Publications by authors named "Siu V"

Aminoacyl-tRNA synthetases catalyze the ligation of a specific amino acid to its cognate tRNA. The resulting aminoacyl-tRNAs are indispensable intermediates in protein biosynthesis, facilitating the precise decoding of the genetic code. Pathogenic alleles in the aminoacyl-tRNA synthetases can lead to several dominant and recessive disorders.

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  • Heterozygous pathogenic variants in the HARS gene are linked to Charcot-Marie-Tooth (CMT) type 2W disease, a form of peripheral neuropathy, with at least 60 variants identified across several aminoacyl-tRNA synthetases.
  • A novel HARS variant, c.412T>C; p.Y138H, was discovered in a patient using a CMT gene panel, prompting further investigation into its effects.
  • Through studies using a humanized yeast model and protein analysis, researchers found that the p.Y138H variant caused protein dimerization issues and growth defects, but these problems showed improvement when histidine was supplied, suggesting a possible avenue for clinical trials.
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Background: Severe combined immunodeficiency (SCID) is a life-threatening genetic disorder caused by critical defects of the immune system. Almost all cases are lethal if not treated within the first two years of life. Early diagnosis and intervention are thus essential for improving patient outcomes.

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Pyruvate kinase (PK) is an essential component of cellular metabolism, converting ADP and phosphoenolpyruvate (PEP) to pyruvate in the final step of glycolysis. Of the four unique isoforms of pyruvate kinase, R (PKR) is expressed exclusively in red blood cells and is a tetrameric enzyme that depends on fructose-1,6-bisphosphate (FBP) for activation. PKR deficiency leads to hemolysis of red blood cells resulting in anemia.

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-related kyphoscoliotic Ehlers-Danlos syndrome is a rare, autosomal recessive connective tissue disorder characterized by congenital hypotonia, early-onset, progressive kyphoscoliosis, and generalized joint hypermobility. -kyphoscoliotic Ehlers-Danlos syndrome is also associated with heightened vascular fragility, resulting in an elevated susceptibility to recurrent vascular complications such as arterial aneurysms, dissection, and spontaneous arterial rupture. We report the cases of two affected brothers: a 13-year-old boy presenting with spontaneous rupture of a celiac artery aneurysm and a 10-year-old boy presenting with a rapidly enlarging celiac artery aneurysm requiring urgent repair.

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We describe the case of a 19-month-old girl presenting with gross motor delays, hypotonia, diminished deep tendon reflexes, hyperCKaemia, extensive white matter changes on MRI brain, and electromyography studies consistent with myopathy. The differential diagnosis for infantile-onset hypotonia and muscle weakness is broad. It includes numerous subtypes of genetic disorders, including congenital muscular dystrophies, congenital myopathies, congenital myasthenic syndromes, spinal muscular atrophy, single-gene genetic syndromes, and inborn errors of metabolism.

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  • The DIP2 gene, first found in fruit flies, is crucial for neuron branching and regeneration, with vertebrate versions (DIP2A, DIP2B, and DIP2C) being highly conserved in the central nervous system.
  • Research showed that mutations in DIP2C are linked to developmental delays in expressive language and speech articulation in 23 affected individuals.
  • Alongside developmental issues, some individuals with DIP2C variants also presented with various cardiac defects and minor facial anomalies, highlighting a connection between the gene's loss-of-function and neurocognitive and physical phenotypes.
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This paper presents a cost-effective, quantitative, point-of-care solution for urinalysis screening, specifically targeting nitrite, protein, creatinine, and pH in urine samples. Detecting nitrite is crucial for the early identification of urinary tract infections (UTIs), while regularly measuring urinary protein-to-creatinine (UPC) ratios aids in managing kidney health. To address these needs, we developed a portable, transmission-based colorimeter using readily available components, controllable via a smartphone application through Bluetooth.

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Background: In 2004, the International Pharmaceutical Federation (FIP) adopted a Statement of Professional Standard on the supply of medicines affecting driving performance, transformed to FIP guidelines in 2014. In 2011, the final report from the European initiative on Driving Under the Influence of Drugs, Alcohol and Medicines (DRUID) was published. Both documents provided recommendations for improving dispensing guidelines for driving-impairing medicines for patients who use psychoactive medicines.

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Purpose: To evaluate the diagnostic utility of publicly funded clinical exome sequencing (ES) for patients with suspected rare genetic diseases.

Methods: We prospectively enrolled 297 probands who met eligibility criteria and received ES across 5 sites in Ontario, Canada, and extracted data from medical records and clinician surveys. Using the Fryback and Thornbury Efficacy Framework, we assessed diagnostic accuracy by examining laboratory interpretation of results and assessed diagnostic thinking by examining the clinical interpretation of results and whether clinical-molecular diagnoses would have been achieved via alternative hypothetical molecular tests.

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Purpose: BCL11B-related disorder (BCL11B-RD) arises from rare genetic variants within the BCL11B gene, resulting in a distinctive clinical spectrum encompassing syndromic neurodevelopmental disorder, with or without intellectual disability, associated with facial features and impaired immune function. This study presents an in-depth clinico-biological analysis of 20 newly reported individuals with BCL11B-RD, coupled with a characterization of genome-wide DNA methylation patterns of this genetic condition.

Methods: Through an international collaboration, clinical and molecular data from 20 individuals were systematically gathered, and a comparative analysis was conducted between this series and existing literature.

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Non-immune hydrops is a prenatal finding which can occur due to an underlying genetic diagnosis such as common chromosomal aneuploidy (Trisomy 21, Turner syndrome etc.). It is extremely rare to have more than one genetic cause of hydrops fetalis in a single pregnancy.

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Purpose Of Program: Glomerulonephritis (GN) is a group of rare kidney diseases that is increasingly being managed with higher cost immunosuppressive (IS) agents in Canada. Ontario Health's Ontario Renal Network (ORN) oversees the management and delivery of GN services in the province. Stakeholder surveys previously conducted by ORN identified that both clinicians and patients do not perceive access to GN medications as comprehensive or timely.

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Purpose Of Review: In-stent restenosis (ISR) is the most common cause of stent failure. Although the rate of ISR is significantly lower with contemporary drug-eluting stents (DES), it remains a challenging clinical entity to treat.

Recent Findings: In this review, we focus on a practical approach to management of DES ISR with intravascular imaging at its core, as supported by several recently published articles.

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  • Cornelia de Lange Syndrome (CdLS) is a rare genetic disorder marked by a variety of symptoms including growth delays, upper limb issues, and other systemic problems, primarily caused by mutations in specific genes associated with the cohesin complex.
  • The majority of CdLS cases (over 60%) are linked to mutations in the NIPBL gene, which leads to the most severe form of the syndrome; other cohesin gene mutations typically result in milder symptoms.
  • The study analyzed the genetic factors in 716 individuals with CdLS to better understand the contributions of cohesin complex genes and identify potential new candidate genes, improving knowledge of genetic variations and their effects on CdLS manifestations.
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The pathophysiologic mechanism of sickle cell disease (SCD) involves polymerization of deoxygenated haemoglobin S (HbS), leading to red blood cell (RBC) sickling, decreased RBC deformability, microvascular obstruction, haemolysis, anaemia and downstream clinical complications. Pharmacological increase in the concentration of oxygenated HbS in RBCs has been shown to be a novel approach to inhibit HbS polymerization and reduce RBC sickling and haemolysis. We report that GBT021601, a small molecule that increases HbS-oxygen affinity, inhibits HbS polymerization and prevents RBC sickling in blood from patients with SCD.

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  • Advances in molecular diagnostics have shown that certain genetic variants linked to neurodegenerative diseases can also cause severe neurodevelopmental disorders when inherited in a biallelic manner.* -
  • The study focuses on TOR1A-associated arthrogryposis multiplex congenita 5 (AMC5), revealing a range of clinical symptoms across a cohort of 57 individuals, including severe flexion contractures, developmental delays, and various motor issues.* -
  • The research identified a phenotypic spectrum from mild symptoms to severe disabilities, with a notable survival rate of 71% and a median mortality age of 1.2 months, mainly due to complications like respiratory failure.*
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Many diseases that cause visual impairment, as well as systemic conditions, manifest in the posterior segment of the eye. With the advent of high-speed, high-resolution, reliable, and noninvasive imaging techniques, ophthalmologists are becoming more dependent on ocular imaging for disease diagnosis, classification, and management in clinical practice. There are rapid advances on the indications of multimodal retinal imaging techniques, including the application of ultra-widefield fundus angiography, fundus autofluorescence, optical coherence tomography, as well as optical coherence tomography angiography.

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Aminoacyl-tRNA synthetases are essential enzymes responsible for charging amino acids onto cognate tRNAs during protein synthesis. In histidyl-tRNA synthetase (HARS), autosomal dominant mutations V133F, V155G, Y330C and S356N in the HARS catalytic domain cause Charcot-Marie-Tooth disease type 2 W (CMT2W), while tRNA-binding domain mutation Y454S causes recessive Usher syndrome type IIIB. In a yeast model, all human HARS variants complemented a genomic deletion of the yeast ortholog HTS1 at high expression levels.

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  • The study focuses on "episignatures," which are unique DNA methylation patterns used as biomarkers for diagnosing various genetic syndromes, particularly neurodevelopmental disorders.
  • Researchers analyzed DNA methylation changes in 65 genetic syndromes, identifying specific differentially methylated probes (DMPs) and regions (DMRs) associated with these conditions.
  • Findings indicated that DMPs and DMRs were mostly located in gene promoters and pathways related to neurodevelopment, highlighting a connection between gene mutations and altered DNA methylation profiles in these disorders.
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