Neonatal-onset autoinflammation and immunodeficiency caused by heterozygous missense mutation of the proteasome subunit β-type 9

ABSTRACTBACKGROUNDDefective proteasome activities due to genetic mutations lead to an autoinflammatory disease, termed as proteasome-associated autoinflammatory syndromes (PRAAS). In PRAAS relapsing inflammations and progressive wasting are common, but immunodeficiency has not been reported.METHODSWe studied two unrelated Japanese infants with PRAAS-like manifestations. We have also generated and analyzed the mice carrying the candidate mutation found in the patients.RESULTSBoth patients showed neonatal-onset skin rash, myositis and basal ganglia calcification, similar to PRAAS patients. Meanwhile, they manifested distinct phenotypes, including pulmonary hypertension and immunodeficiency without lipoatrophy. We identified a novel de novo heterozygous missense mutation, G156D, in a proteasome subunit gene, PSMB9, encoding β1i, in the two patients. Maturation and activity of the immunoproteasome were impaired, but ubiquitin accumulation was hardly detected not only in patient-derived cells and samples but also in Psmb9G156D/+ mice. As an immunodeficient phenotype, one patient showed decrease of B cells and increase of monocytes, while the other patient showed decrease of CD8 T cells. The proteasome defects and immunodeficient phenotypes were recapitulated in Psmb9G156D/+ mice.CONCLUSIONSThe PSMB9 G156D is a unique mutation in proteasome subunits in causing defects by its heterozygosity, affecting two β rings interaction and leading to immunodeficiency. The mutant mice are the first mice model for analyzing proteasome dysfunctions in PRAAS. We here propose the term, proteasome-associated autoinflammation and immunodeficiency disease (PRAID), as an umbrella name for our cases, PRAAS with immunodeficiency, as well as PRAAS described so far.

A Rare Glanzmann Thrombasthenia Pedigree of C.1067T>C Heterozygous Mutation in ITGA2B Gene

Purpose A 50-year-old female with excessive menstruation and severe epistaxis since childhood was studied by using phenotype and genetic diagnosis. She was diagnosed as Glanzmann thrombasthenia (GT), meanwhile, her family members with severe epistaxis were also studied. Mutation sites were detected in them. Bioinformatics software was used to explore the molecular pathogenesis which provide evidence for in vitro and in vivo experiments. Methods Platelet count and morphology, coagulation function and platelet aggregation were detected for phenotype diagnosis. Platelet membrane glycoproteins (GP) αIIb and β3 were measured by flow cytometry (FCM). Exons and their end 15bp introns of 89 genes associated with hemorrhage and thrombosis from proband were amplified by PCR and analyzed by direct DNA sequencing. Mutation site was measured by sanger sequencing in other family members. ClustalX-2.1-win software was used to analyze homology of nucleotide. PROVEAN and SIFT was used to analyze the risk of mutation site. Results The proband, along with her brother and nephew, had normal platelet account and morphology. Coagulation function showed normal while platelet aggregation in response to ADP and AA were reduced. However, they had normal platelet aggregation in response to ristocetin. FCM demonstrated that expression level of CD41 and CD61 were significantly reduced. ITGA2B c.1067T>C heterozygous missense mutation, which led to a Val356→Ala substitution in αIIb protein, existed in the three people. This mutation site was highly conserved among human, mouse, rat and zebrafish. PROVEAN prediction scored -3.48 and SIFT prediction scored 0.001. These results demonstrated ITGA2B p.Val356Ala was pathogenic. Conclusion Glanzmann thrombasthenia is a rare autosomal recessive bleeding disorder results from quantitative or qualitative defect of αIIbβ3 integrin which encoded by ITGA2B and ITGB3. The nature of GT mutations is highly variable and most cases are sporadic. In our study, ITGA2B c.1067T>C (Val356Ala) heterozygous missense mutation caused Glanzmann thrombasthenia and aroused obvious symptoms. And in general, homozygous mutation in ITGA2B were recognized to led to Glanzmann thrombasthenia while ITGA2B heterozygous mutation carriers showed mild symptoms. However, there are also some patients with gain-of-function in ITGA2B showed abnormal platelet function or amount. More experiments should be conducted to identify the function of this heterozygous mutation. Disclosures No relevant conflicts of interest to declare.