COL1A1 and focal segmental glomerulosclerosis: Glomerular and tubulointerstitial fibrosis is an important feature of FSGS.[27] The ADR‐treated Btg2+/− mice showed a marked increase in renal mRNA levels of extracellular matrix genes Col1a1 and fibronectin accompanied by elevated expression of mesenchymal marker genes α‐SMA and vimentin and decreased expression of epithelial marker protein E‐cadherin (Figure3a–e).