Biology subjects

Liao, S.-M.

Publications and source records attributed to Liao, S.-M..

4 recordsLinked to original sources

bioRxiv2025

Identification of cellular and molecular risk signatures for progression to late-stage age-related macular degeneration using the 9-step Minnesota Grading System

Age-related macular degeneration (AMD) is a complex multifactorial disease, and the molecular mechanisms underpinning the progression of intermediate AMD to geographic atrophy are not fully understood. To better understand mechanisms driving progression, we performed bulk RNA sequencing on dissected macular and peripheral RPE/choroid and neural retina tissue from postmortem human eyes graded using the 9-step Minnesota Grading System (MGS). Binning of intermediate AMD cases into three distinct groups (AMD3L, AMD3M, AMD3H) based on the 5-year risk of progression enabled identification of distinct gene and pathway changes associated with progression to late-stage disease. Identified changes in gene expression were validated using ELISA or histological methods. RPE-specific genes and lipid metabolic pathways showed a transient increase in AMD3L followed by a pronounced decrease in AMD3H. In AMD3H, immune response genes such as C3, TREM2, and OLR1 were upregulated when compared to AMD3L samples, as well as genes specific to Muller glia/astrocytes (NGFR, SPP1, GPX3). Our findings support complement inhibition as a promising therapeutic option for slowing conversion to advanced AMD and identify macrophage and Muller/astrocyte genes as potential cell types to target in AMD. Further, we demonstrate the value of combining emerging, outcomes-based, clinically relevant grading systems with profiling technologies to generate new insights into ocular diseases. HighlightsO_LIIntermediate AMD (AMD3) can be further divided into 3 stages - AMD3L (low risk), AMD3M (intermediate risk), AMD3H (high risk) - using the MGS9 grading system based on the risk of disease progression to late AMD. C_LIO_LIRNA sequencing of the macular RPE/choroid shows opposing changes in gene expression of multiple biological pathways for both RPE and immune cells between AMD3L and AMD3H stages. C_LIO_LIIn the macular neural retina, most biological pathways were downregulated in AMD2 (early AMD) but upregulated in AMD4 (late AMD) compared to AMD1 (non-AMD control). C_LIO_LIMolecular and cellular signatures associated with a high risk of progression to AMD4 include activation of complement C3, two subtypes of macrophages expressing either TREM2 or OLR1, and Muller glia/astrocytes as evidenced by the upregulation of GFAP and NGFR. C_LIO_LIUnderstanding the roles of these high-risk associated genes in AMD progression will facilitate the development of new treatments that prevent or delay the irreversible central vision loss in AMD patients. C_LI

neuroscience↗

bioRxiv2025

A brainstem map of orofacial rhythms

Rhythmic orofacial movements, such as eating, drinking, or vocalization, are controlled by distinct premotor oscillator networks in the brainstem. Orofacial movements must be coordinated with rhythmic breathing to avoid aspiration and because they share muscles. Understanding how brainstem circuits coordinate rhythmic motor programs requires neurophysiological measurements in behaving animals. We used Neuropixels probe recordings to map brainstem neural activity related to breathing, licking, and swallowing in mice drinking water. Breathing and licking rhythms were tightly coordinated and phase-locked, whereas intermittent swallowing paused breathing and licking. Multiple clusters of neurons, each recruited during different orofacial rhythms, delineated a lingual premotor network in the intermediate nucleus of the reticular formation (IRN). Local optogenetic perturbation experiments identified a region in the IRN where constant stimulation can drive sustained rhythmic licking, consistent with a central pattern generator for licking. Stimulation to artificially induce licking showed that coupled brainstem oscillators autonomously coordinated licking and breathing. The brainstem oscillators were further patterned by descending inputs at moments of licking initiation. Our results reveal the logic governing interactions of orofacial rhythms during behavior and outline their neural circuit dynamics, providing a model for dissecting multi-oscillator systems controlling rhythmic motor programs.

neuroscience↗

bioRxiv2024

APOE Impacts Lipid Trafficking in Retinal Pigment Epithelium Cells

Age-related macular degeneration (AMD) is typified by the formation of lipid-rich drusen under the retinal pigment epithelium (RPE) layer. Apolipoprotein E (APOE) is a known genetic risk factor for AMD and a substantial component of drusen, however, the mechanism by which APOE variants contribute to AMD pathology remains unclear. APOE is the primary cholesterol and lipid transport protein of the central nervous system, as well as a component circulating lipoproteins. To better understand how APOE-dependent lipid transport may impact AMD risk, we generated isogenic APOE iPS-RPE cells expressing each of the common human APOE isoforms, as well as an APOE knockout line. APOE knockout cells showed significant morphological and barrier function deficits, suggesting that APOE is essential for RPE health. Furthermore, we observed that APOE abundance is isoform-dependent in RPE cells and that lipid transport is deficient in APOE knockout RPE cells, as well as in RPE cells expressing APOE2, a variant associated with higher risk of AMD. Contrastingly, cells expressing APOE4 seem to respond strongly to lipid challenges by upregulating APOE to support efficient lipid transport. Our results suggest that disease associated APOE variants may impact lipid transport in RPE, contributing to the formation of drusen and impairing cellular function.

cell biology↗

bioRxiv2022

A change in behavioral state switches the pattern of motor output that underlies rhythmic head and orofacial movements

The breathing rhythm serves as a reference that paces orofacial motor actions and orchestrates active sensing. Past work reports that pacing occurs solely at a fixed phase relative to sniffing. We reevaluated this constraint as a function of exploratory behavior. Allocentric and egocentric rotations of the head and the electromyogenic activity of the underlying motoneurons for head and orofacial movements were recorded in free-ranging rats as they searched for food. We found that a change in state from foraging to rearing is accompanied by a change in the phase of muscular activation relative to sniffing, so that pacing now occurs at one of two phases. Further, head-turning is biased such that an animal gathers a novel sample of its environment upon inhalation. In toto, the coordination of active sensing has a previously unrealized computational complexity that, in principle, can emerge from hindbrain circuits with fixed architecture and credible synaptic time-delays.

neuroscience↗