Multiple Genetic Rare Variants in Autism Spectrum Disorders: A Single-Center Targeted NGS Study

Many studies based on chromosomal microarray and next-generation sequencing (NGS) have identified hundreds of genes associated with autism spectrum disorder (ASD) risk, demonstrating that there are several complex genetic factors that contribute to ASD risk. We performed targeted NGS gene panels for 120 selected genes, in a clinical population of 40 children with well-characterized ASD. The variants identified were annotated and filtered, focusing on rare variants with a minimum allele frequency <1% in GnomAD. We found 147 variants in 39 of the 40 patients. It was possible to perform family segregation analysis in 28 of the 40 patients. We found 4 de novo and 101 inherited variants. For the inherited variants, we observed that all the variants identified in the patients came equally from the paternal and maternal genetic makeup. We identified 9 genes that are more frequently mutated than the others, and upon comparing the mutational frequency of these 9 genes in our cohort and the mutational frequency in the GnomAD population, we found significantly increased frequencies of rare variants in our study population. This study supports the hypothesis that ASD is the result of a combination of rare deleterious variants (low contribution) and many low-risk alleles (genetic background), highlighting the importance of MET and SLIT3 and the potentially stronger involvement of FAT1 and VPS13B in ASD. Taken together, our findings reinforce the importance of using gene panels to understand the contribution of the different genes already associated with ASD in the pathogenesis of the disease.

Reflection of P53 Phenotype in Tumor Tissue by Genotypic Variants in Glutathione S-Transferases: An Association with DNA Damage in Lung Adenocarcinoma

Background: Genetic deficiency of glutathione S-transferase (GST) enzymes results in accumulating carcinogens from tobacco smoke. Consequently, the elevated risk of lung carcinoma (LC) is due to increased DNA damage and mutational frequency of the P53 caretaker gene.Objective: To determine GST gene variants association with LUAD susceptibility and the relative risk of these variations developing the P53 mutation and DNA damageMethods: We analyzed genetic polymorphisms in GST-M1 (+/-), T1 (+/-), and P1 (Ile 105 Val) genes using restriction fragment length PCR. The P53 phenotype was categorized as the mutant type (>50% and 2-3 + intensity in IHC) in M1 (+/-), T1 (+/-), and P1 (Ile105Val) variants. Lymphocytic DNA damage was assessed using the comet assay. Results: The M1 (-/-) and P1 Val/Val (GG) genotypes were significantly associated with the risk of the P53 mutant phenotype (RR: 1.81, p=0.03) and (RR: 2.23, p=0.05), respectively. In contrast, GSTT1 was not associated with the P53 phenotype. GSTM1 (-/-)/ GSTP1 Ile/Ile (AA) combined genotypes showed a significant synergistic effect on the P53 phenotype (RR: 8.50, p=0.01). DNA damage was significantly associated with GST-M1 (-/-), T1 (-/-), and P1 Val/Val (GG) genotypes and smoking (p=0.001) as compared to GST-T1 (+/+)/M1 (+/+)/P1 Ile/Ile (AA) genotypes. However, P53 expression was not associated with DNA damage. Conclusion: The GSTM1 (-/-) and GSTT1 (-/-) null genotypes act as risk modifiers for LUAD and increase DNA damage. The GSTM1 (-/-)/ GSTP1 Ile/Ile (AA) combined genotype amplified 8-fold the risk of a P53 mutant phenotype.

KRAS/LKB1 and KRAS/TP53 co-mutations create divergent immune signatures in lung adenocarcinomas

Lung adenocarcinomas exhibit various patterns of genomic alterations. During the development of this cancer, KRAS serves as a driver oncogene with a relatively high mutational frequency. Emerging data suggest that lung adenocarcinomas with KRAS mutations can show enhanced PD-L1 expression and additional somatic mutations, thus linking the prospect of applying immune checkpoint blockade therapy to this disease. However, the responses of KRAS-mutant lung adenocarcinomas to this therapy are distinct, which is largely attributed to the heterogeneity in the tumoral immune milieus. Recently, it was revealed that KRAS-mutant lung adenocarcinomas simultaneously expressing either a LKB1 or TP53 mutation typically have different immune profiles of their tumours: tumours with a KRAS/TP53 co-mutation generally present with a significant upregulation of PD-L1 expression and tumoricidal T-cell accumulation, and those with a KRAS/LKB1 co-mutation are frequently negative for PD-L1 expression and have few tumoricidal immune infiltrates. In this regard, interrogating TP53 or LKB1 mutation in addition to PD-L1 expression will be promising in guiding clinical use of immune checkpoint blockade therapy for KRAS-mutant lung adenocarcinomas.

Temporal landscape of mutation accumulation in SARS-CoV-2 genomes from Bangladesh: possible implications from the ongoing outbreak in Bangladesh

SummaryAlong with intrinsic evolution, adaptation to selective pressure in new environments might have resulted in the circulatory SARS-CoV-2 strains in response to the geoenvironmental conditions of a country and the demographic profile of its population. Thus the analysis of genomic mutations of these circulatory strains may give an insight into the molecular basis of SARS-CoV-2 pathogenesis and evolution favoring the development of effective treatment and containment strategies. With this target, the current study traced the evolutionary route and mutational frequency of 198 Bangladesh originated SARS-CoV-2 genomic sequences available in the GISAID platform over a period of 13 weeks as of 14 July 2020. The analyses were performed using MEGA 7, Swiss Model Repository, Virus Pathogen Resource and Jalview visualization. Our analysis identified that majority of the circulating strains in the country belong to B and/or L type among cluster A to Z and strikingly differ from both the reference genome and the first sequenced genome from Bangladesh. Mutations in Nonspecific protein 2 (NSP2), NSP3, RNA dependent RNA polymerase (RdRp), Helicase, Spike, ORF3a, and Nucleocapsid (N) protein were common in the circulating strains with varying degrees and the most unique mutations(UM) were found in NSP3 (UM-18). But no or limited changes were observed in NSP9, NSP11, E (Envelope), NSP7a, ORF 6, and ORF 7b suggesting the possible conserved functions of those proteins in SARS-CoV-2 propagation. However, along with D614G mutation, more than 20 different mutations in the Spike protein were detected basically in the S2 domain. Besides, mutations in SR-rich region of N protein and P323L in RDRP were also present. However, the mutation accumulation showed an association with sex and age of the COVID-19 positive cases. So, identification of these mutational accumulation patterns may greatly facilitate drug/ vaccine development deciphering the age and the sex dependent differential susceptibility to COVID-19.

Bioinformatic Analysis of Structure and Function of Lim Domains of Zyxin Family Proteins

Lim domains are one of the most abundant types of zinc-finger domains and are linked with diverse cellular functions ranging from cytoskeleton maintenance to gene regulation. Zyxin family Lim domains perform the critical cellular functions and are indispensable for cellular integrity. Despite having these important functions the fundamental nature of the sequence, structure, functions, and interactions of the Zyxin family Lim domains are largely unknown. Therefore, we have used a set of in-silico tools and bioinformatics databases to distill the fundamental properties of the Zyxin family proteins/Lim domains from their amino acid sequence, phylogeny, biochemical analysis, post-translational modifications, structure dynamics, molecular interactions, and functions. Consensus analysis of the nuclear export signal suggests a conserved Leucine-rich motif composed of LxxLxL/LxxxLxL. Molecular modeling and structural analysis demonstrate that Lim domains of the members of the Zyxin family proteins share similarities with transcriptional regulators, suggesting they could interact with nucleic acids as well. Normal mode, Covariance, and Elastic Network Model analysis of Zyxin family Lim domains suggest only the Lim1 region has similar internal dynamics properties, compared to Lim2/3. Protein expression/mutational frequency studies of the Zyxin family demonstrated higher expression and mutational frequency rates in various malignancies. Protein-protein interactions indicate that these proteins could facilitate metabolic rewiring and oncogenic addiction paradigm. Our comprehensive analysis of the Zyxin family proteins indicates that the Lim domains function in a variety of ways and could be implicated in rational protein engineering and might lead as a better therapeutic target for various diseases, including cancers.

Comprehensive annotations of the mutational spectra of SARS-CoV-2 spike protein: a fast and accurate pipeline

In order to explore nonsynonymous mutations and deletions in the spike (S) protein of SARS-CoV-2, we comprehensively analyzed 35,750 complete S protein gene sequences from across six continents and five climate zones around the world, as documented in the GISAID database as of June 24th, 2020. Through a custom Python-based pipeline for analyzing mutations, we identified 27,801 (77.77 % of spike sequences) mutated strains compared to Wuhan-Hu-1 strain. 84.40% of these strains had only single amino-acid (aa) substitution mutations, but an outlier strain from Bosnia and Herzegovina (EPI_ISL_463893) was found to possess six aa substitutions. The D614G variant of the major G clade was found to be predominant across circulating strains in all climates. We also identified 988 unique aa substitution mutations distributed across 660 positions within the spike protein, with eleven sites showing high variability – these sites had four types of aa variations at each position. Besides, 17 in-frame deletions at four major regions (three in N-terminal domain and one just downstream of the RBD) may have possible impact on attenuation. Moreover, the mutational frequency differed significantly (p= 0.003, Kruskal–Wallis test) among the SARS-CoV-2 strains worldwide. This study presents a fast and accurate pipeline for identifying nonsynonymous mutations and deletions from large dataset for any particular protein coding sequence and presents this S protein data as representative analysis. By using separate multi-sequence alignment with MAFFT, removing ambiguous sequences and in-frame stop codons, and utilizing pairwise alignment, this method can derive nonsynonymus mutations (Reference:Position:Strain). We believe this will aid in the surveillance of any proteins encoded by SARS-CoV-2, and will prove to be crucial in tracking the ever-increasing variation of many other divergent RNA viruses in the future.

Genomic diversity and hotspot mutations in 30,983 SARS-CoV-2 genomes: moving toward a universal vaccine for the "confined virus"?

The COVID-19 pandemic has been ongoing since its onset in late November 2019 in Wuhan, China. Understanding and monitoring the genetic evolution of the virus, its geographical characteristics, and its stability are particularly important for controlling the spread of the disease and especially for the development of a universal vaccine covering all circulating strains. From this perspective, we analyzed 30,983 complete SARS-CoV-2 genomes from 79 countries located in the six continents and collected from December 24, 2019, to May 13, 2020, according to the GISAID database. Our analysis revealed the presence of 3,206 variant sites, with a uniform distribution of mutation types in different geographic areas. Remarkably, a low frequency of recurrent mutations has been observed; only 169 mutations (5.27%) had a prevalence greater than 1% of genomes. Nevertheless, fourteen non-synonymous hotspot mutations (> 10%) have been identified at different locations along the viral genome; eight in ORF1ab polyprotein (in nsp2, nsp3, transmembrane domain, RdRp, helicase, exonuclease, and endoribonuclease), three in nucleocapsid protein and one in each of three proteins: spike, ORF3a, and ORF8. Moreover, 36 non-synonymous mutations were identified in the RBD of the spike protein with a low prevalence (<1%) across all genomes, of which only four could potentially enhance the binding of the SARS-CoV-2 spike protein to the human ACE2 receptor. These results along with mutational frequency dissimilarity and intra-genomic divergence of SARS-CoV-2 could indicate that the SARS-CoV-2 is not yet adapted to its host. Unlike the influenza virus or HIV viruses, the low mutation rate of SARS-CoV-2 makes the development of an effective global vaccine very likely.