Biology subjects

Hannan, A.

Publications and source records attributed to Hannan, A..

7 recordsLinked to original sources

bioRxiv2026

Molecular profiling implicates immune-driven adaptive homeostasis in maintaining intraocular pressure with age

Aging and ocular hypertension are primary risk factors for glaucoma - a major cause of blindness worldwide. Ocular hypertension results from dysfunction in the outflow tissues - the trabecular meshwork (TM) and Schlemm's canal (SC), which are key regulators of intraocular pressure (IOP) homeostasis. Despite lifelong multifaceted stress to the outflow pathway, ocular hypertension sufficient to develop glaucoma occurs in only a minority of individuals. The mechanisms that preserve physiological IOP with aging in most individuals remain poorly understood. Using single-cell RNA sequencing and protein validation in mouse outflow tissues, we found that aging is accompanied by subtype-specific changes in TM cells, including altered extracellular matrix maintenance, reduced trophic signaling to SC, and increased profibrotic signaling. Coincident with these changes, we observed age-dependent immune remodeling, marked by increased macrophage abundance in outflow tissues. Our model predicts that macrophages maintain SC homeostasis via VEGFA signaling - normally supplied by the TM and required for normal SC function, but impaired with age. This pattern supports a paradigm in which adaptive immune remodeling contributes to preserving IOP homeostasis despite progressive aging-associated cellular dysfunction. More broadly, we identify the TM/SC outflow pathway as a model for understanding how aging tissues preserve physiological function through coordinated structural, trophic, and adaptive immune remodeling.

cell biology↗

bioRxiv2026

FGF Signaling Potentiates Müller Glia for Mammalian Retinal Regeneration

Muller glia possess latent regenerative potential that could be harnessed to restore retinal neurons lost to injury or disease. Although fibroblast growth factor (FGF) signaling is upregulated following retinal damage, its role in mammalian retinal regeneration remains unclear. Here, we investigated the function of FGF signaling in Muller glial reprogramming using genetic, pharmacological, and single-cell transcriptomic approaches. Activation of FGF signaling alone was insufficient to induce Muller glial proliferation in the mouse retina. However, conditional deletion of FGFR1/2 in Muller glia abolished regenerative responses induced by multiple independent pathways, demonstrating that FGF signaling is essential for regenerative competence. Mechanistically, loss of FGF signaling impaired sustained ERK/MAPK activation following injury, while MEK/ERK inhibition phenocopied the regenerative defect. Conversely, constitutive MEK activation induced limited Muller glial proliferation in the absence of injury. Although STAT3/5 inhibition synergized with Activin-A to promote robust proliferation and neurogenic gene expression, it failed to rescue regeneration in FGF-deficient Muller glia. Single-cell RNA sequencing revealed that FGF signaling suppresses multiple anti-regenerative programs, including Hes1, S1pr1, p27, NF-{kappa}B, and p300/CBP activity. Together, these findings identify FGF signaling as a critical permissive regulator of mammalian retinal regeneration that potentiates Muller glia through sustained ERK activation and suppression of transcriptional barriers to regeneration.

Developmental Biology↗

bioRxiv2025

Single-Cell Characterization of Anterior Segment Development: Cell Types, Pathways, and Signals Driving Formation of the Trabecular Meshwork and Schlemm's Canal

Morphogenesis of the anterior segment (AS) is crucial for healthy ocular physiology and vision but is only partially understood. The Schlemms canal (SC) and trabecular meshwork (TM) are essential drainage tissues within the AS, and their proper development and function are critical for maintaining normal intraocular pressure; abnormalities in either tissue can result in elevated pressure and glaucoma. Here, we use single-cell transcriptomic profiling to provide high-resolution molecular detail of AS development with a particular focus on SC and TM. We report transcriptomes for [~]130,000 single cells at key developmental stages from postnatal day 2 (P2) to P60. We provide the first annotation of cell types across these developmental stages and crucial information about dynamic changes in pathways/gene expression. Further, we trace developmental trajectories for TM cell and SC endothelial cell (SEC) subtypes and determine genes and signaling networks driving their specific cell fates. We demonstrate dynamic changes in signaling interactions between SC and the TM cells during their synchronized development. Collectively, our data lay a deep molecular foundation for AS development that will direct understanding of normal ocular physiology, glaucoma, and other AS conditions.

developmental biology↗

bioRxiv2024

Psilocybin Reduces Grooming in the SAPAP3 Knockout Mouse Model of Compulsive Behaviour

Psilocybin is a serotonergic psychedelic compound which shows promise for treating compulsive behaviours. This is particularly pertinent as compulsive disorders require research into new pharmacological treatment options as the current frontline treatments such as selective serotonin reuptake inhibitors, require chronic administration, have significant side effects, and leave almost half of the clinical population refractory to treatment. In this study, we investigated psilocybin administration in male and female SAPAP3 knockout (KO) mice, a well-validated mouse model of obsessive compulsive and related disorders. We assessed the effects of acute psilocybin (1 mg/kg, intraperitoneal) administration on head twitch and locomotor behaviour as well as anxiety- and compulsive-like behaviours at multiple time-points (1-, 3- and 8-days post-injection). While psilocybin did not have any effect on anxiety-like behaviours, we revealed for the first time that acute psilocybin administration led to enduring reductions in compulsive behaviour in male SAPAP3 KO mice and reduced grooming behaviour in female WT and SAPAP3 KO mice. We also found that psilocybin increased locomotion in wild-type littermates but not in SAPAP3 KO mice, suggesting in vivo serotonergic dysfunctions in KO animals. On the other hand, the typical head-twitch response following acute psilocybin (confirming its hallucinogenic-like effect at this dose) was observed in both genotypes. Our novel findings suggest that acute psilocybin may have potential to reduce compulsive-like behaviours (up to 1 week after a single injection). Our study can inform future research directions as well as supporting the utility of psilocybin as a novel treatment option for compulsive disorders.

neuroscience↗

bioRxiv2024

Phospholipase Cgamma regulates lacrimal gland branching by competing with PI3K in phosphoinositide metabolism

Although the regulation of branching morphogenesis by spatially distributed cues is well established, the role of intracellular signaling in determining the branching pattern remains poorly understood. In this study, we investigated the regulation and function of phospholipase C gamma (PLC{gamma}) in Fibroblast Growth Factor (FGF) signaling in lacrimal gland development. We showed that deletion of PLC{gamma}1 in the lacrimal gland epithelium leads to ectopic branching and acinar hyperplasia, which was phenocopied by either mutating the PLC{gamma}1 binding site on Fgfr2 or disabling any of its SH2 domains. PLC{gamma}1 inactivation did not change the level of Fgfr2 or affect MAPK signaling, but instead led to sustained AKT phosphorylation due to increased PIP3 production. Consistent with this, PLC{gamma}1 mutant phenotype can be reproduced by elevation of PI3K signaling in Pten knockout and attenuated by blocking AKT signaling. This study demonstrated that PLC{gamma} modulates PI3K signaling by shifting phosphoinositide metabolism, revealing an important role of signaling dynamics in conjunction with spatial cues in shaping branching morphogenesis.

developmental biology↗

bioRxiv2024

Crk mediates Csk-Hippo signaling independently of Yap tyrosine phosphorylation to induce cell extrusion

Src family kinases (SFKs), including Src, Fyn and Yes, play important roles in development and cancer. Despite being first discovered as the Yes-associated protein, the regulation of Yap by SFKs remains poorly understood. Here, through single-cell analysis and genetic lineage tracing, we show that the pan-epithelial ablation of C-terminal Src kinase (Csk) in the lacrimal gland unleashes broad Src signaling but specifically causes extrusion and apoptosis of acinar progenitors at a time when they are shielded by myoepithelial cells from the basement membrane. Csk mutants can be phenocopied by constitutively active Yap and rescued by deleting Yap or Taz, indicating a significant functional overlap between Src and Yap signaling. Although Src-induced tyrosine phosphorylation has long been believed to regulate Yap activity, we find that mutating these tyrosine residues in both Yap and Taz fails to perturb mouse development or alleviate the Csk lacrimal gland phenotype. In contrast, Yap loses Hippo signaling-dependent serine phosphorylation and translocates into the nucleus in Csk mutants. Further chemical genetics studies demonstrate that acute inhibition of Csk enhances Crk/CrkL phosphorylation and Rac1 activity, whereas removing Crk/CrkL or Rac1/Rap1 ameliorates the Csk mutant phenotype. These results show that Src controls Hippo-Yap signaling through the Crk/CrkL-Rac/Rap axis to promote cell extrusion.

developmental biology↗

bioRxiv2022

KineticMSI, an R-based framework for relative quantification of spatial isotopic incorporation in mass spectrometry imaging experiments

Kinetic mass spectrometry imaging (kMSI) integrates imaging-MS with stable isotope labelling to elucidate metabolic fluxes in a spatiotemporal manner. kMSI studies are hampered by high volumes of complex data and a lack of computational workflows for data analysis that additionally address replicated experiments. To meet these challenges, we developed KineticMSI, an open-source R-based tool for processing and analyzing kMSI datasets. KineticMSI includes statistical tools to quantify tracer incorporation across replicated treatment groups spatially in tissues. It allows users to make data-driven decisions by elucidating affected pathways associated with changes in metabolic turnover. We demonstrate a validation of our method by identifying metabolic changes in the hippocampus of a transgenic Huntingtons disease (HD) mouse model as compared to wild-type mice. We discovered significant changes in metabolism of neuronal cell body lipids (phosphatidylinositol and cardiolipins) in HD mice, previously masked by conventional statistical approaches that compare mean tracer incorporation across brain regions.

bioinformatics↗