Targeted Deletion of the Gene Encoding the La Autoantigen (Sjögren's Syndrome Antigen B) in B Cells or the Frontal Brain Causes Extensive Tissue Loss

Reduction in La protein levels and decreased frontal brain mass following targeted deletion of La. (A) Immunohistochemistry of the hippocampal CA1 regions of 11-week-old αCamKII^Cre La-deleted and control mice, as indicated. (Upper row) Immunohistochemistry with anti-mLa antibody (35); (middle row) H&E stained section; (bottom row) antitubulin antibody-stained section. (B) αCamKII^Cre La-deleted and control mice brains as indicated. Double-sided arrows superimposed on the hindbrains (HB) are the same size; the FB (front brain) is also indicated. (C) Comparison of average brain wet weights of 10 αCamKII^Cre La-deleted and 10 control mice. Error bars indicate standard deviations. P = 1.2 × 10⁻⁵. All of these samples were obtained without prior perfusion-fixation.

La deletion in αCamKII^Cre animals causes developmental postnatal loss of frontal brain mass. (A) Development of αCamKII^Cre La-deleted and sibling control brains at 16 and 32 postnatal weeks. Double-sided arrows on the hindbrain (HB) images are the same size; FB, front brain. (B) Immunohistochemistry of neocortex stained with anti-mLa antibody and H&E counterstaining of 16-week-old mouse cortices. (C) Plot of brain mass versus age of αCamKII^Cre La-deleted and control mice. For mice aged 13 weeks and older, P values ranged from 0.004 (13 weeks) to 0.0001 (17 and 25 weeks). All of the samples were obtained by dissection after perfusion-fixation.

Progressive neurodegeneration in the cerebral cortex and hippocampus of La-deleted mice. Representative sections of the forebrains from the La-deficient (La^F/− Cre^CaMKII) and control littermates (La^F/−) at 12 weeks (A and B), 16 weeks (C and D), and 65 weeks (E and F). Areas of the frontal cortex and hippocampus (CA1 cells) that are outlined in the overview images (H&E, left panels) are shown at a higher magnification in the adjacent, corresponding Nissl-stained sections. Note there was some decrease in cortical thickness and a more pronounced decrease in neuronal density in the hippocampus (CA1) of 16-week-old La-deleted mice than in control littermates. Cortical atrophy and neuron loss in the hippocampus (CA1) were especially pronounced in 65-week-old La-deleted mice compared to controls (compare panels F and E). Bars in the Nissl insets (cortex and hippocampus), 100 μm. (G to J) High-magnification immunohistochemistry images of representative regions of the somatosensory cortex (G and H) and retrosplenial cortex (I and J), stained with anti-mLa antibody and H&E counterstaining, from 16-week-old control brains (upper panels) and matched littermate La knockout mutant brains (lower panels). (K and L) High-magnification immunohistochemistry results for the hippocampal regions of 12-week-old control (K) and matched littermate La knockout mutant (L) mouse brains stained with anti-mLa antibody and H&E counterstaining. The upper panels show low magnification images, which were further magnified for the middle and lower panels, including the circular insets, as annotated.

La deletion by Mb1^Cre causes reduced spleen size, agammaglobulenemia, and absence of cells of the B lineage. (A) Photographs of freshly isolated spleens from typical control and La-deleted 17-week-old mice. The mean ± standard deviation spleen weights from eight control and eight La-deleted mice are indicated under the images. (B) Absence of serum IgG in La-deleted mice. Lane 1, control mouse serum; lane 2, from La-deleted mouse serum. (C to E) Developmental arrest of La-depleted B lineage cells. BM (C), spleen (D), and PerC cells (E) were stained with the indicated Abs and analyzed by flow cytometry using the indicated gating parameters. The numbers are frequencies of cells falling in each gate. Data are representative of multiple mice with similar results. (C) BM IgM⁺ B220^lo cells (top panels) were gated to identify pro-B cells (CD43⁺ B220⁺) and pre-B cells (CD43⁻ B220⁺) (lower panels). (D) Spleen cells were stained to identify B cells (IgM⁺ B220⁺) and non-B cells (IgM⁻ B220⁻) (top panels). (E) PerC cells were examined using the gating parameters shown.