adult; D000595:Amino Acid Sequence; D002648:Child; D002681:China; D003117:Color Vision Defects / Q000235:genetics* / Q000503:physiopathology*; D019295:Computational Biology; D018360:Crystallography, X-Ray; D054815:Cyclic Nucleotide-Gated Cation Channels / Q000235:genetics; D004252:DNA Mutational Analysis / Q000379:methods*; D059472:Exome; D005192:Family Health; D005260:Female; D005808:Genes, Recessive; D056726:Genetic Association Studies; D006579:Heterozygote; D006720:Homozygote; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D009154:Mutation; D020125:Mutation, Missense; D010375:Pedigree; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism; D058499:Retinal Dystrophies / Q000235:genetics
C518238:CNGA3 protein, human; D054815:Cyclic Nucleotide-Gated Cation Channels