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Asian Pacific Journal of Cancer... May 2022Familial adenomatous polyposis (FAP) is a hereditary disorder primarily caused by germline mutations in the APC gene. The most common type of mutation in the APC gene is...
BACKGROUND
Familial adenomatous polyposis (FAP) is a hereditary disorder primarily caused by germline mutations in the APC gene. The most common type of mutation in the APC gene is point mutation, while deletion mutation is much less frequent. The current study was conducted to investigate the mutation spectrum of the APC gene in Vietnamese FAP patients.
METHODS
Patients with the clinical diagnosis of FAP on colorectal endoscopy were screened for mutations in the APC gene using Sanger sequencing. Those who exhibited no point mutation subsequently underwent MLPA assay to detect deletion and duplication mutations. Besides, the relatives of patients with mutated APC genes were recruited for detecting carrier status.
RESULTS
Sixty-three patients with clinical colorectal polyposis were recruited. Mutations in the APC gene were detected in 26/63 patients (41.3%). Genetic analysis of 105 asymptomatic relatives of these 26 patients found mutations in the APC gene in 55 individuals (52.4%).
CONCLUSION
We successfully established the APC gene mutation spectrum in Vietnamese FAP patients for the first time. Of importance, we discovered two novel point mutations in the APC gene. The high prevalence of carrier status in asymptomatic family members of patients with mutation emphasizes the crucial role of appropriate genetic screening for early diagnosis, surveillance, and preventive measurements.
Topics: Adenomatous Polyposis Coli; Adenomatous Polyposis Coli Protein; Asian People; Genes, APC; Humans; Mutation; Point Mutation; Vietnam
PubMed: 35633533
DOI: 10.31557/APJCP.2022.23.5.1517 -
Cellular and Molecular Neurobiology Oct 2023The BAF (BRG1/BRM-associated factor) chromatin remodelling complex is essential for the regulation of DNA accessibility and gene expression during neuronal...
The BAF (BRG1/BRM-associated factor) chromatin remodelling complex is essential for the regulation of DNA accessibility and gene expression during neuronal differentiation. Mutations of its core subunit SMARCB1 result in a broad spectrum of pathologies, including aggressive rhabdoid tumours or neurodevelopmental disorders. Other mouse models have addressed the influence of a homo- or heterozygous loss of Smarcb1, yet the impact of specific non-truncating mutations remains poorly understood. Here, we have established a new mouse model for the carboxy-terminal Smarcb1 c.1148del point mutation, which leads to the synthesis of elongated SMARCB1 proteins. We have investigated its impact on brain development in mice using magnetic resonance imaging, histology, and single-cell RNA sequencing. During adolescence, Smarcb1 mice demonstrated rather slow weight gain and frequently developed hydrocephalus including enlarged lateral ventricles. In embryonic and neonatal stages, mutant brains did not differ anatomically and histologically from wild-type controls. Single-cell RNA sequencing of brains from newborn mutant mice revealed that a complete brain including all cell types of a physiologic mouse brain is formed despite the SMARCB1 mutation. However, neuronal signalling appeared disturbed in newborn mice, since genes of the AP-1 transcription factor family and neurite outgrowth-related transcripts were downregulated. These findings support the important role of SMARCB1 in neurodevelopment and extend the knowledge of different Smarcb1 mutations and their associated phenotypes.
Topics: Animals; Mice; Hydrocephalus; Mutation; Point Mutation; Signal Transduction; Transcription Factor AP-1
PubMed: 37219662
DOI: 10.1007/s10571-023-01361-5 -
Genes Sep 2023Large musculoaponeurotic fibrosarcoma (MAF) transcription factors contain acidic, basic, and leucine zipper regions. Four types of MAF have been elucidated in mice and... (Review)
Review
Large musculoaponeurotic fibrosarcoma (MAF) transcription factors contain acidic, basic, and leucine zipper regions. Four types of MAF have been elucidated in mice and humans, namely c-MAF, MAFA, MAFB, and NRL. This review aimed to elaborate on the functions of MAF transcription factors that have been studied in vivo so far, as well as describe the pathology of human patients and corresponding mouse models with c-MAF, MAFA, and MAFB point mutations. To identify the functions of MAF transcription factors in vivo, we generated genetically modified mice lacking c-MAF, MAFA, and MAFB and analyzed their phenotypes. Further, in recent years, c-MAF, MAFA, and MAFB have been identified as causative genes underpinning many rare diseases. Careful observation of human patients and animal models is important to examine the pathophysiological mechanisms underlying these conditions for targeted therapies. Murine models exhibit phenotypes similar to those of human patients with c-MAF, MAFA, and MAFB mutations. Therefore, generating these animal models emphasizes their usefulness for research uncovering the pathophysiology of point mutations in MAF transcription factors and the development of etiology-based therapies.
Topics: Humans; Mice; Animals; Transcription Factors; Maf Transcription Factors, Large; MafB Transcription Factor; Insulin; Point Mutation
PubMed: 37895232
DOI: 10.3390/genes14101883 -
Frontiers in Cellular and Infection... 2022Mutations may produce highly transmissible and damaging HIV variants, which increase the genetic diversity, and pose a challenge to develop vaccines. Therefore, it is of...
Mutations may produce highly transmissible and damaging HIV variants, which increase the genetic diversity, and pose a challenge to develop vaccines. Therefore, it is of great significance to understand how mutations drive the virulence of HIV. Based on the 11897 reliable genomes of HIV-1 retrieved from HIV sequence Database, we analyze the 12 types of point mutation (A>C, A>G, A>T, C>A, C>G, C>T, G>A, G>C, G>T, T>A, T>C, T>G) from multiple statistical perspectives for the first time. The global/geographical location/subtype/k-mer analysis results report that A>G, G>A, C>T and T>C account for nearly 64% among all SNPs, which suggest that APOBEC-editing and ADAR-editing may play an important role in HIV-1 infectivity. Time analysis shows that most genomes with abnormal mutation numbers comes from African countries. Finally, we use natural vector method to check the k-mer distribution changing patterns in the genome, and find that there is an important substitution pattern between nucleotides A and G, and 2-mer CG may have a significant impact on viral infectivity. This paper provides an insight into the single mutation of HIV-1 by using the latest data in the HIV sequence Database.
Topics: HIV-1; Point Mutation; Mutation; Mutation, Missense; Databases, Nucleic Acid
PubMed: 36457853
DOI: 10.3389/fcimb.2022.1033481 -
Protein Science : a Publication of the... Jan 2021Predicting the effect of missense variations on protein stability and dynamics is important for understanding their role in diseases, and the link between protein...
Predicting the effect of missense variations on protein stability and dynamics is important for understanding their role in diseases, and the link between protein structure and function. Approaches to estimate these changes have been proposed, but most only consider single-point missense variants and a static state of the protein, with those that incorporate dynamics are computationally expensive. Here we present DynaMut2, a web server that combines Normal Mode Analysis (NMA) methods to capture protein motion and our graph-based signatures to represent the wildtype environment to investigate the effects of single and multiple point mutations on protein stability and dynamics. DynaMut2 was able to accurately predict the effects of missense mutations on protein stability, achieving Pearson's correlation of up to 0.72 (RMSE: 1.02 kcal/mol) on a single point and 0.64 (RMSE: 1.80 kcal/mol) on multiple-point missense mutations across 10-fold cross-validation and independent blind tests. For single-point mutations, DynaMut2 achieved comparable performance with other methods when predicting variations in Gibbs Free Energy (ΔΔG) and in melting temperature (ΔT ). We anticipate our tool to be a valuable suite for the study of protein flexibility analysis and the study of the role of variants in disease. DynaMut2 is freely available as a web server and API at http://biosig.unimelb.edu.au/dynamut2.
Topics: Internet; Mutation, Missense; Point Mutation; Protein Stability; Proteins; Software
PubMed: 32881105
DOI: 10.1002/pro.3942 -
Cellular and Molecular Gastroenterology... 2022RUNX transcription factors play pivotal roles in embryonic development and neoplasia. We previously identified the single missense mutation R122C in RUNX3 from human...
BACKGROUND & AIMS
RUNX transcription factors play pivotal roles in embryonic development and neoplasia. We previously identified the single missense mutation R122C in RUNX3 from human gastric cancer. However, how RUNX3 mutation disrupts stem cell homeostasis and promotes gastric carcinogenesis remained unclear.
METHODS
To understand the oncogenic nature of this mutation in vivo, we generated the RUNX3 knock-in mice. Stomach tissues were harvested, followed by histologic and immunofluorescence staining, organoid culture, flow cytometry to isolate gastric corpus isthmus and nonisthmus epithelial cells, and RNA extraction for transcriptomic analysis.
RESULTS
The corpus tissue of RUNX3 homozygous mice showed a precancerous phenotype such as spasmolytic polypeptide-expressing metaplasia. We observed mucous neck cell hyperplasia; massive reduction of pit, parietal, and chief cell populations; as well as a dramatic increase in the number of rapidly proliferating isthmus stem/progenitor cells in the corpus of RUNX3 mice. Transcriptomic analyses of the isolated epithelial cells showed that the cell-cycle-related MYC target gene signature was enriched in the corpus epithelial cells of RUNX3 mice compared with the wild-type corpus. Mechanistically, RUNX3 mutant protein disrupted the regulation of the restriction point where cells decide to enter either a proliferative or quiescent state, thereby driving stem cell expansion and limiting the ability of cells to terminally differentiate.
CONCLUSIONS
RUNX3 missense mutation is associated with the continuous cycling of isthmus stem/progenitor cells, maturation arrest, and development of a precancerous state. This work highlights the importance of RUNX3 in the prevention of metaplasia and gastric cancer.
Topics: Animals; Carcinogenesis; Core Binding Factor Alpha 3 Subunit; Gastric Mucosa; Metaplasia; Mice; Point Mutation; Precancerous Conditions; Stem Cells; Stomach Neoplasms
PubMed: 35074568
DOI: 10.1016/j.jcmgh.2022.01.010 -
Frontiers in Immunology 2022Major histocompatibility complex class II (MHC II) is an essential immune regulatory molecule that plays an important role in antigen presentation and T-cell...
Major histocompatibility complex class II (MHC II) is an essential immune regulatory molecule that plays an important role in antigen presentation and T-cell development. Abnormal MHC II expression can lead to immunodeficiency, clinically termed as type II bare lymphocyte syndrome (BLS), which usually results from mutations in the MHC II transactivator (CIITA) and other coactivators. Here, we present a new paradigm for MHC II deficiency in mice that involves a spontaneous point mutation on H2-Aa. A significantly reduced population of CD4 T cells was observed in mice obtained from the long-term homozygous breeding of (Map1, ) knockout mice; this phenotype was not attributed to the original knocked-out gene. MHC II expression was generally reduced, together with a marked deficiency of H2-Aa in the immune cells of these mice. Using cDNA and DNA sequencing, a spontaneous H2-Aa point mutation that led to false pre-mRNA splicing, deletion of eight bases in the mRNA, and protein frameshift was identified in these mice. These findings led to the discovery of a new type of spontaneous MHC II deficiency and provided a new paradigm to explain type II BLS in mice.
Topics: Animals; CD4-Positive T-Lymphocytes; Histocompatibility Antigens Class II; Mice; Mice, Knockout; Point Mutation; Severe Combined Immunodeficiency; T-Lymphocytes
PubMed: 35309308
DOI: 10.3389/fimmu.2022.810824 -
STAR Protocols Sep 2023Chimeric mouse models have recently been developed to study human microglia in vivo. However, widespread engraftment of donor microglia within the adult brain has been...
Chimeric mouse models have recently been developed to study human microglia in vivo. However, widespread engraftment of donor microglia within the adult brain has been challenging. Here, we present a protocol to introduce the G795A point mutation using CRISPR-Cas9 into the CSF1R locus of human pluripotent stem cells. We also describe an optimized microglial differentiation technique for transplantation into newborn or adult recipients. We then detail pharmacological paradigms to achieve widespread and near-complete engraftment of human microglia. For complete details on the use and execution of this protocol, please refer to Chadarevian et al. (2023)..
Topics: Adult; Animals; Mice; Infant, Newborn; Humans; Microglia; Brain; Disease Models, Animal; Pluripotent Stem Cells; Point Mutation
PubMed: 37516973
DOI: 10.1016/j.xpro.2023.102490 -
The Journal of Biological Chemistry Feb 2022The glucocorticoid (GC) receptor (GR) is essential for normal development and in the initiation of inflammation. Healthy GR mice with reduced dimerization propensity due...
The glucocorticoid (GC) receptor (GR) is essential for normal development and in the initiation of inflammation. Healthy GR mice with reduced dimerization propensity due to a point mutation (A465T) at the dimer interface of the GR DNA-binding domain (DBD) (here GR) have previously helped to define the functions of GR monomers and dimers. Since GR retains residual dimerization capacity, here we generated the dimer-nullifying double mutant GR mice, featuring an additional mutation (I634A) in the ligand-binding domain (LBD) of GR. These mice are perinatally lethal, as are GR mice (these mice have the I634A mutation but not the A465T mutation), displaying improper lung and skin formation. Using embryonic fibroblasts, high and low doses of dexamethasone (Dex), nuclear translocation assays, RNAseq, dimerization assays, and ligand-binding assays (and K values), we found that the lethal phenotype in these mice is due to insufficient ligand binding. These data suggest there is some correlation between GR dimerization potential and ligand affinity. We conclude that even a mutation as subtle as I634A, at a position not directly involved in ligand interactions sensu stricto, can still influence ligand binding and have a lethal outcome.
Topics: Animals; Dexamethasone; Glucocorticoids; Ligands; Mice; Point Mutation; Receptors, Glucocorticoid
PubMed: 35007536
DOI: 10.1016/j.jbc.2022.101574 -
Investigative Ophthalmology & Visual... Mar 2020To investigate the underlying mechanisms for how the mouse Cx50-R205G point mutation, a homologue of the human Cx50-R198W mutation that is linked to cataract-microcornea...
PURPOSE
To investigate the underlying mechanisms for how the mouse Cx50-R205G point mutation, a homologue of the human Cx50-R198W mutation that is linked to cataract-microcornea syndrome, affects proper lens growth and fiber cell differentiation to lead to severe lens phenotypes.
METHODS
EdU labeling, immunostaining, confocal imaging analysis, and primary lens epithelial cell culture were performed to characterize the lens epithelial cell (LEC) proliferation and fiber cell differentiation in wild-type and Cx50-R205G mutant lenses in vivo and in vitro.
RESULTS
The Cx50-R205G mutation severely disrupts the lens size and transparency. Heterozygous and homozygous Cx50-R205G mutant and Cx50 knockout lenses all show decreased central epithelium proliferation while only the homozygous Cx50-R205G mutant lenses display obviously decreased proliferating LECs in the germinative zone of neonatal lenses. Cultured Cx50-R205G lens epithelial cells reveal predominantly reduced Cx50 gap junction staining but no change of the endoplasmic reticulum stress marker BiP. The heterozygous Cx50-R205G lens fibers show moderately disrupted Cx50 and Cx46 gap junctions while the homozygous Cx50-R205G lens fibers have drastically reduced Cx50 and Cx46 gap junctions with severely altered fiber cell shape in vivo.
CONCLUSIONS
The Cx50-R205G mutation inhibits both central and equatorial lens epithelial cell proliferation to cause small lenses. This mutation also disrupts the assembly and functions of both Cx50 and Cx46 gap junctions in lens fibers to alter fiber cell differentiation and shape to lead to severe lens phenotypes.
Topics: Animals; Animals, Newborn; Cataract; Cell Differentiation; Cell Proliferation; Cells, Cultured; Connexins; Corneal Diseases; Epithelial Cells; Fluorescent Antibody Technique, Indirect; Gene Expression Regulation; Lens, Crystalline; Mice; Mice, Inbred C57BL; Mice, Knockout; Microscopy, Confocal; Microscopy, Fluorescence; Point Mutation
PubMed: 32182330
DOI: 10.1167/iovs.61.3.25