Biology subjects

Galazo, M. J.

Publications and source records attributed to Galazo, M. J..

6 recordsLinked to original sources

bioRxiv2024

Shox2 is necessary for normal thalamic spindle function

The cellular identity of thalamocortical neurons (TCNs), namely their firing properties, dictates brain-wide activity patterns, such as sleep spindles. Transcription factors are critical to the determination of cellular identity. Previously, we discovered that a subset of TCNs express the transcription factor, Shox2, and, in a global Shox2 KO, established that TCNs within the anterior nucleus of the thalamus rely on the expression of Shox2 to regulate key ion channels that are necessary to maintain their firing properties. From this, we hypothesized that Shox2 expression, through the regulation of firing properties of TCNs, is critical for the thalamocortical circuit to generate spindle oscillations. We exploited the somatosensory thalamocortical circuit to investigate this by creating a primary somatosensory thalamus (VB) Shox2 knockdown mouse model. We delivered Cre into the VB of P21 Shox2fl/fl mice using viral infection and compared in vitro, patch-clamp recordings from Shox2+ and Shox2 knockdown TCNs, finding that Shox2 expression is indeed critical to maintain burst and tonic firing properties of VB TCNs. Since Shox2 is important developmentally and firing from TCNs to cortex during development structures the circuit, we performed ultrasound-guided P3 injections at P3 to generate an early-stage, Shox2 VB knockdown, but found no changes in the layer four, barrel map (VB cortical target). Despite this, Shox2 knockdown mice exhibit reduced sleep-spindle EEG density. Further, key behaviors associated with spindles and proper VB thalamic function--memory consolidation and somatosensory perception--are significantly impaired. These results indicate that the impact on spindle function is likely due to cell autonomous changes to TCNs rather than circuit changes, confirming our hypothesis that Shox2 is necessary for normal thalamic spindle function and implicating a potential role for Shox2 in autism and schizophrenia pathologies.

neuroscience↗

bioRxiv2024

Loss of Zmiz1 in mice leads to impaired cortical development and autistic-like behaviors

De novo mutations in transcriptional regulators are emerging as key risk factors contributing to the etiology of neurodevelopmental disorders. Human genetic studies have recently identified ZMIZ1 and its de novo mutations as causal of a neurodevelopmental syndrome strongly associated with intellectual disability, autism, ADHD, microcephaly, and other developmental anomalies. However, the role of ZMIZ in brain development or how ZMIZ1 mutations cause neurological phenotypes is unknown. Here, we generated a forebrain-specific Zmiz1 mutant mouse model that develops brain abnormalities, including cortical microcephaly, corpus callosum dysgenesis, and abnormal differentiation of upper-layer cortical neurons. Behaviorally, Zmiz1 mutant mice show alterations in motor activity, anxiety, communication, and social interactions with strong sex differences, resembling phenotypes associated with autism. Molecularly, Zmiz1 deficiency leads to transcriptomic changes disrupting neurogenesis, neuron differentiation programs, and synaptic signaling. We identified Zmiz1-mediated downstream regulation of key neurodevelopmental factors, including Lhx2, Auts2, and EfnB2. Importantly, reactivation of the EfnB2 pathway by exogenous EFNB2 recombinant protein rescues the dendritic outgrowth deficits in Zmiz1 mutant cortical neurons. Overall, our in vivo findings provide insight into Zmiz1 function in cortical development and reveal mechanistic underpinnings of ZMIZ1 syndrome, thereby providing valuable information relevant to future studies on this neurodevelopmental disorder.

neuroscience↗

bioRxiv2024

Symmetry in levels of axon-axon homophilic adhesion establishes topography in the corpus callosum and development of connectivity between brain hemispheres

Specific and highly diverse connectivity between functionally specialized regions of the nervous system is controlled at multiple scales, from anatomically organized connectivity following macroscopic axon tracts to individual axon target-finding and synapse formation. Identifying mechanisms that enable entire subpopulations of related neurons to project their axons with regional specificity within stereotyped tracts to form appropriate long-range connectivity is key to understanding brain development, organization, and function. Here, we investigate how axons of the cerebral cortex form precise connections between the two cortical hemispheres via the corpus callosum. We identify topographic principles of the developing trans-hemispheric callosal tract that emerge through intrinsic guidance executed by growing axons in the corpus callosum within the first postnatal week in mice. Using micro-transplantation of regionally distinct neurons, subtype-specific growth cone purification, subcellular proteomics, and in utero gene manipulation, we investigate guidance mechanisms of transhemispheric axons. We find that adhesion molecule levels instruct tract topography and target field guidance. We propose a model in which transcallosal axons in the developing brain perform a "handshake" that is guided through co-fasciculation with symmetric contralateral axons, resulting in the stereotyped homotopic connectivity between the brains hemispheres.

neuroscience↗

bioRxiv2023

Zmiz1 is a novel regulator of lymphatic endothelial cell gene expression and function

Zinc Finger MIZ-Type Containing 1 (Zmiz1), also known as ZIMP10 or RAI17, is a transcription cofactor and member of the Protein Inhibitor of Activated STAT (PIAS) family of proteins. Zmiz1 is critical for a variety of biological processes including vascular development. However, its role in the lymphatic vasculature is unknown. In this study, we utilized human dermal lymphatic endothelial cells (HDLECs) and an inducible, lymphatic endothelial cell (LEC)-specific Zmiz1 knockout mouse model to investigate the role of Zmiz1 in LECs. Transcriptional profiling of Zmiz1-deficient HDLECs revealed downregulation of genes crucial for lymphatic vessel development. Additionally, our findings demonstrated that loss of Zmiz1 results in reduced expression of proliferation and migration genes in HDLECs and reduced proliferation and migration in vitro. We also presented evidence that Zmiz1 regulates Prox1 expression in vitro and in vivo by modulating chromatin accessibility at Prox1 regulatory regions. Furthermore, we observed that loss of Zmiz1 in mesenteric lymphatic vessels significantly reduced valve density. Collectively, our results highlight a novel role of Zmiz1 in LECs and as a transcriptional regulator of Prox1, shedding light on a previously unknown regulatory factor in lymphatic vascular biology.

molecular biology↗

bioRxiv2022

Tle4 controls both developmental acquisition and postnatal maintenance of corticothalamic projection neuron identity

Identities, circuitry, and function of distinct neuron subtypes are specified during embryonic development, then maintained during postnatal maturation and potential plasticity. Mechanisms that control early acquisition of neuron subtype identities, encompassing circuitry and function, in the cerebral cortex have become increasingly understood. However, mechanisms controlling maintenance of identity, and accompanying regulation of plasticity, are largely unexplored and unknown. Here, we identify two novel functions of the co-repressor Tle4 in both acquisition and maintenance of neuron subtype identity of corticothalamic projection neurons. Embryonically, Tle4 promotes acquisition of corticothalamic molecular and cellular identity, and blocks emergence of core characteristics of subcerebral / corticospinal projection neuron identity, including morphology, gene expression, axonal connectivity, and circuitry. Postnatally, Tle4 is required to maintain corticothalamic molecular and projection identity during circuit maturation, avoiding potentially disruptive plasticity, but also limiting potentially beneficial plasticity. We identify an epigenetic mechanism by which TLE4 controls the activation state of loci regulating the level of Fezf2 expression by corticothalamic neurons during embryonic and postnatal development. This mechanism contributes importantly to distinction of cortical output (corticofugal) subtypes, and ensures appropriate maturation and maintenance of CThPN. HighlightsO_LITle4 promotes CThPN identity and blocks SCPN identity in early-born cortical neurons C_LIO_LITle4 is necessary to maintain CThPN identity during circuit maturation C_LIO_LITLE4-FEZF2 complex epigenetically regulates Fezf2 expression in developing CThPN C_LIO_LITLE4-FEZF2 regulates corticofugal subtypes distinction and maturation of CThPN C_LI

neuroscience↗

bioRxiv2021

A microRNA cluster downstream of the selector gene Fezf2 coordinates fate specification with dendritic branching in cortical neurons

In the cerebral cortex, cortical projection neurons comprise classes of neurons project to distant regions of the central nervous system. These neurons develop from the same progenitor pool, but they acquire strikingly different inputs and outputs to underpin strikingly different functions. The question of how corticospinal projection neurons - involved in motor function and implicated in paralysis - and callosal projection neurons - involved in cognitive function and implicated in autism - develop represents a fundamental and clinically important question in neurodevelopment. A network of transcription factors, including the selector gene Fezf2, is central to specifying cortical projection neuron fates. Gene regulation up- and down-stream of these transcription factors, however, is not well understood, particularly as it relates to the development of the major inputs to cortical projection neurons. Here we show that the miR-193b~365 microRNA cluster downstream of Fezf2 cooperatively represses the signaling molecule Mapk8, and impacts dendritic branching of cortical projection neurons.

developmental biology↗