Biology subjects

Miranda, O. A.

Publications and source records attributed to Miranda, O. A..

4 recordsLinked to original sources

bioRxiv2026

Mtor/Rptor Function Globally Prevents Cortical Microcephaly and Cell-autonomously Promotes Postnatal Neuron Survival in Cell Type Specific Manner

The generation of faithful cell-type diversity and correct projection neuron numbers is essential for cerebral cortex development. Corticogenesis is however susceptible to genetic interference of critical signaling pathways, including mutations in Mtor/Rptor that lead to microcephaly. How the loss of Rptor/mTORC1 function affects cortical developmental programs, at single cell level, is still unknown. Here, we utilized Mosaic Analysis with Double Markers (MADM) technology to probe Rptor gene function upon sparse single cell- or global tissue-wide ablation. We found that tissue-wide effects drive the etiology of cortical microcephaly upon loss of Rptor, rather than deficits in projection neuron genesis. Conversely, Rptor function is cell-autonomously required for postnatal projection neuron survival in a highly cell-type-specific manner. Collectively, our results suggest that the fine balance of precise cell-type-specific cell-autonomous Rptor/mTORC1 function in concert with non-cell-autonomous tissue-wide effects is essential for the development of a properly-sized cerebral cortex with accurate projection neuron diversity.

neuroscience↗

bioRxiv2026

Pten Orchestrates Neurogenic Radial Glia Lineage Progression and Tunes Neocortical Astrocyte Production

The cerebral cortex consists of immense numbers of neuronal and glial cell-types derived from radial glial progenitor (RGP) cells. How RGPs generate appropriate quantities of distinct cortical cell-types to safeguard a brain of correct size, is not well understood. However, genetic aberration in human, including mutations in PTEN, lead to cortical malformation such as macrocephaly, albeit with unknown etiology. Here we utilized Mosaic Analysis with Double Markers (MADM)-based clonal analysis and single cell phenotyping to decipher the role of Pten in neurogenic and gliogenic RGP lineage progression during cortical ontogeny. While neurogenic RGP lineage progression and projection neuron production was moderately altered in the absence of Pten, cortical astrocyte production was drastically increased. Through genetic epistasis experiments we show that the loss of Pten uncouples astrocyte generation from essential growth factor signaling hubs, funneling into MAPK. Collectively, our results suggest that Pten regulates RGP lineage progression with distinct sequential functions in cortical projection neurogenesis and astrocyte production to ensure the emergence of a correctly-sized cerebral cortex.

neuroscience↗

bioRxiv2019

TGFβ superfamily signaling regulates the state of human stem cell pluripotency and competency to create telencephalic organoids

Telencephalic organoids generated from human pluripotent stem cells (hPSCs) are emerging as an effective system to study the distinct features of the developing human brain and the underlying causes of many neurological disorders. While progress in organoid technology has been steadily advancing, many challenges remain including rampant batch-to-batch and cell line-to-cell line variability and irreproducibility. Here, we demonstrate that a major contributor to successful cortical organoid production is the manner in which hPSCs are maintained prior to differentiation. Optimal results were achieved using fibroblast-feeder-supported hPSCs compared to feeder-independent cells, related to differences in their transcriptomic states. Feeder-supported hPSCs display elevated activation of diverse TGF{beta} superfamily signaling pathways and increased expression of genes associated with naive pluripotency. We further identify combinations of TGF{beta}-related growth factors that are necessary and together sufficient to impart broad telencephalic organoid competency to feeder-free hPSCs and enable reproducible formation of brain structures suitable for disease modeling. HIGHLIGHTSO_LIhPSC maintenance conditions influence outcomes in cortical organoid formation C_LIO_LIIdentification of an intermediate pluripotency state optimal for cortical organoids C_LIO_LIFeeder support involves activation of diverse TGF{beta} signaling pathways C_LIO_LIThe organoid-promoting effects of feeders can be mimicked by a TGF{beta} factor mixture C_LI

developmental biology↗

bioRxiv2019

Identification of neural oscillations and epileptiform changes in human brain organoids

Brain organoids represent a powerful tool for the study of human neurological diseases, particularly those impacting brain growth and structure. However, many diseases manifest with clear evidence of physiological and network abnormality in the absence of anatomical changes. This raises the question of whether organoids possess sufficient neural network complexity to model these conditions. Here, we explore the network level functions of brain organoids using calcium sensor imaging and extracellular recording approaches that together reveal the existence of complex network behaviors reminiscent of intact brain preparations. We demonstrate highly abnormal and epileptiform-like activity in organoids derived from MECP2 mutant patients compared to isogenic controls accompanied by modest transcriptomic differences revealed by single cell analyses. We also rescue key physiological activities with an unconventional neuromodulatory drug, Pifithrin-. Together, these findings provide an essential foundation for the utilization of brain organoids to study intact and disordered human brain network formation and illustrate their utility in therapeutic discovery.

neuroscience↗