Citations

Abstract Context Single-minded homologue 1 (SIM1) is a transcription factor with several physiological and developmental functions. Haploinsufficiency of SIM1 is associated with early-onset obesity with or without Prader-Willi–like (PWL) features and may exhibit incomplete penetrance. Case Description Next-generation sequencing was performed for 2 male patients with obesity, including 1 man presenting with intellectual disability (ID), body mass index (BMI) of 47.4, and impulse-control disorder, and the other man with early obesity (BMI of 36); sequencing revealed a missense variant in SIM1 (c.2144G>T; p.G715V) in both individuals. Previous studies have identified several disease-associated variants that fall near the p.G715V variant within the C-terminal domain of SIM1. We examined p.G715V variant stability and activity in a doxycycline-inducible stable cell line transfected with an artificial reporter construct and either ARNT or ARNT2 as a partner protein. Conclusions Functional testing of the p.G715V variant revealed a significant reduction in SIM1-mediated transcriptional activity. We also generated the first ab initio hybrid protein model for full-length SIM1 to show the predicted spatial relationship between p.G715V and other previously described variants in this region and identified a putative mutation hotspot within the C-terminus. Significant clinical heterogeneity has been observed in patients with SIM1 variants, particularly with regards to the PWL phenotype. In the patient with ID, a second variant of uncertain significance in CHD2 was identified that may contribute to his ID and behavioral disturbances, emphasizing the role of additional genetic modifiers.

In-frame decoding in the ribosome occurs through canonical or wobble Watson–Crick pairing of three mRNA codon bases (a triplet) with a triplet of anticodon bases in tRNA. Departures from the triplet–triplet interaction can result in frameshifting, meaning downstream mRNA codons are then read in a different register. There are many mechanisms to induce frameshifting, and most are insufficiently understood. One previously proposed mechanism is doublet decoding, in which only codon bases 1 and 2 are read by anticodon bases 34 and 35, which would lead to −1 frameshifting. In E. coli, tRNASer3GCU can induce −1 frameshifting at alanine (GCA) codons. The logic of the doublet decoding model is that the Ala codon’s GC could pair with the tRNASer3′s GC, leaving the third anticodon residue U36 making no interactions with mRNA. Under that model, a U36C mutation would still induce −1 frameshifting, but experiments refute this. We perform all-atom simulations of wild-type tRNASer3, as well as a U36C mutant. Our simulations revealed a hydrogen bond between U36 of the anticodon and G1 of the codon. The U36C mutant cannot make this interaction, as it lacks the hydrogen-bond-donating H3. The simulation thus suggests a novel, non-doublet decoding mechanism for −1 frameshifting by tRNASer3 at Ala codons.

Schematic representation demonstrating the fabrication and in vivo evaluation of an immune-modulatory nano-formulation consisting of irinotecan and curcumin in immune-competent mouse models of pancreatic adenocarcinoma.

Abstract Quiescin sulfhydryl oxidase 1 (QSOX1) is an enzyme overexpressed by many different tumor types. QSOX1 catalyzes the formation of disulfide bonds in proteins. Because short hairpin knockdowns (KD) of QSOX1 have been shown to suppress tumor growth and invasion in vitro and in vivo, we hypothesized that chemical compounds inhibiting QSOX1 enzymatic activity would also suppress tumor growth, invasion, and metastasis. High throughput screening using a QSOX1-based enzymatic assay revealed multiple potential QSOX1 inhibitors. One of the inhibitors, known as “SBI-183,” suppresses tumor cell growth in a Matrigel-based spheroid assay and inhibits invasion in a modified Boyden chamber, but does not affect viability of nonmalignant cells. Oral administration of SBI-183 inhibits tumor growth in 2 independent human xenograft mouse models of renal cell carcinoma. We conclude that SBI-183 warrants further exploration as a useful tool for understanding QSOX1 biology and as a potential novel anticancer agent in tumors that overexpress QSOX1.

Background and objectives: Loeys–Dietz syndrome 3, also known as aneurysms-–osteoarthritis syndrome, is an autosomal dominant genetic connective tissue disease caused by pathogenic variants in SMAD3, a transcription factor involved in TGF-β signaling. This disorder is characterized by early-onset osteoarthritis and arterial aneurysms. Common features include scoliosis, uvula abnormalities, striae, and velvety skin. Materials and Methods: The pathogenicity of a variant of uncertain significance in the SMAD3 gene was evaluated (variant c.220C > T) through personalized protein informatics and molecular studies. Results: The case of a 44-year-old male, who was originally presumed to have Marfan syndrome, is presented. An expanded gene panel determined the probable cause to be a variant in SMAD3, c.220C > T (p.R74W). His case was complicated by a history of stroke, but his phenotype was otherwise characteristic for Loeys–Dietz syndrome 3. Conclusion: This case emphasizes the importance of comprehensive genetic testing to evaluate patients for connective tissue disorders, as well as the potential benefit of utilizing a protein informatics platform for the assessment of variant pathogenicity.

AbstractBackgroundTransient receptor potential cation channel subfamily V member 4 (TRPV4) is an ion channel permeable to Ca2+ that is sensitive to physical, hormonal, and chemical stimuli. This protein is expressed in many cell types, including osteoclasts, chondrocytes, and sensory neurons. As such, pathogenic variants of this gene are associated with skeletal dysplasias and neuromuscular disorders. Pathogenesis of these phenotypes is not yet completely understood, but it is known that genotype–phenotype correlations for TRPV4 pathogenic variants often are not present.MethodsNewly characterized, suspected pathogenic variant in TRPV4 was analyzed using protein informatics and personalized protein‐level molecular studies, genomic exome analysis, and clinical study.ResultsThis statement is demonstrated in the family of our proband, a 47‐year‐old female having the novel c.2401A>G (p.K801E) variant of TRPV4. We discuss the common symptoms between the proband, her father, and her daughter, and compare her phenotype to known TRPV4‐associated skeletal dysplasias.ConclusionsProtein informatics and molecular modeling are used to confirm the pathogenicity of the unique TRPV4 variant found in this family. Multiple data were combined in a comprehensive manner to give complete overall perspective on the patient disease and prognosis.

Abstract The CHEK2 gene and its encoded protein Chk2 have a well-known role in cancers, especially those related to breast cancer mediated through the BRCA1 gene. Additionally Chk2 has a crucial role in DNA repair, apoptosis and the cell cycle, which is why classification of variants of uncertain significance (VUS) is an area highly sought for a better elucidation of the “genomic effect” that results. Because it can often take years before enough clinical data is accumulated, and the costly and expensive functional analysis for individual variants presents a significant hurdle, it is important to identify other tools to help aid in clarifying the impact of specific variants on a protein's function and eventually the patient's health outcome. Here we describe a newly identified CHEK2 variant and analyze with an integrated approach combining genomics (whole exome analysis), clinical study, radiographic imaging, and protein informatics to identify and predict the functional impact of the VUS on the protein's behavior and predicted impact on the related pathways. The observed and analyzed defects in the protein were consistent with the expected clinical effect. Here, we support the use of personalized protein modeling and informatics and further our goal of developing a large-scale protein deposition archive for all protein-level VUS.

AbstractBackgroundBeta‐galactosidase‐1 (GLB1) is a lysosomal hydrolase that is responsible for breaking down specific glycoconjugates, particularly GM1 (monosialotetrahexosylganglioside). Pathogenic variants in GLB1 cause two different lysosomal storage disorders: GM1 gangliosidosis and mucopolysaccharidosis type IVB. In GM1 gangliosidosis, decreased β‐galactosidase‐1 enzymatic activity leads to the accumulation of GM1 gangliosides, predominantly within the CNS. We present a 22‐month‐old proband with GM1 gangliosidosis type II (late‐infantile form) in whom a novel homozygous in‐frame deletion (c.1468_1470delAAC, p.Asn490del) in GLB1 was detected.MethodsWe used an experimental protein structure of β‐galactosidase‐1 to generate a model of the p.Asn490del mutant and performed molecular dynamic simulations to determine whether this mutation leads to altered ligand positioning compared to the wild‐type protein. In addition, residual mutant enzyme activity in patient leukocytes was evaluated using a fluorometric assay.ResultsMolecular dynamics simulations showed the deletion to alter the catalytic site leading to misalignment of the catalytic residues and loss of collective motion within the model. We predict this misalignment will lead to impaired catalysis of β‐galactosidase‐1 substrates. Enzyme assays confirmed diminished GLB1 enzymatic activity (~3% of normal activity) in the proband.ConclusionsWe have described a novel, pathogenic in‐frame deletion of GLB1 in a patient with GM1 gangliosidosis type II.

AbstractBackgroundAlthough the process of reclassification of a variant of uncertain significance can be complex, they are commonly detected through molecular testing. It often takes years before enough clinical data are acquired, and it can be costly and time‐consuming to perform functional analysis of a single variant. It is important that other tools are developed to aid in clarifying how a specific genetic variant impacts a protein's function, and ultimately the health of the patient.MethodsTwo more newly characterized, suspected pathogenic variants in NBN and PTEN were analyzed through personalized protein modeling. Comparisons between the wild‐type and altered protein were studied using simulations, genomic exome analysis, and clinic study.ResultsModeling of the new NBN and PTEN protein structures suggested loss of essential domains important for normal enzymatic function for these personalized genomic examples which matched the clinical findings.ConclusionThe defects detected through modeling were consistent with the expected clinical effect. Personalized protein modeling is another tool for determination of correct variant classification, which can become further useful through construction of deposition archive.

AbstractBackgroundHaploinsufficiency of TAB2 is known to cause congenital heart defects and cardiomyopathy due to its important roles in cardiovascular tissue, both during development and through adult life. We report a sibling pair displaying adult‐onset cardiomyopathy, hypermobility, and mild myopia. Our proband, a 39‐year‐old male, presents only with the above symptoms, while his 36‐year‐old sister was also notable for a ventricular septal defect in her infancy.MethodsWhole‐exome sequencing was utilized to identify the molecular basis of the phenotype found in two siblings. A molecular modeling technique that takes advantage of conformational sampling advances (Maxwell's demon molecular dynamics and Monte Carlo) were used to make a model of the mutant variant for comparative analytics to the wild‐type.ResultsExome sequencing revealed a novel, heterogeneous pathogenic variant in TAB2, c.1039 C>T (p.R347X), that was present in both individuals. This pathogenic variant removes just over half the residues from the TAB2 protein and severely impacts its functional ability, which we describe in detail.ConclusionsAnalysis of the proband's family showed a history of cardiomyopathy, but no congenital heart defects or connective tissue disease. We highlight the heterogeneity in phenotype of TAB2 pathogenic variants and confirm the pathogenicity of this new variant through neoteric protein modeling techniques.