Ataxia-telangiectasia fibroblasts have less fibronectin mRNA than control cells but have the same levels of integrin and beta-actin mRNA.

The expression of fibronectin, integrin and beta-actin genes in skin fibroblasts from patients with the genetic disorder ataxia-telangiectasia (A-T) was studied. These three genes were selected because their protein products contribute to the shape and function of the fibroblast. Expression of mRNA by these genes was compared with that in fibroblasts from normal individuals and from patients with the genetic disorder, hereditary hemorrhagic telangiectasia (HHT). A-T fibroblasts were found to produce less fibronectin mRNA than normal and HHT fibroblasts. A-T fibroblasts senesce around passage level 15 while normal and HHT fibroblasts can be propagated for many more passages in vitro. However, the expression of the integrin gene in A-T fibroblasts was similar to that in normal fibroblasts, while the beta-actin gene was expressed at a higher level. The increased beta-actin mRNA levels were similar in fibroblasts of patients with the two genetic disorders, A-T and HHT, but higher than in normal fibroblasts. HHT fibroblasts differed markedly from A-T fibroblasts in having a high level of fibronectin and integrin mRNA expression. The results indicate that regulation of the fibronectin gene in A-T fibroblasts differs from that of the integrin and beta-actin genes, and that the decline in fibronectin mRNA may be linked to the shortened in vitro life-span of these cells.