@article {70190, title = {Imp1 acts as a dosage- and stage-dependent temporal rheostat orchestrating radial glial fate transitions and cortical morphogenesis}, journal = {bioRxiv}, year = {2025}, month = {2025 Nov 18}, abstract = {

Cortical neurogenesis proceeds through a precise temporal program in which radial glia sequentially generate distinct neuronal subtypes and later glia, yet how post-transcriptional regulators coordinate these transitions remain poorly understood. We previously identified that a decreasing temporal gradient of the RNA-binding protein Imp encodes neural stem cell age in Drosophila. In this work, we extend our investigation to Imp1, a mammalian homologue of Imp, and its role in murine neocortical development. Using TEMPO to track birth-order dynamics, we demonstrate that sustained Imp1 overexpression during early neurogenesis arrests temporal fate progression, shifting neuronal populations toward deeper cortical layers V-VI. Immunostaining with layer-specific transcription factors Cux1 and Ctip2 confirmed that laminar repositioning results from genuine changes in neuronal identity rather than migratory defects, with neurons adopting molecular identities matching their final positions. Temporal window-specific manipulations reveal distinct stage-specific effects where early-stage Imp1 induction produces cascading effects on fate specification and moderately delays the neuronal-to-gliogenic transition, while mid-stage induction induces neuronal accumulation in the subplate region. Live imaging of organotypic cultures reveals continuous neuronal recruitment within intermediate and ventricular zones, with mid-stage-born neurons accumulating at significantly faster rates than earlier cohorts. Strikingly, mid-stage Imp1 overexpression also induces ectopic glial-like foci distributed throughout the cortical plate, featuring dramatic cellular expansion and morphological heterogeneity. These findings establish Imp1 as a dosage- and stage-dependent temporal rheostat orchestrating developmental transitions in radial glial progenitors, controlling neuronal fate decisions and spatial organization. This work advances our understanding of molecular timing mechanisms governing neuronal diversity in the mammalian cortex.

}, doi = {10.1101/2025.11.18.688993}, url = {https://www.biorxiv.org/content/early/2025/11/18/2025.11.18.688993}, author = {Azur, Romie Angelo G. and Feliciano, Daniel and Espinosa-Medina, Isabel and Adhikari, Raghabendra and Lilao-Garz{\'o}n, Joaquin and Jensen, Ella and Yang, Ching-Po and Lee, Tzumin} } @article {65382, title = {Conservation and divergence of related neuronal lineages in the central brain.}, journal = {eLife}, volume = {9}, year = {2020}, month = {2020 Apr 07}, abstract = {

Wiring a complex brain requires many neurons with intricate cell specificity, generated by a limited number of neural stem cells. central brain lineages are a predetermined series of neurons, born in a specific order. To understand how lineage identity translates to neuron morphology, we mapped 18 central brain lineages. While we found large aggregate differences between lineages, we also discovered shared patterns of morphological diversification. Lineage identity plus Notch-mediated sister fate govern primary neuron trajectories, whereas temporal fate diversifies terminal elaborations. Further, morphological neuron types may arise repeatedly, interspersed with other types. Despite the complexity, related lineages produce similar neuron types in comparable temporal patterns. Different stem cells even yield two identical series of dopaminergic neuron types, but with unrelated sister neurons. Together, these phenomena suggest that straightforward rules drive incredible neuronal complexity, and that large changes in morphology can result from relatively simple fating mechanisms.

}, issn = {2050-084X}, doi = {10.7554/eLife.53518}, author = {Lee, Ying-Jou and Yang, Ching-Po and Miyares, Rosa L and Huang, Yu-Fen and He, Yisheng and Ren, Qingzhong and Chen, Hui-Min and Kawase, Takashi and Ito, Masayoshi and Otsuna, Hideo and Sugino, Ken and Aso, Yoshi and Ito, Kei and Lee, Tzumin} } @article {65374, title = {Neuronal upregulation of Prospero protein is driven by alternative mRNA polyadenylation and Syncrip-mediated mRNA stabilisation.}, journal = {Biology Open}, volume = {9}, year = {2020}, month = {2020 May}, abstract = {

During and vertebrate brain development, the conserved transcription factor Prospero/Prox1 is an important regulator of the transition between proliferation and differentiation. Prospero level is low in neural stem cells and their immediate progeny, but is upregulated in larval neurons and it is unknown how this process is controlled. Here, we use single molecule fluorescent hybridisation to show that larval neurons selectively transcribe a long mRNA isoform containing a 15 kb 3{\textquoteright} untranslated region, which is bound in the brain by the conserved RNA-binding protein Syncrip/hnRNPQ. Syncrip binding increases the mRNA stability of the long isoform, which allows an upregulation of Prospero protein production. Adult flies selectively lacking the long isoform show abnormal behaviour that could result from impaired locomotor or neurological activity. Our findings highlight a regulatory strategy involving alternative polyadenylation followed by differential post-transcriptional regulation.

}, issn = {2046-6390}, doi = {10.1242/bio.049684}, author = {Samuels, Tamsin J and Arava, Yoav and J{\"a}rvelin, Aino I and Robertson, Francesca and Lee, Jeffrey Y and Yang, Lu and Yang, Ching-Po and Lee, Tzumin and Ish-Horowicz, David and Davis, Ilan} } @article {65669, title = {A programmable sequence of reporters for lineage analysis.}, journal = {Nature Neuroscience}, volume = {23}, year = {2020}, month = {2020 Dec 01}, pages = {1618-28}, abstract = {

We present CLADES (cell lineage access driven by an edition sequence), a technology for cell lineage studies based on CRISPR-Cas9 techniques. CLADES relies on a system of genetic switches to activate and inactivate reporter genes in a predetermined order. Targeting CLADES to progenitor cells allows the progeny to inherit a sequential cascade of reporters, thereby coupling birth order to reporter expression. This system, which can also be temporally induced by heat shock, enables the temporal resolution of lineage development and can therefore be used to deconstruct an extended cell lineage by tracking the reporters expressed in the progeny. When targeted to the germ line, the same cascade progresses across animal generations, predominantly marking each generation with the corresponding combination of reporters. CLADES therefore offers an innovative strategy for making programmable cascades of genes that can be used for genetic manipulation or to record serial biological events.

}, issn = {1546-1726}, doi = {10.1038/s41593-020-0676-9}, author = {Garcia-Marques, Jorge and Isabel Espinosa Medina and Ku, Kai-Yuan and Yang, Ching-Po and Koyama, Minoru and Yu, Hung-Hsiang and Lee, Tzumin} } @article {65379, title = {CLADES: a programmable sequence of reporters for lineage analysis}, journal = {bioRxiv}, year = {2019}, month = {2019 May 30}, abstract = {

We present CLADES (Cell Lineage Access Driven by an Edition Sequence), a technology for cell lineage studies based on CRISPR/Cas9. CLADES relies on a system of genetic switches to activate and inactivate reporter genes in a pre-determined order. Targeting CLADES to progenitor cells allows the progeny to inherit a sequential cascade of reporters, coupling birth order with reporter expression. This gives us temporal resolution of lineage development that can be used to deconstruct an extended cell lineage by tracking the reporters expressed in the progeny. When targeted to the germ line, the same cascade progresses across animal generations, marking each generation with the corresponding combination of reporters. CLADES thus offers an innovative strategy for making programmable cascades of genes that can be used for genetic manipulation or to record serial biological events.

}, doi = {https://doi.org/10.1101/655308}, author = {Garcia-Marques, Jorge and Yang, Ching-Po and Isabel Espinosa Medina and Koyama, Minoru and Lee, Tzumin} } @article {65160, title = {Mamo decodes hierarchical temporal gradients into terminal neuronal fate.}, journal = {Elife}, volume = {8}, year = {2019}, month = {2019 Sep 23}, abstract = {

Temporal patterning is a seminal method of expanding neuronal diversity. Here we unravel a mechanism decoding neural stem cell temporal gene expression and transforming it into discrete neuronal fates. This mechanism is characterized by hierarchical gene expression. First, neuroblasts express opposing temporal gradients of RNA-binding proteins, Imp and Syp. These proteins promote or inhibit translation, yielding a descending neuronal gradient. Together, first and second-layer temporal factors define a temporal expression window of BTB-zinc finger nuclear protein, Mamo. The precise temporal induction of Mamo is achieved via both transcriptional and post-transcriptional regulation. Finally, Mamo is essential for the temporally defined, terminal identity of α{\textquoteright}/β{\textquoteright} mushroom body neurons and identity maintenance. We describe a straightforward paradigm of temporal fate specification where diverse neuronal fates are defined via integrating multiple layers of gene regulation. The neurodevelopmental roles of orthologous/related mammalian genes suggest a fundamental conservation of this mechanism in brain development.

}, issn = {2050-084X}, doi = {10.7554/eLife.48056}, author = {Liu, Ling-Yu and Long, Xi and Yang, Ching-Po and Miyares, Rosa L and Sugino, Ken and Singer, Robert H and Lee, Tzumin} } @article {65078, title = {Unlimited genetic switches for cell-type-specific manipulation.}, journal = {Neuron}, volume = {104}, year = {2019}, month = {2019 Oct 23}, pages = {227-38}, abstract = {

Gaining independent genetic access to discrete cell types is critical to interrogate their biological functions as well as to deliver precise gene therapy. Transcriptomics has allowed us to profile cell populations with extraordinary precision, revealing that cell types are typically defined by a unique combination of genetic markers. Given the lack of adequate tools to target cell types based on multiple markers, most cell types remain inaccessible to genetic manipulation. Here we present CaSSA, a platform to create unlimited genetic switches based on CRISPR/Cas9 (Ca) and the DNA repair mechanism known as single-strand annealing (SSA). CaSSA allows engineering of independent genetic switches, each responding to a specific gRNA. Expressing multiple gRNAs in specific patterns enables multiplex cell-type-specific manipulations and combinatorial genetic targeting. CaSSA is a new genetic tool that conceptually works as an unlimited number of recombinases and will facilitate genetic access to cell types in diverse organisms.

}, doi = {https://doi.org/10.1016/j.neuron.2019.07.005}, author = {Garcia-Marques, Jorge and Yang, Ching-Po and Isabel Espinosa Medina and Mok, Kent and Koyama, Minoru and Lee, Tzumin} } @article {48766, title = {Imp and Syp RNA-binding proteins govern decommissioning of Drosophila neural stem cells.}, journal = {Development (Cambridge, England)}, volume = {144}, year = {2017}, month = {2017 Aug 29}, pages = {3454-64}, abstract = {

The termination of the proliferation of Drosophila neural stem cells, also known as neuroblasts (NBs), requires a "decommissioning" phase that is controlled in a lineage-specific manner. Most NBs, with the exception of those of the Mushroom body (MB), are decommissioned by the ecdysone receptor and mediator complex causing them to shrink during metamorphosis, followed by nuclear accumulation of Prospero and cell cycle exit. Here, we demonstrate that the levels of Imp and Syp RNA-binding proteins regulate NB decommissioning. Descending Imp and ascending Syp expression have been shown to regulate neuronal temporal fate. We show that Imp levels decline slower in the MB than other central brain NBs. MB NBs continue to express Imp into pupation, and the presence of Imp prevents decommissioning partly by inhibiting the mediator complex. Late-larval induction of transgenic Imp prevents many non-MB NBs from decommissioning in early pupae. Moreover, the presence of abundant Syp in aged NBs permits Prospero accumulation that, in turn, promotes cell cycle exit. Together our results reveal that progeny temporal fate and progenitor decommissioning are co-regulated in protracted neuronal lineages.

}, issn = {1477-9129}, doi = {10.1242/dev.149500}, author = {Yang, Ching-Po and Samuels, Tamsin J and Huang, Yaling and Yang, Lu and Ish-Horowicz, David and Davis, Ilan and Lee, Tzumin} } @article {48435, title = {Stem cell-intrinsic, seven-up-triggered temporal factor gradients diversify intermediate neural progenitors.}, journal = {Current Biology : CB}, volume = {27}, year = {2017}, month = {2017 Apr 10}, pages = {1303-13}, abstract = {

Building a sizable, complex brain requires both cellular expansion and diversification. One mechanism to achieve these goals is production of multiple transiently amplifying intermediate neural progenitors (INPs) from a single neural stem cell. Like mammalian neural stem cells, Drosophila type II neuroblasts utilize INPs to produce neurons and glia. Within a given lineage, the consecutively born INPs produce morphologically distinct progeny, presumably due to differential inheritance of temporal factors. To uncover the underlying temporal fating mechanisms, we profiled type II neuroblasts{\textquoteright} transcriptome across time. Our results reveal opposing temporal gradients of Imp and Syp RNA-binding proteins (descending and ascending, respectively). Maintaining high Imp throughout serial INP production expands the number of neurons and glia with early temporal fate at the expense of cells with late fate. Conversely, precocious upregulation of Syp reduces the number of cells with early fate. Furthermore, we reveal that the transcription factor Seven-up initiates progression of the Imp/Syp gradients. Interestingly, neuroblasts that maintain initial Imp/Syp levels can still yield progeny with a small range of early fates. We therefore propose that the Seven-up-initiated Imp/Syp gradients create coarse temporal windows within type II neuroblasts to pattern INPs, which subsequently undergo fine-tuned subtemporal patterning.

}, issn = {1879-0445}, doi = {10.1016/j.cub.2017.03.047}, author = {Ren, Qingzhong and Yang, Ching-Po and Liu, Zhiyong and Sugino, Ken and Mok, Kent and He, Yisheng and Ito, Masayoshi and Nern, Aljoscha and Otsuna, Hideo and Lee, Tzumin} } @article {47307, title = {Transcriptomes of lineage-specific Drosophila neuroblasts profiled by genetic targeting and robotic sorting.}, journal = {Development (Cambridge, England)}, volume = {143}, year = {2016}, month = {2016 Feb 1}, pages = {411-21}, abstract = {

A brain consists of numerous distinct neurons arising from a limited number of progenitors, called neuroblasts in Drosophila. Each neuroblast produces a specific neuronal lineage. To unravel the transcriptional networks that underlie the development of distinct neuroblast lineages, we marked and isolated lineage-specific neuroblasts for RNA sequencing. We labeled particular neuroblasts throughout neurogenesis by activating a conditional neuroblast driver in specific lineages using various intersection strategies. The targeted neuroblasts were efficiently recovered using a custom-built device for robotic single-cell picking. Transcriptome analysis of mushroom body, antennal lobe and type II neuroblasts compared with non-selective neuroblasts, neurons and glia revealed a rich repertoire of transcription factors expressed among neuroblasts in diverse patterns. Besides transcription factors that are likely to be pan-neuroblast, many transcription factors exist that are selectively enriched or repressed in certain neuroblasts. The unique combinations of transcription factors present in different neuroblasts may govern the diverse lineage-specific neuron fates.

}, issn = {1477-9129}, doi = {10.1242/dev.129163}, author = {Yang, Ching-Po and Fu, Chi-Cheng and Sugino, Ken and Liu, Zhiyong and Ren, Qingzhong and Liu, Ling-Yu and Yao, Xiaohao and Lee, Luke P and Lee, Tzumin} } @article {47126, title = {Opposing intrinsic temporal gradients guide neural stem cell production of varied neuronal fates.}, journal = {Science (New York, N.Y.)}, volume = {350}, year = {2015}, month = {2015 Oct 16}, pages = {317-20}, abstract = {

Neural stem cells show age-dependent developmental potentials, as evidenced by their production of distinct neuron types at different developmental times. Drosophila neuroblasts produce long, stereotyped lineages of neurons. We searched for factors that could regulate neural temporal fate by RNA-sequencing lineage-specific neuroblasts at various developmental times. We found that two RNA-binding proteins, IGF-II mRNA-binding protein (Imp) and Syncrip (Syp), display opposing high-to-low and low-to-high temporal gradients with lineage-specific temporal dynamics. Imp and Syp promote early and late fates, respectively, in both a slowly progressing and a rapidly changing lineage. Imp and Syp control neuronal fates in the mushroom body lineages by regulating the temporal transcription factor Chinmo translation. Together, the opposing Imp/Syp gradients encode stem cell age, specifying multiple cell fates within a lineage.

}, issn = {1095-9203}, doi = {10.1126/science.aad1886}, author = {Liu, Zhiyong and Yang, Ching-Po and Sugino, Ken and Fu, Chi-Cheng and Liu, Ling-Yu and Yao, Xiaohao and Lee, Luke P and Lee, Tzumin} } @article {6898, title = {Making Drosophila lineage-restricted drivers via patterned recombination in neuroblasts.}, journal = {Nature Neuroscience}, volume = {17}, year = {2014}, month = {2014 Apr}, pages = {631-7}, abstract = {

The Drosophila cerebrum originates from about 100 neuroblasts per hemisphere, with each neuroblast producing a characteristic set of neurons. Neurons from a neuroblast are often so diverse that many neuron types remain unexplored. We developed new genetic tools that target neuroblasts and their diverse descendants, increasing our ability to study fly brain structure and development. Common enhancer-based drivers label neurons on the basis of terminal identities rather than origins, which provides limited labeling in the heterogeneous neuronal lineages. We successfully converted conventional drivers that are temporarily expressed in neuroblasts, into drivers expressed in all subsequent neuroblast progeny. One technique involves immortalizing GAL4 expression in neuroblasts and their descendants. Another depends on loss of the GAL4 repressor, GAL80, from neuroblasts during early neurogenesis. Furthermore, we expanded the diversity of MARCM-based reagents and established another site-specific mitotic recombination system. Our transgenic tools can be combined to map individual neurons in specific lineages of various genotypes.

}, issn = {1546-1726}, doi = {10.1038/nn.3654}, author = {Awasaki, Takeshi and Kao, Chih-Fei and Lee, Ying-Jou and Yang, Ching-Po and Huang, Yaling and Pfeiffer, Barret D and Luan, Haojiang and Jing, Xiaotang and Huang, Yu-Fen and He, Yisheng and Schroeder, Mark David and Kuzin, Alexander and Brody, Thomas and Zugates, Christopher T and Odenwald, Ward F and Lee, Tzumin} } @article {6454, title = {Extremes of lineage plasticity in the Drosophila brain.}, journal = {Current Biology}, volume = {23}, year = {2013}, month = {2013 Sep 19}, pages = {1908-13}, abstract = {

An often-overlooked aspect of neural plasticity is the plasticity of neuronal composition, in which the numbers of neurons of particular classes are altered in response to environment and experience. The Drosophila brain features several well-characterized lineages in which a single neuroblast gives rise to multiple neuronal classes in a stereotyped sequence during development [1]. We find that in the\ intrinsic mushroom body neuron lineage, the numbers for each class are highly plastic, depending on the timing of temporal fate transitions and the rate of neuroblast proliferation. For example, mushroom body neuroblast cycling can continue under starvation conditions, uncoupled from\ temporal fate transitions that depend on extrinsic cues reflecting organismal growth and development. In contrast, the proliferation rates of antennal lobe lineages are closely associated with organismal development, and\ their temporal fate changes appear to be cell cycle-dependent, such that the same numbers and types of uniglomerular projection neurons innervate the antennal lobe following various perturbations. We propose that this surprising difference in plasticity for these brain lineages is adaptive, given their respective roles as parallel\ processors versus discrete carriers of olfactory information.

}, issn = {1879-0445}, doi = {10.1016/j.cub.2013.07.074}, author = {Lin, Suewei and Marin, Elizabeth C and Yang, Ching-Po and Kao, Chih-Fei and Apenteng, Bettye A and Huang, Yaling and O{\textquoteright}Connor, Michael B and Truman, James W and Lee, Tzumin} }