Abstract
Mutations in the RMRP-gene, encoding the lncRNA component of the RNase MRP complex, are the origin of cartilage-hair hypoplasia. Cartilage-hair hypoplasia is associated with severe dwarfism caused by impaired skeletal development. However, it is not clear why mutations in RMRP RNA lead to skeletal dysplasia. Since chondrogenic differentiation of the growth plate is required for development of long bones, we hypothesized that RMRP RNA plays a pivotal role in chondrogenic differentiation. Expression of Rmrp RNA and RNase MRP protein subunits was detected in the murine growth plate and during the course of chondrogenic differentiation of ATDC5 cultures, where Rmrp RNA expression was found to be correlated with chondrocyte hypertrophy. Genetic interference with Rmrp RNA expression in ATDC5 cultures caused a deregulation of chondrogenic differentiation, with a prominent impact on hypertrophy and changes in pre-rRNA processing and rRNA levels. Promoter reporter studies showed that Rmrp RNA expression responds to chondrogenic morphogens. Chondrogenic trans-differentiation of cartilage-hair hypoplasia fibroblasts was impaired with a pronounced impact on hypertrophic differentiation. Together, our data show that RMRP RNA expression is regulated during different stages of chondrogenic differentiation and indicate that RMRP RNA may play a pivotal role in chondrocyte hypertrophy, with potential consequences for CHH pathobiology.
Highlights
Mutations in the RMRP-gene, encoding the long non-coding RNA (lncRNA) component of the RNase MRP complex, are the origin of cartilage-hair hypoplasia
Expression of Rmrp RNA and RNase MRP protein subunits was detected in the murine growth plate and during the course of chondrogenic differentiation of ATDC5 cultures, where Rmrp RNA expression was found to be correlated with chondrocyte hypertrophy
It has been reported to be involved in mitochondrial DNA replication[2], cleaves pre-rRNA in the internal transcribed spacer 1 (ITS1)[3, 4], plays a role in cell cycle regulation by cleaving cyclin b2 mRNA5, and is able to cleave viperin mRNA6
Summary
Mutations in the RMRP-gene, encoding the lncRNA component of the RNase MRP complex, are the origin of cartilage-hair hypoplasia. Cartilage-hair hypoplasia is associated with severe dwarfism caused by impaired skeletal development. It is not clear why mutations in RMRP RNA lead to skeletal dysplasia. Expression of Rmrp RNA and RNase MRP protein subunits was detected in the murine growth plate and during the course of chondrogenic differentiation of ATDC5 cultures, where Rmrp RNA expression was found to be correlated with chondrocyte hypertrophy. Mutations in the RMRP gene are the cause of a severe form of dwarfism known as the cartilage-hair hypoplasia[14] (CHH: OMIM #250250) – anauxetic dysplasia[15] (AAD: OMIM #607095) spectrum of disorders[16]. Many skeletal abnormalities have been described that are often caused by mutations in genes involved in growth plate development[24]
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