A Mendelian Randomization-Based Causal Investigation on Bacterial Infection-Related Genes and Neurodegenerative Diseases.

Neurodegenerative diseases remain the most prevalent and unsolved health problems in human society, especially Alzheimer's disease (AD) and Parkinson's disease (PD). The pathogenesis, pathology, and potential clinical treatments of neurodegenerative diseases still require in-depth research. In the wake of the association between pandemics and a growing number of neurodegeneration patients, there has been growing speculation that infections are linked to AD and PD. The Aß peptide is an important causal-related biomarker of AD and is reported to share structural and functional similarities with certain antimicrobial peptides, suggesting that it has a role in eliciting an immune response against microbes. But how neurodegeneration is related to bacterial chronic infection has not been thoroughly investigated. Using the data from genome-wide association studies (GWAS), we performed Mendelian Randomization (MR) and map 7 genes in multiple bacterial infection pathways as exposure, which show a significant association with the outcome of AD or PD. As co-verification, we perform Gene Set Enrichment Analysis (GSEA) on selected genetic variants incorporating their perturb-seq gene list (combining single-cell RNA-seq and CRISPR-based perturbations). We observed clustering of the differentially expressed genes (DEGs) in the upstream and downstream of AD and PD-related KEGG pathways, hence confirming their causal association with AD and PD and providing new perspectives on the true cause of neurodegeneration.

COG4 mutation in Saul-Wilson syndrome selectively affects secretion of proteins involved in chondrogenesis in chondrocyte-like cells.

Saul-Wilson syndrome is a rare skeletal dysplasia caused by a heterozygous mutation in COG4 (p.G516R). Our previous study showed that this mutation affected glycosylation of proteoglycans and disturbed chondrocyte elongation and intercalation in zebrafish embryos expressing the COG4p.G516R variant. How this mutation causes chondrocyte deficiencies remain unsolved. To analyze a disease-relevant cell type, COG4p.G516R variant was generated by CRISPR knock-in technique in the chondrosarcoma cell line SW1353 to study chondrocyte differentiation and protein secretion. COG4p.G516R cells display impaired protein trafficking and altered COG complex size, similar to SWS-derived fibroblasts. Both SW1353 and HEK293T cells carrying COG4p.G516R showed very modest, cell-type dependent changes in N-glycans. Using 3D culture methods, we found that cells carrying the COG4p.G516R variant made smaller spheroids and had increased apoptosis, indicating impaired in vitro chondrogenesis. Adding WT cells or their conditioned medium reduced cell death and increased spheroid sizes of COG4p.G516R mutant cells, suggesting a deficiency in secreted matrix components. Mass spectrometry-based secretome analysis showed selectively impaired protein secretion, including MMP13 and IGFBP7 which are involved in chondrogenesis and osteogenesis. We verified reduced expression of chondrogenic differentiation markers, MMP13 and COL10A1 and delayed response to BMP2 in COG4p.G516R mutant cells. Collectively, our results show that the Saul-Wilson syndrome COG4p.G516R variant selectively affects the secretion of multiple proteins, especially in chondrocyte-like cells which could further cause pleiotropic defects including hampering long bone growth in SWS individuals.

A Dominant Heterozygous Mutation in COG4 Causes Saul-Wilson Syndrome, a Primordial Dwarfism, and Disrupts Zebrafish Development via Wnt Signaling.

Saul-Wilson syndrome (SWS) is a rare, skeletal dysplasia with progeroid appearance and primordial dwarfism. It is caused by a heterozygous, dominant variant (p.G516R) in COG4, a subunit of the conserved oligomeric Golgi (COG) complex involved in intracellular vesicular transport. Our previous work has shown the intracellular disturbances caused by this mutation; however, the pathological mechanism of SWS needs further investigation. We sought to understand the molecular mechanism of specific aspects of the SWS phenotype by analyzing SWS-derived fibroblasts and zebrafish embryos expressing this dominant variant. SWS fibroblasts accumulate glypicans, a group of heparan sulfate proteoglycans (HSPGs) critical for growth and bone development through multiple signaling pathways. Consistently, we find that glypicans are increased in zebrafish embryos expressing the COG4 p.G516R variant. These animals show phenotypes consistent with convergent extension (CE) defects during gastrulation, shortened body length, and malformed jaw cartilage chondrocyte intercalation at larval stages. Since non-canonical Wnt signaling was shown in zebrafish to be related to the regulation of these processes by glypican 4, we assessed wnt levels and found a selective increase of wnt4 transcripts in the presence of COG4 p.G516R . Moreover, overexpression of wnt4 mRNA phenocopies these developmental defects. LGK974, an inhibitor of Wnt signaling, corrects the shortened body length at low concentrations but amplifies it at slightly higher concentrations. WNT4 and the non-canonical Wnt signaling component phospho-JNK are also elevated in cultured SWS-derived fibroblasts. Similar results from SWS cell lines and zebrafish point to altered non-canonical Wnt signaling as one possible mechanism underlying SWS pathology.

Normal transferrin patterns in congenital disorders of glycosylation with Golgi homeostasis disruption: apolipoprotein C-III at the rescue!

We identified three cases of congenital disorders of glycosylation (CDG) with Golgi homeostasis disruption, one ATP6V0A2-CDG and two COG4-CDG, with normal transferrin screening analyses. Patient 1 (P1) presented at birth with cutis laxa. Patient 2 (P2) and patient 3 (P3) are adult siblings and presented with severe symptoms evocative of inborn errors of metabolism. Targeted gene sequencing in P1 revealed pathogenic ATP6V0A2 variants, shared by her affected older brother. In P2 and P3, whole exome sequencing revealed a homozygous COG4 variant of unknown significance. In all affected individuals, transferrin analysis was normal. Mass-spectrometry based serum N-glycome analysis and two-dimensional electrophoresis (2-DE) of haptoglobin and of mucin core 1 O-glycosylated apolipoprotein C-III (apoC-III) were performed. All results of second-line N-glycosylation analyses were initially normal. However, apoC-III 2-DE revealed characteristic "apoC-III1" pattern in P1 and specific "apoC-III0" patterns in P2 and P3. In P2 and P3, this allowed reclassifying the variant as likely pathogenic according to ACMG guidelines. These cases highlight the existence of normal transferrin patterns in CDG with Golgi homeostasis disruption, putting the clinicians at risk of misdiagnosing patients. Furthermore, they show the potential of apoC-III 2-DE in diagnosing this type of CDG, with highly specific patterns in COG-CDG.

Growth in individuals with Saul-Wilson syndrome.

Saul-Wilson syndrome (SWS) is a rare autosomal recessive disorder characterized by microcephalic primordial dwarfism, spondyloepimetaphyseal dysplasia, characteristic facial findings, clubfoot, brachydactyly, bilateral cataracts, and hearing loss. Recently, recurrent mutations in COG4, encoding a component of the Conserved Oligomeric Golgi (COG) complex, were identified. We created detailed growth curves for stature, weight, and head circumference, as well as weight-for-length and weight velocity charts for younger children, derived from hundreds of data points obtained by retrospective chart review from 14 individuals with molecularly-confirmed SWS. In addition, we performed statistical comparisons of height-for-age model fits before and after initiation of growth hormone supplementation, and found that this therapy does not appear to influence height in individuals with SWS. We hope that these charts will represent valuable tools for clinicians, both in assessing whether SWS seems an appropriate diagnosis, as well as to monitor growth of affected individuals. In particular, we hope that our detailed growth characterization will reduce morbidity resulting from unnecessarily aggressive nutritional interventions by well-intentioned physicians trying to promote weight gain, an unrealistic goal in this genetically-determined cause of primordial dwarfism.

Defining the clinical phenotype of Saul-Wilson syndrome.

PURPOSE: Four patients with Saul-Wilson syndrome were reported between 1982 and 1994, but no additional individuals were described until 2018, when the molecular etiology of the disease was elucidated. Hence, the clinical phenotype of the disease remains poorly defined. We address this shortcoming by providing a detailed characterization of its phenotype. METHODS: Retrospective chart reviews were performed and primary radiographs assessed for all 14 individuals. Four individuals underwent detailed ophthalmologic examination by the same physician. Two individuals underwent gynecologic evaluation. Z-scores for height, weight, head circumference and body mass index were calculated at different ages. RESULTS: All patients exhibited short stature, with sharp decline from the mean within the first months of life, and a final height Z-score between -4 and -8.5 standard deviations. The facial and radiographic features evolved over time. Intermittent neutropenia was frequently observed. Novel findings included elevation of liver transaminases, skeletal fragility, rod-cone dystrophy, and cystic macular changes. CONCLUSIONS: Saul-Wilson syndrome presents a remarkably uniform phenotype, and the comprehensive description of our cohort allows for improved understanding of the long-term morbidity of the condition, establishment of follow-up recommendations for affected individuals, and documentation of the natural history into adulthood for comparison with treated patients, when therapeutics become available.

Cog4 is required for protrusion and extension of the epithelium in the developing semicircular canals.

The semicircular canals in the inner ear sense angular acceleration. In zebrafish, the semicircular canals develop from epithelial projections that grow toward each other and fuse to form pillars. The growth of the epithelial projections is driven by the production and secretion of extracellular matrix components by the epithelium. The conserved oligomeric Golgi 4 protein, Cog4, functions in retrograde vesicle transport within the Golgi and mutations can lead to sensory neural hearing loss. In zebrafish cog4 mutants, the inner ear is smaller and the number of hair cells is reduced. Here, we show that formation of the pillars is delayed and that secretion of extracellular matrix components (ECM) is impaired in cog4-/- mutants. These results show that Cog4 is required for secretion of ECM molecules essential to drive the growth of the epithelial projections and thus regulates morphogenesis of the semicircular canals.

Cog-4 has limited diagnostic test accuracy and validity for cognitive assessment in stroke survivors.

BACKGROUND: Guidelines recommend cognitive screening for all stroke survivors but do not suggest a preferred tool. Certain elements (orientation, executive function, language, and inattention) of the impairment scale, National Institutes of Health Stroke Scale (NIHSS), have been suggested as a short cognitive screening test-Cog-4. We aimed to describe accuracy and validity of Cog-4 against a more detailed cognitive assessment (Montreal Cognitive Assessment [MoCA]). METHODS: We assessed consecutive acute stroke unit admissions in 2 hospitals over 3 months. Four independent blinded assessors performed NIHSS and MoCA between days 1 and 4 poststroke. We described test properties of Cog-4 for MoCA-defined cognitive impairment using usual thresholds (Cog-4≥1 and MoCA<26 of 30) and described the correlations of individual Cog-4 components with broadly equivalent MoCA domains. RESULTS: We assessed 173 participants; 166 had Cog-4 data and 148 MoCA. MoCA described 84% (n=124) of assessed participants as having cognitive impairment and the Cog-4, 37% (n=62). Cog-4 had a sensitivity of .36 (95% confidence interval [CI]: .28-.45) and a specificity of .96 (95% CI: .80-.99) (positive predictive value: .98, negative predictive value: .23) for MoCA-defined cognitive impairment. Individual Cog-4 items correlated with certain MoCA domains, but the strength of association was modest (r=-.44 orientation, -.37 language, -.19 for inattention, and no significant correlation for executive function, P=.72). CONCLUSIONS: Our data suggest that many stroke survivors with MoCA-defined cognitive problems would not be detected by Cog-4. Subtest correlations suggest that Cog-4 may not be a valid measure of the cognitive domains that it purports to describe. Other brief cognitive screening tests may be better suited to acute stroke.