Ribosomal protein mutations in Korean patients with Diamond-Blackfan anemia

Abstract

Diamond-Blackfan anemia (DBA) is a congenital bone marrow failure syndrome characterized by hypoproliferative anemia, associated physical malformations and a predisposition to cancer. DBA has been associated with mutations and deletions in the large and small ribosomal protein genes, and genetic aberrations have been detected in ∼50–60% of patients. In this study, nine Korean DBA patients were screened for mutations in eight known DBA genes (RPS19, RPS24, RPS17, RPS10, RPS26, RPL35A, RPL5 and RPL11) using the direct sequencing method. Mutations in RPS19, RPS26 and RPS17 were detected in four, two and one patient, respectively. Among the mutations detected in RPS19, two mutations were novel (c.26T>A, c.357-2A>G). For the mutation-negative cases, array-CGH analysis was performed to identify copy-number variations, and no deletions involving the known DBA gene regions were identified. The relative mRNA expression of RPS19 estimated using real-time quantitative PCR analysis revealed two- to fourfold reductions in RPS19 mRNA expression in three patients with RPS19 mutations, and p53 protein expression analysis by immunohistochemistry showed variable but significant nuclear staining in the DBA patients. In conclusion, heterozygous mutations in the known DBA genes RPS19, RPS26 and RPS17 were detected in seven out of nine Korean DBA patients. Among these patients, RPS19 was the most frequently mutated gene. In addition, decreased RPS19 mRNA expression and p53 overexpression were observed in the Korean DBA patients, which supports the hypothesis that haploinsufficiency and p53 hyperactivation represent a central pathway underlying the pathogenesis of DBA.

A functional assay for the clinical annotation of genetic variants of uncertain significance in Diamond-Blackfan anemia

“…Table S1). Thirteen of the VUS have already been found to be pathogenic by published functional studies (Angelini et al., ; Badhai et al., ; Chatr‐Aryamontri et al., ; Chae et al., ; Choesmel et al., ; Cmejlova et al., ; Da Costa et al., ; Gazda et al., ; Hamaguchi et al., ; Idol et al., ;) (Supp. Table S1) and so were not tested in our study.…”

“…The DBA database (Boria et al., , ) included 129 RPS19 mutations in 219 patients at its last update in 2010. We reviewed the literature to collect additional RPS19 mutations identified more recently and now have a total of 165 different RPS19 mutations reported in 313 DBA patients (Arbiv et al., ; Chae et al., ; Da Costa et al., ; Delaporta et al., ; Errichiello et al., ; Farrar et al., ; Gerrard et al., ; Ichimura et al., ; Konno et al., ; Kuramitsu et al., ; Landowski et al., ; Ozono et al., ; Pospisilova et al., ; Quarello et al., ; Smetanina et al., ; Solomon et al., ; Tsangaris et al., ; van Dooijeweert et al., ; Wang et al., ; Zhang et al., ). For our study, we selected only those variants for which there was no strong evidence of pathogenicity according to the genetic criteria outlined in Materials and Methods, and obtained 47 VUS reported in 122 patients (39% of RPS19‐mutated patients, approximately 10% of all DBA patients).…”

Current insights into inherited bone marrow failure syndromes

“…Haploinsufficiency of RPs results in ribosome stress and activation of the TP53 tumor suppressor pathway, which is thought to be the main cause of clinical manifestations27). Decreased RPS19 mRNA expression and p53 overexpression were also seen in Korean DBA patients, supporting the idea that haploinsufficiency and p53 overactivation are the central pathways underlying the pathogenesis of DBA26).…”

“…Mutations in RPL5 , RPL11 , and RPS17 were also detected 25) . A recent study investigated the genetic abnormalities in nine Korean DBA patients and noted that seven distinct mutations, including three novel mutations, were identified in three RP genes, RPS19 (4/7), RPS26 (2/7), and RPS17 (1/7) 26) . Haploinsufficiency of RPs results in ribosome stress and activation of the TP53 tumor suppressor pathway, which is thought to be the main cause of clinical manifestations 27) .…”

Ribosomal Protein Rps26 Influences 80S Ribosome Assembly in Saccharomyces cerevisiae

“…Interest in Rps26 was aroused recently due to its possible involvement in the pathogenesis of Diamond-Blackfan anemia, an inherited human bone marrow failure syndrome, characterized by the development of anemia during childhood ( 12 ). Indeed, numerous studies demonstrated that mutations in several genes encoding ribosomal proteins, including RPS26a/b , might be linked to Diamond-Blackfan anemia ( 13 – 15 ). In addition, Rps26 was shown to participate in a variety of cellular processes not directly associated with translation, such as p53 activity, endoplasmic reticulum (ER) stress, the NEDD8 pathway, nonsense-mediated mRNA decay, and filamentous growth ( 2 , 11 , 16 – 18 ).…”