RSAD2 and cartilage-hair hypoplasia: In concert with viperin mRNA as a substrate for RNase MRP cleavage, viperin expression levels have been described to be increased after knockdown of protein components of the RNase MRP complex in HEp-2 cells (2), in leukocytes of CHH patients (10), and recently we demonstrated that viperin expression is also up-regulated after knockdown of RMRP RNA in chondrogenic differentiating ATDC5 cells (11).