Expression profile of OPA1, the gene associated with autosomal dominant optic atrophy in the developing and adult mammalian retina [Abstract]

Purpose: Autosomal dominant optic atrophy (ADOA) is a primary hereditary optic neuropathy leading to loss of visual acuity. The clinical disease is caused by homozygous null mutations in the OPA1 gene. Northern blots have shown that OPA1 is ubiquitously expressed. However, the fundamental pathology of ADOA is primary degeneration of retinal ganglion cells (RGC's) followed by ascending atrophy of the optic nerve. RGC is the first cell commitment made during the development of the retina. In order to understand the pathophysiology of ADOA, we aimed to (1) assess the expression pattern of OPA1 mRNA and protein during different stages of mouse prenatal and postnatal development and (2) assess if OPA1 expression is retained in adult human tissues and compare OPA1 expression between mouse and human ocular tissues. Methods: We have raised a rabbit antibody to a 24 amino acid region from the C-terminal of the predicted human OPA1 protein. This region is conserved between human and mouse sequences. This antibody was used to perform a detailed immunohistochemistry study of OPA1 expression from E9.5 to postnatal day 12 in C57BLKS mouse embryos and postnatal eyes. In order to localise OPA1 mRNA, in situ hybridisation was carried out using sense (as control) and anti-sense digoxigenin-labelled RNA probes. These probes were generated by in-vitro transcription of cloned inserts representing the 3' end of the human OPA1 gene. Sections of the adult human retina were used to localise and compare human OPA1 expression with the murine expression pattern. Results: In mouse embryos, we have observed that the expression of OPA1 begins as early as E13.5 and continues till postnatal day 12. In adult mouse and human eyes, OPA1 is expressed predominantly in the ganglion cell layer and the inner nuclear layer of the retina as well as the optic nerve. Conclusion: We have observed that OPA1 is expressed from the earliest mouse embryonic stage at which it is possible to distinguish forebrain from the developing eye bud. OPA1 is predominantly expressed in the RGC's and the inner retina. As the retinal ganglion cells are among the first cells to be generated in the vertebrate retina, this suggests a possible role for OPA1 in ganglion cell/retinal development. In order to understand the pathophysiology of ADOA, it is important to assess the relevance of OPA1 in retinal development. No commercial interests. Funded by generous support from The Wellcome Trust, UK and The Frost Charitable Trust, UK