Biology subjects

Raja, E.

Publications and source records attributed to Raja, E..

5 recordsLinked to original sources

bioRxiv2026

In vivo effects of inducible transgene expression of the age-associated glycogenes St6gal1 and Man1a on epidermal homeostasis

Glycosylation of cell-surface proteins plays several essential roles in cell-matrix interactions and receptor signaling, thereby contributing to tissue homeostasis and aging. In aged mouse skin, epidermal stem cells exhibit increased levels of a2,6-sialylated complex-type N-glycans alongside upregulation of glycogenes such as St6gal1 and Man1a; however, the functional importance of these glycosylation changes in vivo remains largely unknown. Here, we generated doxycycline-inducible transgenic mice expressing the age-related glycogenes St6gal1 and Man1a, either individually or in combination, using ubiquitous and epidermis-specific drivers. Lectin-based analyses with SNA and rHeltuba demonstrated corresponding alterations in glycosylation patterns in these mice. Transgenic Man1a induction reduced epidermal proliferation and epidermal thickness. In contrast, St6gal1 induction caused splenomegaly and elevated expression of inflammatory signature genes in the skin but did not measurably alter epidermal proliferation or morphology. Double transgenic mice exhibited a hybrid phenotype combining inflammatory and proliferative impairments, although comparison of ubiquitous and epidermis-specific induction indicated that the observed skin phenotypes depended on the epidermal expression of the transgenes. An SNA lectin-based pull-down assay followed by mass spectrometry identified candidate a2,6-sialylated proteins, including integrin family members, junctional proteins, and surface receptors, following induction of St6gal1 and Man1a. Together, these findings suggest that increased expression of the age-associated glycogenes St6gal1 and Man1a perturbs distinct aspects of epidermal homeostasis in vivo and identify candidate glycoproteins that may mediate these effects.

cell biology↗

bioRxiv2026

The epidermal stem cell-supporting matricellular protein fibulin 7 modulates skin inflammatory response in a psoriasis model

ECM composition and organization are greatly altered during inflammation but it is still elusive if ECM dynamics may protect tissue stem cells against aberrant inflammation. Fibulin 7 (encoded by Fbln7) is part of the basement membrane ECM where epidermal stem cells (EpSCs) reside. It supports the long-term potential of fast-cycling EpSCs and moderates aging-related inflammatory markers in keratinocytes. Here, we assessed fibulin 7s role during imiquimod (IMQ)-induced inflammation in 1-year-old mouse dorsal skin. We found that loss of Fbln7 aggravates epidermal inflammation, marked by increased epidermal thickness, proliferation, and phosphorylation of JNK (c-Jun N-terminal kinase). Fast-cycling EpSCs labeled with Slc1a3-creER-TdTomato demonstrated that IMQ-induced proliferation in Fbln7 KO mice is contributed by cell divisions in the suprabasal layers, a hallmark of inflammatory epidermal responses. EpSC transcriptomes further reveal IMQ-modulated genes that are more substantially affected in Fbln7 KO mice, including IL-17 pathway-related genes known in psoriasis pathogenesis. Mechanistically, fibulin 7 directly binds to IL-17A and decreases IL-17A-mediated p38 MAPK activation. In public human psoriasis datasets, FBLN7 is reduced in lesional skin compared with non-lesional or normal skin, and it is significantly correlated with common psoriasis-associated genes. Altogether, fibulin 7 is potentially beneficial to protect against skin inflammation.

cell biology↗

bioRxiv2025

Integrin-binding matricellular protein fibulin-5 maintains epidermal stem cell heterogeneity during skin aging

The extracellular matrix (ECM) is crucial in building the extracellular environment and translating extracellular information into biochemical signals that sustain organ functions. Fibulin-5 (Fbln5) is a multifunctional ECM protein essential for forming elastic fibers and regulating cellular functions by binding to integrins. While fibulin-5 expression decreases with age in human skin, the functional implications of this decrease, particularly in epidermal stem cell regulation, have remained largely unexplored. Here, we find that the knocking out of Fbln5 in mice results in early impairments of epidermal stem cell properties, similar to the chronological aging of the skin. The Fbln5 deficiency suppresses the expression of integrins and other cell junction proteins, leading to the inactivation of YAP signaling in epidermal stem cells. This reduction in YAP signaling results in the downregulation of the fast-cycling epidermal stem cell marker SLC1A3 in human skin and primary keratinocytes. These results suggest that, in addition to its known function in elastic fiber formation, fibulin-5 also plays a critical role in regulating the balance of epidermal stem cell populations during skin aging and coordinating the crosstalk between the extracellular environment and intracellular signaling.

developmental biology↗

bioRxiv2024

A novel genetic mouse model of fatal aortic dissection reveals massive inflammatory cell infiltration in the thoracic aorta

BackgroundAortic dissection (AD) is the separation of medial layers of the aorta and is a major cause of death in patients with connective tissue disorders such as Marfan syndrome. However, molecular triggers instigating AD, its temporospatial progression, and how vascular cells in each vessel layer interact and participate in the pathological process remain incompletely understood. To unravel the underlying molecular mechanism of AD, we generated a spontaneous AD mouse model. MethodsWe incorporated a novel missense variant (p.G234D) in FBN1, the gene for fibrillin-1, identified in a non-syndromic familial AD patient into mice using CRISPR/Cas9 system. We performed histopathological analyses of the aortic lesions by histology, immunofluorescence staining, electron microscopy, synchrotron-based imaging and single-cell (sc)RNA-sequencing. Biochemical analysis was performed to examine the binding capacity of mutant human FBN1G234D protein to latent Tgf{beta} binding proteins (LTBPs), and signaling pathways in the mutant aortic wall were examined by western blot analysis. Results50% of the Fbn1G234D/G234D mutant mice died within 5 weeks of age from multiple intimomedial tears that expanded longitudinally and progressed to aortic rupture accompanied by massive immune cell infiltration. scRNA-sequencing, validated by immunostaining, revealed a significant increase in MHC class II-positive pro-inflammatory macrophages and monocytes at the site of intima tears with upregulation of MMP2/9 and marked disruption of elastic lamina. Subendothelial matrices, such as type IV collagen and laminin, expanded into the medial layer, where fibronectin expression was highly upregulated. Fbn1G234D/G234D endothelial cells exhibited altered mechanosensing with loss of parallel alignment to blood flow and upregulation of VCAM-1 and ICAM-1, all of which likely contributed to the infiltration of immune cells. Biochemically, FBN1G234D lost the ability to bind to latent TGF{beta} binding protein (LTBP)-1, -2, and -4, resulting in the downregulation of TGF{beta} signaling in the aortic wall. ConclusionsWe show that dynamic interactions involving endothelial cells (ECs) and macrophages/monocytes in the intima, where the ECM microenvironment is altered with the reduced TGF{beta} signaling, contributes to the initiation of AD. Our novel AD mouse model provides a unique opportunity to identify target molecules involved in the intimomedial tears that can be utilized for development of therapeutic strategies.

pathology↗

bioRxiv2022

The extracellular matrix fibulin 7 maintains epidermal stem cell heterogeneity during skin aging

Tissue stem cells divide infrequently as a protective mechanism against internal and external stresses associated with aging. Here, we demonstrate that slow- and fast-cycling interfollicular epidermal stem cells in mouse skin undergo distinct aging processes. Two years of lineage tracing reveals that Dlx1+ slow-cycling clones expanded into the fast-cycling stem cell territory, while the number of Slc1a3+ fast-cycling clones gradually declined. Transcriptome analysis further indicated that the molecular properties of each stem cell population are altered with age. Mice lacking fibulin 7, an extracellular matrix (ECM), show early impairments resembling epidermal stem cell aging, such as the loss of fast-cycling clones, delayed wound healing, and increased expression of inflammation- and differentiation-related genes. Fibulin 7 interacts with structural ECM and matricellular proteins, and the overexpression of fibulin 7 in primary keratinocytes results in slower proliferation in the absence or presence of inflammatory cytokine IL-6. Thus, these results suggest that fibulin 7 plays a crucial role in maintaining tissue resilience and epidermal stem cell heterogeneity during skin aging.

developmental biology↗