Clinical And Molecular Genetic Research On Rare Autosomal Dominant Macular Dystrophy

Purpose:To summarize the clinical manifestations of rare autosomal dominant macular dystrophy?ADMD?and to identify the pathogenic genes and variants,as well as study the genotypes and phenotypes correlation of ADMD.Methods:Twelve patients from six unrelated families diagnosed with macular dystrophy at the Ophthalmic Genetics Clinic of Peking Union Medical College Hospital?PUMCH?during 2011 to 2017 were enrolled.Clinical and genetic study were conducted on the participants.1.Clinical study:Family history and medical history of the patients were taken in detail.Each patient underwent ophthalmic examinations including best corrected visual acuity?BCVA?according to decimal Snellen charts,slit-lamp biomicroscopy,dilated indirect ophthalmoscopy.Fundus photography,visual field?VF?,optical coherence tomography?OCT?,electroretinogram?ERG?,electrooculography?EOG?and fundus autofluorescence?FAF?were also performed if possible.2.Genectic study:Venous blood from the patients and their available family members were collected and genomic DNA were isolated using commercial kit according the manufacturer's protocol.The targeted capture sequencing and whole genome sequencing were performed on the selected patients.Then co-segregation was performed among the pedigrees to further confirm the causal variant.Results:Twelve patients from six pedigrees were enrolled,among which 7 were male and 5 were female.The age of the patients ranged from 4 to 62 years old and the median age is 21 years old.1.Clinical manifestations:Twelve patients were diagnosed with ADMD.Their best corrected visual acuity?BCVA?range from 0.07 to 1.2.The fundus showed a range of atrophic lesion in macular area with pigmentation on the edge of or in the lesion.Autofluorescence manifested low fluorescence of the macular area with high surrounding fluorescence?dots,rings?.Different levels of macular atrophy were shown in the OCT.EOG was characterized by decreased Arden ratio and ERG is within normal limits.2.Molecular genetics results:Targeted capture sequencing results revealed that patient SRF₇32 has two variants in the gene including EFEMP1?c.1033C>T?p.R345W??and C1QTNF5?c.G707A?p.Trp236Ter??and the patient SRF₄76 has a variant in the SNRNP200 gene?c.1118G>A?p.Arg373Gln??.The EFEMP1 variant was identified in individuals including SRF₇32?SRF₈57?SRF₁155 and was not found in SRF₁154?normal?.C1QTNF5 variant was found in individuals including SRF₇32?SRF₈57?SRF₁155 and SRF₁154?normal?.In the SRF₇32 family,individuals SRF₁155 and SRF₁154 were normal.WGS results revealed that all patients in family SRF₂2 including SRF₂2,SRP₂3 and SRF₂4 have the duplication in the chromosome 6.Consistent with the known duplications leading to NCMD,the duplication was also located in the MCDR1 locus.Conclusion:The next generation sequencing including whole-genome sequencing and targeted capture sequencing are efficient method for molecular diagnosis of the patients.Our study reveal that EFEMP1 gene was the pathogenic gene of SRF₇32 family which was diagnosed as Malattia leventinese macular dystrophy.All patients in SRF₂2 family had tandem duplication variation on chromosome 6?chr6:100033285-100067462?,so that SRF₂2 family was diagnosed with NCMD,which is the first Chinese NCMD family.