Abstract
Purpose :
Vascular Endothelial Growth Factor (VEGF) is the key cytokine involved in the pathology of diabetic retinopathy (DR) and genetic variations, particularly in its promoter and UTR regions have been known to be associated with DR in various populations. However, not much has been studied on the genetic variations in the coding region of the gene. Therefore, the purpose of our study was to examine the genetic variations in the coding region of VEGF gene to detect their association with DR in an Indian population.
Methods :
We performed targeted sequencing of the coding region of VEGF gene in 45 type 2 diabetes patients without retinopathy (diabetic controls - DC) and 55 type 2 diabetes patients with retinopathy (DR). We used GeneRead DNAseq Targeted Custom Panels V2 (Qiagen) for targeted enrichment followed by sequencing on Next Seq500 platform of Illumina. The adapter sequences, low-quality bases (Q<20) and reads lesser than 50 bp were removed. The processed data was aligned to the human reference genome by Bowtie2 software, subsequently analyzed by SAMtools for variant identification. For variant calling, we considered the minimum read depth 10 and allele ratio 80:20.
Results :
Demographic and clinical data of the study suggested that BMI, duration of diabetes, blood pressure, history of family diabetes etc. were non-significantly different between DC and DR groups. However, hypertensive patients were significantly higher in DR group. Alignment statistics showed average 56% of the targeted bases were covered at 10x, indicating low coverage of the target region. We observed total eleven variations in different patients out of which ten were located in exon1 and were not previously reported in the literature. Allowing 20% missing data, we found one variation (6:43738814) in one DC patient and other two variations, rs541900145 and 6:43738809 in two different DR patients.
Conclusions :
Our study indicated that genetic variation in the coding region of VEGF gene was not a frequent event. Further, the observed genetic variations might not confer risk to develop retinopathy in Indian type 2 diabetic patients.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.