Biology subjects

Chun, S. H.

Publications and source records attributed to Chun, S. H..

3 recordsLinked to original sources

bioRxiv2026

FLRT cell adhesion molecules counteract protocadherin-10-dependent cell segregation during cortical neuron migration

The processes that underlie the folding of the cerebral cortex of large mammals and the evolution of the smooth cortex of modern rodents are incompletely understood. Recent evidence highlighted adhesion-controlled neuronal migration as an important mechanism. Genetic deletion in mice of FLRT1 and FLRT3 cell-adhesion proteins perturbed cortical neuron migration, lead to region-specific neuronal clustering, and introduced cortical folds into the normally smooth mouse cortex, suggesting that Increased expression of FLRT protein may have contributed to cortex smoothening. Here, we identify protocadherin-10 (PCDH10) as a key regulator of neuronal clustering in this context. Using single-cell transcriptomics and spatial proteomics, we describe a cortical neuron subtype in which loss of FLRT1/3 triggers local upregulation of PCDH10 in a specific cortical region. Elevated PCDH10 drives homophilic adhesion and the formation of cell patches that segregate from FLR1/3-deficient migrating neurons. This segregation leads to discrete clustering of Flrt1/3-mutant neurons and correlates with the emergence of cortical folds. Consistent with an evolutionary role, comparative expression analysis showed reciprocal expression of FLRT3 and PCDH10, with high FLRT3 and low PCDH10 expression in the smooth mouse cortex, and the opposite pattern in the developing human cortex. Together, our findings reveal how the antagonism between different classes of cell adhesion molecules affects cortical neuron migration patterns, contributes to region-specific cortical folding and may have promoted evolutionary smoothening of the rodent cortex.

neuroscience↗

bioRxiv2025

Mus Musculus papillomavirus MmuPV1 resists restriction by human APOBEC3B

The single-stranded DNA deaminase APOBEC3B (A3B) is capable of potently restricting the replication of a range of viruses including retroviruses (cDNA) and herpesviruses (genomic DNA). However, these and likely other DNA virus families have evolved host species-specific counter-defenses that are equally potent and serve to protect viral DNA from restriction. Although high-risk human papillomavirus (HPV) infection triggers A3B upregulation, potentially as part of an antiviral response, the impact of this restriction factor on papillomavirus replication and pathogenesis has yet to be assessed. To study human A3B antiviral function in the absence of a species-specific counter-defense, here we ask whether human A3B is capable of restricting Mus musculus papillomavirus (MmuPV1) in cellulo and in vivo. First, we created human A3B and catalytic mutant A3B-E255A expressing FVB/N mice. Second, MmuPV1 gene expression and replication was quantified in primary keratinocytes from these animals and, surprisingly, enzymatically active human A3B caused no measurable impairment in viral transcript or DNA accumulation. Third, A3B, catalytic mutant A3B-E255A, and nontransgenic FVB/N animals were infected with MmuPV1 and similar pathologies were found regardless of A3B functionality. Thus, despite likely never being exposed to human A3B during evolution, MmuPV1 appears to be unaffected by this potent, primate-specific antiviral factor. These results suggest that MmuPV1 and perhaps papillomaviruses more broadly possess a conserved mechanism to efficiently escape restriction by human A3B and related DNA deaminases. IMPORTANCEHuman papillomaviruses (HPVs) are nearly ubiquitous, and persistent infection with high-risk types causes approximately 5% of cancers worldwide. Although HPV vaccination is effective for preventing infection, insufficient global coverage and a rising incidence of HPV-associated malignancies, such as oropharyngeal carcinoma, highlight the need to understand innate virus clearance mechanisms. APOBEC3 enzymes are a central component of the mammalian innate immune system and are hypothesized to restrict papillomavirus infection, particularly between species. Here, we establish mice that express the human antiviral enzyme APOBEC3B (A3B). Surprisingly, we find that human A3B is incapable of blocking the replication of a murine papillomavirus (Mus musculus papillomavirus 1, MmuPV1) in relevant primary cells from these animals or in infected tissues in vivo. These findings highlight the complexity of teasing apart host-pathogen interactions and suggest that papillomaviruses may have a general mechanism for escaping restriction by antiviral enzymes such as A3B.

microbiology↗

bioRxiv2024

Cortex Folding by Combined Progenitor Expansion and Adhesion-Controlled Neuronal Migration

Folding of the mammalian cerebral cortex into sulcal fissures and gyral peaks is the result of complex processes that are incompletely understood. Previously we showed that genetic deletion of Flrt1/3 adhesion molecules causes folding of the smooth mouse cortex into sulci resulting from increased lateral dispersion and faster neuron migration, without progenitor expansion. Here, we find that combining the Flrt1/3 double knockout with an additional genetic deletion that causes progenitor expansion, greatly enhances cortex folding. Expansion of intermediate progenitors by deletion of Cep83 results in enhanced formation of sulci. Expansion of apical progenitors by deletion of Fgf10 results in enhanced formation of gyri. Single cell transcriptomics and simulations suggest that changes in adhesive properties of cortical neurons, their proportions and densities in the cortical plate, combined with lateral dispersion during their radial migration are important folding parameters. These results identify key developmental mechanisms that cooperate to promote cortical gyrification. HIGHLIGHTSO_LICortex folding is enhanced by combining progenitor expansion and divergent migration. C_LIO_LIConcomitant expansion of intermediate progenitors results in the formation of sulci C_LIO_LIConcomitant expansion of apical progenitors results in the formation of gyri C_LIO_LIProgenitors differentially affect cortical neurons with distinct adhesive properties C_LI

neuroscience↗