Jiro Ono

Proteolipid protein gene duplications causing Pelizaeus-Merzbacher disease: Molecular mechanism and phenotypic manifestations

Pelizaeus‐Merzbacher disease (PMD) is an X‐linked disorder characterized by dysmyelination of the central nervous system (CNS) caused by mutations involving the proteolipid protein gene (PLP). In addition to point and frameshift mutations in the coding region, duplications involving the entire PLP have been recognized recently as a major genetic abnormality causing PMD. We devised an interphase fluorescence in situ hybridization (FISH) assay to establish an efficient screening test for PLP duplication. Thirteen patients from 11 Japanese PMD families were determined to have PLP duplications. This molecular diagnostic FISH test also readily detected female carriers. Molecular analysis revealed that the size of the duplication and location of the breakpoints showed striking variation. Fiber FISH demonstrated that the duplication is tandem in nature. Haplotype analysis indicated an intrachromosomal origin for the duplication. These results suggest that an unequal sister chromatid exchange in male meiosis is likely to be the major mechanism leading to the formation of the duplication. Patients with the duplication commonly present with a mild PMD phenotype. Two patients with an exceptionally severe clinical phenotype carried large duplications, suggesting that either the larger duplicated segment incorporates additional dosage‐sensitive genes or that the location of the duplication junction may affect the phenotype. Ann Neurol 1999;45:624–632

Differentiation between dysmyelination and demyelination using magnetic resonance diffusional anisotropy

Using magnetic resonance (MR) diffusion-weighted method, we examined the optic and the trigeminal nerves of jimpy and twitcher mice, considered to be animal models of Pelizaeus-Merzbacher disease, hypomyelination disorder, and Krabbe disease, demyelination disorder, respectively. In jimpy mice, diffusional anisotropy of optic nerve did not show a significant difference compared to age-matched control mice, suggesting that diffusional anisotropy does exist in absence of multiple layers of myelin sheath. In twitcher mice, diffusional anisotropy was attenuated remarkably in the optic and trigeminal nerves. Loss of axonal straightness on longitudinal section confirmed by electron microscopy appeared to be the principal explanation for it. It is further suggested that this MR diffusion-weighted imaging method enables us to differentiate hypomyelination from demyelination in vivo.

Manganese Deposition in the Brain During Long-Term Total Parenteral Nutrition

BACKGROUND Manganese deposition was suspected in a pediatric patient who received long-term total parenteral nutrition. T1-weighted magnetic resonance images revealed high intensity areas in the globus pallidus. This study was designed to clarify if these abnormal findings were related to manganese deposition and clinical neurological manifestations. METHODS Whole-blood manganese concentrations were measured during manganese supplementation to total parenteral nutrition and after 5 months without manganese. Magnetic resonance images were also examined on each occasion and compared with the blood level of manganese. RESULTS The whole-blood manganese level during supplementation was 135 micrograms/L (normal range 14.6 +/- 4.7 micrograms/L), whereas the level was 20 micrograms/L after a manganese-free period of 5 months. Accompanied with normalization of manganese level, abnormal high intensity lesions in the globus pallidus on T1-weighted images also disappeared. No neurological manifestation related to the high manganese level was recognized. CONCLUSIONS It is probable that the high manganese level was elicited by manganese supplementation to total parenteral nutrition. This high manganese condition was confirmed by the measurement of whole-blood manganese level, which was associated with the abnormal high intensity lesions on T1-weighted magnetic resonance images.

Differentiation of dys- and demyelination using diffusional anisotropy

We attempted differential diagnosis of dysmyelination and demyelination in childhood using magnetic resonance diffusion weighted imaging. Pelizaeus-Merzbacher disease, one of the dysmyelination disorders, demonstrated diffuse high intensity of the cerebral white matter on T2-weighted images, which demonstrated diffusional anisotropy on diffusion weighted images. On the other hand, high intensity lesions on T2-weighted images in Krabbe disease, one of the demyelination disorders, lost diffusional anisotropy. Another demyelination disorder, Alexander disease-related disorder, also lost its diffusional anisotropy. In contrast to relatively high signal of the lesions on diffusion-weighted images in Krabbe disease (high signal type), the lesions in Alexander disease-related disorder showed low signal on diffusion-weighted images (low signal type). These results suggest that diffusion-weighted images will be clinically useful to differentiate dysmyelination from demyelination; both of them demonstrate similar high intensity lesions of the white matter on T2-weighted images.

Zonisamide Monotherapy in Newly Diagnosed Infantile Spasms

Summary: Purpose: We determined the short‐term efficacy of zonisamide (ZNS) monotherapy in newly diagnosed patients with infantile spasms (IS).

Ictal video-EEG recording of three partial seizures in a patient with the benign infantile convulsions associated with mild gastroenteritis

Summary: Purpose: In infants, benign convulsions can be triggered by febrile illness or mild diarrhea such as Rotavirus gastroenteritis. The triggering mechanism of these convulsions is still unknown. In spite of several reports concerning clinical features, the ictal EEG recordings were rarely analyzed by a video‐EEG monitoring system. To reveal a clue for the triggering mechanism of these convulsions, we analyzed the correlation of clinical manifestations and the EEG discharges during the ictal events and compared with previous reports.

Evaluation of myelination by means of the T2 value on magnetic resonance imaging

The progress of myelination in the cerebrum was evaluated by visual inspection, and magnetic resonance (MR) imaging and the transverse relaxation time (T2) was calculated from double echo images. Twenty-three pediatric cases, who did not show intracranial organic changes on MR examination, were included. The T2 values in the corpus callosum (CC), frontal deep white matter (FWM), occipital deep white matter (OWM) and centrum semiovale (CS) were calculated, and the changes in these values with age were followed. During the first year of life, a rapid decrease in the T2 value was seen, followed by a more gradual decrease. The T2 value seemed to reach the adult level between 2 and 3 years of life in all areas examined. The T2 values between 2 and 16 years in CC, FWM, OWM and CS were 59.7 +/- 3.6, 64.5 +/- 5.2, 69.8 +/- 4.8 and 66.3 +/- 3.3 ms (mean +/- S.D.), respectively. The T2 values in patients with clinically diagnosed Pelizaeus-Merzbacher disease (PMD) and late onset Krabbe disease were also calculated. In PMD, non-progressive prolongation of the T2 value was observed in all areas. In late onset Krabbe disease, on the other hand, progressive prolongation of the T2 values was mainly demonstrated in OWM and the posterior part of CS. These results suggest that the T2 value in the cerebral white matter allows more objective judgement than visual inspection, and makes it possible to clarify the mechanism underlying abnormal myelination, i.e. progressive or not.

Partial deletion of the long arm of chromosome 11: ten Japanese children

The clinical features of partial deletion 11q were correlated with the size of the deleted region. Ten Japanese children with partial deletion of 11q were investigated. They were divided into three groups. Three patients in the first group had interstitial deletions and preserved subband q24.1. Six patients in the second group demonstrated terminal deletion of 11q including subband q24.1, with typical features of 11q‐syndrome (Jacobsen syndrome). The third group included only one patient, who had terminal deletion of 11q without characteristics of typical 11q—syndrome. Prominent features of patients in the first group included severe mental and motor developmental delay, seizures, cleft lip and palate, and ophthal‐mological findings. Patients in the second group showed mild to moderate developmental delays without deterioration. Abnormalities in neuroimages, high intensity in the cerebral white matter in T2‐weighted magnetic resonance (MR) images, and recurrent infections were not observed after the age of 7 years. The subject in the third group, with the smallest amount of deleted chromosome, did not show developmental delays, suggesting that some unknown genes related to developmental delays may be located adjacent to subband q24.1. Variation in the deleted parts of 11q resulted in different clinical features in each group.

Bone marrow-derived osteoclast-like cells from a patient with craniometaphyseal dysplasia lack expression of osteoclast-reactive vacuolar proton pump.

Craniometaphyseal dysplasia (CMD) is a rare craniotubular bone dysplasia transmitted in autosomal dominant or recessive form. This disease is characterized by cranial bone hyperostosis and deformity of the metaphyses of the long bones. Using osteoclast-like cells formed from patient bone marrow cells, we investigated the pathophysiology of CMD in a 3-yr-old patient. Untreated bone marrow cells from the patient differentiated into osteoclast-like cells in vitro. These cells were shown to have vitronectin beta-receptors using a specific monoclonal antibody, i.e., 23C6 (CD51), which reacts with osteoclasts in human bone biopsy samples. However, the number of these osteoclast-like cells formed from the patients bone marrow was only 40% of the normal controls. 1,25-dihydroxyvitamin-D3, bovine 1-34 parathyroid hormone, recombinant human interleukin-1 beta, recombinant human interleukin-6, or recombinant human macrophage colony-stimulating factor significantly increased, while salmon calcitonin significantly inhibited, the number of osteoclast-like cells. However, these cells could not resorb sperm whale dentin slices and lacked the osteoclast-reactive vacuolar proton pump as evidenced by a monoclonal antibody (E11). Western blot analysis using a monoclonal antibody to pp60c-src (327) revealed that protooncogene c-src expression by the platelets of the CMD patient was comparable to the normal control. These data suggest that: (a) the hyperostosis and the metaphyseal long bone deformity in the present CMD patient might be explained by osteoclast dysfunction due to impaired expression of the osteoclast-reactive vacuolar proton pump; and (b) a protooncogene c-src was not associated with the pathogenesis of the present CMD patient.

Central nervous system abnormalities in chromosome deletion at 11q23

Two Japanese pediatric patients with terminal deletion of the long arm of chromosome 11 are described. Both had the morphological abnormalities of the 11q deletion syndrome, such as prominent epicanthal folds, broad flat nasal bridge with short, upturned nose, short philtrum with carp‐shaped mouth, cardiac anomalies and nonprogressive moderate psychomotor developmental delay. Patient 1 is the first case to be reported with 11q deletion with serial magnetic resonance (MR) examinations of cerebral white matter. The initial MR imaging studies demonstrated multiple areas of T1 and T2 prolongation in the cerebral white matter in both patients at the ages of 2 5/12 and 2 1/12 years, respectively. A second MR imaging, performed 1 year after the first in Patient 1, demonstrated slight improvement of the lesions. Neither patient showed clinical deterioration. These results suggest that the lesions were caused by delayed myelination, rather than by demyelination. It is suggested that an unknown factor which is important for myelination is located on the long arm of chromosome 11: perhaps the neural cell adhesion molecule (NCAM).