Biology subjects

Dokuzluoglu, Z.

Publications and source records attributed to Dokuzluoglu, Z..

5 recordsLinked to original sources

bioRxiv2026

Endogenous SMN Heterogeneity Defines Dynamic States of Motor Neuron Vulnerability and Resilience

Selective neuronal vulnerability, whereby some neurons degenerate while others remain resilient despite a shared genetic and disease context, is a defining feature of neurodegenerative diseases, yet the intrinsic mechanisms underlying these divergent fates remain poorly understood. Here, we identify naturally occurring heterogeneity in endogenous Survival Motor Neuron (SMN) protein abundance as a determinant of dynamic motor neuron (MN) vulnerability states that predict neuronal fate. Longitudinal live-cell imaging of human SMN-Clover reporter MNs shows that neurons with high endogenous SMN survive significantly longer than neighboring low-SMN neurons across healthy, spinal muscular atrophy (SMA) and amyotrophic lateral sclerosis (ALS) genetic backgrounds. These vulnerability states are not fixed: a substantial proportion of MNs progressively increase endogenous SMN abundance, transitioning toward a more resilient state associated with enhanced survival. Low-SMN neurons also exhibit increased spontaneous activity, linking endogenous SMN abundance to neuronal physiology and survival. In vivo, selectively vulnerable MN populations display corresponding shifts in endogenous SMN abundance during disease progression, supporting the relevance of SMN-defined vulnerability states beyond in vitro models. Integrated transcriptomic and proteomic analyses reveal distinct molecular programs associated with resilient and vulnerable states, including RNA metabolism, proteostasis, cytoskeletal organization, neuronal activity and stress responses. Among conserved molecular differences, the anti-apoptotic regulator LMO3 emerged as a candidate mediator of resilience. LMO3 overexpression reduced expression of p53-responsive genes, increased MN survival and shifted neurons toward higher endogenous SMN states. Together, these findings establish endogenous protein heterogeneity as a determinant of dynamic neuronal vulnerability and reveal neuronal resilience as a plastic molecular state that can be identified and therapeutically reinforced.

neuroscience↗

bioRxiv2025

Altered lysosomal biology impairs motor neuron survival via TFEB dysregulation in spinal muscular atrophy

Spinal muscular atrophy (SMA) is a devastating motor neuron disease, caused by recessive mutations or deletions of the SMN1 gene, representing the leading genetic cause of infant mortality. Available therapies, aimed at increasing SMN protein levels, can only partially halt motor neuron (MN) degeneration in a select number of patients, reinforcing the need for combinatorial treatments to improve clinical outcomes. We previously showed that mTORC1 overactivation and impaired autophagosome clearance in SMA MNs lead to the accumulation of protein aggregates, contributing to MN degeneration. However, the mechanistic link between SMN protein deficiency and autophagy-lysosomal dysfunction remained unknown. Here, using patient iPSC-derived MNs along with isogenic and healthy controls, we show that SMA MNs exhibit reduced lysosome numbers and impaired functionality. Furthermore, the master regulator of lysosomal biogenesis and autophagy, TFEB, is downregulated, and its nuclear translocation compromised upon SMN deficiency. We further propose the upregulation of the mTORC1 positive modulator TPT1 as contributor to TFEB dysregulation. Notably, TFEB overexpression ameliorates protein aggregate accumulation in SMA MNs and enhances MN survival both in vitro and in a zebrafish SMA model. Our findings identify lysosomal dysfunction as a key player in SMA pathology and highlight TFEB activation as a potential therapeutic strategy for SMA treatment. One Sentence SummaryTFEB activation restores lysosomal function and improves motor neuron survival in SMA, highlighting its potential as a therapeutic target.

neuroscience↗

bioRxiv2024

Synchronous 3D patterning of diverse CNS progenitors generates motor neurons of broad axial identity

In vitro human organoid models have become transformative tools for studying organogenesis, enabling the generation of spinal cord organoids (SCOs) that mimic aspects of spinal cord biology. However, current models do not produce spinal motor neurons (spMNs) with a wide range of axial identities along spinal cord segments within a single structure, limiting their utility in understanding human neural axial specification and the selective vulnerability of spMN subpopulations in motor neuron diseases. Here, we present a novel approach to enhance spMN axial heterogeneity in an advanced SCO model derived from neural stem cells (NSCs) and retinoic acid (RA)-primed neuromesodermal progenitors (NMPs). RA priming guided NMP differentiation into caudal neural progenitors, generating SCOs enriched in spMNs with posterior axial identities. To further diversify spMN populations, we optimized differentiation by synchronously patterning NSCs with RA-primed NMPs. Incorporating an endothelial-like network and skeletal muscle cells enhanced the organoids physiological complexity and neural maturation and organoid cell viability. This comprehensive approach, termed CASCO, provides a robust platform to study human spMN specification and model neurodegenerative diseases.

neuroscience↗

bioRxiv2023

An isogenic human iPSC model unravels neurodevelopmental abnormalities in SMA

Whether neurodevelopmental defects underlie the selective neuronal death that characterizes neurodegenerative diseases is becoming an intriguing question. To address it, we focused on the motor neuron (MN) disease Spinal Muscular Atrophy (SMA), caused by reduced levels of the ubiquitous protein SMN. Taking advantage of the first isogenic human induced pluripotent stem cell-derived SMA model that we have generated and a spinal cord organoid system, here we report that the relative and temporal expression of early neural progenitor and MN markers is altered in SMA. Furthermore, the corrected isogenic controls only partially reverse these abnormalities. These findings raise the relevant clinical implication that SMN-increasing treatments might not fully amend SMA pathological phenotypes. The approach we have taken demonstrates that the discovery of new disease mechanisms is greatly improved by using human isogenic models. Moreover, our study implies that SMA has a developmental component that might trigger the MN degeneration.

neuroscience↗

bioRxiv2022

HB-EGF promotes horizontal basal cell proliferation and olfactory sensory neuron regeneration in the zebrafish olfactory epithelium

Maintenance and regeneration of the zebrafish olfactory epithelium (OE) are supported by distinct progenitor cell populations that occupy discrete stem cell niches and respond to different tissue conditions. Globose basal cells (GBCs) reside at the inner and peripheral margins of the sensory OE and are constitutively active to replace sporadically dying olfactory sensory neurons (OSNs). In contrast, horizontal basal cells (HBCs) are more uniformly distributed across the tissue, including basal layers of the sensory region, and are selectively activated by acute injury conditions that affect the morphological integrity of the OE. Here we show that expression of the heparin-binding epidermal growth factor-like growth factor (HB-EGF) is strongly and transiently upregulated in response to OE injury and signals through the EGF receptor (EGFR), which is expressed by HBCs. Exogenous stimulation of the OE with recombinant HB-EGF promotes HBC expansion and OSN neurogenesis within the sensory OE, resembling the tissue response to injury. In contrast, pharmacological inhibition of HB-EGF shedding, HB-EGF availability, and EGFR signaling strongly attenuate or delay injury-induced HBC activity and OSN restoration without affecting maintenance neurogenesis by GBCs. Thus, HB-EGF/EGFR signaling appears to be a critical component of a complex signaling network that controls HBC activity and, consequently, repair neurogenesis in the zebrafish OE.

developmental biology↗