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Pathogenic variation in BRCA1 and BRCA2 (BRCA) causes high risk of breast and ovarian cancer, and BRCA variation data are important markers for BRCA-related clinical cancer applications. However, comprehensive BRCA variation data are lacking from the Asian population despite its large population size, heterogenous genetic background and diversified living environment across the Asia continent. We performed a systematic study on BRCA variation in Asian population including extensive data mining, standardization, annotation and characterization. We identified 7587 BRCA variants from 685 592 Asian individuals in 40 Asia countries and regions, including 1762 clinically actionable pathogenic variants and 4915 functionally unknown variants (https://genemutation.fhs.um.edu.mo/Asian-BRCA/). We observed the highly ethnic-specific nature of Asian BRCA variants between Asian and non-Asian populations and within Asian populations, highlighting that the current European descendant population-based BRCA data is inadequate to reflect BRCA variation in the Asian population. We also provided archeological evidence for the evolutionary origin and arising time of Asian BRCA variation. We further provided structural-based evidence for the deleterious variants enriched within the functionally unknown Asian BRCA variants. The data from our study provide a current view of BRCA variation in the Asian population and a rich resource to guide clinical applications of BRCA-related cancer for the Asian population.

Large quantity of variants of uncertain significance (VUS) has been identified in cancer predisposition genes, but classification of VUS remains a big challenge. We proposed that the impact of VUS on protein structure stability can be used to identify these with deleterious effects by using molecular dynamics simulation (MDS)-based approach and developed a MDS-based method for missense VUS classification. In the current study, we applied the system to classify the missense VUS in BRCA2. BRCA2 plays an important role in maintaining genome stability by repairing double-strand DNA damage through homologous recombination. BRCA2 BRC repeats bring RAD51 from cytoplasm to the break sites in nucleus to initiate the repairing process. Missense variants in BRCA2 BRC repeats can interfere the interaction between BRCA2 and RAD51, impair double-strand break repair, cause genome instability and increase cancer risk. We characterized the missense VUS in BRCA2 BRC4 repeat, the primary site of BRCA2 interacting with RAD51. Based on the well-determined BRC4 structure, we applied MDS to measure the impact of BRC4 missense VUS on the stability of BRC4 structure by testing the equilibrium state, flexibility, compactness, hydrogen bonds and surface accessibility. Of the 46 missense VUS analyzed, we were able to differentiate them into 24 Deleterious and 22 Tolerated variants. Comparison between the MDS-based and other 24 existing computational methods for variant classification showed that the MDS-based approach is highly sensitive and specific for classifying missense VUS in cancer predisposition genes.

BackgroundGermline mutation in BRCA1 and BRCA2 (BRCA) is genetic predisposition for breast and ovarian cancer. Identification of mutation carriers is a critical step to prevent and treat the cancer in the mutation carriers. Human BRCA variation has been well determined as ethnic-specific by studies in Ashkenazi Jewish, Polish and Icelandic populations in the 1990s. However, sufficient evidence is lacking to determine if ethnic-specific BRCA variation is also present in Asia population, which is the largest and the most diversified in modern humans. Our current study aims to investigate ethnic-specific BRCA variation in Asian population.MethodsWe performed a comprehensive data mining to collect BRCA variation data in Indian, Chinese, Korean and Japanese populations derived from over 78 000 cancer and 40 000 non-cancer cases. We standardised all BRCA variation data following the international standard. We made a systematic comparison between the datasets including variant composition, variation spectrum, variant type, clinical class, founder mutation and high-frequent variants.ResultsOur analysis showed that over half of the Asian BRCA variants were Asian-specific, and significant differences were present between the four Asia populations in each category analysed.ConclusionData from our study reveal that ethnic-specific BRCA variation is commonly present in Asia population as existing in non-Asian populations. Our study indicates that ethnicity should be an important factor to consider in prevention and treatment of BRCA mutation-related cancer in the Asia population. We recommend that the current BRCA variation databases should include ethnic variation information in order to function as true global BRCA references.

BackgroundPathogenic mutation in BRCA genes causes high cancer risk. Identifying the mutation carriers plays key roles in preventing BRCA mutation-related cancer. Population screening has demonstrated its power for comprehensive identification of the mutation carriers. However, it is only recommended for the Ashkenazi Jewish population with high prevalence of three founder mutations, but not for non-Ashkenazi Jewish populations as the cost-effectiveness could be too low due to their lower mutation prevalence and lack of founder mutation. Population screening would not benefit the majority of the human population for BRCA mutation-related cancer prevention.MethodsWe used population BRCA screening in 6000 residents, 1% of the Macau population, an ethnic Chinese population with unique genetic, linguistic and cultural features, and its BRCA mutation has not been analysed before.ResultsWe called BRCA variants, identified 18 carriers with 14 pathogenic mutations and determined the prevalence of 0.29% in the population (95% CI 0.15% to 0.42%). We compared the testing cost between the Ashkenazi Jewish population, the Sephardi Jewish population and the Macau population, and observed only a few fold differences.ConclusionOur study shows that testing cost is not the most important factor in considering population BRCA screening, at least for the populations in the developed countries/regions, regardless of the status of mutation prevalence and founder mutation.

Purpose DNA mismatch repair (MMR) genes play important roles in maintaining genome stability. Mutations in MMR genes disrupt their mismatch repair function, cause genome instability and lead to increased risk of cancer in the mutation carriers as represented by Lynch Syndrome. Studies have identified a large number of MMR variants, mostly in the Caucasian population, whereas data from non-Caucasian populations remain poorly illustrated. With the population size of 1.4 billion, knowledge of MMR variants in the Chinese population can be valuable in understanding the roles of ethnic MMR variation and cancer and to further guide clinical applications in MMR-related cancer prevention and treatment in the Chinese population. In this study, we systematically analysed the MMR variants from the Chinese population. Experimental design We performed a comprehensive MMR data mining and collected all the MMR variation data reported from 33,998 Chinese individuals consisting of 23,938 cancer and 10,060 non-cancer cases between January 1997 to May 2019. For the collected data, we performed standardisation following Human Genome Variation Society nomenclature and reannotated the MMR variant data following American College of Medical Genetics and Genomics guidelines and comparing with non-Chinese MMR data on various aspects. Results We identified a total of 540 MMR variants in the Chinese population, including 194 in MLH1, 181 in MSH2, 59 in MSH6, 53 in PMS2 single-base/indel changes and 53 large deletions/duplications in MLH1, MSH2, MSH6 and PMS2, respectively. We determined that the pathogenic/likely pathogenic carrier rate in the Chinese population was 1.6%. Comparative analysis in variant spectrum, variant types, clinical classification and founder mutations showed substantial differences of MMR variation between Chinese and non-Chinese populations and the fact that over 90% of the variants were only present in the Chinese ethnicity reveals the highly ethnic-specific nature of the Chinese MMR variation . We also developed an open-access database, dbMMR-Chinese, to host all data ( https://dbMMR-chinese.fhs.um.edu.mo ). The rich MMR data from a large non-Caucasian population should be valuable to study MMR variation and its relationship with cancer and provide a valuable reference resource for MMR-related cancer prevention and treatment. Conclusion Our study provides the largest MMR data set from a single non-Caucasian population and reveals that MMR variation in the humans can be highly ethnic-specific.

BRCA1 and BRCA2 (BRCA) play essential roles in maintaining genome stability. Rapidly evolving human BRCA generates oncogenic variants causing high cancer risk. BRCA variation is ethnic-specific in reflecting adaptation and/or effects of genetic drift. Taiwanese population of 23.8 million is an admixture of multiple ethnic origins; Taiwan’s subtropical and tropical climate and geographically islandic location provide a unique natural environment. Therefore, Taiwanese population provides a unique model to study human BRCA variation. Through collecting, standardizing, annotating, and classifying publicly available BRCA variants derived from Taiwanese general population and the cancer cohort, we identified 335 BRCA variants, of which 164 were from 1,517 non-cancer individuals, 126 from 2,665 cancer individuals, and 45 from both types of individuals. We compared the variant data with those from other ethnic populations such as mainland Chinese, Macau Chinese, Japanese, Korean, Indian, and non-Asians. We observed that the sharing rates with other Asian ethnic populations were correlated with its genetic relationship. Over 60% of the 335 Taiwanese BRCA variants were VUS, unclassified variants, or novel variants, reflecting the ethnic-specific features of Taiwanese BRCA variation. While it remains challenging to classify these variants, our structural and in silico analyses predicted their enrichment of BRCA deleterious variants. We further determined the 3.8% prevalence of BRCA pathogenic variants in the Taiwanese breast cancer cohort, and determined 0.53% prevalence of the BRCA pathogenic variants in Taiwanese general population, with the estimated 126,140 BRCA pathogenic variant carriers. We identified BRCA2 c.5164_5165delAG at BRCA2 BRC6 motif as a potential founder mutation in Taiwanese population. Our study on BRCA variation in Taiwanese and other East Asian populations demonstrates that ethnic specificity is a common phenomenon for BRCA variation in East Asian population; the data generated from the study provide a reference for clinical applications in BRCA-related cancer in Taiwanese population.

BRCA1 and BRCA2 play essential roles in maintaining the genome stability. Pathogenic germline mutations in these two genes disrupt their function, lead to genome instability and increase the risk of developing breast and ovarian cancers. BRCA mutations have been extensively screened in Caucasian populations, and the resulting information are used globally as the standard reference in clinical diagnosis, treatment and prevention of BRCA‐related cancers. Recent studies suggest that BRCA mutations can be ethnic‐specific, raising the question whether a Caucasian‐based BRCA mutation information can be used as a universal standard worldwide, or whether an ethnicity‐based BRCA mutation information system need to be developed for the corresponding ethnic populations. In this study, we used Chinese population as a model to test ethnicity‐specific BRCA mutations considering that China has one of the latest numbers of breast cancer patients therefore BRCA mutation carriers. Through comprehensive data mining, standardization and annotation, we collected 1,088 distinct BRCA variants derived from over 30,000 Chinese individuals, one of the largest BRCA data set from a non‐Caucasian population covering nearly all known BRCA variants in the Chinese population (https://dbBRCA-Chinese.fhs.umac.mo). Using this data, we performed multi‐layered analyses to determine the similarities and differences of BRCA variation between Chinese and non‐Chinese ethnic populations. The results show the substantial differences of BRCA data between Chinese and non‐Chinese ethnicities. Our study indicates that the current Caucasian population‐based BRCA data is not adequate to represent the BRCA status in non‐Caucasian populations. Therefore, ethnic‐based BRCA standards need to be established to serve for the non‐Caucasian populations., What's new? Currently, Caucasian population‐based BRCA mutation data are used worldwide as the standard reference for diagnosis, treatment, and prevention of BRCA‐associated cancers. Recent studies however suggest that BRCA variation can be ethnic specific. Here, the authors carried out a comprehensive comparison of BRCA mutation data between the Chinese and worldwide non‐Chinese populations and found substantial differences. The study suggests that BRCA mutations are highly ethnic specific and that the current Caucasian population‐based BRCA data is not adequate to represent the BRCA status in non‐Caucasian populations. Developing new standard references using ethnic‐based BRCA mutation data is needed to better serve non‐Caucasian ethnic populations.

BackgroundIdentifying genetic disease-susceptible individuals through population screening is considered as a promising approach for disease prevention. DNA mismatch repair (MMR) genes including MLH1, MSH2, MSH6 and PMS2 play essential roles in maintaining microsatellite stability through DNA mismatch repair, and pathogenic variation in MMR genes causes microsatellite instability and is the genetic predisposition for cancer as represented by the Lynch syndrome. While the prevalence and spectrum of MMR variation has been extensively studied in cancer, it remains largely elusive in the general population. Lack of the knowledge prevents effective prevention for MMR variation–caused cancer. In the current study, we addressed the issue by using the Chinese population as a model.MethodsWe performed extensive data mining to collect MMR variant data from 18 844 ethnic Chinese individuals and comprehensive analyses for the collected MMR variants to determine its prevalence, spectrum and features of the MMR data in the Chinese population.ResultsWe identified 17 687 distinct MMR variants. We observed substantial differences of MMR variation between the general Chinese population and Chinese patients with cancer, identified highly Chinese-specific MMR variation through comparing MMR data between Chinese and non-Chinese populations, predicted the enrichment of deleterious variants in the unclassified Chinese-specific MMR variants, determined MMR pathogenic prevalence of 0.18% in the general Chinese population and determined that MMR variation in the general Chinese population is evolutionarily neutral.ConclusionOur study provides a comprehensive view of MMR variation in the general Chinese population, a resource for biological study of human MMR variation, and a reference for MMR-related cancer applications.

Vibrio cholerae, the causative agent of cholera, could proliferate in aquatic environment and infect humans through contaminated food and water. Enormous microorganisms residing in human gastrointestinal tract establish a special microecological system, which immediately responds to the invasion of V. cholerae, through “colonization resistance” mechanisms, such as antimicrobial peptide production, nutrients competition, and intestinal barrier maintenances. Meanwhile, V. cholerae could quickly sense those signals and modulate the expression of relevant genes to circumvent those stresses during infection, leading to successful colonization on the surface of small intestinal epithelial cells. In this review, we summarized the crosstalks profiles between gut microbiota and V. cholerae in the terms of Type VI Secretion System (T6SS), Quorum Sensing (QS), Reactive Oxygen Species (ROS)/pH stress, and Bioactive metabolites. These mechanisms can also be applied to molecular bacterial pathogenesis of other pathogens in host.

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BRCA1 and BRCA2 (BRCA) play essential roles in maintaining genome stability. BRCA germline pathogenic variants increase cancer risk. However, the evolutionary origin of human BRCA pathogenic variants remains largely elusive. We tested the 2,972 human BRCA1 and 3,652 human BRCA2 pathogenic variants from ClinVar database in 100 vertebrates across eight clades, but failed to find evidence to show cross-species evolution conservation as the origin; we searched the variants in 2,792 ancient human genome data, and identified 28 BRCA1 and 22 BRCA2 pathogenic variants in 44 cases dated from 45,000 to 300 yr ago; we analyzed the haplotype-dated human BRCA pathogenic founder variants, and observed that they were mostly arisen within the past 3,000 yr; we traced ethnic distribution of human BRCA pathogenic variants, and found that the majority were present in single or a few ethnic populations. Based on the data, we propose that human BRCA pathogenic variants were highly likely arisen in recent human history after the latest out-of-Africa migration, and the expansion of modern human population could largely increase the variation spectrum.

TP53 plays critical roles in maintaining genome stability. Deleterious genetic variants damage the function of TP53, causing genome instability and increased cancer risk. Of the large quantity of genetic variants identified in TP53, however, many remain functionally unclassified as variants of unknown significance (VUS) due to the lack of evidence. This is reflected by the presence of 749 (42%) VUS of the 1785 germline variants collected in the ClinVar database. In this study, we addressed the deleteriousness of TP53 missense VUS. Utilizing the protein structure-based Ramachandran Plot-Molecular Dynamics Simulation (RPMDS) method that we developed, we measured the effects of missense VUS on TP53 structural stability. Of the 340 missense VUS tested, we observed deleterious evidence for 193 VUS, as reflected by the TP53 structural changes caused by the VUS-substituted residues. We compared the results from RPMDS with those from other in silico methods and observed higher specificity of RPMDS in classification of TP53 missense VUS than these methods. Data from our current study address a long-standing challenge in classifying the missense VUS in TP53, one of the most important tumor suppressor genes.

Sensing and resisting oxidative stress is critical for Vibrio cholerae to survive in either the aquatic environment or the gastrointestinal tract. Previous studies mainly focused on the mechanisms of oxidative stress response regulation that rely on enzymatic antioxidant systems, while functions of non-enzymatic antioxidants are rarely discussed in V. cholerae. For the first time, we investigated the role of hydrogen sulfide (H2S), the simplest thiol compound, in protecting V. cholerae against oxidative stress. We found that degradation of L-cysteine by putative cystathionine β-synthase (CBS) is the major source of endogenous H2S in V. cholerae. Our results indicate that intracellular H2S level has a positive correlation with cbs expression, while the enhanced H2S production can render V. cholerae cells less susceptible to H2O2 in vitro. Using proteome analysis and real-time qPCR assay, we found that cbs expression could stimulate the expression of several enzymatic antioxidants, including reactive oxygen species (ROS) detoxifying enzymes SodB, KatG and AhpC, the DNA protective protein DPS and the protein redox regulator Trx1. Assays of ROS detoxification capacities revealed that CBS-derived H2S could promote catalase activity at the post-translational level, especially for KatB, which serves as an important way that endogenous H2S participates in H2O2 detoxification. The enhancement of catalase activity by H2S is achieved through facilitating the uptake of iron. Adult mice experiments showed that cbs mutant has colonization defect, while either complementation of cbs or exogenous supplement of N-Acetyl-L-Cysteine restores its fitness in the host environment. Herein, we proposed that V. cholerae regulates CBS-dependent H2S production for better survival and proliferation under ROS stress., Author summary Vibrio cholerae is the etiological agent of cholera, the diarrheal disease, according to WHO epidemiological record, has been experiencing a high number of cases over the past few years. Upon ingestion by humans, V. cholerae needs to overcome multiple stresses in the host gastrointestinal tract, including the reactive oxygen species produced by host innate immune system. Here, we resolved the source of endogenous H2S in V. cholerae and its physiological functions. We found that cystathionine β-synthase (CBS)-catalyzed H2S production from L-cysteine enhanced the resistance of V. cholerae to oxidative stress, leading to increased survival in vitro and promoted colonization in an adult mouse model. We identified two mechanisms for the cytoprotective effects of endogenous H2S: 1) stimulating the expression of enzymatic antioxidant systems and 2) promoting the activity of catalases, especially KatB, at the post-translational level. We also found that H2S facilitated iron uptake, which may be responsible for its indirect promotion of KatB activity. Our results broaden the understanding of the physiological functions of H2S in bacteria and provide a new perspective on the contribution of endogenous small molecule gases to the functional adaptability of bacteria.