# Siah2: an E3 ligase organizes polarity and cytoskeletal links in neuron migration > **NIH NIH R01** · ST. JUDE CHILDREN'S RESEARCH HOSPITAL · 2021 · $392,656 ## Abstract A spectrum of human neurological disorders including epilepsies, Lissencephaly or pediatric cancer is due in part to defective neuronal motility or germinal zone (GZ) exit and the resultant errors in neuronal circuit formation. To design strategies to prevent or treat such disorders, the field has sought to clarify the molecular mechanisms regulating neuronal motility and migration initiation. Despite advances implicating various genes essential for neuronal migration, a key gap in our knowledge is to discover how disparate cytoskeletal or signaling molecules cooperatively execute complex neuronal motility programs, such as GZ exit or nucleokinesis. My laboratory has tackled this challenge by dissecting neuronal polarity pathways impacting neuronal differentiation, nucleokinesis and adhesion control during GZ exit using the evolutionarily conserved Partitioning Defective, or Pard, polarity signaling complex as a molecular entry point. We gained insights into the regulatory logic controlling polarity during cerebellar granule neuron (CGN) development by discovering that the Seven in Absentia 2 (Siah2) E3 ubiquitin ligase is a Pard, complex antagonist. Siah2 is heavily expressed in CGN progenitors (GNPs); but not postmitotic CGNs, where Siah2-targeting of Pard3 for degradation constitutes an active pathway for progenitor polarity inhibition. We are uniquely positioned to discover new cellular mechanisms that control the onset of neuronal polarity since others overlooked inhibitory pathways in the past. In preliminary studies, we characterized new Siah2 targets relevant to GZ exit and radial migration: the Deleted in Colorectal Carcinoma (DCC) Netrin-1 (Ntn1) receptor and drebrin microtubule-actin crosslinking protein. Preliminary analysis shows: 1) Ntn1 stimulates CGN GZ exit and that Siah2 inhibits, while Pard3 promotes Ntn1-induced DCC receptor exocytosis, suggesting a hypothesis that Siah2-Pard3 antagonism regulates CGN sensitivity to Ntn1 GZ repulsion possibly through a link between DCC and junctional adhesion molecule-C (JAM-C), an adhesion receptor exocytosed in a Pard3-dependent manner. 2) Drebrin links actin- microtubule dynamics that are in turn regulated by Siah2 ubiquitination, suggesting a hypothesis that Siah2- drebrin antagonism governs the onset of nucleokinesis via microtubule-actin interactions. Remarkably, Siah2 expression is enhanced in Lissencephaly 1 (Lis1) deficient CGNs and Siah2 loss of function (LOF) or drebrin gain of function (LOF) rescues Lis1LOF migration phenotypes, suggesting that altering the balance of microtubule-actin interactions could have therapeutic value in classic neuronal migration disorders. We will build on our expertise examining polarity signaling in neuronal migration to combine in vivo genetics and ex vivo mechanistic studies with the power of transformative imaging technologies like Lattice Light Sheet Microscopy (LLSM) live-cell imaging to explore the following aims: Aim1: Define how Siah2 and Par... ## Key facts - **NIH application ID:** 10213851 - **Project number:** 5R01NS104029-04 - **Recipient organization:** ST. JUDE CHILDREN'S RESEARCH HOSPITAL - **Principal Investigator:** David Joseph Solecki - **Activity code:** R01 (R01, R21, SBIR, etc.) - **Funding institute:** NIH - **Fiscal year:** 2021 - **Award amount:** $392,656 - **Award type:** 5 - **Project period:** 2018-07-01 → 2023-06-30 ## Primary source NIH RePORTER: https://reporter.nih.gov/project-details/10213851 ## Citation > US National Institutes of Health, RePORTER application 10213851, Siah2: an E3 ligase organizes polarity and cytoskeletal links in neuron migration (5R01NS104029-04). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/10213851. Licensed CC0. --- *[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*