Correlation Between Genotype and Age of Onset in Leukoencephalopathy With Vanishing White Matter

Effects of the Small-Molecule ISRIB on the Rapid and Efficient Myelination of Oligodendrocytes in Human Stem Cell-Derived Cerebral Organoids in Patients With Leukoencephalopathy With Vanishing White Matter

INTRODUCTION

Leukoencephalopathy with vanishing white matter (VWM) is a rare genetic disorder caused by mutations in any one of the EIF2B1-5, which encode subunits of eukaryotic translation initiation factor 2B (eIF2B). Previous studies suggested that the dysfunction of astrocytes played a central role in the pathogenic mechanism of VWM. In addition, eIF2B participates in the unfolded protein response(UPR) by coordinating the integrated stress response (ISR). Higher susceptibility to endoplasmic reticulum stress (ERS) and abnormal overactivation of the unfolded protein response (UPR) were found in VWM, which led to logical deterioration and exacerbation of cell death. There are currently no specific treatments available for VWM.

AIM

Previous studies have successfully constructed three-dimensional brain organoids that can be used to study the development of neuronal cells during brain development. In this study, we aimed to develop a more rapid and efficient brain organoid model that would produce mature astrocytes, oligodendrocytes, and myelin within 8 weeks. The small-molecule ISR inhibitor (ISRIB) is a specific eIF2B activator by inhibiting the phosphorylation of eukaryotic translation initiation factor 2 (eIF2). Thus, ISRIB is used on eIF2B mutant organoids to determine its potential as a therapeutic approach for VWM.

RESULTS

We constructed EIF2B4 and EIF2B5 mutants as well as wild-type rapid myelinating oligodendrocyte brain organoids using human induced pluripotent stem cells (iPSCs). We observed mature astrocytes, oligodendrocytes, and myelin within 8 weeks, greatly shortening the culture period. Compared with the wild type, mutant organoids displayed a smaller size and contained increased immature and dysfunctional astrocytes, oligodendrocytes, and sparse myelin. Abnormal overactivation of the UPR pathway was also present in mutant cerebral organoids. Additionally, we found that the maturation and function of these cells in mutant organoids were significantly improved after ISRIB treatment, which also inhibited hyperactivation of the unfolded protein response (UPR) signaling pathway.

CONCLUSIONS

Our study established a rapid myelinating oligodendrocyte brain model in VWM for the first time, providing a more effective and tractable platform for further study of this condition and other white matter diseases. Furthermore, our findings suggested that ISRIB may have potential as a clinical treatment for VWM.

Human-induced pluripotent stem cell-derived cerebral organoid of leukoencephalopathy with vanishing white matter

INTRODUCTION

Leukoencephalopathy with vanishing white matter (VWM) is a rare autosomal recessive leukoencephalopathy resulting from mutations in EIF2B1-5, which encode subunits of eukaryotic translation initiation factor 2B (eIF2B). Studies have found that eIF2B mutation has a certain influence on embryonic brain development. So far, the effect of the eIF2B mutations on the dynamic process of brain development is not fully understood yet.

AIMS

Three-dimensional brain organoid technology has promoted the study of human nervous system developmental diseases in recent years, providing a potential platform for elucidating the pathological mechanism of neurodevelopmental diseases. In this study, we aimed to investigate the effects of eIF2B mutation on the differentiation and development of different nerve cells during dynamic brain development process using 3D brain organoids.

RESULTS

We constructed eIF2B mutant and wild-type brain organoid model with induced pluripotent stem cell (iPSC). Compared with the wild type, the mutant brain organoids were significantly smaller, accompanied by increase in apoptosis, which might be resulted from overactivation of unfolded protein response (UPR). Neuronal development was delayed in early stage, but with normal superficial neuronal differentiation in later stage. eIF2B mutations resulted in immature astrocytes with increased expression of GFAPδ, nestin, and αB-crystallin, and there were increased oligodendrocyte progenitor cells, decreased mature oligodendrocytes, and sparse myelin in mutant cerebral organoids in the later stage.

CONCLUSION

we constructed the first eIF2B mutant cerebral organoids to explore the dynamic brain development process, which provides a platform for further research on the specific pathogenesis of VWM.

The Coexistence of Two Genetic Astrocytopathies-Megalencephalic Leukoencephalopathy and Vanishing White Matter Disease-in an Indian Child

A 9-month-old male child, born of second-degree consanguinity, presented with a progressively enlarging head since early infancy. The child had normal early development, but further acquisition of milestones after 6 months was delayed. He had afebrile seizures at 9 months, followed by the appearance of appendicular spasticity. First magnetic resonance imaging (MRI) showed nonenhancing, diffuse, bilaterally symmetrical T1/fluid-attenuated inversion recovery (FLAIR) hypointensity and T2 hyperintensity of the cerebral white matter and anterior temporal cysts. Subsequently, the periventricular and deep white matter developed microcystic changes with a pattern of radial stripes. Next-generation sequencing revealed homozygous autosomal recessive variations in the MLC1 gene [c.188T > G, (p.Leu63Arg)] on exon 3 and also in the EIF2B3 gene [c.674G > A, (p.Arg225Gln)] on exon 7, the parents being heterozygous carriers for both variations. This article highlights the rare occurrence of two leukodystrophies of diverse pathogenesis in a child from a nonpredisposed community.