Biology subjects

Shaffer, J.

Publications and source records attributed to Shaffer, J..

9 recordsLinked to original sources

bioRxiv2026

Pre-analytical delay as a dominant confounder in blood RNA-seq: Rapid ex vivo gene expression changes in EDTA blood

Although the impact of delayed processing on gene expression in EDTA blood has been well documented using targeted assays and microarray platforms, the emergence of next-generation RNA sequencing (RNA-seq) has not yet been leveraged to systematically compare these effects against stabilized whole blood collection systems. Notably, no study has performed a time course RNA-seq analysis with human bulk RNA of matched EDTA and PAXgene blood RNA samples drawn from the same subjects. EDTA is still widely used for gene expression analysis studies. Yet, the genome-wide dynamics by which EDTA blood transcriptomes deviate from a stabilized reference over time remain poorly defined. This represents an important methodological gap, given the increasing reliance on RNA-seq for biomarker discovery, clinical transcriptomics and diagnostics.

Molecular Biology↗

bioRxiv2025

Dynamic and Catalytic Multiphase Coacervates

Subcellular organization is critical for myriad cellular functions, including spatiotemporal regulation of biocatalysts. Liquid-liquid phase separation contributes to intracellular organization by providing microenvironments that sequester biomolecules and control their activities. Although catalytic reactions in multiphase coacervate systems are important for living cells, provide functionality to artificial systems, and may aid understanding of how metabolism first arose, they are not well understood. Here we report an artificial multiphase system in which catalytically active droplets containing three distinct coexisting coacervate phases undergo reorganization in response to pH, enabling control over chemical reactions. Catalysis is performed by an inner, polyhistidine-dense coacervate phase with inherent nonenzymatic activity. We show how phase composition, in addition to pH, affects catalytic activity, and how the addition of enzymes that alter local pH provides a means to regulate composition and catalysis. By exploiting competitive interplay between intramolecular self-association and intermolecular complexation among polymers within multiphase coacervate systems, it was possible to (re)organize and tune the reactivity of dynamic synthetic biological systems beyond what is possible for single-phase coacervates. Such approaches could prove valuable in designing artificial cells and related microreactor systems capable of catalyzing and controlling complex chemical and biochemical processes.

biochemistry↗

bioRxiv2024

AI-readiness for Biomedical Data: Bridge2AI Recommendations

Biomedical research is rapidly adopting artificial intelligence (AI). Yet the inherent complexity of biomedical data preparation requires implementing actionable, robust criteria for ethical and explainable AI (XAI) at the "pre-model" stage, encompassing data acquisition, detailed transformations, and ethical governance. Simple conformance to FAIR (Findable, Accessible, Interoperable, Reusable) Principles is insufficient. Here, we define criteria and practices for reliable AI-readiness of biomedical data, developed by the NIH Bridge to Artificial Intelligence (Bridge2AI) Standards Working Group across seven core dimensions of dataset AI-readiness: FAIRness, Provenance, Characterization, Ethics, Pre-model Explainability, Sustainability, and Computability. Conformance to these criteria provides a basis for pre-model scientific rigor and ethical integrity, mitigating downstream risks of bias and error prior to AI modeling. We apply and evaluate these standards across all four Bridge2AI flagship datasets, spanning functional genomics to clinical medicine, and encode them in machine-actionable metadata bound to the datasets. This framework sets a benchmark for preparing ethical, reusable datasets in biomedical AI and provides standardized methods for reliable pre-model data evaluation.

bioinformatics↗

bioRxiv2022

The carnitine shuttle links mitochondrial metabolism to histone acetylation and lipogenesis

Acetyl-CoA is a central metabolite used for lipid synthesis in the cytosol and histone acetylation in the nucleus, among other pathways. The two major precursors to acetyl-CoA in the nuclear-cytoplasmic compartment are citrate and acetate, which are processed to acetyl-CoA by ATP-citrate lyase (ACLY) and acyl-CoA synthetase short-chain 2 (ACSS2), respectively. While some evidence has suggested the existence of additional routes to nuclear-cytosolic acetyl-CoA, such pathways remain poorly defined. To investigate this, we generated cancer cell lines lacking both ACLY and ACSS2. Unexpectedly, and in contrast to observations in fibroblasts, ACLY and ACSS2 double knockout (DKO) cancer cells remain viable and proliferate, maintain pools of cytosolic acetyl-CoA, and are competent to acetylate proteins in both cytosolic and nuclear compartments. Using stable isotope tracing, we show that both glucose and fatty acids feed acetyl-CoA pools and histone acetylation in DKO cells. Moreover, we provide evidence for the carnitine shuttle and carnitine acetyltransferase (CrAT) as a substantial pathway to transfer two-carbon units from mitochondria to cytosol independent of ACLY. Indeed, in the absence of ACLY, glucose can feed fatty acid synthesis in a carnitine responsive and CrAT-dependent manner. This work defines a carnitine-facilitated route to produce nuclear-cytosolic acetyl-CoA, shedding light on the intricate regulation and compartmentalization of acetyl-CoA metabolism

cell biology↗

bioRxiv2021

Targeted Neuronal Activation of the Gastrointestinal Tract Shapes the Environment of the Gut in Mice

The gastrointestinal (GI) tract is extensively innervated by intrinsic neurons of the enteric nervous system (ENS) and extrinsic neurons of the central nervous system and peripheral ganglia, which together regulate gut physiology. The GI tract also harbors a diverse microbiome, but interactions between the ENS and the microbiome remain poorly understood. Herein, we activate choline acetyltransferase (ChAT)-expressing or tyrosine hydroxylase (TH)-expressing gut-associated neurons in mice to determine effects on intestinal microbial communities and their metabolites, as well as on host physiology. The resulting multi-omics datasets support broad roles for discrete peripheral neuronal subtypes in shaping microbiome structure, including modulating bile acid profiles and fungal colonization. Physiologically, activation of either ChAT+ or TH+ neurons increases fecal output, while only ChAT+ activation results in increased colonic migrating motor complexes and diarrhea-like fluid secretion. These findings suggest that specific subsets of peripherally-activated ENS neurons differentially regulate the gut microbiome and GI physiology in mice, without involvement of signals from the brain.

physiology↗

bioRxiv2019

Ultra-low input single tube linked-read library method enables short-read NGS systems to generate highly accurate and economical long-range sequencing information for de novo genome assembly and haplotype phasing

Long-range sequencing information is required for haplotype phasing, de novo assembly and structural variation detection. Current long-read sequencing technologies can provide valuable long-range information but at a high cost with low accuracy and high DNA input requirement. We have developed a single-tube Transposase Enzyme Linked Long-read Sequencing (TELL-Seq) technology, which enables a low-cost, high-accuracy and high-throughput short-read next generation sequencer to routinely generate over 100 Kb long-range sequencing information with as little as 0.1 ng input material. In a PCR tube, millions of clonally barcoded beads are used to uniquely barcode long DNA molecules in an open bulk reaction without dilution and compartmentation. The barcode linked reads are used to successfully assemble genomes ranging from microbes to human. These linked-reads also generate mega-base-long phased blocks and provide a cost-effective tool for detecting structural variants in a genome, which are important to identify compound heterozygosity in recessive Mendelian diseases and discover genetic drivers and diagnostic biomarkers in cancers.

genomics↗

bioRxiv2019

Novel genetic loci affecting facial shape variation in humans

The human face represents a combined set of highly heritable phenotypes, but knowledge on its genetic architecture remains limited despite the relevance for various fields of science and application. A series of genome-wide association studies on 78 facial shape phenotypes quantified from 3-dimensional facial images of 10,115 Europeans identified 24 genetic loci reaching genome-wide significant association, among which 17 were previously unreported. A multi-ethnic study in additional 7,917 individuals confirmed 13 loci including 8 unreported ones. A global map of polygenic face scores assembled facial features in major continental groups consistent with anthropological knowledge. Analyses of epigenomic datasets from cranial neural crest cells revealed abundant cis-regulatory activities at the face-associated genetic loci. Luciferase reporter assays in neural crest progenitor cells highlighted enhancer activities of several face-associated DNA variants. These results substantially advance our understanding of the genetic basis underlying human facial variation and provide candidates for future in-vivo functional studies.

genomics↗

bioRxiv2019

Rapid phenotypic and metabolomic domestication of wild Penicillium molds on cheese

Fermented foods provide novel ecological opportunities for natural populations of microbes to evolve through successive recolonization of resource-rich substrates. Comparative genomic data have reconstructed the evolutionary histories of microbes adapted to food environments, but experimental studies directly demonstrating the process of domestication are lacking for most fermented food microbes. Here we show that during the repeated colonization of cheese, phenotypic and metabolomic traits of wild Penicillium molds rapidly change to produce mutants with properties similar to industrial cultures used to make Camembert and other bloomy rind cheeses. Over a period of just a few weeks, populations of wild Penicillium strains serially passaged on cheese resulted in the reduction or complete loss of pigment, spore, and mycotoxin production. Mutants also had a striking change in volatile metabolite production, shifting from production of earthy or musty volatile compounds (e.g. geosmin) to fatty and cheesy volatiles (e.g. 2-nonanone, 2-undecanone). RNA-sequencing demonstrated a significant decrease in expression of 356 genes in domesticated mutants, with an enrichment of many secondary metabolite production pathways in these downregulated genes. By manipulating the presence of neighboring microbial species and overall resource availability, we demonstrate that the limited competition and high nutrient availability of the cheese environment promote rapid trait evolution of Penicillium molds.\n\nIMPORTANCEIndustrial cultures of filamentous fungi are used to add unique aesthetics and flavors to cheeses and other microbial foods. How these microbes adapted to live in food environments is generally unknown as most microbial domestication is unintentional. Our work demonstrates that wild molds closely related to the starter culture Penicillium camemberti can readily lose undesirable traits and quickly shift toward producing desirable aroma compounds. In addition to experimentally demonstrating a putative domestication pathway for P. camemberti, our work suggests that wild Penicillium isolates could be rapidly domesticated to produce new flavors and aesthetics in fermented foods.

microbiology↗

bioRxiv2018

A novel method for systematic genetic analysis and visualization of phenotypic heterogeneity applied to orofacial clefts

Phenotypic heterogeneity is a hallmark of complex traits, and genetic studies may focus on the trait as a whole or on individual subgroups. For example, in orofacial clefting (OFC), three subtypes - cleft lip (CL), cleft lip and palate (CLP), and cleft palate (CP) have been studied separately and in combination. It is more challenging, however, to dissect the genetic architecture and describe how a given locus may be contributing to distinct subtypes of a trait. We developed a framework for quantifying and interpreting evidence of subtype-specific or shared genetic effects in complex traits. We applied this technique to create a \"cleft map\" of the association of 30 genetic loci with three OFC subtypes. In addition to new associations, we found loci with subtype-specific effects (e.g., GRHL3 (CP), WNT5A (CLP)), as well as loci associated with two or all three subtypes. We cross-referenced these results with mouse craniofacial gene expression datasets, which identified promising candidate genes. However, we found no strong correlation between OFC subtypes and expression patterns. In aggregate, the cleft map revealed neither subtype-specific nor shared genetic effects operate in isolation in OFC architecture. Our approach can be easily applied to any complex trait with distinct phenotypic subgroups.

genetics↗