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Diagnostic and Monitoring Strategies for VEXAS Syndrome: Evaluating Sanger Sequencing, NGS, and the SWIM-Score.

VEXAS syndrome is an adult-onset autoinflammatory disorder caused by somatic UBA1 variants, but there are no standardized criteria for genetic testing or diagnostics. This study compared Sanger sequencing and next-generation sequencing (NGS) for detecting UBA1 variants in patients with suspected VEXAS, assessed the ability of Sanger sequencing to estimate variant allele fractions (VAFs), and evaluated the Maeda et al. scoring system for selecting patients for genetic testing in a primary cohort and a validation cohort. In the primary cohort of 104 patients, Sanger sequencing identified VEXAS variants in 12%, with no additional cases detected by NGS. Sanger sequencing accurately quantified VAFs ranging from 0.1 to 0.9. In a small longitudinal subset (n = 3), VAFs in blood correlated with CRP levels, increased over time despite various treatments, but decreased in two patients after initiation of Azacitidine treatment. The novel parameters, VAF in myeloid cells and VEXAS cell concentration, showed promise as exploratory markers for patient monitoring. The Maeda-score, requiring a threshold score of 2 for 100% sensitivity, exhibited low specificity-29% in the primary cohort and 41% in the validation cohort (n = 62, with 2 carrying VEXAS variants). In contrast, the simplified SWIM-score-based on Skin involvement, Weight loss, Inflammation, and Macrocytic anemia-achieved 100% sensitivity in both cohorts, with higher specificities of 47% and 65%, respectively. In conclusion, Sanger sequencing reliably detected UBA1 variants and quantified VAFs. Monitoring VAF and VEXAS cell concentration may track disease progression, and the SWIM-score demonstrated potential for accurately selecting patients for UBA1 testing.

Humans

Obstacles in quantifying A-to-I RNA editing by Sanger sequencing.

Adenosine-to-Inosine (A-to-I) RNA editing is the most prevalent type of RNA editing, in which adenosine within a completely or largely double-stranded RNA (dsRNA) is converted to inosine by deamination. RNA editing was shown to be involved in many neurological diseases and cancer; therefore, detection of A-to-I RNA editing and quantitation of editing levels are necessary for both basic and clinical biomedical research. While high-throughput sequencing (HTS) is widely used for global detection of editing events, Sanger sequencing is the method of choice for precise characterization of editing site clusters (hyper-editing) and for comparing levels of editing at a particular site under different environmental conditions, developmental stages, genetic backgrounds, or disease states. To detect A-to-I editing events and quantify them using Sanger sequencing, RNA samples are reverse transcribed, cDNA is amplified using gene-specific primers, and then sequenced. The chromatogram outputs are then compared to the genomic DNA sequence. As editing occurs in the context of dsRNA, the reverse transcription step is performed at a temperature as high as 65 °C, using thermostable reverse transcriptase to open double-stranded structures. However, this measure alone is insufficient for transcripts possessing long stems comprised of hundreds of nucleotide pairs. Consequently, the editing levels detected by Sanger sequencing are significantly lower than those obtained by HTS, and the amplification yield is low. We suggest that the reverse transcription is biased towards unedited transcripts, and the severity of the bias is dependent on the transcript's secondary structure. Here, we show how this bias can be significantly reduced to allow reliable detection of editing levels and sufficient product yield.

RNA Editing

Targeted ORF8-N Sanger Sequencing as a SARS-CoV-2 Surveillance Contingency During Supply Shortages.

BACKGROUND: Global shortages of next-generation sequencing (NGS) reagents threatened SARS-CoV-2 genomic surveillance in low- and middle-income countries during the COVID-19 pandemic. METHODS: During the 2021 NGS reagent shortages, we implemented targeted ORF8-N Sanger sequencing for SARS-CoV-2 variant surveillance in Brazilian public health laboratories. RESULTS: In silico analysis of whole-genome sequencing (WGS)-derived SARS-CoV-2 genomes from the Federal District, Brazil, showed that the ORF8-N target discriminated the major 2021 lineages (Gamma and Delta) and enabled analysis of ˃300 samples despite constrained NGS access. CONCLUSIONS: Targeted ORF8-N Sanger sequencing was a useful temporary contingency during NGS reagent shortages but offered lower phylogenetic resolution than WGS.

SARS-CoV-2

A comparison of the 16S ribosomal RNAs from mesophilic and thermophilic bacilli: some modifications in the Sanger method for RNA sequencing.

Two modifications in the Sanger two dimensional electrophoretic procedure for RNA analysis are reported. One increases resolution on the primary fingerprint to the point that digests of large RNAs, of the size 1500-3000 nucleotides yield well resolved fingerprint patterns. The other is a novel endonucleolytic procedure that proves useful in determining sequences of the large oligonucleotides produced by T1 ribonuclease. These modifications have been used in determining the catalogs of oligomers produced by T1 ribonuclease digestion of 16S rRNAs from three related organisms, Bacillus subtilis, B.pumilus and B.stearothermophilus. The possible effects of adaptation to a thermophilic niche on ribosomal RNA primary structure and the phylogenetic relatedness of the two mesophilic Bacilli are discussed.

Animals

Automated Sanger dideoxy sequencing reaction protocol.

The protocol for Sanger dideoxy chain termination reactions in DNA sequencing is tedious and prone to errors due to the repetitive character of the pipetting steps. An industrial robot, with the addition of a few simple parts, was programmed to automate the dideoxy sequencing reactions. The system is set up in a short time for routine operation and it is faster and more reliable than a human operator. It is flexible and allows variations and optimization of the standard procedure. Disposable microtiter plates at a controlled temperature are used. In one reaction cycle (about 50 min) up to 48 templates are processed. Up to 450 bases were resolved in automated DNA sequencing on samples prepared by the robot. The protocol is applicable to fluorescent as well as to radioactive labeling.

Autoanalysis

Automated Sanger DNA sequencing with one label in less than four lanes on gel.

Novel Sanger dideoxy sequencing with only one fluorescent dye label for the four bases of one clone and sequence determination in two lanes on polyacrylamide gel is presented, loading A greater than G in one lane and T greater than C in the other. Sequencing reactions for the two bases in each lane are carried out in one tube. At present the ratio of ddATP:ddGTP and ddTTP:ddCPT is set to 5:1 in the two tubes. Distinction between the two bases in one lane is done by comparing the different magnitudes of the peaks. This method increases the capacity since more clones may be run simultaneously on one gel, while keeping the reliability and simplicity that comes with the use of only one fluorescent dye for the four bases of one clone. At present about 200 bases are determined with the one-dye two-lane method on the EMBL's automated fluorescent DNA sequencer, using T7 DNA polymerase. The error rate in the deduced sequence is about 1%. The technique is used for the determination of overlaps in mapping projects. In principle, it is possible to determine the sequence with one dye in only one lane on the gel by choosing the proper ddNTP ratios for all four bases, carrying out reactions in one tube and applying the product in one lane, but the error rate for this one-lane method seems too high at present and further improvements in the uniformity of peaks obtainable with the T7 DNA polymerase or other enzymes are required.

Base Sequence