Biology subjects

Saenz, J.

Publications and source records attributed to Saenz, J..

4 recordsLinked to original sources

bioRxiv2025

Multimerin1, not Galectin-8, Promotes Gastric Chief Cell Differentiation by Tempering WNT Signaling

Galectins are a family of proteins that bind galactose-containing glycans. One member, galectin-8, preferentially binds galactose that contains a terminal sulfate. Aberrant expression and secretion of sulfated glycosylation epitopes, such as 3-Sulfo-LeA/C, is a feature of high-risk human foregut metaplasias. In addition, recent work has demonstrated that 3-Sulfo-LeC is a marker of mature murine zymogenic chief cells of the stomach and that 3-Sulfo-LeC epitope is secreted via cathartocytosis during the cellular transition to a metaplastic state. Based on those findings, we used Lgals8-/-mice, to determine whether galectin-8 might play a role in chief cell homeostasis. We observed delayed gastric differentiation in the Lgals8-/-mice and discovered that this phenotype was due to an unappreciated deletion of Mmrn1 and Snca in the Lgals8-/- line. We show that multimerin-1 tempers WNT stimulation of the gastric corpus at an early age, as evidenced by nuclear beta-catenin staining and proliferation throughout the gland. Because multimerin-1 is synthesized and secreted from endothelial cells and not from the epithelial compartment, these data uncover a role for mesodermal cells in epithelial developmental and maturation of the mouse stomach. As prior studies have suggested galectin-8 and multimerin-1 have overlapping functions albeit, divergent with respect to bone, future studies using pure knockouts are necessary to refine these phenotypes.

developmental biology↗

bioRxiv2025

Illuminating the Role of A-to-I Editing in Gastric Cancer using EndoVIA 2.0

Background & AimsAdenosine-to-inosine (A-to-I) RNA editing is an essential post-transcriptional modification catalyzed by ADAR enzymes, and emerging evidence suggests its dysregulation can contribute to cancer. However, technical barriers have hindered spatial analysis of editing activity in formalin-fixed paraffin-embedded (FFPE) tissues--an abundant but challenging sample type. Here, we introduce EndoVIA 2.0, an optimized immunostaining assay that enables spatial detection of edited RNAs in FFPE tissues. MethodsUsing human Endonuclease V (hEndoV) as a molecular affinity reagent, we developed a calcium-dependent staining workflow compatible with crosslinked tissues. EndoVIA 2.0 was validated in cell lines with altered ADAR1 expression, fresh frozen tissues, gastric organoids, and FFPE tissue sections. Quantitative imaging was combined with machine-learning segmentation and spatial analysis. ResultsEndoVIA 2.0 successfully detected A-to-I editing changes in ADAR1 knockout and overexpression models and revealed differential editing patterns across tissues. In gastric organoids and FFPE tissues, the assay spatially resolved editing heterogeneity and distinguished ADAR1-deficient from ADAR1-sufficient cells. Application to long-archived lung and breast cancer FFPE tissues suggest EndoVIA 2.0s broad utility and potential of capturing disease-associated hyper-editing in malignant samples. ConclusionsEndoVIA 2.0 enables robust, spatial detection of A-to-I editing in FFPE tissues--circumventing the limitations of RNA extraction and unlocking access to archived clinical specimens. This platform lays the foundation for mapping RNA editing dynamics in cancer progression and may support future biomarker discovery.

molecular biology↗

bioRxiv2023

KAT2 paralogs prevent dsRNA accumulation and interferon signaling to maintain intestinal stem cells

Histone acetyltransferases KAT2A and KAT2B are paralogs highly expressed in the intestinal epithelium, but their functions are not well understood. In this study, double knockout of murine Kat2 genes in the intestinal epithelium was lethal, resulting in robust activation of interferon signaling and interferon-associated phenotypes including the loss of intestinal stem cells. Use of pharmacological agents and sterile organoid cultures indicated a cell-intrinsic double-stranded RNA trigger for interferon signaling. Acetyl-proteomics and dsRIP-seq were employed to interrogate the mechanism behind this response, which identified mitochondria-encoded double-stranded RNA as the source of intrinsic interferon signaling. Kat2a and Kat2b therefore play an essential role in regulating mitochondrial functions as well as maintaining intestinal health. Highlights of the workO_LIKat2a and Kat2b double knockout in the murine intestinal epithelium triggers activation of the interferon signaling pathway C_LIO_LIKat2a/Kat2b knockout leads to intestinal stem cell loss and other mucosal phenotypes consistent with interferon activation C_LIO_LIHistone PTM mass spec profiling reveals the first in vivo study showing H3K9ac-specific loss with Kat2a and Kat2b double knockout, yet without correlation to interferon signaling pathway genes C_LIO_LIComprehensive proteomic analysis identifies non-histone acetyl-lysine targets of KAT2 in the mouse intestine in vivo, including mitochondrial proteins C_LIO_LIMitochondrial function is compromised upon Kat2 loss C_LIO_LIdsRIP-seq identifies double-stranded RNA from the mitochondria as a trigger for the intrinsic immune response upon Kat2 double knockout C_LI

molecular biology↗

bioRxiv2022

A novel pH-sensitive reporter reveals the cocaine-regulated trafficking of dopamine transporters in neuronal processes

The dopamine transporter (DAT) mediated DA reuptake is a major molecular mechanism for termination of dopaminergic signaling in the brain. Psychoactive substances such as cocaine act by inhibition of plasma membrane DAT function as well as by altering its expression. The precise manner and mechanism by which cocaine regulates DAT trafficking, especially at neuronal processes, are poorly understood. We have now engineered a novel pH-sensitive reporter for DAT by conjugating pHluorin to the second exofacial loop of human DAT. We show that DAT-pHluorin can be used to study DAT localization and its dynamic trafficking at neuronal processes. Using DAT-pHluorin we show that unlike neuronal soma and dendrites, which contain majority of the DATs in weakly acidic intracellular compartments, axonal DATs at both shafts and boutons are primarily (75%) localized to the plasma membrane, while varicosities contain abundant intracellular DAT within acidic intracellular structures. Using this novel reporter, we show, for the first time, that cocaine exposure leads to a brief DAT internalization followed by membrane reinsertion that lasts for days. We further show that the cocaine-induced DAT trafficking is sensitive to the activities of Synaptojanin1 phosphatase. Thus, our study using the newly engineered DAT optical reporter reveals the previously unknown dynamics and molecular regulation for cocaine-regulated DAT trafficking in neuronal processes.

neuroscience↗