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

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 of wild-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.

Extracellular adenosine 5'-triphosphate and lipopolysaccharide induce interleukin-1ß release in canine blood.

Binding of extracellular adenosine 5'-triphosphate (ATP) or lipopolysaccharide (LPS) to the damage-associated molecular pattern receptor P2X7 or the pathogen-associated molecular pattern receptor Toll-like receptor (TLR)4, respectively, can induce the release of the pleiotropic cytokine interleukin (IL)-1ß in humans and mice. However, the release of IL-1ß in dogs remains poorly defined. Using a canine IL-1ß enzyme-linked immunosorbent assay, this study investigated whether ATP or LPS could induce IL-1ß release in a canine blood-based assay. Short-term incubations (30 min) with ATP induced IL-1ß release in LPS-primed canine blood, and this process could be near-completely impaired by the P2X7 antagonist, A438079. In contrast, ATP failed to induce IL-1ß release from blood not primed with LPS. ATP-induced IL-1ß release was observed with LPS-primed blood from eight different pedigrees or cross breeds. Long-term incubations (24h) with LPS induced IL-1ß release in canine blood in a concentration-dependent manner. This process was not altered by co-incubation with A438079. LPS-induced IL-1ß release was observed with blood from 10 different pedigrees or cross breeds. These results demonstrate that both extracellular ATP and LPS can induce IL-1ß release in dogs, and that ATP- but not LPS-induced IL-1ß release in blood is dependent on P2X7 activation. These findings support the role of both P2X7 and TLR4 in IL-1ß release in dogs.