A novel pathogenic variant in the 3' end of the AGTPBP1 gene gives rise to neurodegeneration without cerebellar atrophy: an expansion of the disease phenotype?

Extracellular vesicles highlight many cases of photoreceptor degeneration

The release of extracellular vesicles is observed across numerous cell types and serves a range of biological functions including intercellular communication and waste disposal. One cell type which stands out for its robust capacity to release extracellular vesicles is the vertebrate photoreceptor cell. For decades, the release of extracellular vesicles by photoreceptors has been documented in many different animal models of photoreceptor degeneration and, more recently, in wild type photoreceptors. Here, I review all studies describing extracellular vesicle release by photoreceptors and discuss the most unifying theme among them-a photoreceptor cell fully, or partially, diverts its light sensitive membrane material to extracellular vesicles when it has defects in the delivery or morphing of this material into the photoreceptor's highly organized light sensing organelle. Because photoreceptors generate an enormous amount of light sensitive membrane every day, the diversion of this material to extracellular vesicles can cause a massive accumulation of these membranes within the retina. Little is known about the uptake of photoreceptor derived extracellular vesicles, although in some cases the retinal pigment epithelial cells, microglia, Müller glia, and/or photoreceptor cells themselves have been shown to phagocytize them.

Evaluation of both expression and serum protein levels of caspase-8 and mitogen-activated protein kinase 1 genes in patients with different severities of COVID-19 infection

AIM

The current study aimed to evaluate the effects of caspase-8 (CASP8) and mitogen-activated protein kinase 1 (MAPK1) gene expression levels and their products on preventing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection.

METHODS

A total of 40 patients (men, 15 [37.5%]; women, 25 [62.5%]) with COVID-19 infection were included in the current study. The patients were divided into four main groups based on disease severity: mild (n = 7), moderate (n = 10), severe (n = 14), and critical (n = 9). Individuals aged < 18 years and pregnant women were excluded. Patients were classified according to the World Health Organization (WHO) classification system (WHO/2019-nCoV/clinical/2021.1).

RESULTS

Considering all groups, statistically significant differences were detected among all groups for both CASP8^2-ΔΔCt (p = 0.006) and MAPK1 2^-ΔΔCt values (p = 0.015). Moreover, statistically significant differences were detected between mild and moderate (p = 0.013), moderate and critical (p = 0.018), and severe and critical (p = 0.023) groups for lymphocytes.

CONCLUSION

The CASP8/MAPK1 expression levels and/or its products are essential in preventing injury caused by COVID-19 infection. They play crucial roles in maintaining cellular homeostasis and viability. Furthermore, CASP8/MAPK1 levels can provide information about disease severity.

Apoptosis-associated speck-like protein containing a CARD (ASC), TNF Like Factor 1a(TL-1a) and B Cell Chemoattractant Chemokine Ligand 13(CXCL-13) expression profiles in familial Mediterranean fever (FMF) patients

Objectives: This study was carried out to compare the expression levels of ASC(Apoptosis Associated Speck Like Protein Containing a CARD), TL-1a(TNF Like Factor 1a) and CXCL 13(B Cell Chemoattractant Chemokine Ligand 13) genes in FMF patients According to Tell-Hashomer Criteria and Genetic analysis result in Düzce University Research and Application Hospital with healthy controls and to determine their clinical significance in FMF. Method: 36 patients (20 girls, 16 boys) and 12 healthy controls (7 girls, 5 boys) were included in the study. RNA was isolated from the peripheral blood of each individual and expression levels of ASC, TL-1a and CXCL 13 genes were determined. Routine biochemical parameters were also determined. Result: CXCL 13 and TL-1a gene expression levels were significantly increased in patients with FMF, the expression level of the ASC gene was found to be increased in FMF patients, but not significantly. Conclusion: The expression levels of these genes may be related to the pathogenesis of the disease and these genes could be used as a marker in the early diagnosis of the disease.

Childhood-Onset Neurodegeneration with Cerebellar Atrophy Syndrome: Severe Neuronal Degeneration and Cardiomyopathy with Loss of Tubulin Deglutamylase Cytosolic Carboxypeptidase 1

The cytoskeleton is a dynamic filamentous network with various cellular and developmental functions. The loss of cytosolic carboxypeptidase 1 (CCP1) causes neuronal death. Childhood-onset neurodegeneration with cerebellar atrophy (CONDCA, OMIM no.: 618276) is an extremely rare disease caused by ATP/GTP binding protein 1 (AGTPBP1) gene-related CCP1 dysfunction of microtubules affecting the cerebellum, spinal motor neurons, and peripheral nerves. Also, possible problems are expected in tissues where the cytoskeleton plays a dynamic role, such as cardiomyocytes. In the present study, we report a novel homozygous missense (NM_015239: c.2447A > C, p. Gln816Pro) variant in the AGTPBP1 gene that c.2447A > C variant has never been reported in a homozygous state in the Genome Aggregation (gnomAD; v2.1.1) database, identified by whole-exome sequencing in a patient with a seizure, dystonia, dilated cardiomyopathy (DCM)-accompanying atrophy of caudate nuclei, putamen, and cerebellum. Unlike other cases in the literature, we expand the phenotype associated with AGTPBP1 variants to include dysmorphic features, idiopathic DCM which could be reversed with supportive treatments, seizure patterns, and radiological findings. These findings expanded the spectrum of the AGTPBP1 gene mutations and associated possible manifestations. Our study may help establish appropriate genetic counseling and prenatal diagnosis for undiagnosed neurodegenerative patients.

The AGTPBP1 gene in neurobiology

The function of the Agtpbp1 gene has mainly been delineated by studying Agtpbp1pcd (pcd) mutant mice, characterized by losses in cerebellar Purkinje and granule cells along with degeneration of retinal photoreceptors, mitral cells of the olfactory bulb, thalamic neurons, and alpha-motoneurons. As a result of cerebellar degeneration, cerebellar GABA and glutamate concentrations in Agtpbp1pcd mutants decreased while monoamine concentrations increased. The salient behavioral phenotypes include cerebellar ataxia, a loss in motor coordination, and cognitive deficits. Similar neuropathogical and behavioral profiles have been described in childhood-onset human subjects with biallelic variants of AGTPBP1, including cerebellar ataxia and hypotonia.

The Childhood-Onset Neurodegeneration with Cerebellar Atrophy (CONDCA) Disease Caused by AGTPBP1 Gene Mutations: The Purkinje Cell Degeneration Mouse as an Animal Model for the Study of this Human Disease

Recent reports have identified rare, biallelic damaging variants of the AGTPBP1 gene that cause a novel and documented human disease known as childhood-onset neurodegeneration with cerebellar atrophy (CONDCA), linking loss of function of the AGTPBP1 protein to human neurodegenerative diseases. CONDCA patients exhibit progressive cognitive decline, ataxia, hypotonia or muscle weakness among other clinical features that may be fatal. Loss of AGTPBP1 in humans recapitulates the neurodegenerative course reported in a well-characterised murine animal model harbouring loss-of-function mutations in the AGTPBP1 gene. In particular, in the Purkinje cell degeneration (pcd) mouse model, mutations in AGTPBP1 lead to early cerebellar ataxia, which correlates with the massive loss of cerebellar Purkinje cells. In addition, neurodegeneration in the olfactory bulb, retina, thalamus and spinal cord were also reported. In addition to neurodegeneration, pcd mice show behavioural deficits such as cognitive decline. Here, we provide an overview of what is currently known about the structure and functional role of AGTPBP1 and discuss the various alterations in AGTPBP1 that cause neurodegeneration in the pcd mutant mouse and humans with CONDCA. The sequence of neuropathological events that occur in pcd mice and the mechanisms governing these neurodegenerative processes are also reported. Finally, we describe the therapeutic strategies that were applied in pcd mice and focus on the potential usefulness of pcd mice as a promising model for the development of new therapeutic strategies for clinical trials in humans, which may offer potential beneficial options for patients with AGTPBP1 mutation-related CONDCA.