The involvement of the neuronal Golgi apparatus and trans-Golgi network in the human olivary hypertrophy

The Guillain-Mollaret triangle: a key player in motor coordination and control with implications for neurological disorders

The dentato-rubro-olivary pathway, also known as the Guillain-Mollaret triangle (GMT) or myoclonic triangle, consists of the dentate nucleus, the red nucleus, and the inferior olivary nucleus (ION). GMT is important for motor coordination and control, and abnormalities in this network can lead to various neurological disorders. The present study followed a systematic approach in conducting a review on GMT studies. The inclusion criteria were limited to human subjects with primary objectives of characterizing and evaluating GMT syndromes, and the methodology used was not a determining factor for eligibility. The search strategy used MeSH terms and keywords relevant to the study's objective in various databases until August 2022. A total of 76 studies were included in the review after assessing 527 articles for eligibility based on the final inclusion criteria. Most of the studies evaluated the GMT in human subjects, with the majority utilizing magnetic resonance imaging (MRI), diffusion tensor imaging (DTI), or combination of them. The review found that Hypertrophic olivary degeneration (HOD), a common consequence of GMT damage, has diverse underlying causes, including stroke, brainstem cavernous malformations, and structural impairments. Palatal tremor, ocular myoclonus, ataxia, nystagmus, and vertigo were frequently reported symptoms associated with HOD. This systematic review provides comprehensive insights into the association between GMT and various neurological syndromes, shedding light on the diagnostic, etiological, and prognostic aspects of GMT dysfunction. Understanding the role of the GMT and its implications in movement disorders could pave the way for improved treatment options and better management of neurological conditions related to this critical brainstem pathway.

Cerebellar networks and neuropathology of cerebellar developmental disorders

The cerebellar system is a series of axonal projections and synaptic circuits as networks, similar to those of the limbic system and those subserving the propagation and spread of seizures. Three principal cerebellar networks are identified and cerebellar disease often affects components of the networks other than just the cerebellar cortex. Contemporary developmental neuropathology of the cerebellum is best considered in the context of alterations of developmental processes: embryonic segmentation and genetic gradients along the three axes of the neural tube, individual neuronal and glial cell differentiation, migration, synaptogenesis, and myelination. Precisely timed developmental processes may be delayed or precocious rhombencephalosynapsis and pontocerebellar hypoplasia exemplify opposite gradients in the horizontal axis. Chiari II malformation may be reconsidered as a disorder of segmentation rather than simply due to mechanical forces upon normally developing hindbrain structures. Cellular nodules in the roof of the fourth ventricle are heterotopia of histologically differentiated but architecturally disoriented and disorganized neurons and glial cells; they often are less mature immunocytochemically than similar cells in adjacent normal folia. Cell rests are nodules of undifferentiated neuroepithelial cells. Both are frequent in human fetuses and neonates. Axonal projections from heterotopia to adjacent cerebellar folia or nuclei are few or absent, hence these nodules are clinically silent despite neuronal differentiation.

Pathology of protein synthesis and degradation systems in ALS

Protein synthesis and degradation systems in neurons are among the major subjects of study in neurobiology. These systems are believed to be the main pathways involved in ALS; however, the essential pathomechanisms that underlie this disease remain obscure. In addition to the ubiquitin-proteasomal and autophagic systems, several cytoplasmic organelles are also involved in ALS. Here, we present our data and discuss the main morphological abnormalities detected in the anterior horn cells of ALS patients.

Protein kinase D controls the integrity of Golgi apparatus and the maintenance of dendritic arborization in hippocampal neurons

Protein kinase D (PKD) is known to participate in various cellular functions, including secretory vesicle fission from the Golgi and plasma membrane-directed transport. Here, we report on expression and function of PKD in hippocampal neurons. Expression of an enhanced green fluorescent protein (EGFP)-tagged PKD activity reporter in mouse embryonal hippocampal neurons revealed high endogenous PKD activity at the Golgi complex and in the dendrites, whereas PKD activity was excluded from the axon in parallel with axonal maturation. Expression of fluorescently tagged wild-type PKD1 and constitutively active PKD1(S738/742E) (caPKD1) in neurons revealed that both proteins were slightly enriched at the trans-Golgi network (TGN) and did not interfere with its thread-like morphology. By contrast, expression of dominant-negative kinase inactive PKD1(K612W) (kdPKD1) led to the disruption of the neuronal Golgi complex, with kdPKD1 strongly localized to the TGN fragments. Similar findings were obtained from transgenic mice with inducible, neuron-specific expression of kdPKD1-EGFP. As a prominent consequence of kdPKD1 expression, the dendritic tree of transfected neurons was reduced, whereas caPKD1 increased dendritic arborization. Our results thus provide direct evidence that PKD activity is selectively involved in the maintenance of dendritic arborization and Golgi structure of hippocampal neurons.

Golgi apparatus and neurodegenerative diseases

Neurodegenerative disorders are typically characterized by progressive and extensive neuronal loss in specific populations of neurons and brain areas which lead to the observed clinical manifestations. Despite the recent advances in molecular neuroscience, the subcellular bases such as Golgi apparatus (GA) for most neurodegenerative diseases are poorly understood. This review gives a brief overview of the contribution of the neuronal GA in the pathogeneses of neurodegeneration, summarizes what is known of the GA machinery in these diseases, and present the relationship between GA fragmentation and the aggregation and accumulation of misfolded or aberrant proteins including mutant SOD1, a-synuclein, tau, which is considered to be a key event in the pathogenic process, and perturbating in calcium homeostasis, regulation of hormones, lipid metabolism are also linkage to the function of the GA thought to underlie neurodegeneration. Although these precise diseases mechanisms remain to be clarified, more research is needed to better understand how GA function for it and to enable physicians to use this knowledge for the benefit of the patients.

Increased neuronal expression of alpha B-crystallin in human olivary hypertrophy

We studied morphologic changes in olivary hypertrophy from dentato-olivary tract lesions by immunohistologic methods with antialpha B-crystallin and antiheat shock protein 27 (HSP 27). The majority of central chromatolysis-like enlarged neurons, which are frequently seen in the early stages of olivary hypertrophy on ipsilateral lesions, showed a marked expression of alpha B-crystallin; however, HSP 27 did not show increased expression in those neurons. In the later stages of olivary hypertrophy, increased expressions of alpha B-crystallin varied in the remaining neurons and the expression of HSP 27 increased in hypertrophied astrocytes, although the expression of alpha B-crystallin in hypertrophic astrocytes was not prominent. The accumulation of alpha B-crystallin and HSP 27 may represent responses to pathologic conditions.

Golgi apparatus of the motor neurons in patients with amyotrophic lateral sclerosis and in mice models of amyotrophic lateral sclerosis

We examined the Golgi apparatus (GA) of motor neurons of patients with ALS and in mice models of ALS by immunohistological method using antiserum against MG160 and against components of the trans-Golgi network (TGN46). The GA of half of the remaining spinal cord motor neurons of patients with sporadic ALS showed fragmentation, where the GA were dispersed or fragmented into numerous small, isolated elements. The GA of Betz cells in sporadic ALS were fragmented similar to that of anterior horn cells, and the GA of spinal cord motor neurons of those with familial ALS and of those with ALS with basophilic inclusions were fragmented or diminished. The GA in the majority of the motor neurons contained Bunina bodies, basophilic inclusions and superoxide dismutase 1 (SOD1)-positive aggregates were fragmented. The motor neurons in transgenic mice expressing G93A mutation of the SOD1 gene showed the fragmentation of the GA months before the onset of paralysis. These findings suggest that the fragmentation of GA may be related to the neuronal degeneration in patients with ALS.

Masses of phosphorylated neurofilaments are associated with abnormal golgi apparatus of anterior horn neurons of beta, beta'-iminodipropionitrile-intoxicated rats

The Golgi apparatus (GA) of anterior horn neurons of rats chronically intoxicated with beta,beta'-iminodipropionitrile (IDPN) in drinking water was examined with an organelle-specific antibody. The neuropile of the anterior horns contained the typical axonal spheroids associated with IDPN toxicity while the perikarya of approximately one-third of the neurons contained phosphorylated neurofilaments, which are not found in the perikarya of control rat neurons. By serial or double immunostaining with the SMI-31 and anti-MG 160 antibodies, there were no morphological changes of the GA in the majority of neurons including neurons with a mild to moderate degree of neurofilamentous accumulation. However, a few neurons with a massive accumulation of phosphorylated neurofilaments contained abnormal profiles of the GA which consisted of focal clustering, reduction in size and fragmentation. The results suggest that masses of phosphorylated neurofilaments are associated with structural abnormalities of the GA.