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IER3IP1 mutations cause neonatal diabetes due to impaired proinsulin trafficking

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posted on 2024-10-23, 18:47 authored by Hossam Montaser, Sonja Leppänen, Eliisa Vähäkangas, Nils Bäck, Alicia Grace, Solja Eurola, Hazem Ibrahim, Väinö Lithovius, Samuel B. Stephens, Tom Barsby, Diego Balboa, Jonna Saarimäki-Vire, Timo Otonkoski

Abstract

Immediate early response 3 interacting-protein 1 (IER3IP1) is an endoplasmic reticulum resident protein, highly expressed in pancreatic cells and the developing brain cortex. Homozygous mutations in IER3IP1 have been found in individuals with microcephaly and neonatal diabetes, yet the underlying mechanism causing beta cell failure remains unclear. Here, we utilized differentiation of genome edited-stem cells into pancreatic islet cells to elucidate the molecular basis of IER3IP1 neonatal diabetes. Using CRISPR-Cas9, we generated two distinct IER3IP1-mutant human embryonic stem cell lines: a homozygous knock-in model of a patient mutation (IER3IP1V21G), and a knockout model (IER3IP1-/-). While these mutant stem cell lines differentiated normally into definitive endoderm and pancreatic progenitors, we observed that IER3IP1-KO stem cell derived-islets (SC-islets) presented a significant decrease in beta cell numbers and elevated ER stress. Retention Using Selective Hooks (RUSH) assay revealed three-fold reduction in ER-to-Golgi trafficking of proinsulin in IER3IP1 mutant beta cells. Additionally, IER3IP1 mutant SC-islets implanted into immunocompromised mice displayed defective human insulin secretion, indicating the deleterious impact of IER3IP1 mutations on beta cell function. Our study provides valuable insights into the role of IER3IP1 in human beta cell biology and establishes a useful model to investigate ER-to-Golgi trafficking defects within beta cells.

Article Highlights:

· IER3IP1 mutations are linked to the development of microcephaly, epilepsy, and early-onset diabetes (MEDS1). However, the underlying molecular mechanisms of cell dysfunction are unknown.

· Using targeted genome-editing, we generated specific IER3IP1 mutations in hESC lines which were differentiated into pancreatic islet lineages.

· Loss of IER3IP1 resulted in a three-fold reduction in ER-to-Golgi trafficking of proinsulin in stem-cell derived beta cells, leading to beta cell dysfunction both in vitro and in vivo.

· Loss of IER3IP1 also triggered increased markers of endoplasmic reticulum stress, indicating the pivotal role of the ER-to-Golgi trafficking pathway for beta cell homeostasis and function.

Funding

Biomedicum Helsinki-säätiö

Diabetestutkimussäätiö

Finska Läkaresällskapet

Helsingin Yliopisto

Kyllikki and Uolevi Lehikoinen Foundation

Maud Kuistilan Muistosäätiö

MetaStem center of excellence x 312437

Novo Nordisk Fonden

Orion Corporation > Orionin Tutkimussäätiö

Research Council of Finland 297466

Sigrid Juséliuksen Säätiö

Stiftelsen Dorothea Olivia, Karl Walter och Jarl Walter Perkléns Minne

History