No abstract

SUMMARYCalreticulin is a molecular chaperone to newly synthesized polypeptides. Previous studies suggested that calreticulin is probably a protein member of the Ro/La RNP complex. The aims of this study were (a) to investigate whether linear B cell epitopes of the Ro/La RNP complex are bound to calreticulin and (b) if the complex peptide-calreticulin is recognized specifically by anti-Ro autoantibodies. Calreticulin was isolated from either human or pig spleen using a multi-step purification method and found to interact preferentially with biotinylated peptides derived from the sequence of the Ro60 kD 175-184aa(10p) and 216-232aa(17p). The interaction of the peptide-calreticulin complex was favoured by the combination of heat treatment, divalent cations and ATP. La/SSB epitopes did not react with calreticulin. Peptides corresponding to La/SSB epitopes as well as the common epitope of Sm did not interact with calreticulin. Thirty-eight anti-Ro60 KD positive and 23 anti-Ro60 kD negative sera of patients with systemic lupus erythematosus (SLE) and primary Sjögren's syndrome (pSS) were tested. All antiRo60 kD positive sera bound the complex calreticulin-17p, while 95% of the same sera had activity against the complex calreticulin -10p. Tested individually, calreticulin, pep10p and pep17p presented very low reactivity (8%, 11% and 29%, respectively) against anti-Ro60 kD positive sera. Anti-Ro60 KD negative sera did not exhibit significant reactivity either with calreticulin, 10 r and 17 r or with the complexes calreticulin -10p and calreticulin-17p ( < 5%). These results suggest that calreticulin can induce conformation-dependent recognition of the Ro60 kD epitopes, leading eventually to their recognition by autoantibodies. This is the first time that such a relationship is shown between a chaperone protein and fragments of an intracellular autoantigen. This work also provides insights into the understanding of mechanisms for autoantibody production. Furthermore, this association can be proved useful for the development of new sensitive assays for autoantibody detection.

This report describes a paediatric patient population with MEN1 in whom CD was the initial manifestation, confirming a previous observation that paediatric patients with MEN1 may present first with an ACTH-producing adenoma. Therefore, germline MEN1 mutations should be sought in paediatric CD and tested for when there is a suggestive family history and/or other manifestations.

The search for expression quantitative trait loci (eQTL) has traditionally centered entirely on the process of transcription, whereas variants with effects on mRNA translation have not been systematically studied. Here we present a high throughput approach for measuring translational cis-regulation in the human genome. Using ribosomal association as proxy for translational efficiency of polymorphic mRNAs, we test the ratio of polysomal/nonpolysomal mRNA level as a quantitative trait for association with single-nucleotide polymorphisms on the same mRNA transcript. We identify one important ribosomal-distribution effect, from rs1131017 in the 5’UTR of RPS26 , that is in high linkage disequilibrium (LD) with the 12q13 locus for susceptibility to type 1 diabetes. The effect on translation is confirmed at the protein level by quantitative Western blots, both ex vivo and after in vitro translation. Our results are a proof-of-principle that allelic effects on translation can be detected at a transcriptome-wide scale.