Decreased number of Gemini of coiled bodies and U12 snRNA level in amyotrophic lateral sclerosis.

Disappearance of TAR-DNA-binding protein 43 kDa (TDP-43) from the nucleus contributes to the pathogenesis of amyotrophic lateral sclerosis (ALS), but the nuclear function of TDP-43 is not yet fully understood. TDP-43 associates with nuclear bodies including Gemini of coiled bodies (GEMs). GEMs contribute to the biogenesis of uridine-rich small nuclear RNA (U snRNA), a component of splicing machinery. The number of GEMs and a subset of U snRNAs decrease in spinal muscular atrophy, a lower motor neuron disease, suggesting that alteration of U snRNAs may also underlie the molecular pathogenesis of ALS. Here, we investigated the number of GEMs and U11/12-type small nuclear ribonucleoproteins (snRNP) by immunohistochemistry and the level of U snRNAs using real-time quantitative RT-PCR in ALS tissues. GEMs decreased in both TDP-43-depleted HeLa cells and spinal motor neurons in ALS patients. Levels of several U snRNAs decreased in TDP-43-depleted SH-SY5Y and U87-MG cells. The level of U12 snRNA was decreased in tissues affected by ALS (spinal cord, motor cortex and thalamus) but not in tissues unaffected by ALS (cerebellum, kidney and muscle). Immunohistochemical analysis revealed the decrease in U11/12-type snRNP in spinal motor neurons of ALS patients. These findings suggest that loss of TDP-43 function decreases the number of GEMs, which is followed by a disturbance of pre-mRNA splicing by the U11/U12 spliceosome in tissues affected by ALS.

Minor splicing pathway is not minor any more: implications for the pathogenesis of motor neuron diseases.

To explore the molecular pathogenesis of amyotrophic lateral sclerosis (ALS), the nuclear function of TAR-DNA binding protein 43 kDa (TDP-43) must be elucidated. TDP-43 is a nuclear protein that colocalizes with Cajal body or Gem in cultured cells. Several recent studies have reported that the decreasing number of Gems accompanied the depletion of the causative genes for ALS, TDP-43 and FUS. Gems play an important role in the pathogenesis of spinal muscular atrophy. Gems are the sites of the maturation of spliceosomes, which are composed of uridylate-rich (U) snRNAs (small nuclear RNAs) and protein complex, small nuclear ribonuclearprotein (snRNP). Spliceosomes regulate the splicing of pre-mRNA and are classified into the major or minor classes, according to the consensus sequence of acceptor and donor sites of pre-mRNA splicing. Although the major class of spliceosomes regulates most pre-mRNA splicing, minor spliceosomes also play an important role in regulating the splicing or global speed of pre-mRNA processing. A mouse model of spinal muscular atrophy, in which the number of Gems is decreased, shows fewer subsets U snRNAs. Interestingly, in the central nervous system, U snRNAs belonging to the minor spliceosomes are markedly reduced. In ALS, the U12 snRNA is decreased only in the tissue affected by ALS and not in other tissues. Although the molecular mechanisms underlying the decreased U12 snRNA resulting in cell dysfunction and cell death in motor neuron diseases remain unclear, these findings suggest that the disturbance of nuclear bodies and minor splicing may underlie the common molecular pathogenesis of motor neuron diseases.

Chorea as the first sign in a patient with elderly-onset systemic lupus erythematosus.

The case of an elderly patient who had chorea as an initial symptom of systemic lupus erythematosus (SLE) accompanied by antiphospholipid syndrome (APS) is reported. A 68-year-old woman suddenly developed chorea of her left arm and leg. Magnetic resonance imaging (MRI) of the brain demonstrated a focal lesion in the right caudate head, which showed hyperintensity on fluid-attenuated inversion recovery and diffusion-weighted imaging. This condition was thought to be a common form of vascular chorea, which is likely to occur in elderly individuals; however, the laboratory data of this patient finally fulfilled the diagnostic criteria of SLE and APS. Physicians should be careful in diagnosing elderly individuals simply as having a vascular chorea because this symptom can be the initial manifestation of SLE or APS.

[FTLD/ALS as TDP-43 proteinopathies].

Frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS) often coexist in the same patients: FTLD/MND. However, it is unclear whether FTLD/MND can be distinguished from ALS or FTLD. TAR DNA binding protein 43 KDa (TDP-43) has been identified as the major component of the ubiquitin-positive inclusion bodies in ALS, FTLD, and FTLD/MND. On the basis of this finding, a new concept of neurodegenerative disorders, namely TDP-43 proteinopathy, has been proposed for these disorders. In ALS, more than 30 mutations of the TDP-43 gene have been identified. The clinical features and neuropathological findings of ALS with TDP-43 mutation are identical to those of sporadic ALS. Therefore, TDP-43 plays a primary role in the pathogenesis of ALS. In contrast, only few patients with FTLD phenotype have TDP-43 mutations. Therefore, we have speculated that TDP-43 does not play a primary role in the pathogenesis of FTLD. The analysis of distribution of TDP-43 inclusion bodies in ALS patients revealed that ALS has two subtypes: (1) limited in the motor neuron system and (2) extended into the frontotemporal lobe. Additionally, causative genes of familial FTLD/MND have not been mapped to TDP-43. These results suggest that FTLD/MND is a disease distinct from FTLD and ALS.