Disease processes, genes involved

Cyclosporin-A In 1972, the immunosuppressive effect of cyclosporin-A, an antibiotic secreted by some fungi, was discovered. Other antibiotics also have immunosuppressive effects. They interfere with proliferation of T-helper cells by preventing the entry of a transcription factor into the nucleus. This prevents transcription of the genes involved in the proliferative process. Their use is restricted to patients after transplantation, since there are serious side-effects, for example, toxic effects on the mbules of the kidney. This precludes their use for treatment of non-life-threatening autoimmune diseases. 

The possible involvement in disease of relatively common alleles of a large number of loci, each with a relatively small effect overall, requiring study of many hundreds, and usually thousands, of affected sib pairs to establish linkage, can explain this phenomenon (24,43,44). The additional possible involvement in some cases of complex disease of relatively rare variants further confounds our abilities to detect all genes involved in the disease process. 

The potential power of association studies to detect disease genes depends on several unknown parameters, and cannot be determined accurately, especially given that common genetic variants may often be involved in complex diseases (50,70-73). For example, the nature of mutations involved in the disease process will influence the power of association studies to detect disease genes (70). Also, the power of genome association scans will vary across the genome, due to variation in LD values (10), as well as between populations. The full development of SNPs will eventually permit... 

Gene expressions may differ in different cell types (for example, in normal and disease tissues). These may occur even for genes not involved in the disease process (housekeeping genes) which are functional in all cells (see, for example,... 

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