Biology subjects

Machold, R. P.

Publications and source records attributed to Machold, R. P..

6 recordsLinked to original sources

bioRxiv2025

Differences in Cajal-Retzius cell density and postnatal persistence across cortical areas revealed by a novel intersectional genetic labeling approach

Cajal-Retzius (CR) cells are glutamatergic neurons that transiently populate the most superficial layer of the isocortex and allocortex during development, serving an essential role during both prenatal and early postnatal brain development. Notably, these cells disappear from most cortical areas by postnatal day 14, but persist for much longer in the hippocampus. We developed a novel intersectional genetic labeling approach for CR cells that captures almost all of the TRP73-positive CR cells throughout the isocortex and allocortex. This intersectional strategy offers several advantages over previous methods commonly used for CR cell targeting. Here, we applied this new CR cell labeling strategy to investigate the distribution and persistence of CR cells throughout the whole mouse brain, at four different postnatal ages. We observed that the initial CR cell density and the rate of their disappearance varies substantially across different brain areas during development. Strikingly, we observed variation in cell death rate even between adjacent cortical subregions: comparing the medial and the lateral entorhinal cortex, the former retains a high density of CR cells for several months in contrast to the latter. Our results present a necessary revision of the phenomenon of CR cell persistence, showing that, in addition to hippocampus, several other cortical areas maintain a high density of these cells beyond the first two postnatal weeks.

neuroscience↗

bioRxiv2025

Inhibitory and disinhibitory VIP IN-mediated circuits in neocortex

Cortical GABAergic interneurons (INs) expressing the neuropeptide vasoactive-intestinal peptide (VIP) predominantly function by inhibiting dendritic-targeting somatostatin (SST) expressing INs, thereby disinhibiting pyramidal cells (PCs) and facilitating cortical circuit plasticity. VIP INs are a molecularly heterogeneous group, but the physiological significance of this diversity is unclear at present. Here, we have characterized the functional diversity of VIP INs in the primary somatosensory cortex (vS1) using intersectional genetic approaches. We found that VIP INs are comprised of four primary populations that exhibit different laminar distributions, axonal and dendritic arbors, intrinsic electrophysiological properties, and efferent connectivity. Furthermore, we observe that these populations are differentially activated by long-range inputs, and display distinct responses to neuromodulation by endocannabinoids, acetylcholine and noradrenaline. Stimulation of VIP IN subpopulations in vivo results in differential effects on the cortical network, thus providing evidence for specialized modes of VIP IN-mediated regulation of PC activity during cortical information processing.

neuroscience↗

bioRxiv2023

Functional specialization of hippocampal somatostatin-expressing interneurons

Hippocampal somatostatin-expressing (Sst) GABAergic interneurons (INs) exhibit considerable anatomical and functional heterogeneity. Recent single cell transcriptome analyses have provided a comprehensive Sst-IN subtype census, a plausible molecular ground truth of neuronal identity whose links to specific functionality remain incomplete. Here, we designed an approach to identify and access subpopulations of Sst-INs based on transcriptomic features. Four mouse models based on single or combinatorial Cre- and Flp- expression differentiated functionally distinct subpopulations of CA1 hippocampal Sst-INs that largely tiled the morpho-functional parameter space of the Sst-INs superfamily. Notably, the Sst;;Tac1 intersection revealed a population of bistratified INs that preferentially synapsed onto fast-spiking interneurons (FS-INs) and were both necessary and sufficient to interrupt their firing. In contrast, the Ndnf;;Nkx2-1 intersection identified a population of oriens lacunosum-moleculare (OLM) INs that predominantly targeted CA1 pyramidal neurons, avoiding FS-INs. Overall, our results provide a framework to translate neuronal transcriptomic identity into discrete functional subtypes that capture the diverse specializations of hippocampal Sst-INs. Significance statementGABAergic interneurons are important regulators of neuronal activity. Recent transcriptome analyses have provided a comprehensive classification of interneuron subtypes, but the connections between molecular identities and specific functions are not yet fully understood. Here, we developed an approach to identify and access subpopulations of interneurons based on features predicted by transcriptomic analysis. Functional investigation in transgenic animals revealed that hippocampal somatostatin-expressing interneurons (Sst-INs) can be divided into at least four subfamilies, each with distinct functions. Most importantly, the Sst;;Tac1 intersection targeted a population of bistratified cells that overwhelmingly targeted fast-spiking interneurons. In contrast, the Ndnf;;Nkx2-1 intersection revealed a population of oriens lacunosum-moleculare interneurons that selectively targeted CA1 pyramidal cells. Overall, this study reveals that genetically distinct subfamilies of Sst-INs form specialized circuits in the hippocampus with differing functional impact.

neuroscience↗

bioRxiv2022

Id2 GABAergic interneurons comprise a neglected fourth major group of cortical inhibitory cells

Cortical GABAergic interneurons (INs) represent a diverse population of mainly locally projecting cells that provide specialized forms of inhibition to pyramidal neurons and other INs. Most recent work on INs has focused on subtypes distinguished by expression of Parvalbumin (PV), Somatostatin (SST), or Vasoactive Intestinal Peptide (VIP). However, a fourth group that includes neurogliaform cells (NGFCs) has remained enigmatic due to a lack of genetic tools. Here, we show that these INs can be accessed experimentally using intersectional genetics with the gene Id2. We find that outside of layer 1 (L1), the majority of Id2 INs are NGFCs that express high levels of neuropeptide Y (NPY) and exhibit a late-spiking firing pattern, with extensive local connectivity. While much sparser, non-NGFC Id2 INs had more variable properties, with most cells corresponding to a diverse group of INs that strongly expresses the neuropeptide CCK. In vivo, using silicon probe recordings, we observed several distinguishing aspects of NGFC activity, including a strong rebound in activity immediately following the cortical down state during NREM sleep. Our study provides insights into IN diversity and NGFC distribution and properties, and outlines an intersectional genetics approach for further study of this neglected group of INs.

neuroscience↗

bioRxiv2020

Motor neurons involved in fine motor control are labeled by tracing Atoh1-lineage neurons in the spinal cord

Motor neurons (MNs) innervating the digit muscles of the intrinsic hand and foot (IH and IF) control fine motor movements. Previous studies suggest that the IH and IF MN pools have a unique developmental history in comparison to limb MN pools. Consistent with having this unique development, we find that the IH and IF MN pools are labeled postnatally using a CRE knock-in mouse line of Atoh1, a developmentally expressed basic helix-loop-helix (bHLH) transcription factor, while limb-innervating MN pools are not. Approximately 60% of the IH and IF MN pools are labeled and are a mixture of alpha and gamma-MNs. In addition, because Atoh1 is known developmentally to specify many cerebellar-projecting neurons, we tested the hypothesis that IH and IF MNs can send axon collaterals to the cerebellum as a mechanism of corollary discharge. Using intersectional genetic, viral labeling, and retrograde labeling strategies, we were unable to provide evidence in support of this idea. As a secondary finding of our viral labeling experiments, we report here that injection of both AAV and Lentiviruses in the periphery can cross the blood-brain barrier to infect Purkinje cells within the central nervous system. Altogether, though, we find that labeling of the IH and IF motor neurons using the Atoh1 CRE knock-in mouse suggests that IH and IF MNs have a unique developmental history and that this mouse strain might be a useful tool to target these specific sets of neurons allowing for functional studies of fine motor control. Significance StatementMotor neurons (MNs) of the intrinsic hand and foot (IH and IF) are labeled postnatally using a CRE knock-in mouse line of the basic helix-loop-helix (bHLH) transcription factor Atoh1 indicating a unique developmental history. We tested whether IH and IF MNs send axon collaterals rostrally to the cerebellum as a mechanism of direct corollary discharge from MNs, but the question remains unresolved. As a resource for the community, we report that injection of both AAV and Lentiviruses in the periphery can cross the blood-brain barrier and infect Purkinje cells within the central nervous system.

developmental biology↗

bioRxiv2017

Conserved properties of Drosophila Insomniac link sleep regulation and synaptic function

Sleep is an ancient animal behavior that is regulated similarly in species ranging from flies to mammals. Various genes that regulate sleep have been identified in invertebrates, but whether the functions of these genes are conserved in mammals remains poorly explored. Drosophila insomniac (inc) mutants exhibit severely shortened and fragmented sleep. Inc protein physically associates with the Cullin-3 (Cul3) ubiquitin ligase, and neuronal depletion of Inc or Cul3 strongly curtails sleep, suggesting that Inc is a Cul3 adaptor that directs the ubiquitination of neuronal substrates that regulate sleep. Three proteins similar to Inc exist in vertebrates--KCTD2, KCTD5, and KCTD17--but are uncharacterized within the nervous system and their functional conservation with Inc has not been addressed. Here we show that Inc and its mouse orthologs exhibit striking biochemical and functional interchangeability within Cul3 complexes. Remarkably, KCTD2 and KCTD5 restore sleep to inc mutants, indicating that they can substitute for Inc in vivo and engage its neuronal targets that impact sleep. Inc and its orthologs traffic similarly within fly and mammalian neurons and are present at synapses, suggesting that their substrates include synaptic proteins. Consistent with such a mechanism, inc mutants exhibit defects in synaptic structure and physiology, indicating that Inc is vital for both synaptic function and sleep. Our findings reveal that molecular functions of Inc are conserved through ~600 million years of evolution and support the hypothesis that Inc and its orthologs participate in an evolutionarily conserved ubiquitination pathway that links synaptic function and sleep regulation.\n\nAuthor summarySleep is ubiquitous among animals and is regulated in a similar manner across phylogeny, but whether conserved molecular mechanisms govern sleep is poorly defined. The Insomniac protein is vital for sleep in Drosophila and is a putative adaptor for the Cul3 ubiquitin ligase. We show that two mammalian orthologs of Insomniac can restore sleep to flies lacking Insomniac, indicating that the molecular functions of these proteins are conserved through evolution. Our comparative analysis reveals that Insomniac and its mammalian orthologs localize to neuronal synapses and that Insomniac impacts synaptic structure and physiology. Our findings suggest that Insomniac and its mammalian orthologs are components of an evolutionarily conserved ubiquitination pathway that links synaptic function and the regulation of sleep.

neuroscience↗