A Drosophila genetic model of nephrolithiasis: transcriptional changes in response to diet induced stone formation

Background

Urolithiasis is a significant healthcare issue but the pathophysiology of stone disease remains poorly understood. Drosophila Malpighian tubules were known to share similar physiological function to human renal tubules. We have used Drosophila as a genetic model to study the transcriptional response to stone formation secondary to dietary manipulation.

Methods

Wild-type male flies were raised on standard medium supplemented with lithogenic agents: control, sodium oxalate (NaOx) and ethylene glycol (EG). At 2 weeks, Malpighian tubules were dissected under polarized microscope to visualize crystals. The parallel group was dissected for RNA extraction and subsequent next-generation RNA sequencing.

Results

Crystal formation was visualized in 20%(±2.2) of flies on control diet, 73%(±3.6) on NaOx diet and 84%(±2.2) on EG diet. Differentially expressed genes were identified in flies fed with NaOx and EG diet comparing with the control group. Fifty-eight genes were differentially expressed (FDR <0.05, p < 0.05) in NaOx diet and 20 genes in EG diet. The molecular function of differentially expressed genes were assessed. Among these, Nervana 3, Eaat1 (Excitatory amino acid transporter 1), CG7912, CG5404, CG3036 worked as ion transmembrane transporters, which were possibly involved in stone pathogenesis.

Conclusions

We have shown that by dietary modification, stone formation can be manipulated and visualized in Drosophila Malpighian tubules. This genetic model could be potentially used to identify the candidate genes that influence stone risk hence providing more insight to the pathogenesis of human stone disease.

Proteomic changes in response to crystal formation in Drosophila Malpighian tubules

Kidney stone disease is a major health burden with a complex and poorly understood pathophysiology. Drosophila Malpighian tubules have been shown to resemble human renal tubules in their physiological function. Herein, we have used Drosophila as a model to study the proteomic response to crystal formation induced by dietary manipulation in Malpighian tubules. Wild-type male flies were reared in parallel groups on standard medium supplemented with lithogenic agents: control, Sodium Oxalate (NaOx) and Ethylene Glycol (EG). Malpighian tubules were dissected after 2 weeks to visualize crystals with polarized light microscopy. The parallel group was dissected for protein extraction. A new method of Gel Assisted Sample Preparation (GASP) was used for protein extraction. Differentially abundant proteins (p<0.05) were identified by label-free quantitative proteomic analysis in flies fed with NaOx and EG diet compared with control. Their molecular functions were further screened for transmembrane ion transporter, calcium or zinc ion binder. Among these, 11 candidate proteins were shortlisted in NaOx diet and 16 proteins in EG diet. We concluded that GASP is a proteomic sample preparation method that can be applied to individual Drosophila Malpighian tubules. Our results may further increase the understanding of the pathophysiology of human kidney stone disease.

Abstract AS03: Epithelial-mesenchymal transition driven by transcriptional feedback loops contributes to intertumoral molecular heterogeneity in the metastasis and relapse of epithelial ovarian cancer

Epithelial ovarian cancer (EOC) is highly heterogeneous with five molecular subgroups, Epi-A, Epi-B, Mes, Stem-A and Stem-B, being identified. The mechanisms behind the clonal evolution and intertumoral molecular heterogeneity are not fully elucidated. Previously, we performed EOC profiling meta-analysis to identify epithelial-mesenchymal transition (EMT) as the crucial mechanism for molecular heterogeneity. Transcription factors SNAI1, SNAI2, ZEB1, ZEB1, TWIST1, and GRHL2 were identified as crucial regulators for the Mes subtype which has undergone EMT. Here, we utilized three in-vitro EOC cell lines, PEO1, OVCA420, and OVCA429, to model the EMT-driven clonal evolution by manipulating the expression levels of these EMT transcriptional regulators. We analysed the molecular subtypes of matched primary tumor versus peritoneal metastases. Six out of 11 pairs showed concordant molecular subtypes. We also analysed a dataset of matched primary tumor versus omental metastases. Four out of 9 pairs showed concordant molecular subtypes. Among the 10 pairs showing a shift of molecular subtypes, 5 out of 5 omental metastases were designated as Mes. The variation in the evolution of molecular heterogeneity can be explained by the differences in the EMT transcriptional cross-regulation of the in-vitro models. Manipulating EMT regulators in PEO1 did not induce any transcriptional cross-regulation with no molecular subtype switching observed. However, manipulating EMT regulators in OVCA420 and OVCA429 caused hierarchical transcriptional control and feedback loop regulation, respectively. The OVCA429 model showed molecular subtype switch from Epi-A to Mes. In conclusion, the heterogeneity caused by EMT-driven clonal evolution is the consequence of transcriptional feedback loops of EMT regulators.

Citation Format: Chung VY, Tan M, Tan TZ, Kuay KT, Ye J, Thiery JP & Huang RY. Epithelial-mesenchymal transition driven by transcriptional feedback loops contributes to intertumoral molecular heterogeneity in the metastasis and relapse of epithelial ovarian cancer [abstract]. In: Proceedings of the 10th Biennial Ovarian Cancer Research Symposium; Sep 8-9, 2014; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2015;21(16 Suppl):Abstract nr AS03.

Severe acute pyelonephritis: a review of clinical outcome and risk factors for mortality

OBJECTIVE. To review demographics of patients with acute pyelonephritis, their outcomes of severe upper urinary tract infection, and to identify risk factors for long hospital stay and mortality. DESIGN. Case series. SETTING. A regional hospital in Hong Kong. PATIENTS. Patients admitted between June 2007 and June 2012 for acute pyelonephritis were identified. Those with the most severe outcomes were analysed of their mortality, need for care in the intensive care unit, or necessitation of urological intervention. RESULTS. Overall, 68 patients fulfilled our criteria for severe acute pyelonephritis. The female-to-male ratio was 7:3. Their mean age was 58 years. Overall, 57% of the patients had impaired renal function and 37% were diabetic; 47% developed shock after admission and 56% required further intensive care unit care; 75% of the patients demonstrated radiological evidence of urinary tract obstruction and required subsequent drainage procedures. Five patients died due to severe acute pyelonephritis. The prevalence of bacteraemia and bacteriuria was 57% and 74%, respectively. Escherichia coli accounted for the majority of causative organisms. Four risk factors-bacteraemia, shock, need for intensive care, and suppurative pyelonephritis-were associated with hospital stay of longer than 14 days. Old age (≥65 years), male sex, deranged renal function, and presence of disseminated intravascular coagulation were associated with mortality. CONCLUSION. There was high prevalence of bacteraemia and septic shock in patients with severe acute pyelonephritis. The factors of old age (≥65 years), male sex, deranged renal function, and presence of disseminated intravascular coagulation were associated with mortality. With the support of intensive care, early recognition of urinary tract obstruction and timely drainage, patients with severe acute pyelonephritis generally carry a good prognosis.