Pathogenic Missense Mutations Research Articles

Responsivity to light in familial hemiplegic migraine type 1 mutant mice reveals frequency-dependent enhancement of visual network excitability.

Migraine patients often report (inter)ictal hypersensitivity to light, but the underlying mechanisms remain an enigma. Both hypo‐ and hyperresponsivity of the visual network have been reported, which may reflect either intra‐individual dynamics of the network or large inter‐individual variation in the measurement of human visual evoked potential data. Therefore, we studied visual system responsivity in freely behaving mice using combined epidural electroencephalography and intracortical multi‐unit activity to reduce variation in recordings and gain insight into visual cortex dynamics. For better clinical translation, we investigated transgenic mice that carry the human pathogenic R192Q missense mutation in the α1A subunit of voltage‐gated CaV2.1 Ca2+ channels leading to enhanced neurotransmission and familial hemiplegic migraine type 1 in patients. Visual evoked potentials were studied in response to visual stimulation paradigms with flashes of light. Following intensity‐dependent visual stimulation, FHM1 mutant mice displayed faster visual evoked potential responses, with lower initial amplitude, followed by less pronounced neuronal suppression compared to wild‐type mice. Similar to what was reported for migraine patients, frequency‐dependent stimulation in mutant mice revealed enhanced photic drive in the EEG beta‐gamma band. The frequency‐dependent increases in visual network responses in mutant mice may reflect the context‐dependent enhancement of visual cortex excitability, which could contribute to our understanding of sensory hypersensitivity in migraine.

Next generation sequencing in sudden cardiac death (pilot study)

Aim.To search for causal mutations in candidate genes responsible for the development of sudden cardiac death (SCD) in men who died under the age of 45.Materialandmethods.The SCD group (n=37) was formed using the criteria the World Health Organization and the European Society of Cardiology. Autopsy material was collected from men who died suddenly outside medical institutions and underwent forensic medical examination according to the standard protocol. Autopsy revealed no morphological changes that could explain sudden death. The mean age was 32,4±6,4 years. Genomic DNA was isolated from myocardial tissue using phenol-chloroform extraction. Clinical exome sequencing was performed. At first, we analyzed the results of sequencing of 24 genes, mutations in which lead to cardiovascular diseases associated with an increased risk of SCD:KCNQ1,KCNH2,SCN5A,AKAP9,ANK2,CACNA1C,CALM1,CALM2,CAV3,KCNE1,KNCJNE2,KCNE2,SCN4B,SNTA1,MYH2,APOB,KCNA5,TGFB3,NEB,PDX1,FLNC,PLEC,KCND3.Results.Of 37 samples, we revealed 13 probable pathogenic missense mutations in 9 samples (24,3%). Of 13 probable pathogenic variants, 5 were new.Conclusion.This pilot study provides following conclusions: it is necessary to continue molecular autopsy research in Russia; to increase the effectiveness of detecting causal mutations, it is necessary to reduce the age of patients with SCD included in the study; studying the families of deceased; cooperation of experienced specialists — forensic pathologist, laboratory geneticist, cardiologist.

A Novel ALAS2 Missense Mutation in Two Brothers With Iron Overload and Associated Alterations in Serum Hepcidin/Erythroferrone Levels.

Iron loading anemias are characterized by ineffective erythropoiesis and iron overload. The prototype is non-transfusion dependent ß-thalassemia (NTDT), with other entities including congenital sideroblastic anemias, congenital dyserythropoietic anemias, some hemolytic anemias, and myelodysplastic syndromes. Differential diagnosis of iron loading anemias may be challenging due to heterogeneous genotype and phenotype. Notwithstanding the recent advances in linking ineffective erythropoiesis to iron overload, many pathophysiologic aspects are still unclear. Moreover, measurement of hepcidin and erythroferrone (ERFE), two key molecules in iron homeostasis and erythropoiesis, is scarcely used in clinical practice and of uncertain utility. Here, we describe a comprehensive diagnostic approach, including next-generation sequencing (NGS), in silico modeling, and measurement of hepcidin and erythroferrone (ERFE), in two brothers eventually diagnosed as X-linked sideroblastic anemia (XLSA). A novel pathogenic ALAS2 missense mutation (c.1382T>A, p.Leu461His) is described. Hyperferritinemia with high hepcidin-25 levels (but decreased hepcidin:ferritin ratio) and mild-to-moderate iron overload were detected in both patients. ERFE levels were markedly elevated in both patients, especially in the proband, who had a more expressed phenotype. Our study illustrates how new technologies, such as NGS, in silico modeling, and measurement of serum hepcidin-25 and ERFE, may help in diagnosing and studying iron loading anemias. Further studies on the hepcidin-25/ERFE axis in additional patients with XLSA and other iron loading anemias may help in establishing its usefulness in differential diagnosis, and it may also aid our understanding of the pathophysiology of these genetically and phenotypically heterogeneous entities.

Targeted Next-Generation Sequencing Identifies Molecular and Genetic Events in Dedifferentiated Chondrosarcoma.

Dedifferentiated chondrosarcoma is a rare adult bone tumor with a dismal prognosis and is composed of a conventional chondrosarcoma juxtaposed to high-grade nonchondrogenic sarcoma. Dedifferentiated chondrosarcomas may represent tumor progression from a differentiated to a primitive histotype. To determine the genetic and molecular events that drive progression from a conventional chondrosarcoma to high grade nonchondrogenic sarcoma. We analyzed the genomic landscape of paired conventional and dedifferentiated components of 11 dedifferentiated chondrosarcoma using targeted next-generation DNA sequencing with immunohistochemical validation. Clinical, radiographic, and pathologic features of tumors were reviewed. Capture-based DNA sequencing targeting the coding regions of 479 cancer genes and select introns was performed. The tumors arose in the femur (n = 4; 36%), scapula (n = 3; 27%), pelvis (n = 3; 27%), and humerus (n = 1; 9%) of 7 men (64%) and 4 women (36%; median age, 61 years). DNA was adequate for sequencing from all 11 dedifferentiated components (100%) and 9 paired conventional chondrosarcoma components (82%). All tumors (100%) harbored either IDH1 p.R132 or IDH2 p.R172S hotspot mutations. Seven tumors (64%) displayed COL2A1 alterations. TERT promoter mutations were present in 5 of 9 pairs (56%) and 2 (22%) additional unpaired dedifferentiated components. IDH1/2, COL2A1, and TERT mutations were identical in both components of the paired samples. Pathogenic missense or truncating mutations in TP53 and large-scale copy number alterations were more common in dedifferentiated components than in those of matched conventional components. The results support IDH1/2, COL2A1, and TERT promoter mutations being common in dedifferentiated chondrosarcoma and as likely early events in progression, whereas inactivating mutation of TP53 and high-level copy number alterations may be later events in the dedifferentiated phenotype.

The pathogenic S688Y mutation in the ligand-binding domain of the GluN1 subunit regulates the properties of NMDA receptors

Although numerous pathogenic mutations have been identified in various subunits of N-methyl-D-aspartate receptors (NMDARs), ionotropic glutamate receptors that are central to glutamatergic neurotransmission, the functional effects of these mutations are often unknown. Here, we combined in silico modelling with microscopy, biochemistry, and electrophysiology in cultured HEK293 cells and hippocampal neurons to examine how the pathogenic missense mutation S688Y in the GluN1 NMDAR subunit affects receptor function and trafficking. We found that the S688Y mutation significantly increases the EC50 of both glycine and d-serine in GluN1/GluN2A and GluN1/GluN2B receptors, and significantly slows desensitisation of GluN1/GluN3A receptors. Moreover, the S688Y mutation reduces the surface expression of GluN3A-containing NMDARs in cultured hippocampal neurons, but does not affect the trafficking of GluN2-containing receptors. Finally, we found that the S688Y mutation reduces Ca2+ influx through NMDARs and reduces NMDA-induced excitotoxicity in cultured hippocampal neurons. These findings provide key insights into the molecular mechanisms that underlie the regulation of NMDAR subtypes containing pathogenic mutations.

The pathogenic T387A missense mutation in the gene encoding signal transducer and activator of transcription 1 exhibits a differential gene expression profile

Heterozygous gain-of-function (GOF) mutations in the interferon-driven transcription factor STAT1 (signal transducer and activator of transcription 1) cause chronic mucocutaneous candidiasis (CMC). In this study, we characterized the molecular basis of a CMC-associated missense mutation by introducing a threonine-to-alanine exchange in the STAT1 DNA-binding domain at position 387. This substitution had previously been described in a CMC patient with suppurative eyelid infection and cutaneous abscesses, which are both unusual symptoms in this immunodeficiency. The STAT1-T387A mutant generated was compared to the wild-type protein and, in addition, to the missense mutant in the neighbouring position 386. Our results showed that the T387A mutant displayed distinct properties different from the wild-type molecule, namely elevated levels of tyrosine phosphorylation in conjunction with increased DNA-binding activity, hyperactive transcriptional regulation, and prolonged nuclear accumulation. The elevated tyrosine phosphorylation of the T387A mutant did not result in an increased mRNA production above the level of the wild-type molecule for all transcripts tested, indicating that the transcriptional activity of this mutant is largely gene-dependent. Nonetheless, these data demonstrate that the pathogenic T387A mutation associated with an atypical CMC symptomatology is biochemically similar to other well-characterized GOF mutants, while the H386A mutant was indistinguishable from the wild-type molecule. Our findings are in line with the assumption that the phenotype of this dominant STAT1 GOF mutation probably results from a disturbed shift in the equilibrium between the parallel and antiparallel dimer conformation, which is required for physiological gene activation.

MITOCHONDRIAL DISEASES & METABOLIC MYOPATHIES: P.321 Mitochondrial myopathy in X-linked creatine transporter deficiency due to a novel mutation of SLC6A8 gene

Creatine (Cr) is essential in energy metabolism since it allows the ADP-ATP conversion. Creatine transporter (CRTR) gene SLC6A8 is required for brain and muscle creatine uptake from the blood. Mutations in SLC6A8 are responsible for X-linked CRTR deficiency (CRTR-D) leading to mental retardation, global development delay, seizures and behavioral disorders. Excepted motor milestone delay, muscle involvement has been only exceptionally reported in CRTR-D. We aim to report a novel SLC6A8 mutation in a family with a particular clinical picture including a muscle mitochondrial phenotype. A 44-year-old man developed early infantile hypotonia and mental retardation and delayed motor milestones. At the time of assessment, he harbored a profound intellectual disability associated with mutism, facial dysmorphia, epilepsy, generalized muscle weakness and diarrhea. His eldest brother had severe intellectual disability, epilepsy, ptosis, muscle weakness and died at the age of 35 years. The proband's work-up results were: normal CK level, a major increase of urinary creatine/creatinine ratio: 2.5 (N≤0.37), a decreased creatine peak on brain magnetic resonance imaging spectroscopy and mitochondrial myopathic changes on muscle biopsy. A severe decrease of Cr uptake was measured on cultured fibroblasts: 0.3/8.6 nmol/mg-protein (N>18.8/31.9) with [Cr] of 25/500 µM. Clinical exome (4427 genes) allowed the identification of the novel missense mutation c.827T>C (p.Leu276Pro) on the SLC6A8 gene. It was inherited from his asymptomatic mother, absent in an asymptomatic brother and in the control database gnomAD (gnomad.broadinstitute.org). Moreover, it was predicted pathogenic from 4 prediction tools (SIFT, PolyPhen2, Mutation Taster, Mutation Assessor). In conclusion, reporting a novel pathogenic missense mutation in SLC6A8 gene associated with an unexpected mitochondrial myopathy taking part of the clinical picture, we expand the genetic and phenotypic spectrum of CRTR-D.

Identification of pathogenic missense mutations using protein stability predictors

Attempts at using protein structures to identify disease-causing mutations have been dominated by the idea that most pathogenic mutations are disruptive at a structural level. Therefore, computational stability predictors, which assess whether a mutation is likely to be stabilising or destabilising to protein structure, have been commonly used when evaluating new candidate disease variants, despite not having been developed specifically for this purpose. We therefore tested 13 different stability predictors for their ability to discriminate between pathogenic and putatively benign missense variants. We find that one method, FoldX, significantly outperforms all other predictors in the identification of disease variants. Moreover, we demonstrate that employing predicted absolute energy change scores improves performance of nearly all predictors in distinguishing pathogenic from benign variants. Importantly, however, we observe that the utility of computational stability predictors is highly heterogeneous across different proteins, and that they are all inferior to the best performing variant effect predictors for identifying pathogenic mutations. We suggest that this is largely due to alternate molecular mechanisms other than protein destabilisation underlying many pathogenic mutations. Thus, better ways of incorporating protein structural information and molecular mechanisms into computational variant effect predictors will be required for improved disease variant prioritisation.

Prevalence of germline TP53 variants among early-onset breast cancer patients from Polish population

BackgroundThe objective of this study was to determine spectrum and prevalence of germline mutations in TP53 gene among Polish women with early-onset breast cancer (BC), which has not been determined until now.MethodsA cohort of 100 females with BC diagnosed ≤ 30 years of age and with a positive family history of cancer was used as a discovery cohort. 1880 women with BC ≤ 45 years old and a control group of 2000 healthy women were genotyped as a replication phase of this study.ResultsFour heterozygous pathogenic missense mutations were detected in a group of 100 patients with early-onset breast cancer. On the basis of software prediction and available literature data, all these variants were defined as pathogenic. None of these TP53 variants were detected among 1880 breast cancer patients and 2000 healthy controls. No large mutations were found among early-onset cases using MLPA reaction.ConclusionGermline pathogenic TP53 variants were found in 4% early-onset Polish BC patients. No founder mutations were identified in Polish population. To improve the treatment and surveillance screening, the search for germline TP53 pathogenic variants is recommended for all female BC cases diagnosed ≤ 30 years old.

Unexpected expression of mismatch repair protein is more commonly seen with pathogenic missense than with other mutations in Lynch syndrome

It has been observed that some patients with colorectal cancer due to germline or double somatic pathogenic variants in the mismatch repair (MMR) genes may have intact protein expression in their tumors as assessed by immunohistochemistry (IHC). This has been speculated to occur more frequently in Lynch syndrome (LS) cases due to pathogenic missense mutations, leading to expression of a full-length but nonfunctional protein with retained antigenicity. Our goals were to study the frequency of unexpected MMR expression in colorectal cancers among LS cases with missense mutations, LS cases with truncating mutations, as well as cases with double somatic MMR mutationsand evaluate if the unexpected MMR expression is more common in certain categories. IHC slides were available for 82 patients with MMR deficiency without methylation, which included 56 LS cases and 26 double somatic MMR mutation cases. Sixteen of 82 MMR-defective cases showed unexpected MMR expression, with 10 cases showing tumor staining weaker than the control and 6 cases (7%) showing intact staining. Unexpected MMR expression was most commonly seen with LS cases with missense mutations (4 of 9, 44%), followed by MMR double somatic mutation cases (7 of 26, 27%), and finally by LS cases with truncating mutations (5 of 47, 11%). Cautious interpretation of MMR IHC is advised when dealing with tumor staining that is weaker than the control regardless of the percentage of tumor stainingas these cases may harbor pathogenic MMR gene mutations. Missense mutations may account for some LS cases that may be missed by IHC alone. Strict adherence to proper interpretation of IHC with attention to staining intensity and the status of heterodimer partner protein will prevent many potential misses.

Molecular profiling of lamellar ichthyosis pathogenic missense mutations on the structural and stability aspects of TGM1 protein

Lamellar ichthyosis (LI) is a rare inherited disease where affected infants present a extensive skin scaling characterized by hyperkeratosis. Inherited mutations in the Transglutaminase 1 (TGM1) protein is one of the known causative genetic factor for the LI. The main objective of this study is to explore the impact of LI causative missense mutations on the structural and stability aspects of TGM1 protein using structural modeling, molecular docking and molecular dynamics approaches. By testing all LI causative TMG1 mutations against multiple stability prediction methods, we found that L362R and L388P mutations positioned in the Transglut_core domain were most destabilizing to the stability of TGM1 protein. These 2 mutations were 3D protein modeled and further analyzed by molecular docking and dynamic simulation methods. Molecular docking of these TGM1 mutant structures with chitosan, a natural polyphenolic compound and known inducer for transglutaminase enzyme, has shown stable molecular interactions between the native TGM1-chitosan and TGM1(L388P)-chitosan complex, when compared to the TGM1(L362R)-chitosan complex. Interestingly, molecular dynamics analysis have also yielded similar findings, where L388P-chitosan complex is shown to develop B-sheets and attain better stability, whereas TGM1-L362R complex possessed coils over the simulation period, pointing its highly destabilizing behavior on the protein structure. This study concludes that missense mutations in Transglut_core domain of the TGM1 are deleterious to the stability and structural changes of TGM1 protein and also suggest that chitosan molecule could act as a natural activator against few pathogenic TGM1 mutations. Communicated by Ramaswamy H. Sarma

Computational approach towards identification of pathogenic missense mutations in AMELX gene and their possible association with amelogenesis imperfecta.

Amelogenin gene (AMEL-X) encodes an enamel protein called amelogenin, which plays a vital role in tooth development. Any mutations in this gene or the associated pathway lead to developmental abnormalities of the tooth. The present study aims to analyze functional missense mutations in AMEL-X genes and derive an association with amelogenesis imperfecta. The information on missense mutations of human AMEL-X gene was collected from Ensembl database (https://asia.ensembl.org). Three different computational tools viz., SIFT, PolyPhen and PROVEAN were used to identify the deleterious or pathogenic forms of mutations in the gene studied. I-Mutant Suit was used to identify the stability of the proteins identified as deleterious by the three tools. Further, MutPred analysis revealed the pathogenicity of these mutations. Among 96 missense variants reported in AMEL-X gene, 18 were found to be deleterious using the three prediction tools (SIFT, PolyPhen and PROVEAN). When these variants were subjected to protein stability analysis, about 14 missense variants showed decreased stability whereas the other 8 variants showed increased stability. Further, these variants were analyzed using MutPred which identified 9 variants to be highly pathogenic. ExAC database revealed that all the pathogenic mutations had a minor allele frequency less than 0.01. The in silico analysis revealed highly pathogenic mutations in amelogenin gene which could have a putative association with amelogenesis imperfecta. These mutations should be screened in patients for early diagnosis of susceptibility to AI.

Identification of SDHA germline mutations in sporadic SDHA mutant gastrointestinal stromal tumors (GIST): The need of a genetic counselling.

11537 Background: SDH- deficient GIST, as defined by the loss of expression of SDHB, account up to about 10% of all gastric GIST and generally affect younger population. Germline mutations in SDHB, SDHC, and SDHD occur in about 20–30% of SDH- deficient, that may be referred to a hereditary condition known as hereditary GIST-paraganglioma syndrome (Carney-Stratakis Syndrome), whereas germline SDHA mutations have been rarely described in apparently sporadic cases. Currently, even germline testing is recommended for SDH- deficient GIST, there are no clear guidelines for genetic counselling and follow-up of SDH x mutation carriers and relatives, especially for SDHA mutant GIST not yet linked to well-defined hereditary syndrome. The aim of this work was to study the SDHA gene in the normal DNA of patients with SDHA mutant GIST. Methods: Thirteen patients carrying SDHA-mutant GIST were studied (8F/5M). Median age of diagnosis was 45,9 years (range 25-74). All GIST were located in the stomach and 3 patients out 13 presented a metastatic disease. In all cases except one, the GIST was the only cancer presentation and no personal or familial history of cancer was revealed. All cases were negative for SDHB immunohistochemistry. Germline mutations were identified through Sanger sequencing of SDHA in the normal counterpart. Results: Germline mutations were identified in all patients for which normal counterpart was available: 4 cases harboured truncating mutations (S384X, R31X and W119X); 5 cases carried pathogenic missense mutations (G233V, R171H, R589Q, G257A and R600Q) and 2 cases had splice site alterations (c.457-3_457-1 delCAG and c.456+9 C > T). In 8 cases the tumor DNA showed the loss of the corresponding wild-type allele, while in the other 3 cases compound heterozygosity for an additional somatic mutation was detected (R589W, R451C,and R171C). In 2 patients, unfortunately, normal DNA was not available, however both tumours carried two mutational hits on SDHA (one with heterozygous G419R and E564K, and one with homozygous R585Q). Of note, 5 patients presented un-usaul SDHA related clinical characteristics as were not young adult ( > 50 years-old) or no multifocal GIST. Conclusions: We demonstrated that germline SDHA mutations are highly frequent in SDHA- deficient GIST. Therefore, although a clear syndrome has not been defined, genetic counselling and follow-up of SDHA mutation carriers and relatives should be clarified.

SUN-LB13 Idiopathic Infantile Hypercalcemia Secondary to CYP24A1 Mutation: A Rare Case Without Exogenous Vitamin D Supplementation

Background: Mutations in CYP24A1, which encodes 24-hydroxylase, the key enzyme for Vitamin D breakdown, cause symptomatic hypercalcemia and nephrocalcinosis in infants on Vitamin D supplementation. New, symptomatic diagnoses of idiopathic infantile hypercalcemia without exogenous supplementation are rare. Previous case reports describe a seasonal effect with worsening hypercalcemia and hypercalciuria during summertime, attributed to increased sun exposure and endogenous Vitamin D production. Clinical Case: A 10-month-old female presented to endocrine care with hypercalcemia and nephrocalcinosis, detected on renal ultrasound (US) due to history of UTI. Her first renal US and serum calcium (Ca) at 3mo of age were normal. Subsequent renal US at 6mo and 9mo of age demonstrated nephrocalcinosis, prompting nephrology and endocrine evaluation. History was significant for failure to thrive. She was born in the fall, with worsening hypercalcemia and nephrocalcinosis during the summer. Diet consisted of standard infant formula and age appropriate solid foods with no added Vitamin D supplementation (~300 IU/day in her formula). She had no family history of nephrocalcinosis, nephrolithiasis, bone disease, or disorders of Ca regulation. Initial labs were notable for Ca corrected for albumin 11.5 (7.8-11.1 mg/dL), PTH <4 (8.7-77.1 pg/mL), 25-OH-Vitamin D 81 (30-96 ng/mL), 1,25-OH-Vitamin D 23.1 (26.1-95 pg/mL), Urine Ca/creatinine ratio of 0.9 mg/mg (<0.81), normal chromosomal microarray, and normal thyroid function tests. She was started on reduced mineral formula PM 60/40. One week later, repeat Ca level increased to Ca corrected 14.2 (7.8-11.1 mg/dL). She was admitted for IV fluids and pamidronate, and was transitioned to a low Ca and Vitamin D formula (Calcilo), with improvement in Ca levels. Testing revealed an increased ratio of 25-OH-Vitamin D to 24,25-OH-Vitamin D of 192 (normal <25), and genetic testing showed 2 pathogenic missense mutations in CYP24A1 genes: c.1226T>C p.(Leu409Ser) and c.1186C>T p.(Arg396Trp). The Leu409Ser mutation has shown a small amount of 24-hydroxylase activity in previous in vitro analysis. She has continued a low Ca diet with stable Ca corrected of 10.7-10.8 (8.7-9.8 mg/dL) and significantly improved weight gain. Conclusion: This is one of the few documented cases of symptomatic idiopathic infantile hypercalcemia secondary to CYP24A1 mutation in an infant without exogeneous Vitamin D supplementation. Her nephrocalcinosis and hypercalcemia worsened over the summer, suggesting increased sun exposure may have been a contributing factor. This case demonstrates that 1,25-OH-Vitamin D levels may be normal or low in this condition, particularly for individuals with the Leu409Ser mutation who may retain partial 24-hydroxylase function.

Molecular dynamics simulations to decipher the structural and functional consequences of pathogenic missense mutations in the galactosylceramidase (GALC) protein causing Krabbe’s disease

Krabbe disease (KD), also known as globoid cell leukodystrophy disease, is an autosomal recessive lysosomal storage genetic disorder, which is caused by the deficiency of galactocerebrosidase (GALC) coding gene (GALC). This study aimed to use extensive computational pipelines in understanding the missense mutations in GALC. We retrieved 176 mutations from the public databases and subjected them to pathogenicity, stability, and conservation analyses. The PredictSNP, iStable, and ConSurf prediction tools predicted 45, 95, and 47 mutations to be deleterious, destabilizing, and highly conserved, respectively. The R396L and R396W were the most deleterious and destabilizing to GALC, and were therefore prioritized for further analysis. Systematic validation on the impact of the R396L and R396W mutations to the chaperone alpha lobeline was performed using the molecular docking approach. The docking analysis revealed that the mutant R396W interacted with minimal binding affinity compared with both the R396L mutant and native GALC. Furthermore, the repetitive molecular dynamics simulation analysis showed that the mutant R396W demonstrated less compactness and reduced number of intramolecular hydrogen bonds compared with the mutant R396L and the native GALC. Overall, we observed higher structural and functional modifications in R396W positioned in the substrate-binding site. This was highly supported by the MMPBSA and DSSP analysis of the GROMACS. DSSP showed the transformation of turns to bends, indicating a loss of stability due to the R396W mutation. This study is expected to serve as a platform for prioritizing mutant proteins that could be a platform for both drug and target therapeutics Communicated by Ramaswamy H. Sarma

Oral-Facial-Digital Syndrome Type 1: Further Clinical and Molecular Delineation in 2 New Families.

Oral-facial-digital syndrome type 1 (OFD1) [OMIM 311200] is a rare genetic disorder associated with congenital anomalies of the oral cavity, face, and digits. This condition is associated with mutations in the OFD1 gene. Our objective was to recruit patients with the OFD1 clinical phenotype without genetic confirmation, aiming to identify genetic variants in the OFD1 gene. Three patients from 2 unrelated families were recruited into our study. We employed a variety of genomic techniques on these patients, including candidate gene analysis, array comparative genomic hybridization, whole-exome sequencing, and whole-genome sequencing. We investigated 3 affected patients from 2 unrelated families with a clinical diagnosis of OFD1. We discovered a novel pathogenic dominant missense mutation c.635G>C (p.Arg212Pro) in the OFD1 gene in one family. A novel frameshift, loss-of-function mutation c.306delA (p.Glu103LysfsTer42) was detected in the affected patient in the second family. These new genetic variants will add to the spectrum of known OFD1 mutations associated with the OFD1 disorder. Our study also confirms the variable phenotypic presentation of OFD1 and its well-recognized association with central nervous system malformations and renal anomalies. Molecular diagnostic confirmation achieved in these families will have positive implications for their medical management.

Map of Genetically Constrained Regions in Human Intrinsically Disordered Proteins

Intrinsically disordered proteins (IDPs) and regions (IDRs) are pivotal for biological processes like signaling, recognition, and regulation, and have been found to be implicated in many diseases. Evolutionary selection of IDPs thus has been extensively investigated through multiple sequence alignment (MSA) methods. Recent large-scale catalogues of human genome sequences have enabled the detection of constrained regions depleted of genetic variation. Here, we aim to identify the prevalence, characteristics, and functions of genetically constrained IDRs. We mapped the missense tolerance ratio (MTR), quantifying the depletion of amino acid substitutions in genome aggregation database (a sample of 138,632 individuals) on 210 human IDPs from DisProt7.0 database. We identified 63 IDRs (length<100 residues) having 25th percentile MTR, indicating these IDRs are >75% constrained. For further verification, we annotated IDRs using MPC (Missense badness, PolyPhen-2, and Constraint) score to identify regions in genes that are depleted of substitutions. We found 70 more IDRs with MPC < 1.0 (lower observed versus expected substitutions). We then investigated the functions and interactions of the 133 missense constrained IDRs (mcIDRs). We spotted 25 mcIDRs carrying molecular recognition features (assemblers or effectors), 14 acting as flexible linkers/spacers, 51 to have disordered state and 45 involved in protein-protein interactions. Looking further into the cross-species MSA (BLAST search, 50% identity cut-off), we found 53 mcIDRs with >90% and 26 mcIDRs with <30% conserved residues. We further examined the enrichment of disease-associated loci in mcIDRs, and found 645 rare singletons (new mutations in evolution) and 635 pathogenic missense mutations. We exploited two genetic constraint metrics to identify IDRs that are restricted against substitutions. The observed functional diversity of the constrained IDRs, their contrast with evolutionary conservations, and their accumulation of disease-associated loci will advance our understanding of IDP-based regulations in human pathology.

Interpretation of somatic POLE mutations in endometrial carcinoma.

Pathogenic somatic missense mutations within the DNA polymerase epsilon (POLE) exonuclease domain define the important subtype of ultramutated tumours (‘POLE‐ultramutated’) within the novel molecular classification of endometrial carcinoma (EC). However, clinical implementation of this classifier requires systematic evaluation of the pathogenicity of POLE mutations. To address this, we examined base changes, tumour mutational burden (TMB), DNA microsatellite instability (MSI) status, POLE variant frequency, and the results from six in silico tools on 82 ECs with whole‐exome sequencing from The Cancer Genome Atlas (TCGA). Of these, 41 had one of five known pathogenic POLE exonuclease domain mutations (EDM) and showed characteristic genomic alterations: C>A substitution > 20%, T>G substitutions > 4%, C>G substitutions < 0.6%, indels < 5%, TMB > 100 mut/Mb. A scoring system to assess these alterations (POLE‐score) was developed; based on their scores, 7/18 (39%) additional tumours with EDM were classified as POLE‐ultramutated ECs, and the six POLE mutations present in these tumours were considered pathogenic. Only 1/23 (4%) tumours with non‐EDM showed these genomic alterations, indicating that a large majority of mutations outside the exonuclease domain are not pathogenic. The infrequent combination of MSI‐H with POLE EDM led us to investigate the clinical significance of this association. Tumours with pathogenic POLE EDM co‐existent with MSI‐H showed genomic alterations characteristic of POLE‐ultramutated ECs. In a pooled analysis of 3361 ECs, 13 ECs with DNA mismatch repair deficiency (MMRd)/MSI‐H and a pathogenic POLE EDM had a 5‐year recurrence‐free survival (RFS) of 92.3%, comparable to previously reported POLE‐ultramutated ECs. Additionally, 14 cases with non‐pathogenic POLE EDM and MMRd/MSI‐H had a 5‐year RFS of 76.2%, similar to MMRd/MSI‐H, POLE wild‐type ECs, suggesting that these should be categorised as MMRd, rather than POLE‐ultramutated ECs for prognostication. This work provides guidance on classification of ECs with POLE mutations, facilitating implementation of POLE testing in routine clinical care. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Myosin Sequestration Regulates Sarcomere Function, Cardiomyocyte Energetics, and Metabolism, Informing the Pathogenesis of Hypertrophic Cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is caused by pathogenic variants in sarcomere protein genes that evoke hypercontractility, poor relaxation, and increased energy consumption by the heart and increased patient risks for arrhythmias and heart failure. Recent studies show that pathogenic missense variants in myosin, the molecular motor of the sarcomere, are clustered in residues that participate in dynamic conformational states of sarcomere proteins. We hypothesized that these conformations are essential to adapt contractile output for energy conservation and that pathophysiology of HCM results from destabilization of these conformations. We assayed myosin ATP binding to define the proportion of myosins in the super relaxed state (SRX) conformation or the disordered relaxed state (DRX) conformation in healthy rodent and human hearts, at baseline and in response to reduced hemodynamic demands of hibernation or pathogenic HCM variants. To determine the relationships between myosin conformations, sarcomere function, and cell biology, we assessed contractility, relaxation, and cardiomyocyte morphology and metabolism, with and without an allosteric modulator of myosin ATPase activity. We then tested whether the positions of myosin variants of unknown clinical significance that were identified in patients with HCM, predicted functional consequences and associations with heart failure and arrhythmias. Myosins undergo physiological shifts between the SRX conformation that maximizes energy conservation and the DRX conformation that enables cross-bridge formation with greater ATP consumption. Systemic hemodynamic requirements, pharmacological modulators of myosin, and pathogenic myosin missense mutations influenced the proportions of these conformations. Hibernation increased the proportion of myosins in the SRX conformation, whereas pathogenic variants destabilized these and increased the proportion of myosins in the DRX conformation, which enhanced cardiomyocyte contractility, but impaired relaxation and evoked hypertrophic remodeling with increased energetic stress. Using structural locations to stratify variants of unknown clinical significance, we showed that the variants that destabilized myosin conformations were associated with higher rates of heart failure and arrhythmias in patients with HCM. Myosin conformations establish work-energy equipoise that is essential for life-long cellular homeostasis and heart function. Destabilization of myosin energy-conserving states promotes contractile abnormalities, morphological and metabolic remodeling, and adverse clinical outcomes in patients with HCM. Therapeutic restabilization corrects cellular contractile and metabolic phenotypes and may limit these adverse clinical outcomes in patients with HCM.

Identification of potential inhibitors against pathogenic missense mutations of PMM2 using a structure-based virtual screening approach

The autosomal recessive phosphomannomutase 2-congenital disorder of glycosylation (PMM2-CDG) is characterized by defective functioning of the PMM2 enzyme, which is necessary for the conversion of mannose-6-phosphate into mannose-1-phosphate. Here, a computational pipeline was drawn to identify the most significant mutations, and further, we used a virtual screening approach to identify a new lead compound to treat the identified significant mutations. We searched for missense mutation data related to PMM2-CDG in HGMD®, UniProt, and ClinVar. Our search yielded a total of 103 mutations, of which 91 are missense mutations. The D65Y, I132N, I132T, and F183S mutations were classified as deleterious, destabilizing, and altering the biophysical properties using the PredictSNP, iStable, and Align GVGD in silico prediction tools. Additionally, we applied a multistep protocol to screen for an alternative lead compound to the existing CID2876053 (1-(3-chlorophenyl)-3,3-bis(pyridine-2-yl)urea) with affinity to these identified significant mutants. Two compounds, CHEMBL1491007 (6-chloro-4-phenyl-3-(4-pyridin-2-ylpiperazin-1-yl)-1H-quinolin-2-one) and CHEMBL3653029 (5-chloro-4-[6-[(3-fluorophenyl)methylamino]pyridin-2-yl]-N-(piperidin-4-ylmethyl)pyridin-2-amine), exhibited the highest binding affinity with the selected mutants and were chosen for further analysis. Through molecular docking, molecular dynamics simulation, and MMPBSA analysis, we found that the known compound, i.e. CID2876053, has stronger interaction with the D65Y mutant. The newly identified lead compound CHEMBL1491007 showed stronger interaction with the I132N and I132T mutants, whereas the most deleterious mutant, F183S, showed stronger interaction with CHEMBL3653029. This study is expected to aid in the field of precision medicine, and further to in vivo and in vitro analysis of these lead compounds might shed light on the treatment of PMM2-CDG. Communicated by Ramaswamy H. Sarma