Spinocerebellar ataxia type 6 (SCA6) is a neurodegenerative disease caused by the expansion of a polyglutamine tract in the Ca v 2.1 voltage-gated calcium channel. To elucidate how the expanded polyglutamine tract in this plasma membrane protein causes the disease, we created a unique knockin mouse model that modestly overexpressed the mutant transcripts under the control of an endogenous promoter (MPI-118Q). MPI-118Q mice faithfully recapitulated many features of SCA6, including selective Purkinje cell degeneration. Surprisingly, analysis of inclusion formation in the mutant Purkinje cells indicated the lysosomal localization of accumulated mutant Ca v 2.1 channels in the absence of autophagic response. The lack of cathepsin B, a major lysosomal cysteine proteinase, exacerbated the loss of Purkinje cells and was accompanied by an acceleration of inclusion formation in this model. Thus, the pathogenic mechanism of SCA6 involves the endolysosomal degradation pathway, and unique pathological features of this model further illustrate the pivotal role of protein context in the pathogenesis of polyglutamine diseases.

Objective To compare the accumulated T cell clonotypes in peripheral blood (PB) samples obtained at various times, and the accumulated T cell clonotypes in a PB sample and in an affected kidney, from patients with systemic lupus erythematosus (SLE). Methods Peripheral blood mononuclear cells (PBMC) were obtained at 2–4 different times from each of 5 SLE patients, with or without flare‐up of the disease; in addition, a biopsied kidney tissue sample was obtained from 1 of the patients. RNA was extracted from each sample and complementary DNA was prepared. Genes that encode the variable region of T cell receptor (TCR) B chains (BV) of 3 BV families, 5S1, 8, and 14, were amplified by reverse transcription–polymerase chain reaction (PCR), and the PCR products were cloned for sequencing. Results A total of 877 cloned TCR genes was detected in the PBMC samples and the kidney sample. Oligoclonal T cell expansion was detected in 34 of the 36 PCR‐amplified BV samples from PBMC (amplification of 3 BV families in 2–4 samples from 5 patients). The composition of clonally expanded T cell clonotypes was relatively stable in the patients with inactive SLE. In contrast, the composition of clonotypes in the PB changed drastically after the patient experienced the active phase of the disease. T cell clonotypes that had accumulated in the kidney appeared to be restricted and distinct from those that had accumulated in the PB of the same patient. Conclusion Different T cell clonotypes expand at different times and at different sites in patients with active SLE. The sensitizing antigens may change over the course of the disease and may be different at each site.

Objective. This study was undertaken to clarify the mechanisms responsible for the generation of anti–52‐kd SS‐A/Ro autoantibodies and to elucidate why, as has recently been reported, anti–52‐kd autoantibodies preferentially recognize the denatured form rather than the native 52‐kd molecule. Methods. Using a series of truncated 52‐kd auto‐antigens, produced as β‐galactosidase fusion proteins in Escherichia coli, the B cell epitope distribution was probed with 18 anti‐Ro–positive sera by immunoblotting and by enzyme‐linked immunosorbent assay. Results. Nearly all the antigenicity of the molecule was found to be linked to its leucine zipper region. In a further study using 9 of the 18 sera, the antigenicity of the molecule was found to be mainly formed by multiple conformational epitopes, and one of these epitopes appeared to be universally recognized by all the sera tested. Conclusion. The recognition of multiple epitopes indicates that the Ro 52‐kd antigen itself drives the autoimmunity to this molecule. Further, the concentration of the antigenicity at the leucine zipper region may explain why anti–52‐kd antibodies preferentially recognize the denatured protein rather than its native form.

To clarify whether there is a bias in the V-D-J combination of T cell receptor (TcR) genes, J beta gene usage has been investigated in a total of 743 TcR beta genes of V beta 2, V beta 8.2, and V beta 14 families expressed in C57BL/6 mouse spleens. Genes of TcR beta chains, amplified by a reverse transcriptase-polymerase chain reaction, were individually cloned into plasmids. Cloned genes (61 to 106), randomly selected in each respective V beta family from three different mice, were tested by means of hybridization with 12 oligo DNA probes which were designed to differentiate 12 murine functional J beta gene segments. The results are enumerated below. (1) The J beta 2.6 gene segment was found to be most frequently used (V beta 2, 19.8%; V beta 8.2, 21.2%; and V beta 14, 19.2%). In contrast, usage of the J beta 1.6 gene segment was most infrequent (V beta 2, 1.9%; V beta 8.2, 2.9%; and V beta 14, 0.5%); (2) High frequency of the J beta 2.1 gene segment and low frequency of the J beta 1.3 and J beta 1.5 gene segments were also observed; (3) The J beta 2 cluster was used in preference to the J beta 1 cluster (usages of the J beta 2 cluster: V beta 2, 67.8%; V beta 8.2, 65.9%; and V beta 14, 70.4%); and (4) These biases were generally common to all three V beta families examined and differences among individual mice were mostly small. Considering these findings, we conclude that the TcR J beta gene segments in C57BL/6 mice splenocytes are selected with a bias, but are selected independently of the V beta families.