Genomic Observations of a Rare/Pathogenic SMAD3 Variant in Loeys⁻Dietz Syndrome 3 Confirmed by Protein Informatics and Structural Investigations.

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-ß 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.

Fatal Presentation of Susac Syndrome in a Congenitally Deaf Patient With a Cochlear Implant.

OBJECTIVE: To report a fatal case of Susac syndrome in a congenitally deaf patient with a cochlear implant and a history of migraines, emphasizing the diagnostic challenges in patients with preexisting conditions. PATIENT: A 33-year-old male with congenital hearing loss, a cochlear implant, and chronic migraines who presented with mild subacute auditory disturbance and headaches that later progressed to severe encephalopathy. INTERVENTION: Explantation of a non-magnetic resonance imaging (MRI) compatible cochlear implant followed by MRI, fundoscopy, and the administration of immunosuppressive medications. MAIN OUTCOME MEASURES: Diagnosis was confirmed by characteristic MRI appearance and the presence of a hemi-retinal artery occlusion. RESULTS: After weeks of immunosuppressive treatment, the patient died of a global cerebral ischemic event of unknown origin. CONCLUSIONS: For patients with preexisting sensorineural hearing loss and cochlear implants, Susac syndrome poses a diagnostic challenge. Auditory disturbances in the absence of cochlear implant failure should prompt further evaluation for visual disturbances and encephalopathy. MRI and fundoscopy should be performed to detect other features of the disease.

Clinical description & molecular modeling of novel MAX pathogenic variant causing pheochromocytoma in family, supports paternal parent-of-origin effect.

The titular member of the MAX network of proteins, MYC-associated factor X (MAX), serves an important regulatory function in transcription of E-box genes associated with cell proliferation, differentiation, and apoptosis. Wild type MAX dimerizes with both MYC and MAD, both of which are members of the MAX network, and can promote or repress cell functions as needed. However, pathogenic variants in MAX are known to upset this balance, leading to uncontrolled oncogenic activity and disease phenotypes such as paragangliomas and pheochromocytomas. We report a 58-year-old male and his 32-year-old daughter, both of which have a history of pheochromocytoma and the unique nonsense MAX variant c.271C>T (p.Q91X). These individuals were diagnosed with pheochromocytomas in their early twenties that were later removed through corrective surgery. The father now presents with recurrent symptoms of hypertension, hyperhidrosis, and headaches, which accompany new pheochromocytomas of his remaining adrenal gland. Pathogenicity of this MAX variant is proven through molecular modeling. The case of this father-daughter pair supports both heritability of pheochromocytoma and the paternal parent-of-origin effect for MAX pathogenic variants.

Genomics combined with a protein informatics platform to assess a novel pathogenic variant c.1024 A>G (p.K342E) in OPA1 in a patient with autosomal dominant optic atrophy.

BACKGROUND: Autosomal Dominant Optic Atrophy (ADOA) is caused by mutations in the Optic Atrophy 1 Gene which disrupts the OPA1 protein. This disruption affects the normal function of the protein; impairs fusion of the mitochondrial inner membrane; and prevents normal OPA1 protein degradation. These events cause damage in retinal ganglion cells that could affect the patients with symptoms ranging from none to legally blind. MATERIALS AND METHODS: Our study identifies a missense variant mutation, c.1024 A > G (p.K342E), in OPA1 gene causing ADOA. Diagnosed clinically in three family members and the presence of this mutation was confirmed in two members by genetic testing. Pathogenic variants in OPA1 impact the secondary protein structure and function by causing non-conservative amino acid substitutions. We also modeled this mutation and compared it to the wild type using statistical mechanics. RESULTS AND CONCLUSIONS: The proband's pathogenic variant, c.1024 A > G (p.K342E), is located in the GTPase domain of OPA1 and causes changes in the protein structure by affecting the oligomerization pattern thus resulting in ADOA. Identifying the pathogenic potential of the missense mutations in the OPA1 gene using neoteric protein modeling techniques would help in the early detection of ADOA in patients who have family history of blindness. This action would help in providing early follow up, possible treatment in the future, and genetic counseling. Abbreviations: ADOA: Autosomal Dominant Optic Atrophy; CYCS: Caspase Activator Cytochrome C; OPA1: Optic Atrophy Gene 1; RGC: Retinal Ganglion Cells; VUS: Variant of Uncertain Significance.

Characterization of a Pathogenic Variant in the ABCD1 Gene Through Protein Molecular Modeling.

BACKGROUND: The ATP-binding cassette, subfamily D, member 1 (ABCD1) protein is a peroxisomal half-transporter that allows for very long chain fatty acid (VLCFA) degradation. Pathogenic variants of ABCD1 cause VLCFAs to build up in various tissues and bodily fluids, resulting in a disorder called X-linked adrenoleukodystrophy (X-ALD). This disorder is most commonly marked by adrenocortical insufficiency and high VLCFA concentration, and has varying levels of neurological involvement depending on phenotype. For example, the Addison-only form of X-ALD has no neurological impact, while the cerebral form of X-ALD often causes severe sensory loss, motor function impairment, cognitive decline, and death. METHODS: A newly characterized and suspected pathogenic variant in ABCD1 cause VLCFAs to build up in various tissues and bodily fluids, resulting in a disorder called X-linked adrenoleukodystrophy (X-ALD). This disorder is most commonly marked by adrenocortical insufficiency and high VLCFA concentration, and has varying levels of neurological involvement depending on phenotype. For example, the Addison-only form of X-ALD has no neurological impact, while the cerebral form of X-ALD often causes severe sensory loss, motor function impairment, cognitive decline, and death. RESULTS: A case of adult onset adrenomyeloneuropathy (AMN) and a novel ABCD1 cause VLCFAs to build up in various tissues and bodily fluids, resulting in a disorder called X-linked adrenoleukodystrophy (X-ALD). This disorder is most commonly marked by adrenocortical insufficiency and high VLCFA concentration, and has varying levels of neurological involvement depending on phenotype. For example, the Addison-only form of X-ALD has no neurological impact, while the cerebral form of X-ALD often causes severe sensory loss, motor function impairment, cognitive decline, and death. CONCLUSIONS: Data fusion from multiple sources was combined in a comprehensive approach yielding an enriched assessment of the patient's disease and prognosis. Molecular modeling was performed on the variant to better characterize its clinical significance and confirm pathogenicity.

Protein informatics combined with multiple data sources enriches the clinical characterization of novel TRPV4 variant causing an intermediate skeletal dysplasia.

BACKGROUND: Transient 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. METHODS: Newly characterized, suspected pathogenic variant in TRPV4 was analyzed using protein informatics and personalized protein-level molecular studies, genomic exome analysis, and clinical study. RESULTS: This 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. CONCLUSIONS: Protein 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.

Protein molecular modeling techniques investigating novel TAB2 variant R347X causing cardiomyopathy and congenital heart defects in multigenerational family.

BACKGROUND: Haploinsufficiency 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. METHODS: Whole-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. RESULTS: Exome 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. CONCLUSIONS: Analysis 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.

Protein molecular modeling shows residue T599 is critical to wild-type function of POLG and description of a novel variant associated with the SANDO phenotype.

Sensory ataxic neuropathy with dysarthria and ophthalmoparesis (SANDO) is a rare phenotype resulting from pathogenic variants of mitochondrial DNA polymerase gamma (POLG). We modeled a novel POLG variant, T599P, that causes the SANDO phenotype and another variant at the same residue, p.T599E, to observe their effect on protein function and confirm the pathogenicity of T599P. Through neoteric molecular modeling techniques, we show that changes at the T599 residue position introduce extra rigidity into the surrounding helix-loop-helix, which places steric pressure on nearby nucleotides. We also provide a clinical description of the T599P variant, which was found in a 42-year-old female proband. The proband presented a 1-year history of progressive gait instability, dysarthria and foot numbness. Her neurologic examination revealed ataxic dysarthria, restricted eye movements, head and palatal tremors, reduced lower limb reflexes, distal multimodal sensory loss and a wide, unsteady ataxic gait. Electromyography studies indicated a sensory neuropathy. Whole-exome sequencing was pursued after tests for infectious, inflammatory and paraneoplastic causes were negative.

Protein modeling and clinical description of a novel in-frame GLB1 deletion causing GM1 gangliosidosis type II.

BACKGROUND: Beta-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 ß-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. METHODS: We used an experimental protein structure of ß-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. RESULTS: Molecular 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 ß-galactosidase-1 substrates. Enzyme assays confirmed diminished GLB1 enzymatic activity (~3% of normal activity) in the proband. CONCLUSIONS: We have described a novel, pathogenic in-frame deletion of GLB1 in a patient with GM1 gangliosidosis type II.

Whole Exome Sequencing and Molecular Modeling of a Missense Variant in TNFAIP3 That Segregates with Disease in a Family with Chronic Urticaria and Angioedema.

Chronic urticaria is a common condition characterized by recurrent hives lasting several weeks or months and is usually idiopathic. Approximately half of the individuals with chronic urticaria will present with episodes of angioedema that can be severe and debilitating. In this report, we describe a 47-year-old Hispanic male who presented initially for an evaluation of chronic hives following hospitalization due to hive-induced anaphylaxis. The individual had a history significant for urticaria and angioedema beginning in his early 30s. Interestingly, both the individual's 41-year-old sister and 12-year-old daughter were also affected with chronic urticaria and severe angioedema. Whole exome sequencing of the proband and several family members revealed a heterozygous variant of uncertain significance in exon 2 of TNFAIP3, denoted as c.65G>A (p.R22Q), in all affected members. Variants in TNFAIP3 have been associated with multiple autoimmune diseases, susceptibility to allergy and asthma, and periodic fever syndromes, suggesting that this variant could potentially play a role in disease.