Kenji Jinnai

Loss of serotonin‐containing neurons in the raphe of patients with myotonic dystrophy A quantitative immunohistochemical study and relation to hypersomnia

Hypersomnia occurs frequently in patients with myotonic dystrophy (MyD). We performed a quantitative immunohistochemical study of serotonin (5—HT) containing neurons linked to hypersomnia in the dorsal raphe nucleus (DRN) and the superior central nucleus (SCN) in 8 patients with MyD, 5 of whom showed hypersomnia, and in 12 age-matched controls. The densities of 5—HT neurons in the DRN and the SCN were significantly lower in MyD patients with hypersomnia than in MyD patients without hypersomnia and controls. These data suggest that the loss of 5—HT neurons of the DRN and the SCN is associated with the presence of hypersomnia in MyD.

Neuropathological changes of the brain in myotonic dystrophy - some new observations

Brain autopsy materials from 2 patients with myotonic dystrophy (MyD) were studied. The results obtained in these 2 cases were quite similar. Besides thalamic inclusion bodies and minor abnormalities in gyral architecture with a disordered cortical cellular arrangement, some new observations have been made. First, no more than one intracytoplasmic inclusion body per cell was present in the cerebral cortex, the thalamus, the caudate nucleus and the putamen; this inclusion body was oval or elongated with smooth, sharply defined contours and was usually located at the periphery of the cell. Second, irregular intracytoplasmic inclusion bodies, often multiple and not surrounded by a halo, were found at the periphery or within accumulations of neuromelanin granules in the pigmented cells of the substantia nigra. All the bodies described above stained highly eosinophilic with hematoxylin-eosin and the ultrastructure of the bodies in the thalamus and the substantia nigra was almost the same; these bodies were composed of stacks of alternating parallel, light and dark rectilinear profiles oriented perpendicularly to the longitudinal axis of the bodies. Third, Marinesco bodies were observed with a very high frequency in the pigmented cells of the substantia nigra.

Loss of catecholaminergic neurons in the medullary reticular formation in myotonic dystrophy

Objective: To clarify the possible relation between the extent of involvement of catecholaminergic neurons and the presence of alveolar hypoventilation in patients with myotonic dystrophy (MyD). Background: Respiratory insufficiency has been reported frequently in MyD patients. Recent data support the hypothesis that this respiratory failure results from a primary dysfunction of the CNS. Methods: The authors performed a quantitative immunoreactive study of tyrosine hydroxylase immunoreactive (TH+) neurons linked to hypoventilation in the dorsal central medullary nucleus (DCMN), the ventral central medullary nucleus (VCMN), and the subtrigeminal medullary nucleus (SMN)-where the automatic respiratory center is thought to be located-in eight MyD patients and in 10 age-matched control subjects. Alveolar hypoventilation of the central type was present in three of the MyD patients but not in the remaining MyD patients or the control subjects. Results: The densities of TH+ neurons of the DCMN, the VCMN, and the SMN in MyD patients with hypoventilation were significantly lower than in those without hypoventilation (p < 0.02, p < 0.01, and p < 0.01, respectively) and control subjects (p < 0.01, p < 0.01, and p < 0.01, respectively). Conclusions: These data suggest that the loss of TH+ neurons of the DCMN, the VCMN, and the SMN is associated with the presence of hypoventilation in MyD and may be an important feature of MyD.

Neuronal loss in the medullary reticular formation in myotonic dystrophy A clinicopathological study

Article abstract-Respiratory insufficiency occurs frequently in patients with myotonic dystrophy (MyD). We have performed a quantitative study of neurons linked to respiratory function in the dorsal central medullary nucleus (DCMN), the ventral central medullary nucleus (VCMN), and the subtrigeminal medullary nucleus (SMN) in seven patients with MyD and eight age-matched controls. Alveolar hypoventilation of the central type occurred in three of the MyD patients but not in the remaining MyD patients or controls. The densities of neurons of the DCMN, the VCMN, and the SMN in MyD patients with hypoventilation were significantly lower than in MyD without hypoventilation and controls. These data suggest that the neuronal loss of the DCMN, VCMN, and SMN is associated with the presence of hypoventilation in MyD and may be an important feature of MyD. NEUROLOGY 1996;46: 228-231

Immunohistochemical characterization of microglia in Nasu-Hakola disease brains

Nasu‐Hakola disease (NHD) is a rare autosomal recessive disorder, characterized by progressive presenile dementia and formation of multifocal bone cysts, caused by genetic mutations of DNAX‐activation protein 12 (DAP12) or triggering receptor expressed on myeloid cells 2 (TREM2). TREM2 and DAP12 constitute a receptor/adapter signaling complex expressed on osteoclasts, dendritic cells (DC), macrophages and microglia. Previous studies using knockout mice and mouse brain cell cultures suggest that a loss‐of‐function of DAP12/TREM2 in microglia plays a central role in the neuropathological manifestation of NHD. However, there exist no immunohistochemical studies that focus attention on microglia in NHD brains. To elucidate a role of microglia in the pathogenesis of NHD, we searched NHD‐specific biomarkers and characterized their expression on microglia in NHD brains. Here, we identified allograft inflammatory factor 1 (AIF1, Iba1) and sialic acid binding Ig‐like lectin 1 (SIGLEC1) as putative NHD‐specific biomarkers by bioinformatics analysis of microarray data of NHD DC. We studied three NHD and eight control brains by immunohistochemistry with a panel of 16 antibodies, including those against Iba1 and SIGLEC1. We verified the absence of DAP12 expression in NHD brains and the expression of DAP12 immunoreactivity on ramified microglia in control brains. Unexpectedly, TREM2 was not expressed on microglia but expressed on a small subset of intravascular monocytes/macrophages in control and NHD brains. In the cortex of NHD brains, we identified accumulation of numerous Iba1‐positive microglia to an extent similar to control brains, while SIGLEC1 was undetectable on microglia in all the brains examined. These observations indicate that human microglia in brain tissues do not express TREM2 and DAP12‐deficient microglia are preserved in NHD brains, suggesting that the loss of DAP2/TREM2 function in microglia might not be primarily responsible for the neuropathological phenotype of NHD.

Intracytoplasmic inclusion bodies of the thalamus and the substantia nigra, and Marinesco bodies in myotonic dystrophy: a quantitative morphological study

SummaryIntracytoplasmic inclusion bodies of the thalamus and the substantia nigra, and Marinesco bodies have been studied in four patients with myotonic dystrophy (MyD), eight patients with other neurological diseases (control A), and eight patients without neurological diseases (control B). The percentages of the affected cells were calculated by dividing the number of neurons including intracytoplasmic inclusion bodies of the thalamus and the substantia nigra, and Marinesco bodies, by the total cell count in these respective regions. Statistical analyses were performed with regard to the frequency of these bodies by using Studentst test. There was a significantly higher incidence of intracytoplasmic inclusion bodies of the thalamus (13.2% versus 0.7%,P<0.001) and the substantia nigra (20.4% versus 2.7%,P<0.001), and Marinesco bodies (37.4% versus 4.1%,P<0.001) in patients with MyD than in controls A and B. From our observations, it is suggested that the presence with a high frequency, in combination, of these bodies is not an incidental finding but may have an intimate and important relationship with the pathogenesis of MyD, and may be a conspicuous and diagnostically important feature of MyD.

Decreased type IV collagen of skin and serum in patients with amyotrophic lateral sclerosis

Objective: To study type IV collagen of skin and serum in patients with ALS. Background: Collagen abnormalities of skin have been reported in ALS patients. However, little is known concerning type IV collagen in ALS. Methods: We studied type IV collagen immunoreactivity of skin and measured serum levels of the 7S fragment of the N-terminal domain of type IV collagen (7S collagen) in patients with ALS and control subjects. Results: The basement membrane as well as blood vessels of skin in ALS patients was weakly positive for type IV collagen as compared with those of diseased control subjects. This weak immunostaining became more pronounced as ALS progressed. The optical density for type IV collagen immunoreactivity in ALS patients was significantly lower (p < 0.001) than in diseased control subjects and was significantly decreased with duration of illness(r = -0.85, p < 0.01). Serum 7S collagen levels in patients with ALS were significantly decreased (p < 0.01) as compared with those in diseased and healthy control subjects and were negatively and significantly associated with duration of illness (r= -0.81, p < 0.001). There was an appreciable positive correlation between concentrations of serum 7S collagen and the density for type IV collagen immunoreactivity in ALS patients (r = 0.81, p < 0.02). Conclusions: These data suggest that a metabolic alteration of type IV collagen may take place in the skin of ALS patients and that the decreased levels of serum 7S collagen may reflect a decreased type IV collagen immunoreactivity of skin in patients with ALS.

Elongation of (CTG)n repeats in myotonic dystrophy protein kinase gene in tumors associated with myotonic dystrophy patients

Length of (CTG)n triplet repeats in myotonic dystrophy protein kinase gene (DMPK) was estimated in tumors, normal tissues of the same organs, muscles, and leukocytes from three myotonic dystrophy (DM) patients and a non‐DM patient. Using cDNA 25 as a probe, a Southern blot analysis of EcoRI‐ and BglI‐digested DNA from these tissues demonstrated the longest expansion of the repeats in the tumors of DM patients. In all tissues from a non‐DM patient, the repeat length was confirmed to be stable by PCR analysis. Our data suggest that expanded (CTG)n repeat in tumor tissues may have increased the instability. This study emphasizes the importance of a long‐term prospective study on the incidence of tumors in DM to clarify the pathological interrelation between the two entities.

Phosphorylated Syk expression is enhanced in Nasu‐Hakola disease brains

Nasu‐Hakola disease (NHD) is a rare autosomal recessive disorder, characterized by progressive presenile dementia and formation of multifocal bone cysts, caused by a loss‐of‐function mutation of DNAX‐activation protein 12 (DAP12) or triggering receptor expressed on myeloid cells 2 (TREM2). TREM2 and DAP12 constitute a receptor/adaptor complex on myeloid cells. The post‐receptor signals are transmitted via rapid phosphorylation of the immunoreceptor tyrosine‐based activating motif (ITAM) of DAP12, mediated by Src protein tyrosine kinases, followed by binding of phosphorylated ITAM to Src homology 2 (SH2) domains of spleen tyrosine kinase (Syk), resulting in autophosphorylation of the activation loop of Syk. To elucidate the molecular mechanism underlying the pathogenesis of NHD, we investigated Syk expression and activation in the frontal cortex and the hippocampus of three NHD and eight control brains by immunohistochemistry. In NHD brains, the majority of neurons expressed intense immunoreactivities for Syk and Y525/Y526‐phosphorylated Syk (pSyk) chiefly located in the cytoplasm, while more limited populations of neurons expressed Src. The levels of pSyk expression were elevated significantly in NHD brains compared with control brains. In both NHD and control brains, substantial populations of microglia and macrophages expressed pSyk, while the great majority of reactive astrocytes and myelinating oligodendrocytes did not express pSyk, Syk or Src. These observations indicate that neuronal expression of pSyk was greatly enhanced in the cerebral cortex and the hippocampus of NHD brains, possibly via non‐TREM2/DAP12 signaling pathways involved in Syk activation.

Decrease of neurons in the medullary arcuate nucleus in myotonic dystrophy

Abstract. Respiratory insufficiency has been reported frequently in patients with myotonic dystrophy (MyD). Recent data support the hypothesis that this respiratory failure results from a primary dysfunction of the central nervous system. The medullary arcuate nucleus (ARC) has been shown to be involved in the regulation of respiration. We performed a quantitative study of neurons in the ARC in eight MyD patients, ten control subjects with other neurological diseases (control group A) and eight control subjects without neurological diseases (control group B). Alveolar hypoventilation of the central type occurred in three of the MyD patients but not in the remaining MyD patients or controls. The density of neurons in the ARC in MyD patients with hypoventilation was significantly lower than in MyD patients without hypoventilation and control groups A and B. There was no significant difference in the neuronal density of the ARC between MyD patients without hypoventilation and control groups A and B. These data suggest that the neuronal loss of the ARC is associated with the presence of hypoventilation in MyD.