SAMD9L autoinflammatory or ataxia pancytopenia disease mutations activate cell-autonomous translational repression

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 118; no. 34; pp. 1 - 11
• Main Authors: Russell, Amanda J., Gray, Paul E., Ziegler, John B., Kim, Yae Jean, Smith, Sandy, Sewell, William A., Goodnow, Christopher C.
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 24.08.2021
• Subjects: Amino acids; Anemia; Ataxia; Ataxia - genetics; Ataxia - pathology; Basal ganglia; Biological Sciences; Child; Children; Female; Fluorescence; Frameshift mutation; Fusion protein; Ganglia; Gene Expression Regulation; Gene sequencing; Genomes; Green fluorescent protein; Heterozygote; Homology; Humans; Infant, Newborn; Inflammation; Inflammatory diseases; Interferon; Lymphocytes B; Male; mRNA; Mutation; Mutation, Missense; Myelodysplastic Syndromes - genetics; Myelodysplastic Syndromes - pathology; Neonates; Neutrophilia; Nucleotides; Oligomerization; Pancytopenia; Pancytopenia - genetics; Pancytopenia - pathology; Protein Biosynthesis; Proteins; Red fluorescent protein; Thrombocytopenia; Translation; Tumor Suppressor Proteins - genetics; Viruses; Whole genome sequencing; pathogen-associated molecular pattern receptor; translational repression; nucleotide-binding and oligomerization domain; autoinflammatory disease; virus sensing
• DOI: 10.1073/pnas.2110190118
• ISSN: 0027-8424

Sterile α motif domain-containing protein 9-like (SAMD9L) is encoded by a hallmark interferon-induced gene with a role in controlling virus replication that is not well understood. Here,we analyze SAMD9L function from the perspective of human mutations causing neonatal-onset severe autoinflammatory disease. Whole-genome sequencing of two children with leukocytoclastic panniculitis, basal ganglia calcifications, raised blood inflammatory markers, neutrophilia, anemia, thrombocytopaenia, and almost no B cells revealed heterozygous de novo SAMD9L mutations, p.Asn885Thrfs*6 and p.Lys878Serfs*13. These frameshift mutations truncate the SAMD9L protein within a domain a region of homology to the nucleotide-binding and oligomerization domain (NOD) of APAF1, ∼80 amino acids C-terminal to the Walker B motif. Single-cell analysis of human cells expressing green fluorescent protein (GFP)-SAMD9L fusion proteins revealed that enforced expression ofwild-type SAMD9L repressed translation of red fluorescent protein messenger RNA and globally repressed endogenous protein translation, cell autonomously and in proportion to the level of GFP-SAMD9L in each cell. The children’s truncating mutations dramatically exaggerated translational repression even at low levels of GFP-SAMD9L per cell, as did a missense Arg986Cys mutation reported recurrently as causing ataxia pancytopenia syndrome. Autoinflammatory disease associated with SAMD9L truncating mutations appears to result from an interferon-induced translational repressor whose activity goes unchecked by the loss of C-terminal domains that may normally sense virus infection.