Tubulointerstitial nephritis antigen: An extracellular matrix protein thatselectively regulates tubulogenesis vs. glomerulogenesis during mammalian renal development

Tubulointerstitial nephritis antigen (TIN-ag) is an extracellular matrix pr otein and is expressed in the renal tubular basement membranes. Its role in metanephric development was investigated. TIN-ag cDNA, isolated from the n ewborn mouse library, had an ORF of 1,425 nucleotides, a putative signal se quence, and an ATP/GTP-binding site. The translated sequence had approximat e to 80% identity with rabbit TIN-ag. Among various tissues, TIN-ag mRNA wa s primarily expressed in the newborn kidney. In. the embryonic metanephros, TIN-ag expression was confined to the distal convolution or pole of the S- shaped body, the segment of the nascent nephron that is the progenitor of r enal tubules. Treatment with TIN ag antisense oligodeoxynucleotide induced dysmorphogenesis of the embryonic metanephroi, malformation of the S-shaped body, and a decrease in the tubular population, whereas the glomeruli were unaffected. Treatment also led to a decrease of TIN-Ag mRNA, de novo synth esis of TIN-ag protein, and its antibody reactivity. The mRNA expression of glomerular epithelial protein 1 (a marker for renal podocytes), anti-hepar an-sulfate-proteoglycan antibody reactivity, and wheat germ agglutinin lect in staining of the metanephros were unaffected. The anti-TIN-ag antibody tr eatment also caused deformation of the S-shaped body and a reduction in the tubular population, whereas the glomeruli were unchanged. The data suggest that the TIN-ag, unlike other basement membrane proteins, selectively regu lates tubulogenesis, whereas glomerulogenesis is largely unaffected.