Gattaca: Base pair resolution mutation tracking for somatic evolution studies using agent-based models

Gattaca provides the first base-pair resolution artificial genomes for tracking somatic mutations within agent based modeling. Through the incorporation of human reference genomes, mutational context, sequence coverage/error information Gattaca is able to realistically provide comparable sequence data for in-silico comparative evolution studies with human somatic evolution studies. This user-friendly method, incorporated into each in-silico cell, allows us to fully capture somatic mutation spectra and evolution.

Demographic Analysis of Mutations in Indian SARS-CoV-2 Isolates

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) originally emerged from Hubei province, Wuhan, China, and has caused a worldwide pandemic with millions affected since December 2019. Since the first case of SARS-CoV-2 reported on 27th Jan 2020 in India, over 11 million people have been affected by the virus in the country in the past one year. To understand its demographic distribution, in this study we carried out the early distribution of clades and subclades state-wise based on the analysis of shared mutations in Indian SARS-CoV-2 isolates collected during the period 27th Jan – 27th May 2020. A total of 1279 mutations have been identified in 685 Indian isolates during this period. Principal component analysis on the mutational profile of Indian isolates revealed clusters corresponding to clades in Nextstrain and some state-specific clusters. Phylogenetic analysis of these isolates indicates multiple independent sources of introduction of the virus in the country. It is observed that clade 20A defining mutations C241T (ORF1ab: 5′ UTR), C3037T (ORF1ab: F924F), C14408T (ORF1ab: P4715L), and A23403G (S: D614G) are the predominant mutation set in Indian isolates during this period. Higher number of coronavirus cases were observed in certain states, viz., Delhi, Tamil Nadu, and Telangana. Genetic analysis of isolates from these states revealed a cluster with shared mutations, C6312A (ORF1ab: T2016K), C13730T (ORF1ab: A4489V), C23929T, and C28311T (N: P13L). Contact tracing led the spread of this cluster to a super spreader event, the Tablighi Jamaat religious congregation, and the efficacy of lockdown in containing it. Analysis of region-specific shared mutations carried out to understand the large number of deaths in Gujarat and Maharashtra identified shared mutations defining subclade, I/GJ-20A (C18877T, C22444T, G25563T (ORF3a: H57Q), C26735T, C28854T (N: S194L), C2836T) in Gujarat and two sets of co-occurring mutations C313T, C5700A (ORF1ab: A1812D) and A29827T, G29830T in Maharashtra. From the genetic analysis of mutation spectra of Indian isolates, the insights gained in its transmission, geographic distribution, containment, and impact are discussed.

Predominance of the SARS-CoV-2 Lineage P.1 and Its Sublineage P.1.2 in Patients from the Metropolitan Region of Porto Alegre, Southern Brazil in March 2021

Almost a year after the COVID-19 pandemic had begun, new lineages (B.1.1.7, B.1.351, P.1, and B.1.617.2) associated with enhanced transmissibility, immunity evasion, and mortality were identified in the United Kingdom, South Africa, and Brazil. The previous most prevalent lineages in the state of Rio Grande do Sul (RS, Southern Brazil), B.1.1.28 and B.1.1.33, were rapidly replaced by P.1 and P.2, two B.1.1.28-derived lineages harboring the E484K mutation. To perform a genomic characterization from the metropolitan region of Porto Alegre, we sequenced viral samples to: (i) identify the prevalence of SARS-CoV-2 lineages in the region, the state, and bordering countries/regions; (ii) characterize the mutation spectra; (iii) hypothesize viral dispersal routes by using phylogenetic and phylogeographic approaches. We found that 96.4% of the samples belonged to the P.1 lineage and approximately 20% of them were assigned as the novel P.1.2, a P.1-derived sublineage harboring signature substitutions recently described in other Brazilian states and foreign countries. Moreover, sequences from this study were allocated in distinct branches of the P.1 phylogeny, suggesting multiple introductions in RS and placing this state as a potential diffusion core of P.1-derived clades and the emergence of P.1.2. It is uncertain whether the emergence of P.1.2 and other P.1 clades is related to clinical or epidemiological consequences. However, the clear signs of molecular diversity from the recently introduced P.1 warrant further genomic surveillance.

Genotype Profile of Global EYS-Associated Inherited Retinal Dystrophy and Clinical Findings in a Large Chinese Cohort

PurposeThe aim of this study was to probe the global profile of the EYS-associated genotype-phenotype trait in the worldwide reported IRD cases and to build a model for predicting disease progression as a reference for clinical consultation.MethodsThis retrospective study of 420 well-documented IRD cases with mutations in the EYS gene included 39 patients from a genotype-phenotype study of inherited retinal dystrophy (IRD) conducted at the Beijing Institute of Ophthalmology and 381 cases retrieved from global reports. All patients underwent ophthalmic evaluation. Mutations were revealed using next-generation sequencing, followed by Sanger DNA sequencing and real-time quantitative PCR analysis. Multiple regression models and statistical analysis were used to assess the genotype and phenotype characteristics and traits in this large cohort.ResultsA total of 420 well-defined patients with 841 identified mutations in the EYS gene were successfully obtained. The most common pathogenic variant was a frameshift c.4957dupA (p.S1653Kfs∗2) in exon 26, with an allele frequency of 12.7% (107/841), followed by c.8805C > A (p.Y2935X) in exon 43, with an allele frequency of 5.9% (50/841). Two new hot spots were identified in the Chinese cohort, c.1750G > T (p.E584X) and c.7492G > C (p.A2498P). Several EYS mutation types were identified, with CNV being relatively common. The mean age of onset was 20.54 ± 11.33 (4–46) years. Clinical examinations revealed a typical progression of RPE atrophy from the peripheral area to the macula.ConclusionThis large global cohort of 420 IRD cases, with 262 distinct variants, identified genotype-phenotype correlations and mutation spectra with hotspots in the EYS gene.

Predominance of the SARS-CoV-2 lineage P.1 and its sublineage P.1.2 in patients from the metropolitan region of Porto Alegre, Southern Brazil in March 2021: a phylogenomic analysis

Almost a year after the COVID-19 pandemic had begun, The United Kingdom, South Africa, and Brazil became the epicenter of new lineages, the Variant of Concern (VOCs), B.1.1.7, B.1.351, and P.1, respectively. These VOCs are increasingly associated with enhanced transmissibility, immunity evasion, and mortality. The previous most prevalent lineages in the state of Rio Grande do South (Brazil), B.1.1.28 and B.1.1.33 were rapidly replaced by P.1 and P.2, two B.1.1.28-derived lineages harboring the E484K mutation. To perform a genomic characterization of SARS-CoV-2 samples from COVID-19 patients from the metropolitan region of Porto Alegre (Rio Grande do Sul, Southern Brazil), in this second pandemic wave, we sequenced viral samples from patients of this region to: (i) identify the prevalence of SARS-CoV-2 lineages in the region, the state and bordering countries/states, (ii) characterize the mutation spectra, and (iii) hypothesize possible viral dispersal routes by using phylogenetic and phylogeographic approaches. As results, we not only confirmed that 96.4% of the samples belonged to the P.1 lineage but also that approximately 20% of which could be assigned as the newer P.1.2 (a P.1 derived new sublineage harboring new signature substitutions recently described and present in other Brazilian states and foreign countries). Moreover, P.1 sequences from this study were allocated in several distinct branches (four clades and five clusters) of the P.1 phylogeny, suggesting multiple introductions of P.1 in Rio Grande do Sul still in 2020 and placing this state as a potential core of diffusion and emergence of P.1-derived clades. It is still uncertain if the emergence of P.1.2 and other P.1 clades are related to further virological, clinical, or epidemiological consequences. However, the clear signs of viral molecular diversification from recently introduced P.1 warrant further genomic surveillance.

Genetic mutations in patients with nonsyndromic hearing impairment of minority and Han Chinese ethnicities in Qinghai, China

Objective Mutations in GJB2, SLC26A4, and mitochondrial (mt)DNA 12S rRNA genes are the main cause of nonsyndromic hearing impairment. The present study analyzed these mutations in ethnic minority and Han Chinese patients with nonsyndromic hearing impairment from Qinghai, China. Methods The SNPscan assay was used to analyze mutation spectra and frequencies in the two patient groups. Results GJB2 mutations were detected in 9.5% (20/210) of minority patients and 20.88% (48/230) of Han Chinese patients. The most common Han Chinese GJB2 variants were c.235delC and c.299_300delAT, whereas c.235delC and c.109G > A were the most prevalent in minority patients. SLC26A4 mutations were detected in 5.71% (12/210) of minority patients and 14.35% (33/230) of Han Chinese patients, and mtDNA 12S rRNA mutations were detected in 4.28% (9/210) of minority patients and 9.13% (21/230) of Han Chinese patients. Conclusions These data indicate that the mutation frequencies of three deafness-associated genes were significantly higher in Han Chinese patients than in minority patients. Moreover, the GJB2 mutation spectrum was shown to differ between these two patient groups.

A selection-based next generation sequencing approach to develop robust, genotype-specific mutation profiles in Saccharomyces cerevisiae

Distinct mutation signatures arise from environmental exposures and/or from defects in metabolic pathways that promote genome stability. The presence of a particular mutation signature can therefore predict the underlying mechanism of mutagenesis. These insults to the genome often alter dNTP pools, which itself impacts replication fidelity. Therefore, the impact of altered dNTP pools should be considered when making mechanistic predictions based on mutation signatures. We developed a targeted deep-sequencing approach on the CAN1 gene in Saccharomyces cerevisiae to define information-rich mutational profiles associated with distinct rnr1 backgrounds. Mutations in the activity and selectivity sites of rnr1 lead to elevated and/or unbalanced dNTP levels, which compromises replication fidelity and increases mutation rates. The mutation spectra of rnr1Y285F and rnr1Y285A alleles were characterized previously; our analysis was consistent with this prior work but the sequencing depth achieved in our study allowed a significantly more robust and nuanced computational analysis of the variants observed, generating profiles that integrated information about mutation spectra, position effects, and sequence context. This approach revealed previously unidentified, genotype-specific mutation profiles in the presence of even modest changes in dNTP pools. Furthermore, we identified broader sequence contexts and nucleotide motifs that influenced variant profiles in different rnr1 backgrounds, which allowed specific mechanistic predictions about the impact of altered dNTP pools on replication fidelity.

Genomic Heterogeneity of Multiple synchronous lung cancers (MSLCs) in Chinese population

IntroductionIt is clinically challenging to infer the phylogenetic relationship between different tumor lesions of patient with multiple synchronous lung cancers (MSLC), whether these lesions are the result of independently evolved tumor or intrapulmonary metastases.MethodsUsing Illumina X10 platform, we sequenced a total number of 128 stage I lung cancer samples collected from 64 patients with MSLC. All samples were analyzed for mutation spectra and phylogenetic inference.ResultsWe detected genetic aberrations within genes previously reported to be recurrently altered in lung adenocarcinoma including EGFR, ERBB2, TP53, BRAF and KRAS. Other identified putative driver mutations are enriched in RTK-RAS signaling, TP53 signaling and cell cycle. Also we found some interesting cases, two cases which carried EGFR L858R and T790M co-mutation in one tumor and another tumor with only EGFR 19del, and 1 case with two KRAS hotspots in the same tumor. Due to the short follow-up time and early stage, whether the special mutation profile will affect the PFS and OS of these patients need further investigation. For the genetic evolution, among 64 tumor samples, 50 of them display distinct mutational profile, suggesting these are independently evolved tumors, which is consistent with histopathological assessment. On the other hand, 7 patients were identified to be intrapulmonary metastasis as the mutations harbored in different lesions are clonally related. ConclusionIn summary, unlike intrapulmonary metastases, patients with MSLC harbor distinct genomic profile in different tumor lesions and we may distinguish MSLC from intrapulmonary metastases via clonality estimation.