Dan Binyamin Varshavsky is a physician-scientist and biomedical researcher specializing in pediatric nephrology, molecular biology, and computational biology. He completed his medical studies at the Hebrew University of Jerusalem through the Tzameret Military Medicine Track and earned an M.Sc. in Biotechnology Research from the same university’s Faculty of Medicine.

His research focuses on the molecular mechanisms underlying kidney disease, particularly tuberous sclerosis complex (TSC)-associated cystic kidney disease, alternative RNA splicing, and the role of Pin1 in mTOR-driven signaling pathways and kidney cystogenesis. His technical expertise includes RNA-seq analysis, transcriptomic profiling, alternative splicing quantification, and bioinformatics tools such as rMATS, STAR, Python, and R.

Dan has conducted research in pediatric nephrology at Hadassah Medical Center and undertook a visiting research fellowship at the University of Pennsylvania’s Perelman School of Medicine in 2026, working with Professors Yoseph Barash and Rotem Karni. His research contributions include publications on kidney development, maternal metabolic conditions, and kidney function, as well as first-author research on Pin1-mediated alternative splicing in TSC-associated kidney disease.

He has presented his findings at several scientific conferences and received multiple honors, including a Master’s Degree Excellence Award, an Outstanding Poster Award at the HIPAC Conference, a Doctoral Excellence Award, and the James Sivartsen Award in Pediatric Cancer Research. His interdisciplinary research integrates molecular mechanisms and computational approaches to advance the understanding of kidney disease and identify potential therapeutic targets.

PIN1 AS A THERAPEUTIC TARGET IN TUBEROUS SCLEROSIS COMPLEX: UNVEILING PIN1'S ROLE IN MTOR-DRIVEN ALTERNATIVE SPLICING AND KIDNEY CYSTOGENESIS

Introduction

Tuberous sclerosis complex (TSC) is a genetic disorder characterized by the formation of cystic kidney disease, which often progresses to chronic kidney disease. A key driver of TSC pathogenesis is the hyperactivation of mechanistic target of rapamycin (mTOR) signaling. However, the molecular mechanisms linking mTOR dysregulation to kidney cystogenesis remain poorly understood, particularly in the context of alternative splicing and post-translational modifications. This study investigates the role of Pin1, a peptidyl-prolyl cis-trans isomerase, in regulating mTOR-mediated signaling and alternative splicing events, and its contribution to TSC-associated kidney cystogenesis.

Methods

We combined nephron progenitor-specific Tsc1 knockout mice, a Tsc1/Pin1 double-knockout line, CRISPR-engineered TSC1-deficient human proximal tubule cells, and fetal kidney specimens.Pin1 interactome profiling, RNA sequencing (n=4/group), and biochemical and histological analyses defined pathway activity. Genetic We assessed Pin1’s functional contribution using genetic depletion and prenatal treatment with sulfopin, a selective Pin1 inhibitor.

Results

Tsc1 loss increased Ser/Thr-Pro phosphorylation and Pin1 activity while reducing inhibitory Pin1 phosphorylation at Ser16 and Ser71. Pin1 interacted with phosphorylated SRRM2 and SC-35, promoting their accumulation in nuclear speckles. Substitution of SC-35 Ser191 with alanine abolished Pin1 binding, and PIN1 knockdown reversed enhanced SC-35 protein stability. Everolimus disrupted these interactions, placing Pin1-mediated spliceosome regulation downstream of mTORC1. At birth, genetic Pin1 ablation reduced renal cystic burden by approximately 70% and attenuated splicing factor accumulation without suppressing mTORC1 activity. The selective covalent Pin1 inhibitor sulfopin similarly reduced cyst burden, left pS6 and p4EBP1 unchanged, and modestly prolonged median postnatal survival. RNA sequencing identified 2,263 alternative splicing events in Tsc1-deficient kidneys versus controls. Most of the 328 events shared with the sulfopin treatment comparison changed in the opposite direction. Sulfopin reversed Pkd1 intron retention confirmed by RT-PCR and normalized polycystin-1 expression. Human fetal TSC kidneys showed increased SRRM2 and SC-35 expression and nuclear speckle localization, together with elevated polycystin-1 expression.

Conclusion

Pin1 connects mTORC1 hyperactivation to phosphorylation-dependent spliceosome remodeling and renal cystogenesis. Concordant genetic and pharmacological evidence identifies Pin1 as a tractable therapeutic target whose inhibition could complement mTOR-targeted treatment for TSC-associated kidney disease.