Characterizing a rare neurogenetic disease, SLC13A5 citrate transporter disorder, utilizing clinical data in a cloud-based medical record collection system

Introduction: SLC13A5 citrate transporter disorder is a rare autosomal recessive genetic disease that has a constellation of neurologic symptoms. To better characterize the neurologic and clinical laboratory phenotype, we utilized patient medical records collected by Ciitizen, an Invitae company, with support from the TESS Research Foundation.Methods: Medical records for 15 patients with a suspected genetic and clinical diagnosis of SLC13A5 citrate transporter disorder were collected by Ciitizen, an Invitae company. Genotype, clinical phenotypes, and laboratory data were extracted and analyzed.Results: The 15 patients reported all had epilepsy and global developmental delay. Patients continued to attain motor milestones, though much later than their typically developing peers. Clinical diagnoses support abnormalities in communication, and low or mixed tone with several movement disorders, including, ataxia and dystonia. Serum citrate was elevated in the 3 patients in whom it was measured; other routine laboratory studies assessing renal, liver and blood function had normal values or no consistent abnormalities. Many electroencephalograms (EEGs) were performed (1 to 35 per patient), and most but not all were abnormal, with slowing and/or epileptiform activity. Fourteen of the patients had one or more brain magnetic resonance imaging (MRI) reports: 7 patients had at least one normal brain MRI, but not with any consistent findings except white matter signal changes.Discussion: These results show that in addition to the epilepsy phenotype, SLC13A5 citrate transporter disorder impacts global development, with marked abnormalities in motor abilities, tone, coordination, and communication skills. Further, utilizing cloud-based medical records allows industry, academic, and patient advocacy group collaboration to provide preliminary characterization of a rare genetic disorder. Additional characterization of the neurologic phenotype will be critical to future study and developing treatment for this and related rare genetic disorders

Genetic and phenotypic spectrum associated with IFIH1 gain-of-function

IFIH1 gain-of-function has been reported as a cause of a type I interferonopathy encompassing a spectrum of autoinflammatory phenotypes including Aicardi–Goutières syndrome and Singleton Merten syndrome. Ascertaining patients through a European and North American collaboration, we set out to describe the molecular, clinical and interferon status of a cohort of individuals with pathogenic heterozygous mutations in IFIH1. We identified 74 individuals from 51 families segregating a total of 27 likely pathogenic mutations in IFIH1. Ten adult individuals, 13.5% of all mutation carriers, were clinically asymptomatic (with seven of these aged over 50 years). All mutations were associated with enhanced type I interferon signaling, including six variants (22%) which were predicted as benign according to multiple in silico pathogenicity programs. The identified mutations cluster close to the ATP binding region of the protein. These data confirm variable expression and nonpenetrance as important characteristics of the IFIH1 genotype, a consistent association with enhanced type I interferon signaling, and a common mutational mechanism involving increased RNA binding affinity or decreased efficiency of ATP hydrolysis and filament disassembly rate

Histone H3.3 beyond cancer: Germline mutations in Histone 3 Family 3A and 3B cause a previously unidentified neurodegenerative disorder in 46 patients

Although somatic mutations in Histone 3.3 (H3.3) are well-studied drivers of oncogenesis, the role of germline mutations remains unreported. We analyze 46 patients bearing de novo germline mutations in histone 3 family 3A (H3F3A) or H3F3B with progressive neurologic dysfunction and congenital anomalies without malignancies. Molecular modeling of all 37 variants demonstrated clear disruptions in interactions with DNA, other histones, and histone chaperone proteins. Patient histone posttranslational modifications (PTMs) analysis revealed notably aberrant local PTM patterns distinct from the somatic lysine mutations that cause global PTM dysregulation. RNA sequencing on patient cells demonstrated up-regulated gene expression related to mitosis and cell division, and cellular assays confirmed an increased proliferative capacity. A zebrafish model showed craniofacial anomalies and a defect in Foxd3-derived glia. These data suggest that the mechanism of germline mutations are distinct from cancer-associated somatic histone mutations but may converge on control of cell proliferation

Investigating the Function of GTF2I and its Contribution to the Williams-Beuren Syndrome Neurological Profile

Williams-Beuren Syndrome (WBS) is a genetic neurodevelopmental disorder caused by the deletion of 25 protein-coding genes at chromosome 7q11.23. It is associated with a highly penetrant constellation of phenotypes, including aortic stenoses, characteristic facial features, and unique cognitive and behaviour profiles. I hypothesize that the gene GTF2I, a putative transcription factor, plays a role in signaling pathways that affect neuronal function and contribute to the WBS neurological profile. Genome-wide expression analysis of WBS patient-derived induced pluripotent stem cells and cortical neurons isolated from mice with a duplication or deletion of Gtf2i identified moderate changes in the expression of a few genes. Additionally, affinity purification and tandem mass spectrometry of GFP-tagged GTF2I validated a previously identified interaction with ZMYM3, a candidate for X-linked intellectual disability. Future studies to determine the consequence of this interaction in the brain will assist in characterizing GTF2I function in neurons and its contribution to WBS phenotypes.M.Sc

4-Phenylbutyrate inhibits tunicamycin-induced acute kidney injury via CHOP/GADD153 repression.

Different forms of acute kidney injury (AKI) have been associated with endoplasmic reticulum (ER) stress; these include AKI caused by acetaminophen, antibiotics, cisplatin, and radiocontrast. Tunicamycin (TM) is a nucleoside antibiotic known to induce ER stress and is a commonly used inducer of AKI. 4-phenylbutyrate (4-PBA) is an FDA approved substance used in children who suffer from urea cycle disorders. 4-PBA acts as an ER stress inhibitor by aiding in protein folding at the molecular level and preventing misfolded protein aggregation. The main objective of this study was to determine if 4-PBA could protect from AKI induced by ER stress, as typified by the TM-model, and what mechanism(s) of 4-PBA's action were responsible for protection. C57BL/6 mice were treated with saline, TM or TM plus 4-PBA. 4-PBA partially protected the anatomic segment most susceptible to damage, the outer medullary stripe, from TM-induced AKI. In vitro work showed that 4-PBA protected human proximal tubular cells from apoptosis and TM-induced CHOP expression, an ER stress inducible proapoptotic gene. Further, immunofluorescent staining in the animal model found similar protection by 4-PBA from CHOP nuclear translocation in the tubular epithelium of the medulla. This was accompanied by a reduction in apoptosis and GRP78 expression. CHOP(-/-) mice were protected from TM-induced AKI. The protective effects of 4-PBA extended to the ultrastructural integrity of proximal tubule cells in the outer medulla. When taken together, these results indicate that 4-PBA acts as an ER stress inhibitor, to partially protect the kidney from TM-induced AKI through the repression of ER stress-induced CHOP expression

Human induced pluripotent stem cell derived neurons as a model for Williams-Beuren syndrome

Abstract Background Williams-Beuren Syndrome (WBS) is caused by the microdeletion of approximately 25 genes on chromosome 7q11.23, and is characterized by a spectrum of cognitive and behavioural features. Results We generated cortical neurons from a WBS individual and unaffected (WT) control by directed differentiation of induced pluripotent stem cells (iPSCs). Single cell mRNA analyses and immunostaining demonstrated very efficient production of differentiated cells expressing markers of mature neurons of mixed subtypes and from multiple cortical layers. We found that there was a profound alteration in action potentials, with significantly prolonged WBS repolarization times and a WBS deficit in voltage-activated K+ currents. Miniature excitatory synaptic currents were normal, indicating that unitary excitatory synaptic transmission was not altered. Gene expression profiling identified 136 negatively enriched gene sets in WBS compared to WT neurons including gene sets involved in neurotransmitter receptor activity, synaptic assembly, and potassium channel complexes. Conclusions Our findings provide insight into gene dysregulation and electrophysiological defects in WBS patient neurons

Anatomical structures affected by tunicamycin (TM)-induced acute kidney injury.

<p>C57BL/6 wild type mice were treated with saline (VEH), TM for 3 days, or pre-treated with 4-PBA for 7 days followed by 3 days of TM and 4-PBA co-treatment. PAS staining of mouse kidney sections indicate that TM causes acute kidney injury primarily in the outer stripe of the outer medulla (Outer Stripe Outer Medulla, arrows) of the kidney. 4-PBA treatment combined with TM inhibits this effect. TM also induced cortical proximal convoluted tubule (Cortical Prox. Conv. Tubule, arrow) damage; this effect was only partially inhibited by 4-PBA (arrow). Vascular bundles (Vasc Bundle Inner Medulla) were unaffected by TM-induced acute kidney injury at this dose (0.5 mg/kg) or 4-PBA treatment (A; bar = 100 µm). Higher magnification images show the pars recta of the outer medulla in all treatment groups (arrows) and the damage induced by TM and its inhibition by 4-PBA (B; 40×, bar = 100 µm; 60×, bar = 50 µm). The PAS-stained kidneys were scored for tubular damage as follows: (0) 0% kidney damage, (1) 1–25% kidney damage, (2) 26–50% kidney damage, (3) >50% kidney damage. Results indicate that 4-PBA inhibits tubular damage mediated by TM treatment (C). N = 10. *, P<0.05 vs VEH; ^#, P<0.05 vs TM.</p

Damage to the outer stripe of the outer medulla is induced by tunicamycin (TM).

<p>C57BL/6 wild type mice were treated with saline (VEH), TM for 3 days, or pre-treated with 4-PBA for 7 days followed by 3 days of TM and 4-PBA co-treatment. Masson's Trichrome staining of mouse kidney sections indicate that TM causes acute kidney injury in the outer stripe of the outer medulla (arrows). This damage is prevented by co-treatment with 4-PBA. However, renal interstitial fibrosis was not induced by treatment with TM or 4-PBA (20×, bar = 200 µm; 60×, bar = 50 µm).</p

CHOP deficiency protects against tunicamycin (TM)-induced acute kidney injury.

<p>Kidney sections from C57BL/6 wild type mice and CHOP^−/− mice treated with saline (VEH) or TM for 3 days were PAS stained. Staining demonstrates that CHOP^−/− mice treated with TM did not display pathological signs of acute kidney injury like wild type mice, including those found in the pars recta (*). High magnification images are of the outer stripe of the outer medulla, the main area of damage in the wild type mice (arrow). 10×, bar = 350 µm; 20×, bar = 200 µm; 60×, bar = 50 µm.</p