👤 Katsiaryna Belaya

Tumor-induced osteomalacia (TIO) is a rare disorder caused by a phosphaturic mesenchymal tumor (PMT) secreting fibroblast growth factor 23 (FGF23). The aim of this study was to analyze PMTs for their transcriptomic characteristics. We performed single-cell RNA (n = 3) alongside bulk RNA sequencing of PMTs (n = 5) and surrounding bone tissue (n = 4) obtained during tumor removal in 10 patients (age 44 (41;64), serum phosphate (Pi)- 0.54 (0.43; 0.59) mM/L, FGF23-113 (40; 205) pg/ml). We revealed a total of 22,449 cells divided into 13 different categories. We identified the heterogeneity of the PMT cell cluster and subsequently divided it into two tumor clusters 1 and 2 characterized by the deeper epithelial-mesenchymal phenotype transition, higher FGF23 expression as well as various SNP and CNV. We further identified tumor cell differentiation driving regulons ERG and EGR3, based on scoring by allele expression and velocity based pseudotime on a trajectory that may play a critical role in the tumorigenesis of PMTs. In both single-cell and bulk transcriptome analysis we found upregulation of vesicle-specific and exocytosis associated genes (SLC30A3, SYT1, STX1A and SNAP25) which most likely represent molecular mechanisms of active secretion in all PMT samples. We report transmembrane protein coding genes expressed in all PMTs specifically in tumor cell clusters (PHEX, ERBB4, PCDH7, LRRFIP2) which are suggested as potential diagnostic targets. We confirmed the presence of FN1-FGFR1 fusion genes and Klotho expression in most PMTs (6 out of 8). Conclusion: specific SNARE proteins gene upregulation along with transcriptional signatures of PMT offer new insights into its pathogenesis which may be further studied for diagnostic and therapeutic interventions. Show less

Adult growth hormone (GH) deficiency (AGHD) is a condition characterized by alterations in body composition, lipid and carbohydrate metabolism, bone mineral density and poor quality of life; however, clinical presentations of AGHD are mostly non-specific. Untreated AGHD is associated with increased cardiovascular morbidity and mortality. Stimulation tests are used for the diagnosis: insulin tolerance test, glucagon stimulation test, growth-hormone releasing hormone and arginine stimulation test. Moreover, in 2017 FDA approved the use of macimorelin (oral GH secretagogue) for the diagnosis of AGHD. In childhood GH-deficiency, apolipoprotein A-IV, CFHR4 (complement factor H-related protein 4) and PBP (platelet basic protein) were identified as potential biomarkers of the disease, however, this was not investigated in AGHD. GH treatment starts from the minimal dose, which allows minimizing the adverse effects. According to published meta-analyses, AGHD treatment generally does not lead to increased risk of malignancy and recurrence of sellar neoplasms in adult patients. Published data on GH receptor polymorphism associations with treatment efficacy remains controversial. Development of long-acting GH formulations is a currect perspective for the increase of treatment compliance. Show less

Congenital myasthenic syndromes (CMS) usually present neonatally or in early childhood. When they present later, they may be mistaken for seronegative autoimmune myasthenia, and unnecessary immunosuppressive treatment may be administered. Patients who met criteria for seronegative generalized myasthenia without congenital or early childhood onset, but with an affected sibling were tested for CMS associated genes using exome and Sanger sequencing. Four sibling pairs from nonconsanguineous families were identified. Three had mutations in the RAPSN gene, and 1 had a mutation in CHRNA1. One sibling of a pair with symptoms of fatigue but no convincing features of neuromuscular dysfunction tested negative on genetic studies. The definite CMS cases comprised 7 of 25 seronegative patients with definite generalized myasthenia in the clinic, and over half had been treated for autoimmune myasthenia. CMS is probably underdiagnosed in seronegative myasthenic disorders and should be considered in the differential diagnosis. Muscle Nerve 54: 721-727, 2016. Show less