The genetics of systemic lupus erythematosus

There is a genetic predisposition to human systemic lupus erythematosus (SLE). The genes that contribute to susceptibility are, for the most part, unknown. The introduction of new gene mapping techniques has opened the way to explore lupus genetics on a genome-wide basis.

Microsatellites are simple sequence repeats widely distributed throughout eukaryotic genomes. They exhibit length variation. This polymorphism can be exploited to provide a panoply of genome-wide markers. Thereby, loci linked with lupus have been mapped in lupus-prone mouse strains and in recently published studies in multi-case human families.

More than 20 non-MHC (major histocompatibility complex) loci have now been linked with murine lupus. Nine non-MHC loci have been corroborated in human SLE. Some of the mouse intervals are syntenic with human loci raising the tantalizing possibility of common susceptibility genes. Although we await the results of formal gene identification, functional studies in back-cross and congenic analyses indicate that, in the mouse at least, disease genes act at multiple levels in disease development.

A large number of genes are involved in the pathogenesis of SLE. The data also suggest that even the MHC contribution is multiple. Having mapped disease loci, geneticists now face the task of closing down on the actual aetiological alleles and demonstrating how they might operate. This undertaking will add significantly to our understanding of disease development.