Biology subjects

Jansen, E.

Publications and source records attributed to Jansen, E..

4 recordsLinked to original sources

bioRxiv2025

Imp1 acts as a dosage- and stage-dependent temporal rheostat orchestrating radial glial fate transitions and cortical morphogenesis

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.

developmental biology↗

bioRxiv2024

Full-season spring migration counts reveal seasonal contrasts in raptor migration through the eastern Black Sea flyway

The extent to which geographical features like coastlines and mountain ranges funnel migrating birds depends on the seasonal context and direction of migration. Near Batumi, in the Republic of Georgia, the eastern Black Sea coast and Lesser Caucasus funnel over one million raptors through a 10-20 km wide coastal strip every autumn. The funnelling effect of the Lesser Caucasus appears much less evident for northbound migrants. Yet historical data suggest tens of thousands of raptors pass through the region in spring. To elucidate the composition and timing of spring raptor migration we conducted full-season migration surveys near Batumi in 2019, 2020 and 2022. In total, we recorded 33 species and, on average, counted 542,161 raptors (min. 455,799 - max. 618,848) annually. The bulk of the spring passage consisted of Black Kite Milvus migrans (239,649 {+/-} 22,547) and Steppe Buzzard Buteo buteo vulpinus (194,029 {+/-} 102,702). The most diverse and intense spring migration occurred from late March through mid-April, when the median passage date of 12 of 15 common species (>100 ind. y-1) occurred. Species with longer autumn migration periods tended to have longer spring migration periods, and most species had a longer migration period in spring than in autumn, likely due to larger age differences in timing during spring. Species abundance was up to an order of magnitude lower in spring than in autumn, consistent with a weaker bottleneck-effect in spring. Nevertheless, our results confirm the eastern Black Sea coast as a principal spring flyway and help redraw the map of East African-Eurasian migration for several Palearctic raptors. While we will not continue annual spring migration surveys, our data provides a baseline for detecting changes in raptor migration through short-term surveys and can help plan migration-based conservation and research at Batumi in spring.

ecology↗

bioRxiv2019

Dynamic regulation of CD45 by tetraspanin CD53

T cells are central to the adaptive immune response, playing a role in both the direct and indirect killing of pathogens and transformed cells. The activation of T cells is the result of a complex signaling cascade, initiated at the T cell receptor (TCR), and ending with the induction of proliferation. CD45, a member of the protein tyrosine phosphatase family, is one of the most abundant membrane proteins on T cells and functions by regulating activation directly downstream of the TCR. As a result of alternative splicing, CD45 can be expressed in multiple isoforms, naive T cells express the CD45RA isoform, while activated T cells gain expression of CD45RO, which has been proposed to increase signaling. Though the importance of CD45 in TCR signaling, proliferation and cytokine production is well established, little is known about the regulation of CD45 activity. We discovered that the immune-specific tetraspanin CD53 directly affects the stability and function of CD45RO in T cells. We have identified CD53 as a T cell co-stimulatory molecule in primary human and murine cells. Furthermore, we have shown that the absence of CD53 leads to an altered CD45 isoform expression as a result of decreased CD45RO stability on the cell surface. This instability was accompanied by increased mobility as measured by FRAP. Together, this indicates that CD53 functions as a stabilizer of CD45RO, and therefore as a positive regulator of TCR signaling at the T cell surface. Our data provides novel insight into the role of tetraspanins in the regulation of immune signaling and may provide a new avenue for the regulation of T cell signaling.

immunology↗

bioRxiv2017

C-type lectin-like receptor 2 (CLEC-2)-dependent DC migration is controlled by tetraspanin CD37

Cell migration is central to evoke a potent immune response. Dendritic cell (DC) migration to lymph nodes is dependent on the interaction of C-type lectin-like receptor 2 (CLEC-2) expressed by DCs, with podoplanin expressed by lymph node stromal cells (LNSCs). However, the underlying molecular mechanisms by which CLEC-2 influences DC migration remain elusive. Here, we show that CLEC-2-dependent DC migration is tightly controlled by tetraspanin CD37, a membrane-organizing protein. Our findings demonstrate a specific molecular interaction between CLEC-2 and CD37. Myeloid cells lacking CD37 (Cd37-/-) expressed less CLEC-2 on their surface compared to wild-type cells, indicating that CD37 is required to stabilize membrane expression of CLEC-2. In addition, CLEC-2-expressing DCs lacking CD37 showed impaired adhesion, migration velocity and displacement on LNSCs. Moreover, Cd37-/- DCs failed to form actin protrusions in a 3D collagen matrix upon podoplanin-induced CLEC-2 stimulation, phenocopying CLEC-2-deficient DCs (CD11c{Delta}CLEC-2). Microcontact printing experiments revealed that CD37 is required for CLEC-2 recruitment in the membrane to its ligand podoplanin. This study demonstrates that tetraspanin CD37 controls CLEC-2 membrane organization and provides new molecular insights underlying CLEC-2-dependent DC migration.

cell biology↗