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RPL15 mutations in DBA
Results
Identification of novel RPL15 mutations in 6 patients within EuroDBA registries
Approximately 30% of all registered DBA patients who have been tested for mutations in the most common DBA-linked genes (RPS19, RPL5, RPL11, RPS10, RPS26, RPS7, RPS17, RPS24, and RPL35a) still do not have an established genotype. Because a whole gene deletion of RPL15 has been reported before in one DBA patient but not in our cohorts,23 we used targeted Sanger sequencing of RPL15 to determine if mutations in this gene could be driving disease in patients without an established geno- type. The national patient registries from EuroDBA part- ners in Germany, France, Italy and Israel were included in this study. As of November 2017, these cohorts represent a total of 985 patients. A complete description of the his- tory and composition of the EuroDBA consortium has been recently published.45 Study outline and screening strategy are illustrated in Online Supplementary Figure S1.
Four unrelated DBA patients from the German, and one each from the French and Israeli registries were identified carrying mutations in the RPL15 gene (NM_001253379.1), which encodes ribosomal protein eL15/RPL15 (Figure 1A and B). Out of the 6 RPL15-mutated patients, 3 unrelated patients (P1-3) carried the same novel indel mutation c.242dupA altering the tyrosine at position 81 to a stop codon: p.Tyr81* (Table 1 and Online Supplementary Table S1). Patient 4 (P4) carried another stop-gain mutation in RPL15 resulting in an even earlier protein truncation: c.85C>T; p.Gln29*. The Exome Aggregation Consortium (ExAC) reports that RPL15 is very intolerant to loss-of- function mutations with no reported cases present in over 60,000 individuals (pLI score =0.96), strongly suggesting the novel mutations p.Gln29* and p.Tyr81* found in our patients are highly deleterious (Online Supplementary Table S1). In addition, the analysis of family trios revealed that hotspot mutations arose de novo in two families (Table 1 and Figure 1A), while one patient (P1/DE071) inherited the mutation from her father who had been categorized as
A
B
Figure 1. Mutations in RPL15 are identified in patients with Diamond-Blackfan anemia (DBA). (A) Six unrelated pedigrees of individuals affected by DBA associated with RPL15 mutations. All families have one DBA-affected individual who is also a mutation carrier, as indicated with filled squares (male) or circles (female). Unaffected individuals are indicated by unfilled symbols. Unaffected mutation carriers are denoted by a dot symbol (). NA: unaffected family members who were not investigated for the presence of mutations. Families 1-4 harbor heterozygous stopgain mutations in RPL15; families 5-6 carry heterozygous missense RPL15 mutations. (B) Schematic representation of human RPL15 depicting localization of the mutations identified in families 1-6.
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