Summary: Researchers converted skin cells from patients with a rare congenital brain defect into pluripotent stem cells to generate brain organoids.
Source: University of Bonn.
Organoids offer new insight into human brain development
Researchers at the University of Bonn have applied an advanced organoid method to study developmental brain disorders, demonstrating a promising approach for investigating human cortical formation. In a recent study, scientists reprogrammed skin cells from patients with a rare congenital disorder into induced pluripotent stem cells (iPSCs) and used these cells to grow three-dimensional brain organoids that mimic early human brain structure and organization. The findings were published in Cell Reports.
Traditional cell cultures grow as flat monolayers and cannot recreate the three-dimensional architecture of the developing brain. Animal models, such as mice, provide insight but cannot fully capture the complexity of human cortical development. Brain organoids—sometimes called “mini brains”—are small, self-organizing three-dimensional tissues derived from human pluripotent cells that reproduce many features of early human brain formation. These organoids allow researchers to study how nerve cells organize into layered structures, migrate, and differentiate during development in ways that two-dimensional cultures and many animal models cannot.
“The organoid method opens up entirely new possibilities for studying disorders of the developing human brain,” says Dr. Julia Ladewig, head of the brain development research group at the Institute of Reconstructive Neurobiology.
Investigating a rare cortical malformation: Miller-Dieker syndrome
The team focused on Miller-Dieker syndrome (MDS), a hereditary condition caused by a deletion on chromosome 17p13.3 that typically includes the LIS1 and YWHAE genes. MDS patients show severe malformations of cortical architecture: the normally folded brain surface is greatly reduced, producing a smoother cortical surface (lissencephaly). The cellular and tissue-level mechanisms that produce these malformations have been incompletely understood.
To explore the underlying causes, researchers generated iPSCs from skin biopsies taken from Miller-Dieker patients and from healthy controls. From these iPSCs they produced forebrain-type organoids that recapitulate early cortical development. Within these organoids, stem cells divide, some daughter cells differentiate into neurons, and those neurons migrate and assemble into layered structures—processes that resemble the coordinated activity of an orchestra directed by genetic and signaling cues.
In organoids derived from Miller-Dieker patients, the team observed fundamental disruptions in these developmental processes. Dr. Philipp Koch, who co-led the study, explains: “Stem cells in patient-derived organoids divide differently. In healthy organoids, stem cells undergo a phase of extensive symmetric proliferation to form organized, densely packed layers, while only a subset differentiates into neurons. In the patient-derived tissue this balance is altered.”
Specifically, the researchers found that some proteins and cell adhesion molecules that support tight, uniform packing of neural stem cells are improperly formed or expressed in MDS-derived organoids. This leads to less compact and less regularly arranged progenitor layers. As a result, many progenitor cells differentiate prematurely into neurons rather than continuing symmetric expansion. The altered three-dimensional niche thus changes cell division behavior and disrupts cortical growth and organization—phenomena that are difficult or impossible to detect in animal models or two-dimensional cultures.
Importantly, the study identifies a non-cell-autonomous disturbance of the N-cadherin/β-catenin signaling axis in the disrupted cortical niche. The authors report that reinstating active β-catenin signaling can rescue progenitor division modes and partially alleviate growth deficits in patient-derived organoids, linking molecular signaling changes to tissue-level architecture.
Dr. Ladewig emphasizes that this research is fundamental and does not immediately produce new treatments. “We are conducting basic science,” she says, “but organoid models can usher in a new era of brain research. A clearer, mechanistic understanding of human cortical development may, over the long term, point toward new therapeutic strategies for developmental brain disorders.”
Source: Dr. Julia Ladewig – University of Bonn
Original research: An Organoid-Based Model of Cortical Development Identifies Non-Cell-Autonomous Defects in Wnt Signaling Contributing to Miller-Dieker Syndrome. Published in Cell Reports (online March 13, 2017). Authors include Vira Iefremova, George Manikakis, Olivia Krefft, Ammar Jabali, Kevin Weynans, Ruven Wilkens, Fabio Marsoner, Björn Brändl, Franz-Josef Müller, Philipp Koch, and Julia Ladewig.
- Homogeneous forebrain-type organoids faithfully model early cortical development in vitro.
- MDS-derived organoids are significantly smaller, showing reduced expansion due to premature neurogenesis.
- MDS organoids display disrupted cortical niche architecture and altered expression of cell adhesion molecules.
- Disruption of the niche causes a non-cell-autonomous disturbance of β-catenin signaling, and activation of β-catenin can rescue division behavior and growth defects.
Abstract summary
Miller-Dieker syndrome arises from a heterozygous deletion of chromosome 17p13.3 that includes LIS1 and YWHAE (14.3.3ε) and leads to cortical malformations. Using patient-specific forebrain organoids, this study shows that organoids derived from MDS patients are reduced in size and shift from symmetric to asymmetric division in ventricular zone radial glia cells (vRGCs). These organoids exhibit altered microtubule organization in vRGCs and disrupted cortical niche architecture, including changes in cell adhesion molecule expression. These structural and signaling changes produce a non-cell-autonomous disturbance of the N-cadherin/β-catenin axis. Restoring β-catenin activity rescues division modes and partially corrects growth defects, highlighting the roles of LIS1 and 14.3.3ε in maintaining cortical niche integrity and demonstrating the value of organoid systems for modeling complex cell–cell interactions in human cortical development.
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