Biology subjects

Pierani, A.

Publications and source records attributed to Pierani, A..

8 recordsLinked to original sources

bioRxiv2024

Differential contribution of P73+ Cajal-Retzius cells and Reelin to cortical morphogenesis

Cajal-Retzius cells (CRs) are a peculiar neuronal type within the developing mammalian cerebral cortex. One of their best documented feature is the robust secretion of Reln, a glycoprotein essential for the establishment of cortical layers through the control of radial migration of glutamatergic neurons. We previously identified Gmnc as a critical fate determinant for P73+ CRs subtypes from the hem, septum and thalamic eminence. In Gmnc-/- mutants, P73+ CRs are initially produced, cover the telencephalic vesicle but undergo massive apoptosis resulting in their complete depletion at mid-corticogenesis. Here we investigated the consequence of such a CRs depletion on dorsal cortex lamination and hippocampal morphogenesis. We found preplate splitting occurs normally in Gmnc-/- mutants but is followed by defective radial migration arrest in the dorsal cortex, altered cellular organization in the lateral cortex, aberrant hippocampal progenitor proliferation resulting in abnormal CA1 folding and lack of vasculature development in the hippocampal fissure. We then performed conditional Reln deletion in P73+ CRs to evaluate its relative contribution and found that only radial migration defects were recapitulated. We concluded that at mid-corticogenesis, CRs-derived Reln is required for radial migration arrest and additionally identified Reln-independent functions for CRs in the control of hippocampal progenitor proliferation and vessel remodelling.

neuroscience↗

bioRxiv2023

Slitrk/LAR-RPTP and disease-associated variants control neuronal migration in the developing mouse cortex independently of synaptic organizer activity

Slitrks and their ligands LAR-RPTPs are type I transmembrane proteins previously implicated in the etiology of various neuropsychiatric disorders including obsessive-compulsive disorders (OCDs) and schizophrenia. Over the last decade, their functions were extensively studied in hippocampal neurons in vitro and shown to shape synapse organization. Although both protein families are highly expressed prior to synapse formation, their function in earlier steps of cerebral cortex development remains unknown. Here we investigated the role of Slitrk1, Slitrk2, Slitrk3 and LAR-RPTPs (Ptprs and Ptprd) in the embryonic mouse cortex by acute genetic manipulation using in utero electroporation. All genes, except Slitrk3, promoted specific alterations in radial migration of glutamatergic neurons. Slitrk1 and Slitrk2 overexpression was associated with accumulation of neurons in distinct regions of the cortical plate. Using deletion mutants and a series of Slitrk variants associated with neurodevelopmental disorders (NDDs), we showed that distinct domains are crucial for intracellular Slitrk1 distribution and/or density and shape of VAMP2+ presynaptic boutons. Interestingly, bouton alterations did not correlate with the observed migration delays, suggesting that Slitrk1 influence cell migration independently on its synaptogenic function. Furthermore, co-electroporation experiments with LAR-RPTPs, mimicking their co-expression observed by scRNAseq, rescued the migration deficits, suggesting possible cis-interactions between Slitrks and LAR-RPTPs. Together, these data indicate that in the embryonic cerebral cortex Slitrks and LAR-RPTPs cooperate in consecutive steps of radial migration through distinct mechanisms than in synapse organization and support a relevant role of Slitrk/LAR-RPTP dysfunctions in NDDs at earlier stages of cortical development.

neuroscience↗

bioRxiv2023

Bidirectional interaction between Protocadherin 8 and transcription factor Dbx1 regulates cerebral cortex development

Brain development requires correct tissue patterning and production of appropriate cell types. Transcription factors (TFs) play essential roles in these processes, regulating the expression of target genes responsible for neuronal subtypes specific features. Cell adhesion molecules are key components of developmental processes that control cell sorting, migration, neurite outgrowth/guidance and synaptogenesis. To date, the link between TFs and cell adhesion molecules is considered to be unidirectional. Here, we demonstrate that ectopic expression of Dbx1 leads to spatio-temporally restricted increased expression of Pcdh8 and cell aggregation, together with changes in neuronal identity. Surprisingly, Pcdh8 overexpression also induces Dbx1 expression as well as a complete reorganisation of apico-basal polarity and dorso-ventral patterning via Notch signalling. Altogether, our work therefore points to cell adhesion molecules as unexpected, yet important, players in the regulation of cell identity and, in particular, Pcdh8 through its bidirectional interaction with the Dbx1 transcription factor.

neuroscience↗

bioRxiv2022

Diversity within olfactory sensory derivatives revealed by the contribution of Dbx1 lineages

In vertebrates, the embryonic olfactory epithelium contains progenitors that will give rise to distinct classes of neurons, including olfactory sensory neurons (OSN, involved in odor detection), vomeronasal sensory neurons (VSN, responsible for pheromone sensing) and GnRH neurons that control the hypothalamic-pituitary-gonadal axis. Currently, these three neuronal lineages are usually believed to emerge from uniform pools of progenitors. Here we found that the homeodomain transcription factor Dbx1 is expressed by neurogenic progenitors in the developing and adult mouse olfactory epithelium. We demonstrate that Dbx1 itself is dispensable for neuronal fate specification and global organization of the olfactory sensory system. Using lineage tracing we characterize the contribution of Dbx1 lineages to OSN, VSN and GnRH neuron populations and reveal an unexpected degree of diversity. Furthermore, we demonstrate that Dbx1-expressing progenitors remain neurogenic in the absence of the proneural gene Ascl1. Our work therefore points to the existence of distinct neurogenic programs in Dbx1-derived and other olfactory lineages.

developmental biology↗

bioRxiv2021

Functional characterization of RELN missense mutations involved in recessive and dominant forms of Neuronal Migration Disorders

RELN is a large secreted glycoprotein that acts at multiple steps of cerebral cortex development, including neuronal migration. Only recessive mutations of the Reelin gene (RELN) have been associated with human cortical malformations and none has been functionally characterized. We identified novel missense RELN mutations in both compound and de novo heterozygous patients exhibiting an array of neuronal migration disorders (NMDs) as diverse as pachygyria, polymicrogyria and heterotopia. Most mutations caused defective RELN secretion in vitro and, when ectopically expressed in the embryonic mouse cortex, affected neuronal aggregation and/or migration in vivo. We determined the de novo heterozygous mutations acted as dominant negative and demonstrated that RELN mutations mediate not only recessive, but also dominant NMDs. This work assesses for the first time the pathogenicity of RELN mutations showing a strong genotype-phenotype correlation. In particular, the behavior of the mutant proteins in vitro and in vivo predicts the severity of cortical malformations and provides valuable insight into the pathogenesis of these disorders.

neuroscience↗

bioRxiv2020

Single-cell transcriptomics of the early developing mouse cerebral cortex disentangles the spatial and temporal components of neuronal fate acquisition

In the developing cerebral cortex, how progenitors that seemingly display limited diversity end up in producing a vast array of neurons remains a puzzling question. The prevailing model that recently emerged suggests that temporal maturation of these progenitors is a key driver in the diversification of the neuronal output. However, temporal constrains are unlikely to account for all diversity across cortical regions, especially in the ventral and lateral domains where neuronal types significantly differ from their dorsal neocortical counterparts born at the same time. In this study, we implemented single-cell RNAseq to sample the diversity of progenitors and neurons along the dorso-ventral axis of the early developing pallium. We first identified neuronal types, mapped them on the tissue and performed genetic tracing to determine their origin. By characterising progenitor diversity, we disentangled the gene expression modules underlying temporal vs spatial regulations of neuronal specification. Finally, we reconstructed the developmental trajectories followed by ventral and dorsal pallial neurons to identify gene waves specific of each lineage. Our data suggest a model by which discrete neuronal fate acquisition from a continuous gradient of progenitors results from the superimposition of spatial information and temporal maturation.

developmental biology↗

bioRxiv2020

Lack of adaptation to centriolar defects leads to p53-independent microcephaly in the absence of Cep135

Autosomal Recessive Primary Microcephaly (MCPH) is a rare disease associated to proteins involved in centrosomal and spindle dynamics including Cep135 (MCPH8). Although Cep135 has been associated to centriolar assembly, the mechanisms associated to the pathogenesis underlying MCPH8 mutations are unclear. By using a series of CRISPR/Cas9-edited murine Cep135 alleles, we report here that lack of Cep135 results in perinatal lethality accompanied by significant microcephaly in a dosis-dependent manner. Cep135 deficiency, but not that of other centrosomal microcephaly proteins such as Aspm or Cdk5rap2, induces centrosome duplication defects, and perturbed centriole structure and dynamics. Whereas other cell types are able to quickly adapt to these defects, neural progenitors display a prolonged response leading to chromosomal instability and cell death in later developmental stages. Genetic ablation of Trp53 in these mutant embryos prevents apoptotic cell death but does not rescue the microcephaly induced by Cep135 loss. These results suggest that microcephaly can arise from the lack of adaptation to centriole defects in neural progenitors of the developing neocortex in a p53-independent manner.

cell biology↗

bioRxiv2018

Extracellular Pax6 regulates tangential Cajal-Retzius cell migration

The embryonic mouse cortex displays a striking low caudo-medial and high rostro-lateral graded expression of the homeoprotein transcription factor Pax6, which presents both cell autonomous and direct non-cell autonomous activities. Through the genetic induction of anti-Pax6 single-chain antibody secretion, we have analyzed Pax6 non-cell autonomous activity on the migration of cortical hem- and septum-derived Cajal-Retzius (CR) neurons by live imaging of flat mount developing cerebral cortices. We observed that blocking extracellular Pax6 disrupts tangential CR cell migration patterns. We found a decrease in the distance travelled and changes both in directionality and in the depth at which CR cells migrate. Tracking of single CR cells in mutant cortices revealed that extracellular Pax6 neutralization enhances or reduces contact repulsion in medial and lateral regions, respectively. This study demonstrates that secreted Pax6 controls neuronal migration thus acting as a bona fide morphogen at an early stage of cerebral cortex development.\n\nSummary statementCajal-Retzius cell distribution in the embryonic cortex participates in determining the size and positioning of cortical areas. Here, Kaddour et al. establish that the direct non-cell autonomous activity of the Pax6 transcription factor regulates Cajal-Retzius cell migration.

neuroscience↗