Clinical and molecular analysis of neurodegenerative diseases

Assessment of swallowing in motor neuron disease and Asidan/SCA36 patients with new methods

BACKGROUND

We report on a unique complication of cerebellar ataxia and motor neuron disease named Asidan/SCA36 with a high frequency of tongue atrophy. We aimed to elucidate dysphagia in amyotrophic lateral sclerosis (ALS) and spinal, bulbar muscular atrophy (SBMA), and Asidan/SCA36 patients with new methods.

METHODS

Patients diagnosed with ALS (n=20), SBMA (n=6), and Asidan (n=12) were included. A videofluoroscopic swallow study (VFS), an assessment of maximal tongue pressure (MTP), and impedance pharyngography (IPG) were applied.

RESULTS

The frequencies of VFS abnormalities were 70%, 50%, and 33% in ALS, SBMA, and Asidan/SCA36, respectively. Compared with control subjects (31.6 ± 6.3 kPa, mean ± SD), MTP was significantly decreased in ALS patients and SBMA patients, but was relatively preserved in Asidan patients. ALS patients performed more swallowing actions (Ns) detected by IPG than did control subjects, but SBMA and Asidan/SCA36 patients performed similar Ns to control subjects.

CONCLUSIONS

VFS showed a higher frequency of swallowing abnormalities in ALS patients. MTP and IPG measurements showed the most severe involvement in ALS patients and a relatively preserved swallowing function in SBMA and Asidan/SCA36 patients.

[Clinicoepidemiological analysis of genetic testing in 1,000 cases of hereditary neurological disorders]

A total of 1,000 neurological patients were examined for genetic testings at the Department of Neurology, Okayama University, from 1992 to 2010. To investigate the role and significance of genetic testings in neurological diagnostic consultation, we divided the analysis period into two, the former period (1992 to 2000) and the latter period (2001 to 2010). The number of genetic testings was 669 cases in the former period, and 331 cases in the latter period. However, the positive rate of genetic testings was 25.3% in the former period, and 48.1% in the latter period. The reason of this remarkable rise of the positive rate in the latter period was mainly attributable to our feedback inquiry to the doctors from 2001, noticing them the total number of test in a year, positive rate with or without family history, and an encouragement to examine more clinical details of their patients. The genetic testing plays an essential role in clinical neurology. It is important that the application of genetic testing to each case should be considered more carefully and properly.

Protein aggregation and protein instability govern familial amyotrophic lateral sclerosis patient survival

The nature of the "toxic gain of function" that results from amyotrophic lateral sclerosis (ALS)-, Parkinson-, and Alzheimer-related mutations is a matter of debate. As a result no adequate model of any neurodegenerative disease etiology exists. We demonstrate that two synergistic properties, namely, increased protein aggregation propensity (increased likelihood that an unfolded protein will aggregate) and decreased protein stability (increased likelihood that a protein will unfold), are central to ALS etiology. Taken together these properties account for 69% of the variability in mutant Cu/Zn-superoxide-dismutase-linked familial ALS patient survival times. Aggregation is a concentration-dependent process, and spinal cord motor neurons have higher concentrations of Cu/Zn-superoxide dismutase than the surrounding cells. Protein aggregation therefore is expected to contribute to the selective vulnerability of motor neurons in familial ALS.

Dysregulated IP3 signaling in cortical neurons of knock-in mice expressing an Alzheimer's-linked mutation in presenilin1 results in exaggerated Ca2+ signals and altered membrane excitability

Disruptions in intracellular Ca2+ signaling are proposed to underlie the pathophysiology of Alzheimer's disease (AD), and it has recently been shown that AD-linked mutations in the presenilin 1 gene (PS1) enhance inositol triphosphate (IP3)-mediated Ca2+ liberation in nonexcitable cells. However, little is known of these actions in neurons, which are the principal locus of AD pathology. We therefore sought to determine how PS1 mutations affect Ca2+ signals and their subsequent downstream effector functions in cortical neurons. Using whole-cell patch-clamp recording, flash photolysis, and two-photon imaging in brain slices from 4-5-week-old mice, we show that IP3-evoked Ca2+ responses are more than threefold greater in PS1(M146V) knock-in mice relative to age-matched nontransgenic controls. Electrical excitability is thereby reduced via enhanced Ca2+ activation of K+ conductances. Action potential-evoked Ca2+ signals were unchanged, indicating that PS1(M146V) mutations specifically disrupt intracellular Ca2+ liberation rather than reduce cytosolic Ca2+ buffering or clearance. Moreover, IP3 receptor levels are not different in cortical homogenates, further suggesting that the exaggerated cytosolic Ca2+ signals may result from increased store filling and not from increased flux through additional IP3-gated channels. Even in young animals, PS1 mutations have profound effects on neuronal Ca2+ and electrical signaling: cumulatively, these disruptions may contribute to the long-term pathophysiology of AD.