A disease-linked lncRNA mutation in RNase MRP inhibits ribosome synthesis

Mutations in the non-coding RNA RMRP cause primary immunodeficiency. Robertson et al show that a disease-associated mutation in RMRP impairs pre-ribosomal RNA processing and reduces ribosome abundance, establishing this disorder as a ribosomopathy. RMRP encodes a non-coding RNA forming the core of the RNase MRP ribonucleoprotein complex. Mutations cause Cartilage Hair Hypoplasia (CHH), characterized by skeletal abnormalities and impaired T cell activation. Yeast RNase MRP cleaves a specific site in the pre-ribosomal RNA (pre-rRNA) during ribosome synthesis. CRISPR-mediated disruption of RMRP in human cells lines caused growth arrest, with pre-rRNA accumulation. Here, we analyzed disease-relevant primary cells, showing that mutations in RMRP impair mouse T cell activation and delay pre-rRNA processing. Patient-derived human fibroblasts with CHH-linked mutations showed similar pre-rRNA processing delay. Human cells engineered with the most common CHH mutation (70(AG) in RMRP) show specifically impaired pre-rRNA processing, resulting in reduced mature rRNA and a reduced ratio of cytosolic to mitochondrial ribosomes. Moreover, the 70(AG) mutation caused a reduction in intact RNase MRP complexes. Together, these results indicate that CHH is a ribosomopathy.

Automated summary

Mutations in the non-coding RNA RMRP cause primary immunodeficiency and impair the processing of pre-ribosomal RNA, resulting in reduced ribosome abundance. This study establishes that this disorder, known as Cartilage Hair Hypoplasia, is a ribosomopathy. The mutations in RMRP also delay T cell activation and affect pre-rRNA processing.