Lrrc34, a Novel Nucleolar Protein, Interacts withNpm1andNcland Has an Impact on Pluripotent Stem Cells

Abstract

The gene Lrrc34 (leucine rich repeat containing 34) is highly expressed in pluripotent stem cells and its expression is strongly downregulated upon differentiation. These results let us to suggest a role for Lrrc34 in the regulation and maintenance of pluripotency. Expression analyses revealed that Lrrc34 is predominantly expressed in pluripotent stem cells and has an impact on the expression of known pluripotency genes, such as Oct4. Methylation studies of the Lrrc34 promoter showed a hypomethylation in undifferentiated stem cells and chromatin immunoprecipitation-quantitative polymerase chain reaction analyses of histone modifications revealed an enrichment of activating histone modifications on the Lrrc34 promoter region. Further, we could verify the nucleolus-the place of ribosome biogenesis-as the major subcellular localization of the LRRC34 protein. We have verified the interaction of LRRC34 with two major nucleolar proteins, Nucleophosmin and Nucleolin, by two independent methods, suggesting a role for Lrrc34 in ribosome biogenesis of pluripotent stem cells. In conclusion, LRRC34 is a novel nucleolar protein that is predominantly expressed in pluripotent stem cells. Its altered expression has an impact on pluripotency-regulating genes and it interacts with proteins known to be involved in ribosome biogenesis. Therefore we suggest a role for Lrrc34 in ribosome biogenesis of pluripotent stem cells.

A genome-wide association study yields five novel thyroid cancer risk loci

“…At 3q26.2, the lead variant, rs6793295[T] (OR=1.23; P =2.7 × 10 −8 ), is a missense mutation (p.Ser249Gly) in LRRC34 and has (either itself or through a highly correlated variant) been previously reported to associate with several diseases and other traits, specifically: pulmonary fibrosis 27 , bladder cancer 28 , multiple myeloma 29 30 and telomere length 25 31 32 . Little is known about the function of LRRC34 but its role has been suggested to be in ribosome biogenesis in pluripotent stem cells 33 . No significant association with expression of any gene is reported for rs6793295[T] in thyroid tissue, according to GTEx, but the strongest eQTL associations are with decreased expression of LRRC34 in transformed fibroblasts, tibial tissue and subcutaneous adipose tissue ( β =−0.35 s.d., −0.39 s.d., and −0.28 s.d., respectively; P =1.5 × 10 −8 , 6.7 × 10 −8 and 7.9 × 10 −8 , respectively).…”

Efficient Killing of Murine Pluripotent Stem Cells by Natural Killer (NK) Cells Requires Activation by Cytokines and Partly Depends on the Activating NK Receptor NKG2D

“…In ESC BTL1 cells, the pluripotency marker proteins OCT4, SALL4, SOX2, KLF4, and ZPF206 were detected by immunoblotting and α-tubulin served as loading control. The antibodies used are given in Table S1 in Supplementary Material, and the immunoblotting was done as described previously ( 53 ).…”

“…The iPSC lines and their differentiation products were analyzed by qualitative RT-PCR as described previously ( 10 , 54 ). The expression of pluripotency genes in ESC BTL1 cells was determined by qPCR as described before ( 53 ).…”

Ribosome and Translational Control in Stem Cells

“…Although the molecular impact of UBR2 on ribosome biogenesis has not been addressed, both UBR2 and UBR5 depletion cause a p53 pathway-dependent reduction in HSC and ESC proliferation. Similarly, the nucleolar protein LRRC34 is enriched in mouse ESCs, interacts with two important RBFs, NCL and NPM1, and is required for pluripotent cell proliferation [94].…”