ARHGAP10, which encodes Rho GTPase-activating protein 10, is a novel gene for schizophrenia risk

Schizophrenia (SCZ) is known to be a heritable disorder; however, its multifactorial nature has significantly hampered attempts to establish its pathogenesis. Therefore, in this study, we performed genome-wide copy-number variation (CNV) analysis of 2940 patients with SCZ and 2402 control subjects and identified a statistically significant association between SCZ and exonic CNVs in the ARHGAP10 gene. ARHGAP10 encodes a member of the RhoGAP superfamily of proteins that is involved in small GTPase signaling. This signaling pathway is one of the SCZ-associated pathways and may contribute to neural development and function. However, the ARHGAP10 gene is often confused with ARHGAP21, thus, the significance of ARHGAP10 in the molecular pathology of SCZ, including the expression profile of the ARHGAP10 protein, remains poorly understood. To address this issue, we focused on one patient identified to have both an exonic deletion and a missense variant (p.S490P) in ARHGAP10. The missense variant was found to be located in the RhoGAP domain and was determined to be relevant to the association between ARHGAP10 and the active form of RhoA. We evaluated ARHGAP10 protein expression in the brains of reporter mice and generated a mouse model to mimic the patient case. The model exhibited abnormal emotional behaviors, along with reduced spine density in the medial prefrontal cortex (mPFC). In addition, primary cultured neurons prepared from the mouse model brain exhibited immature neurites in vitro. Furthermore, we established induced pluripotent stem cells (iPSCs) from this patient, and differentiated them into tyrosine hydroxylase (TH)-positive neurons in order to analyze their morphological phenotypes. TH-positive neurons differentiated from the patient-derived iPSCs exhibited severe defects in both neurite length and branch number; these defects were restored by the addition of the Rho-kinase inhibitor, Y-27632. Collectively, our findings suggest that rare ARHGAP10 variants may be genetically and biologically associated with SCZ and indicate that Rho signaling represents a promising drug discovery target for SCZ treatment.

P300 and the thought disorder factor extracted by factor-analytic procedures in schizophrenia

BACKGROUND

In order to clarify the clinical significance of P300 as a biologic marker that can reflect schizophrenic symptomatology, many previous studies have evaluated the relationship of P300 with the symptoms on the basis of a positive/negative dichotomy, but yielded inconsistent conclusions. Such a dichotomy has been criticized as being too reductionistic. Recently, most studies with factor-analytic procedures have extracted some symptom factors outside this dichotomy. Therefore, it is important to examine associations of P300 with the symptom factors extracted by these statistical analyses.

METHODS

In the present study, the amplitudes of P300 were measured by using an auditory oddball paradigm for 73 schizophrenics whose psychopathology was assessed with the Positive and Negative Syndrome Scale (PANSS).

RESULTS

The principal component analysis of the PANSS items revealed five factors labeled the thought disorder, negative, hostile/excitable, delusional/hallucinatory, and depressive factors. The score for the thought disorder factor correlated negatively with the amplitude of P300 recorded at Pz T5, and T6, but that for the other factors did not.

CONCLUSIONS

These findings suggest that the reduction of P300 amplitudes recorded at the midline parietal and bilateral temporoparietal regions may be one of the electrophysiologic indices representing the thought disorder clinically observed in schizophrenia.

Borrelia burgdorferi-seropositive chronic encephalomyelopathy: Lyme neuroborreliosis? An autopsied report

A 36-year-old Japanese woman presented with progressive cerebellar signs and mental deterioration of subacute course after her return from the USA. Her serum antibody to spirochete Borrelia burgdorferi was significantly elevated. A necropsy 4 years after her initial neurological signs revealed multifocal inflammatory change in the cerebral cortex, thalamus, superior colliculus, dentate nucleus, inferior olivary nucleus and spinal cord. The lesions showed spongiform change, neuronal cell loss, astrocytosis and proliferation of activated microglial cells. The internal capsule was partially vacuolated and the spinal cord, notably at the thoracic level, was demyelinated and cavitated in the lateral funiculus. Microglial cells aggregated within and around the spongiform lesions and microglial nodules were present in the medulla oblongata. Use of Warthin-Starry stain demonstrated silver-impregnated organisms strongly suggesting B. burgdorferi in the central nervous tissues. The dentate nucleus and inferior olivary nucleus showed the most advanced lesions with profound fibrillary gliosis. Occlusive vascular change was relatively mild, and fibrous thickening of the leptomeninges with lymphocyte infiltrates was localized in the basal midbrain. The ataxic symptoms were due to the dentate and olivary nucleus lesions and mental deterioration was attributable to the cortical and thalamic lesions. Spongiform change, neuronal cell loss, and microglial activation are characteristic pathological features in the present case. The cerebellar ataxia and subsequent mental deterioration are unusual clinical features of Lyme neuroborreliosis. Spirochete B. burgdorferi can cause focal inflammatory parenchymal change in the central nervous tissues and the present case may be an encephalitic form of Lyme neuroborreliosis.

Brain perfusion SPECT in Lyme neuroborreliosis

SPECT imaging brain perfusion using 99mTc-HMPAO was performed on a 38-yr-old women with Lyme neuroborreliosis confirmed by autopsy. The patient had been suspected of spinocerebellar degeneration. Cerebral blood flow was diffusely decreased throughout cerebral cortices but cerebellar blood flow was not impaired, which indicated that the diagnosis was unlikely spinocerebellar degeneration. These findings suggested that brain perfusion SPECT provides useful information in diagnosing the patients with Lyme neuroborreliosis, especially when spinocerebellar degeneration is included in the differential diagnosis.

Simultaneous observation of regional cerebral blood flow and event-related potential during performance of an auditory task

Reduced amplitude of the P300 component has been reported consistently in patients with neurological and psychiatric disorders. It is unclear, however, how such patients' cognitive dysfunction is related to their P300 abnormality. Further basic knowledge regarding neural substrates for P300 generation is required for gaining an understanding of the pathological significance of the P300 amplitude reduction. To determine the brain structures involved in P300 generation, we observed the event-related potential and the regional cerebral blood flow (rCBF) in 10 normal subjects performing an oddball discrimination of pure tones. The rCBF value was assessed quantitatively with the aid of single photon emission computed tomography using technetium-99m hexamethylpropylene amine oxime. During the task performance, significant activation was observed in the posterior superior temporal and inferior parietal regions of the right hemisphere. In addition, positive correlation of the task-related increase in rCBF with the simultaneously recorded P300 amplitude was observed in the right but not the left posterior superior temporal region. These findings indicate that activation of the right non-verbal auditory area might modulate P300 generation during pure-tone discrimination.

Detection of Plasmodium falciparum in human blood by a nested polymerase chain reaction

We have developed a simple method for direct detection of Plasmodium falciparum parasites in infected human blood using a nested polymerase chain reaction. Whole blood (10 microliters) was obtained by finger puncture and suspended in a microcentrifuge tube containing phosphate-buffered saline. For removal of components that might inhibit the PCR, blood samples were treated with saponin and washed by centrifugation. After three cycles of a two-step incubation (3 min at 94 degrees C and 3 min at 55 degrees C), the first amplification was done with oligonucleotide primers specific for the junction region of the gene coding for the dihydrofolate reductase-thymidylate synthase in P. falciparum. A 1-microliter portion of the first amplification was then amplified again with a second set of primers, and 226-basepair fragments were generated. The amplified products were analyzed by agarose gel electrophoresis with ethidium bromide staining. Experiments with cultured parasites showed that the method could detect as few as 13 parasites in 10 microliters of whole blood. In 1991, 101 samples from 98 donors were collected in Guadalcanal, Solomon Islands. Eight of these samples gave positive results by both examination of thin blood smears and by the nested PCR. There was a correlation between parasite densities and the intensity of the results by the nested PCR. The method is suitable for detection of asymptomatic parasite carriers and evaluation of medical treatment on clinical cases.