The complement regulatory receptor CRIT is expressed in the developing kidney

The regulatory receptor complement receptor inhibitor trispanning (CRIT), on binding complement C2, is able to limit the amount of C3 convertase formed on the surface of cells. Recently CRIT was shown to be expressed in highly differentiated cells including glomerular podocytes in the kidney, keratinocytes in oesophagus and sertoli cells in the testis. The pattern of CRIT mRNA transcription in adult kidney corresponds with expression of CRIT protein in glomerular podocytes, and in a mature podocyte cell line. CRIT mRNA and protein are expressed in fetal kidney from 14 weeks’ gestation with increasing expression levels at gestational week 21. Some expression of CRIT was noted in parietal epithelial cells in the Bowman's capsule where podocyte precursor cells form, but only in the more immature glomerulus. Our results indicate that besides complement regulation, CRIT may play a role in podocyte maturation.