1. Background of Programme Area and Objectives

1.1 The genetic register of patients with a variety of inherited eye diseases at Moorfields Eye Hospital, provides a unique resource and the opportunity to undertake molecular genetic investigations to identify the genes involved in these diseases.

1.2 Monogenic retinal disorders including retinal dystrophies, chorioretinal dystrophies and stationary retinopathies although less common than AMD and diabetic retinopathy, affect approximately 1 in 2000 persons. Because these disorders are untreatable and often severe, they place a high burden in terms of rehabilitation and care for those people affected.

1.3 Over and above the direct burden of disease, these disorders also allow a special opportunity for the identification of key molecules in retinal biology and disease. Through the strategies of linkage analysis and physical mapping, many causative genes for retinal disease have been determined; each discovery elucidates a key molecule in retinal biology which directs further research into protein structure, interaction, function and pharmacology. To date, over 69 such genes have been characterised as causing retinal disease and a further 59 distinct chromosomal loci have also been identified. The impact of these discoveries on all retinal disease and the development of novel therapies is likely to be highly promising if funding is directed towards a research programme targeted at strategies that follow-on from gene discovery.

   2. Programme plan

2.1 Each newly discovered gene generates further research opportunities. Downstream projects include:

· Determining the expression profile of the gene in different tissues;
· Characterising the structure of the expressed protein and localisation of the protein within the cell,
· The identification of interacting and homologous proteins; and
· The effect on protein function, structure and interaction of the genetic mutations found in families from the clinic.

Only with the further investigation of gene function and protein biochemistry will understanding emerge to develop therapeutic strategies.

2.2 Further genes and loci remain to be found for retinal disease, and although the techniques for linkage analysis and positional cloning have improved, the standard technologies of DNA and RNA analysis and sequencing remain expensive and hence the costs of such research remain large. The experimentation needed to realise those laboratory projects downstream of gene discovery include the use of animal models. Animal models with naturally occurring mutations in retinal genes or those with generated knock-out mutations, allow the assessment of novel treatment approaches. Such techniques include gene-replacement therapy in which the missing gene is inserted into a viral vector and injected into the animal (for instance the sub-retinal space or vitreous cavity). Encouraging results have been shown for the replacement of the rds gene in rds -/- mice, and more recently the RPE65 gene in RPE65 -/- dogs (Nature Genetics May 2001). This approach is a paradigm for the treatment of disorders that occur due to reduced gene dosage in the retina in humans (the majority of autosomal and X-linked recessive retinal disease).

2.3 Other approaches include the insertion of genes designed to express ribozymes capable of catalysing mutant alleles in vivo such as those with missense mutations that cause the majority of autosomal dominant retinal disease. Also, the use of genes and proteins designed to interfere with and suppress apoptosis of retinal cells (such as ciliary neurotrophic factor - CNTF) is a promising strategy. Novel drugs designed on the basis of the laboratory investigations described above will also require evaluation in animal models as in the recent evaluation of systemic diltiazem on the retinal degeneration of mice lacking rod photoreceptor phosphodiesterase (rd-/-).

2.4 Following the determination of causative genes, in parallel with further laboratory investigation, there remains an important opportunity to study the clinical phenotype of resulting disease in the light of genetic discovery. The work of the interested clinician, in concert with the genetic laboratory, can identify subsets of patients with particular molecular diagnoses and carefully characterise the disease phenotype given such specific molecular data. Only with these phenotype-genotype correlation studies will the ultimate effect of genetic mutation on human biology be elucidated and the appropriate families and individuals for future novel therapies identified. Such careful clinical characterisation of selected patients and families in terms of retinal imaging, psychophysics and electrophysiology is not inexpensive and requires substantial devoted funding.

2.5 Research Priorities

· Elucidation of novel genes and chromosomal loci causing monogenic retinal disease.
· Evaluation of gene function, protein structure, chemistry and interaction in cell systems and animal models.
· Elucidation of novel therapies including gene replacement therapy, modulation of retinal cell apoptosis, catalysis of harmful gene mutations in vivo (ribozymes) and retinal cell transplantation.
· Phenotype-genotype characterisation of monogenic retinal disorders

  3. Future development work in the programme during 2002/3

3.1 Three forms of biological treatment are being developed in the Institute of Ophthalmology, namely the use of growth factors to delay cell death, gene transfection and cell transplantation. All have been shown to modify naturally occurring retinal degeneration. If these become applicable the availability of the genetic register, and a large body of well-characterised patients will be crucial to the identification of those suitable for treatment. We have established longitudinal recording of visual function in some patients to establish the speed of visual loss. This information will be important in the design of therapeutic trials.