Abstract
Purpose: :
To determine the transcriptome profiling of the human ciliary body with the purpose of identifying novel genes abundantly expressed, involved in metabolic processes and genes of neural and retinal origin.
Methods: :
The ciliary body and retina were excised 24h postmortem from adult human donors. Total RNA was isolated with TRIzol and further purified with Qiagen RNeasy. The quality of the RNA was verified with a bioanalizer and samples with RIN scores above 7.5 were further processed to examine the whole-genome expression profiling using the Illumina BeadChip array platform. Differences in gene expression between tissues were expressed as fold-change. Quantitative RT-PCR was further used to validate differences of expression between tissues.
Results: :
Out of approximately 40,000 transcripts registered in the Illumina platform, 2959 genes were overexpressed in the ciliary body when compared to the retina, 9333 genes were equally expressed in both tissues, and 2858 genes were subexpressed. Among the genes particularly enriched in the ciliary body included: apolipoprotein D (184-fold), lipocalin 2 (92-fold), opticin (65-fold), myoclin (48-fold), prostaglandin D2 synthase (12.7-fold), bone morphogenetic protein 4 (10.6-fold), alpha-2-macrogobulin (9.4-fold), GABA-A receptor epsilon (8.7-fold), paired-liked homeodomain transcription factor Pitx2 (8.12-fold), retinol binding protein 1 (6.5-fold), hydroxysteroid (17-beta) dehydrogenase 2 (6.1-fold), beta-2-microglobulin (5.7-fold), 3-alpha hydroxysteroid dehydrogenase, type II (5.3-fold), gastrin-releasing peptide (4.3-fold), secretogranin V (7B2) (4.2-fold), nestin (3.2-fold); cholesterol 25-hydroxylase (2.2-fold); galanin (1.5-fold); retinol dehydrogenase 14 (1.4-fold) and glutamate (EAAT1, EAAT5), betaine/GABA (2.3-fold), and GABA (GAT2) (1.3-fold) transporters. These quantitative differences were also validated by qRT-PCR.
Conclusions: :
Collectively, these results provide molecular support of metabolic pathways in the ciliary body associated with the transport and metabolism of cholesterol, retinoids, oxidoreduction of steroid hormones, prostaglandins, detoxification of aldehydes and ketones, synthesis and processing of propeptides. It suggests also a potential glutamatergic and GABA signaling systems and the expression of markers restricted to neural and retinal progenitor cells.
Keywords: gene microarray • ciliary body • metabolism