No COL4A3 staining was detected indicating that focal absence of α1.α1.α2(IV) does not lead to compensatory α3.α4.α5(IV) expression (Fig. 3B), in contrast to the continued expression of α1.α1.α2(IV) in response to absence of α3.α4.α5(IV) in some Alport syndrome patients (14). This evidence concerns the gene COL4A3 and Alport syndrome.