Ontogeny of Ro hYRNAs in human heart.

The Ro complex is composed of three ribonucleoproteins of 60, 54, and 52 kDa. The Ro60 is associated with the 1-5 hYRNAs. Autoantibodies against Ro are found in sera from lupus patients. Lupus frequently presents in female patients during childbearing years and transplacental passage of maternal anti-Ro/La autoantibodies has been implicated in triggering neonatal lupus and congenital heart block (CHB). Since expression of Ro ribonucleoproteins occurs before the onset of CHB, epitope spreading of Ro hYRNAs could arise during cardiac ontogeny, thus maternal autoantibodies would damage a previously developed AV node. To explore the cardiac ontogeny of Ro hYRNAs, embryonic and adult tissues were obtained from legal autopsies. In situ hybridization using oligonucleotides for hY1, hY3, hY4, hY5, and Ro60 was performed on sections of cardiac tissue; their corresponding cDNAs were amplified by RT-PCR. The principal results were as follows: expression of hY4/5RNAs was greater in fetal tissues from 8-12 weeks of development. The subcellular distribution of hYRNAs in embryonic tissues was nucleocytoplasmic, whereas in the adult heart it was cytoplasmic. In conclusion, hYRNAs expression occurs during early cardiac development.