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The myosin-directed chaperone UNC-45B is essential for sarcomeric organization and muscle function from Caenorhabditis elegans to humans. The pathological impact of UNC-45B in muscle disease remained elusive. We report ten individuals with bi-allelic variants in UNC45B who exhibit childhood-onset progressive muscle weakness. We identified a common UNC45B variant that acts as a complex hypomorph splice variant. Purified UNC-45B mutants showed changes in folding and solubility. In situ localization studies further demonstrated reduced expression of mutant UNC-45B in muscle combined with abnormal localization away from the A-band towards the Z-disk of the sarcomere. The physiological relevance of these observations was investigated in C. elegans by transgenic expression of conserved UNC-45 missense variants, which showed impaired myosin binding for one and defective muscle function for three. Together, our results demonstrate that UNC-45B impairment manifests as a chaperonopathy with progressive muscle pathology, which discovers the previously unknown conserved role of UNC-45B in myofibrillar organization.

Macrophages are essential for innate immunity and inflammatory responses and differentiate into various functional phenotypes. Tribbles homolog 1 (Trib1), a member of the mammalian Tribbles homolog pseudokinase family, has been implicated in regulation of cell differentiation, proliferation, and metabolism, but its role in macrophage biology has not been fully elucidated. Here, we investigated the consequences of Trib1 deficiency on macrophage functions and M1/M2 polarization. Bone marrow–derived macrophages (BMDMs) from Trib1-deficient (Trib1(−/−)) mice exhibited elevated phagocytic capacity, correlating with up-regulation of several scavenger receptors. Concomitantly, uptake of modified low-density lipoprotein was increased in Trib1(−/−) BMDMs. Trib1(−/−) macrophages also exhibited diminished migration in the presence of the chemokine MCP-1, associated with reduced expression of the MCP-1 receptor Ccr2. Furthermore, Trib1 deficiency attenuated the response of BMDMs to both M1 and M2 stimuli; induction of the M1-marker genes Il6, Il1b, and Nos2 upon LPS/IFNγ stimulation and of the M2-marker genes Cd206, Fizz1, and Arg1 upon IL-4 stimulation was reduced. Functionally, Trib1 deficiency decreased secretion of proinflammatory cytokines (IL-6, TNFα, IL-1β, and CXCL1) and reduced nitric oxide and reactive oxygen species production in M1-polarized macrophages. Supporting the attenuated M2 phenotype, IL-4–stimulated Trib1(−/−) macrophages secreted less IL-10 and TGFβ. Mechanistically, Trib1(−/−) BMDMs displayed lower levels of Janus kinase 1 (JAK1), resulting in reduced activation of LPS/IFNγ-mediated STAT1 signaling. Likewise, decreased levels of JAK1 along with lower activation of STAT6 and STAT3 were observed in M2-polarized Trib1(−/−) BMDMs. Our findings suggest that Trib1 extensively controls macrophage M1/M2 polarization via the JAK/STAT signaling pathway.

BACKGROUND: Antibodies against tissue transglutaminase (TTG) of isotype IgA (IgA‐aTTG) represent reliable diagnostic markers to confirm or exclude celiac disease (CD). Hemolysis (HL) is an important pre‐analytical factor. HL can be quantified as HL index (HI) correlating with the concentration of free hemoglobin. TTG is abundant in erythrocytes and released upon HL. In immunoassays, the released TTG may interfere with binding of IgA‐aTTG to the coated TTG. METHODS: We selected 17 HL‐free sera from children with biopsy‐confirmed CD: 7 with low‐positive (1‐5 multiples of upper limit of normal [×ULN]), 5 with intermediate (5‐10 × ULN) and 5 with high IgA‐aTTG (10‐15 × ULN). Sera were spiked with hemolysates resulting in HIs ranging from 12.5 to 800 (12.5‐800 mg/dL free hemoglobin). RESULTS: IgA‐aTTG values were significantly decreased (>10%) after addition of hemolysates even if HL was invisible (HI