Journal Article

Cystatin B is essential for proliferation and interneuron migration in individuals with EPM1 epilepsy

Götz, Magdalena, Hoffmann, Anke, Cappello, Silvia, Russo, Rosita, Di Giaimo, Rossella, Crispino, Marianna, Tovecci, Isabella, Giordano, Martina, Pipicelli, Fabrizia, Canafoglia, Laura, Kyrousi, Christina, Penna, Eduardo, Ciusani, Emilio, Ayo‐Martin, Ane Cristina, Di Matteo, Francesco, Chambery, Angela

2020

Overview

Progressive myoclonus epilepsy (PME) of Unverricht–Lundborg type (EPM1) is an autosomal recessive neurodegenerative disorder with the highest incidence of PME worldwide. Mutations in the gene encoding cystatin B (CSTB) are the primary genetic cause of EPM1. Here, we investigate the role of CSTB during neurogenesis in vivo in the developing mouse brain and in vitro in human cerebral organoids (hCOs) derived from EPM1 patients. We find that CSTB (but not one of its pathological variants) is secreted into the mouse cerebral spinal fluid and the conditioned media from hCOs. In embryonic mouse brain, we find that functional CSTB influences progenitors’ proliferation and modulates neuronal distribution by attracting interneurons to the site of secretion via cell‐non‐autonomous mechanisms. Similarly, in patient‐derived hCOs, low levels of functional CSTB result in an alteration of progenitor's proliferation, premature differentiation, and changes in interneurons migration. Secretion and extracellular matrix organization are the biological processes particularly affected as suggested by a proteomic analysis in patients’ hCOs. Overall, our study sheds new light on the cellular mechanisms underlying the development of EPM1. Synopsis Mutations in the cystatin B (CSTB) gene cause EPM1 epilepsy in patients. CSTB secretion induces the recruitment of migrating interneurons and promotes progenitor cells expansion in the mouse cortex and human cerebral organoids (hCOs). Both functions are impaired in EPM1‐derived hCOs. CSTB overexpression induces progenitor cells expansion in hCOs and in the developing mouse cortex. CSTB is secreted and induces recruitment of migrating interneurons. Downregulation of Cstb and R68X overexpression result in decreased number of progenitors and migrating interneurons in the developing mouse cortex. Proliferation is reduced in EPM1‐derived cerebral organoids in a cell non‐autonomous manner. EPM1‐derived cerebral organoids exhibit premature differentiation. Graphical Abstract Mutations in the cystatin B (CSTB) gene cause EPM1 epilepsy in patients. CSTB secretion induces the recruitment of migrating interneurons and promotes progenitor cells expansion in the mouse cortex and human cerebral organoids (hCOs). Both functions are impaired in EPM1‐derived hCOs.

• Publisher: Nature Publishing Group UK,John Wiley and Sons Inc,Springer Nature
• Subject: Animals / Cell Proliferation / cystatin B / Cystatin B - genetics / EMBO11 / EMBO27 / EMBO34 / EPM1 / Humans / interneuron migration / Interneurons / Mice / Neurogenesis / Proteomics / secretion / Unverricht-Lundborg Syndrome