UCL Institute of Ophthalmology

Prof Shomi Bhattacharya

Prof Shomi Bhattacharya

Emeritus Proffessor of Experimental Opthalmology

Institute of Ophthalmology

Faculty of Brain Sciences

Joined UCL
1st Aug 1995

Research summary

Molecular Genetics defines a field of study where in the absence of a detectable biochemical defect (true for a majority of inherited diseases), a reverse genetics approach allows the chromosomal assignment and isolation of the disease causing genes. Advent of recombinant DNA technology led to the cloning of chromosome specific DNA markers in the early 1980s. The ability to detect restriction fragment length polymorphisms (RFLPs) in the Human Genome, permitted the use of these markers as genetic tools for linkage studies in families segregating for a particular disease trait. Inherited retinal dystrophies are a major cause of incurable blindness in the Western World. Amongst these a significant proportion is accounted for by a clinically heterogeneous group of diseases collectively known as Retinitis pigmentosa (RP). Based on pedigree analysis, all three modes of Mendelian inheritance (Autosomal dominant, Autosomal recessive and X-linked) have been observed. RP is initially characterised by night blindness and progressive loss of peripheral vision due to the loss of rod photoreceptor cells. As the disease progresses cone cells in the central retina are also involved, often leading to total blindness in later stages of the disease. Decades of research into the biochemical basis of the disease failed to identify even a single causative factor. With the help of recombinant DNA technology, development of X-chromosome specific probes allowed successful mapping of the X-linked form of RP (Ref 1) and laid the foundations of ophthalmic genetic research. Linkage studies demonstrated the existence of at least two genes for XLRP (RP2 and RP3) which eventually facilitated the isolation of these genes through a positional cloning approach (1997/98). With the finding of genetic heterogeneity in XLRP, involvement of multiple genes in the causation of the dominant or recessive forms of the disease was expected.