GPATCH4 contributes to nucleolus morphology and its dysfunction impairs cell viability.

The nucleolus serves a multifaceted role encompassing not only rRNA transcription and ribosome synthesis, but also the intricate orchestration of cell cycle regulation and the modulation of cellular senescence. G-patch domain containing 4 (GPATCH4) stands as one among the nucleolar proteins; however, its functional significances remain still unclear. In order to elucidate the functions of GPATCH4, we examined the effects of its dysfunction on cellular proliferation, alterations in nucleolar architecture, apoptotic events, and cellular senescence. Through experimentation conducted on cultured neuroblastoma SH-SY5Y cells, the reduction of GPATCH4 caused inhibition of cellular proliferation, concurrently fostering escalated apoptotic susceptibilities upon exposure to high-dose etoposide. In the realm of nucleolar morphology comparisons, a discernible decline was noted in the count of nucleoli per nucleus, concomitant with a significant expansion in the area occupied by individual nucleoli. Upon induction of senescence prompted by low-dose etoposide, GPATCH4 knockdown resulted in decreased cell viability and increased expression of senescence-associated markers, namely senescence-associated ß-galactosidase (SA-ß-GAL) and p16. Furthermore, GPATCH4 dysfunction elicited alterations in the gene expression profile of the ribosomal system. In sum, our findings showed that GPATCH4 is a pivotal nucleolar protein that regulates nucleolar morphology and is correlated with cell viability.

Loss of GBA in zebrafish leads to dopaminergic neurodegeneration, but overexpression of α-synuclein does not further worsen degeneration.

OBJECTIVES: Parkinson's disease is a neurodegenerative disorder that causes motor and nonmotor symptoms due to the loss of dopaminergic nerves and is characterized by the presence of Lewy bodies, which are mainly composed of α-synuclein. Glucosylceramidase beta (GBA), which is a causative gene of autosomal recessive Gaucher disease, is also known to be a risk gene for Parkinson's disease. In this study, we tried to detect synergistic effects of α-synuclein accumulation and gba depletion on dopaminergic neurodegeneration in zebrafish. METHODS: We generated a transgenic line of zebrafish overexpressing the A53T α-synuclein and gba mutant fish, and analyzed pathologies of α-synuclein aggregation and neurodegeneration. RESULTS: Zebrafish overexpressing the A53T α-synuclein did not exhibit α-synuclein aggregate formation. After the loss of gba function in this mutant α-synuclein transgenic line, we observed the marked presence of α-synuclein aggregates. Loss of gba function in zebrafish resulted in dopaminergic and noradrenergic neurodegeneration but this level of neurodegeneration was not exacerbated by overexpression of mutant α-synuclein. CONCLUSIONS: These results indicate that loss of gba function was sufficient to generate a neurodegenerative phenotype in zebrafish regardless of the expression of α-synuclein.

Zebrafish, Medaka and Turquoise Killifish for Understanding Human Neurodegenerative/Neurodevelopmental Disorders.

In recent years, small fishes such as zebrafish and medaka have been widely recognized as model animals. They have high homology in genetics and tissue structure with humans and unique features that mammalian model animals do not have, such as transparency of embryos and larvae, a small body size and ease of experiments, including genetic manipulation. Zebrafish and medaka have been used extensively in the field of neurology, especially to unveil the mechanisms of neurodegenerative diseases such as Parkinson's and Alzheimer's disease, and recently, these fishes have also been utilized to understand neurodevelopmental disorders such as autism spectrum disorder. The turquoise killifish has emerged as a new and unique model animal, especially for ageing research due to its unique life cycle, and this fish also seems to be useful for age-related neurological diseases. These small fishes are excellent animal models for the analysis of human neurological disorders and are expected to play increasing roles in this field. Here, we introduce various applications of these model fishes to improve our understanding of human neurological disorders.

An infant in whom contrast-enhanced fluid attenuated inversion recovery (FLAIR) MRI was useful for the diagnosis of meningitis and devising a treatment strategy.

A 3-month-old male was brought to our hospital due to fever, poor sucking, and a bulging anterior fontanel. His general condition was poor. Analysis of the cerebrospinal fluid (CSF) showed increases in the cell count (8/µl) and the polymorphonuclear leukocyte count (2/µl) but normal sugar (66 mg/dl) and protein (28 mg/dl) levels. A CSF smear showed no bacterial cells. The administration of antibacterial drugs was initiated, and head MRI was performed on the next day. Plain images revealed no abnormalities. However, contrast-enhanced fluid-attenuated inversion recovery (FLAIR) MRI showed clear contrast enhancement along the brain surface in the meninges of the left and right frontal and left parietal lobes and fluid retention accompanied by contrast enhancement in a part of the adjacent subdural space. These findings could be confirmed only by contrast-enhanced FLAIR MRI. A diagnosis of bacterial meningitis with an unknown cause was made, and the administration of 2 antibacterial drugs was continued. MRI on day 8 of the illness showed the disappearance of contrast enhancement, and plain FLAIR also facilitated a diagnosis of a subdural hygroma. The treatment was effective. At present, the patient is 1 year and 6 months old without sequelae. The diagnosis of bacterial meningitis in infants is difficult based on only symptoms. In its early stage with few abnormal findings in the CSF, diagnosis is sometimes difficult. Antibacterial drug administration should be immediately initiated. However, definite findings are necessary for the continuation of large amounts of antibacterial drugs. Contrast-enhanced FLAIR allows the sensitive visualization of meningeal inflammation and is useful as a complementary diagnostic method for meningitis. In addition, this technique can reveal marked inflammatory lesions such as a subdural hygroma in the early stage, providing information useful for making a diagnosis of bacterial meningitis.