Biology subjects

Bernard, D. J.

Publications and source records attributed to Bernard, D. J..

16 recordsLinked to original sources

bioRxiv2026

An efficient system for production of highly purified inhibins using mammalian cell expression and tandem affinity purification

Inhibin A and B (InhA and InhB) are potent negative regulators of follicle-stimulating hormone (FSH), which is essential for female fertility. InhA and InhB are heterodimeric transforming growth factor {beta} (TGF-{beta}) family ligands consisting of an inhibin (inh) subunit disulfide linked to an inhibin {beta}A or {beta}B (inh{beta}A, inh{beta}B) subunit, respectively. During purification, inhibins must be separated from activins (inh{beta}A or inh{beta}B homodimers), which always form when producing inhibins, and have the opposite effect on FSH synthesis. Current inhibin purification methods are technically challenging, require reagents that are not generally available, result in low purity or contamination with activins, or employ substitutions within the growth factor domain to favor inhibin formation over activin. We developed a simple and high-yielding expression and purification system for inhibins by transfection of suspension-cultured mammalian cells and tandem affinity chromatography, followed by reverse-phase purification of the mature ligands. We purified 1.4 mg (n = 3, SD = 0.47) and 0.093 mg (n = 3, SD = 0.043) of wild-type InhA and InhB per liter of culture medium with little to no contaminating activin A or B, at equal to higher purity and bioactivity than commercially available inhibins. Thus, we present a simple, robust, and versatile system for producing inhibins to interrogate their functions and mechanisms of action in vitro and in vivo.

biochemistry↗

bioRxiv2026

Single-nucleus multiomic analysis reveals modulation of the gene regulatory circuit landscape in pituitary cell types during mouse estrous cycle.

Summary/AbstractThe estrous cycle transcriptional and chromatin dynamics in pituitary cell types have not been investigated. We report single-nucleus multiomics assays in 18 adult mouse pituitaries (102,069 post quality-control nuclei) across 6 cycle time points. Differential analysis revealed cycle stage-dependent epigenetic and transcriptional remodeling across the major pituitary cell populations. In gonadotropes and lactotropes, we identified temporal patterns of differential gene expression linked to various biological processes, notably neuronal and synaptic-related ontologies. Pseudotime trajectory analysis was consistent with a rapid transition of individual gonadotropes through different cellular states. In gonadotropes and lactotropes, we uncovered gene regulatory circuits whose activity varies between consecutive cycle time points. We experimentally validated a gonadotrope ETS2-driven circuit that differentially regulates Fshb gene expression between 2 and 9 am on estrus. Our data and analyses, available at https://rstudio-connect.hpc.mssm.edu/snpit_estrous_browser/, provide a window into gene regulatory mechanisms underlying estrous cycle stage transitions. HighlightsO_LIPituitary cells show chromatin and transcriptome plasticity across the estrous cycle C_LIO_LIWe identify stage-modulated gene regulatory circuits across pituitary cell types C_LIO_LIGonadotrope DEGs form distinct pathway-annotated temporal trajectory clusters C_LIO_LIWe validate a gonadotrope ETS2-driven circuit regulating the Fshb gene C_LI eTOC blurbZhang et al. conduct a single-nucleus multiomics analysis of mouse pituitaries in vivo across the estrous cycle. They reveal an epigenetic and transcriptomic plasticity in pituitary cell populations. In gonadotropes and lactotropes, they demonstrate that DEGs clustered by temporal trajectories are enriched for distinct biological processes and identify stage-modulated gene regulatory circuits. They experimentally validate a gonadotrope ETS2-driven circuit regulating Fshb expression. Their dynamic molecular atlas of the cycling pituitary captures key cis-regulatory mechanisms underlying estrous cycle stage transitions.

genomics↗

bioRxiv2025

Regulation of murine follicle-stimulating hormone β subunit transcription by newly identified enhancers

Activin-class ligands of the transforming growth factor {beta} family induce follicle-stimulating hormone (FSH) production by pituitary gonadotrope cells in mice via the actions of the transcription factors SMAD3, SMAD4, and FOXL2, which bind to cis-elements in the FSH{beta} subunit (Fshb) promoter. An enhancer region for murine Fshb transcription was identified in vitro. However, deletion of the region using CRISPR-Cas9 did not affect FSH synthesis or secretion in mice. Using single-nucleus ATAC-seq of whole murine pituitaries, we identified three additional open chromatin regions upstream of Fshb exclusively in gonadotropes. These regions, as well as the Fshb gene, were fully or partially closed in gonadotropes of FSH-deficient mice with genetically or pharmacologically inactivated activin type II receptors. The initially characterized enhancer region did not significantly alter basal or activin-stimulated murine Fshb promoter-reporter activity in homologous L{beta}T2 cells. In contrast, the other three open chromatin regions enhanced basal and activin A-stimulated Fshb promoter-reporter activity in L{beta}T2 cells, with the two most distal showing the greatest effects. These two regions were open, exhibited enrichment of the enhancer mark H3K27ac, and were bound by SMAD2/3 and FOXL2 in response to activin A in L{beta}T2 cells. The most distal enhancer exhibited strong FOXL2 and weak SMAD4 binding in gel shift assays. SMAD4, but not FOXL2, directly bound the other distal enhancer. Mutation of defined FOXL2 and SMAD4 cis-elements diminished enhancer activity in reporter assays in L{beta}T2 cells. Collectively, the data indicate that there may be as many as four activin-sensitive enhancers upstream of murine Fshb.

molecular biology↗

bioRxiv2025

Consensus Pituitary Atlas, a scalable resource for annotation, novel marker discovery and analyses in pituitary gland research

Previous single-cell profiling studies of the pituitary gland have yielded minimally reproducible insights largely due to their low statistical power and methodological inconsistencies. To address this problem, we generated a uniformly pre-processed Consensus Pituitary Atlas (CPA) using all existing mouse pituitary single-cell datasets (267 biological replicates, >1.1 million high-quality cells). The CPA revealed novel cell typing and lineage markers, including low-expression transcripts that previous analyses could not detect. The scale of the CPA enabled the development of machine learning models to automate and standardize cell type annotation and doublet identification for future studies. Leveraging the curated metadata, we identified sex-biased and age-dependent gene expression patterns at cell type resolution. To identify drivers of cell fates, first we determined consensus cell communication patterns. Secondly, we used RNA-sequencing and chromatin accessibility data to identify transcription factors associated with cell fates across modalities. The epitome platform acts as an interface with the CPA, allowing streamlined user-friendly analyses. HighlightsO_LIUniform processing of 267 mouse pituitary single-cell datasets (>1.1M cells) C_LIO_LIThe statistical power enabled cell type, sex- and age-specific marker discovery C_LIO_LIMachine learning models facilitate doublet detection and cell typing in new datasets C_LIO_LIepitome platform provides programming-free data access and visualizations C_LI

bioinformatics↗

bioRxiv2024

Structures of TGF-beta with betaglycan and the signaling receptors reveal the mechanism whereby betaglycan potentiates receptor complex assembly and signaling

Betaglycan (BG) is a transmembrane co-receptor of the transforming growth factor-{beta} (TGF-{beta}) family of signaling ligands. It is essential for embryonic development and tissue homeostasis and fertility in adults. It functions by enabling binding of the three TGF-{beta} isoforms to their signaling receptors and is additionally required for inhibin A (InhA) activity. Despite its requirement for the functions of TGF-{beta}s and InhA in vivo, structural information explaining BG ligand selectivity and its mechanism of action is lacking. Here, we determine the structure of TGF-{beta} bound both to BG and the signaling receptors, TGFBR1 and TGFBR2. We identify key regions responsible for ligand engagement, which has revealed novel binding interfaces that differ from those described for the closely related co-receptor of the TGF-{beta} family, endoglin, thus demonstrating remarkable evolutionary adaptation to enable ligand selectivity. Finally, we provide a structural explanation for the hand-off mechanism underlying TGF-{beta} signal potentiation.

biophysics↗

bioRxiv2024

Brain-specific Gata4 downregulation in Greywick female mice models the metabolic subtype of polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is a heterogenous disorder characterized by reproductive and metabolic abnormalities. PCOS etiology remains poorly understood, although the hypothalamus is suspected to play a central role in many cases. Human genetic studies have also shown an association with the transcription factor-coding gene GATA4, but without providing a functional link. Here, we show that adult Greywick female mice may bridge this gap. These mice phenocopy PCOS with partial penetrance, due to serendipitous insertion of a Gata4 promoter-driven transgene in a strong enhancer region. Resulting robust transgene expression in subsets of hypothalamic neurons and glia impairs endogenous Gata4 expression, resulting in misexpression of genes linked to the control of fertility and food intake. We also show that this previously overlooked role of GATA4 in the hypothalamus can be replicated by conditional knockout approaches. Overall, this study sheds light not only on PCOS etiology but also on the role played by GATA4 in the central control of reproduction.

physiology↗

bioRxiv2023

Automated single-cell omics end-to-end framework with data-driven batch inference

To facilitate single-cell multi-omics analysis and improve reproducibility, we present SPEEDI (Single-cell Pipeline for End to End Data Integration), a fully automated end-to-end framework for batch inference, data integration, and cell type labeling. SPEEDI introduces data-driven batch inference and transforms the often heterogeneous data matrices obtained from different samples into a uniformly annotated and integrated dataset. Without requiring user input, it automatically selects parameters and executes pre-processing, sample integration, and cell type mapping. It can also perform downstream analyses of differential signals between treatment conditions and gene functional modules. SPEEDIs data-driven batch inference method works with widely used integration and cell-typing tools. By developing data-driven batch inference, providing full end-to-end automation, and eliminating parameter selection, SPEEDI improves reproducibility and lowers the barrier to obtaining biological insight from these valuable single-cell datasets. The SPEEDI interactive web application can be accessed at https://speedi.princeton.edu/.

bioinformatics↗

bioRxiv2023

Activin E is a TGFβ ligand that signals specifically through activin receptor-like kinase 7.

Activins are one of the three distinct subclasses within the greater Transforming Growth Factor {beta} (TGF{beta}) superfamily. First discovered for their critical roles in reproductive biology, activins have since been shown to alter cellular differentiation and proliferation. At present, members of the activin subclass include activin A (ActA), ActB, ActC, ActE, and the more distant members myostatin and GDF11. While the biological roles and signaling mechanisms of most activins class members have been well-studied, the signaling potential of ActE has remained largely unknown. Here, we characterized the signaling capacity of homodimeric ActE. Molecular modeling of the ligand:receptor complexes showed that ActC and ActE shared high similarity in both the type I and type II receptor binding epitopes. ActE signaled specifically through ALK7, utilized the canonical activin type II receptors, ActRIIA and ActRIIB, and was resistant to the extracellular antagonists follistatin and WFIKKN. In mature murine adipocytes, ActE invoked a SMAD2/3 response via ALK7, similar to ActC. Collectively, our results establish ActE as an ALK7 ligand, thereby providing a link between genetic and in vivo studies of ActE as a regulator of adipose tissue. SignificanceActivin E is a homodimeric member of the TGF{beta} family belonging to the activin subclass. Currently, the signaling capacity of ActE is unknown due to a lack of reliable reagents to study the protein. Here, we demonstrate that ActE acts as a canonical TGF{beta} ligand that signals through SMAD2/3 in an ALK7-dependent manner, similar to ActC. ActE also utilizes the activin type II receptors, ActRIIA and ActRIIB, to signal and is unable to be antagonized by FS288 and WFIKKN2. This study shows that ActE is a signaling ligand and provides a connection between genetic and in vivo studies that links ActE to adiposity.

biochemistry↗

bioRxiv2023

Myostatin is a major endocrine driver of follicle-stimulating hormone synthesis

Myostatin is a paracrine myokine that regulates muscle mass in a variety of species, including humans. Here, we report a functional role for myostatin as an endocrine hormone directly promoting pituitary follicle-stimulating hormone (FSH) synthesis and thereby ovarian function. Previously, this FSH-stimulating role was attributed to other members of the transforming growth factor {beta} family, the activins. The results both challenge activins eponymous role in FSH synthesis and establish an endocrine axis between skeletal muscle and the pituitary gland. The data also suggest that efforts to antagonize myostatin to treat muscle wasting disorders may have unintended consequences on fertility. One-Sentence SummaryHormone synthesis and reproduction depend on crosstalk between skeletal muscle and the pituitary gland.

physiology↗

bioRxiv2023

Peak-agnostic high-resolution cis-regulatory circuitry mapping using single cell multiome data

Single same cell RNAseq/ATACseq multiome data provide unparalleled potential to develop high resolution maps of the cell-type specific transcriptional regulatory circuitry underlying gene expression. We present CREMA, a framework that recovers the full cis-regulatory circuitry by modeling gene expression and chromatin activity in individual cells without peak-calling or cell type labeling constraints. We demonstrate that CREMA overcomes the limitations of existing methods that fail to identify about half of functional regulatory elements which are outside the called chromatin "peaks". These circuit sites outside called peaks are shown to be important cell type specific functional regulatory loci, sufficient to distinguish individual cell types. Analysis of mouse pituitary data identifies a Gata2-circuit for the gonadotrope-enriched disease-associated Pcsk1 gene, which is experimentally validated by reduced gonadotrope expression in a gonadotrope conditional Gata2-knockout model. We present a web accessible human immune cell regulatory circuit resource, and provide CREMA as an R package.

bioinformatics↗

bioRxiv2023

Vitamin B12 status and folic acid supplementation influence mitochondrial heteroplasmy levels in mice as they age.

One-carbon metabolism is a complex network of metabolic reactions that are essential for cellular function including DNA synthesis. Vitamin B12 and folate are micronutrients that are utilized in this pathway and their deficiency can result in the perturbation of one-carbon metabolism and subsequent perturbations in DNA replication and repair. This effect has been well characterized in nuclear DNA but to date, mitochondrial DNA (mtDNA) has not been investigated extensively. Mitochondrial variants have been associated with several inherited and age-related disease states; therefore, the study of factors that impact heteroplasmy are important for advancing our understanding of the mitochondrial genomes impact on human health. Heteroplasmy studies require robust and efficient mitochondrial DNA enrichment to carry out in-depth mtDNA sequencing. Many of the current methods for mtDNA enrichment can introduce biases and false positive results. Here we use a method that overcomes these limitations and have applied it to assess mitochondrial heteroplasmy in mouse models of altered one-carbon metabolism. Vitamin B12 deficiency was found to cause increased levels of mitochondrial DNA heteroplasmy across all tissues that were investigated. Folic acid supplementation also contributed to elevated mitochondrial DNA heteroplasmy across all mouse tissues investigated. Heteroplasmy analysis of human data from the Framingham Heart Study suggested a potential sex-specific effect of folate and vitamin B12 status on mitochondrial heteroplasmy. This is a novel relationship that may have broader consequences for our understanding of one-carbon metabolism, mitochondrial related disease and the influence of nutrients on DNA mutation rates. Significance StatementUsing a sensitive method for mitochondrial heteroplasmy analysis, we show that both vitamin B12 and folic acid can impact mitochondrial DNA mutation. This effect requires further investigation of the potential impact on humans.

molecular biology↗

bioRxiv2022

Mito-SiPE: A sequence-independent, PCR-free mitochondrial DNA enrichment method for ultra-deep sequencing that minimises amplification and alignment artifacts.

BackgroundDeep sequencing is often used to measure somatic variation in the mitochondrial genome. Selective enrichment methods, such as PCR amplification or probe hybridization/capture are commonly used. These methods can introduce bias and are prone to contamination by nuclear-mitochondrial sequences (NUMTs); elements that can introduce artefacts into analyses such as an assessment of mitochondrial heteroplasmy. ResultsHere, we demonstrate a method to obtain ultra-deep (>80,000X) sequencing coverage of the mitochondrial genome by selectively purifying the intact organelle itself using differential centrifugation and alkaline lysis. We applied this approach to seven different mouse tissues. Isolation of mitochondria yields a preparation of highly enriched mtDNA. We compared this method to the commonly used PCR-based method. Mito-SiPE avoids false-heteroplasmy calls that occur when long-range PCR amplification is used for mtDNA enrichment. DiscussionWe have described a modified version of a long-established protocol for purifying mtDNA and have quantified the increased level of mitochondrial DNA post-enrichment in 7 different mouse tissues. This method will enable researchers to identify changes in low-frequency heteroplasmy without introducing PCR biases or NUMT contamination that are falsely identified as heteroplasmy when long-range PCR is used.

genomics↗

bioRxiv2022

The orphan ligand, Activin C, signals through activin receptor-like kinase 7

Activin ligands are formed from two disulfide-linked inhibin {beta} subunit chains. They exist as homodimeric proteins, as in the case of activin A (ActA; Inh{beta}A/Inh{beta}A) or activin C (ActC; Inh{beta}C/Inh{beta}C), or as heterodimers, as with activin AC (ActAC; Inh{beta}A:Inh{beta}C). While the biological functions of ActA and activin B (ActB) have been well-characterized, little is known about the biological function of ActC or ActAC. One thought is that the Inh{beta}C chain functions to interfere with ActA production by forming less active ActAC heterodimers. Here, we assessed and characterized the signaling capacity of ligands containing the Inh{beta}C chain. ActC and ActAC activated SMAD2/3-dependent signaling via the type I receptor, activin receptor-like kinase 7 (ALK7). Relative to ActA and ActB, ActC exhibited lower affinity for the cognate activin type II receptors and was resistant to neutralization by the extracellular antagonist, follistatin. In mature adipocytes, which exhibit high ALK7 expression, ActC elicited a SMAD2/3 response similar to ActB, which can also signal via ALK7. Collectively, these results establish that ActC and ActAC are active ligands that exhibit a distinct signaling receptor and antagonist profile compared to other activins.

biochemistry↗

bioRxiv2021

Addition of a carboxy terminal tail to the normally tailless gonadotropin-releasing hormone receptor impairs fertility in female mice

Gonadotropin-releasing hormone (GnRH) is the primary neuropeptide controlling reproduction in vertebrates. GnRH stimulates follicle-stimulating hormone (FSH) and luteinizing hormone (LH) synthesis via a G protein-coupled receptor, GnRHR, in the pituitary gland. In mammals, GnRHR lacks a C-terminal cytosolic tail (Ctail) and does not exhibit homologous desensitization. This might be an evolutionary adaptation that enables LH surge generation and ovulation. To test this idea, we fused the chicken GnRHR Ctail to the endogenous murine GnRHR in a transgenic model. The LH surge was blunted, but not blocked in these mice. In contrast, they showed reductions in FSH production, ovarian follicle development, and fertility. Addition of the Ctail altered the nature of agonist-induced calcium signaling required for normal FSH production. The loss of the GnRHR Ctail during mammalian evolution is unlikely to have conferred a selective advantage by enabling the LH surge. The adaptive significance of this specialization remains to be determined.

physiology↗

bioRxiv2021

Single nucleus pituitary transcriptomic and epigenetic landscape reveals human stem cell heterogeneity with diverse regulatory mechanisms

Despite their importance in tissue homeostasis and renewal, human pituitary stem cells (PSCs) are incompletely characterized. We describe a human single nucleus (sn) RNAseq and ATACseq resource from pediatric, adult, and aged pituitaries (snpituitaryatlas.princeton.edu) and characterize cell type-specific gene expression and chromatin accessibility programs for all major pituitary cell lineages. We identify uncommitted PSCs, committing progenitor cells, and sex differences. Pseudotime trajectory analysis indicates that early life PSCs are distinct from the other age groups. Linear modeling of same-cell multiome data identifies regulatory domain accessibility sites and transcription factors (TFs) that are significantly associated with gene expression in PSCs compared to other cell types and within PSCs. Modeling the heterogeneous expression of two markers for committing cell lineages among PSCs shows significant correlation with regulatory domain accessibility for GATA3, but with TF expression for POMC. These findings characterize human stem cell lineages and reveal diverse mechanisms regulating key PSC genes.

cell biology↗

bioRxiv2020

Single nucleus multi-omics regulatory atlas of the murine pituitary

The pituitary regulates growth, reproduction and other endocrine systems. To investigate transcriptional network epigenetic mechanisms, we generated paired single nucleus (sn) transcriptome and chromatin accessibility profiles in single mouse pituitaries and genome-wide sn methylation datasets. Our analysis provided insight into cell type epigenetics, regulatory circuit and gene control mechanisms. Latent variable pathway analysis detected corresponding transcriptome and chromatin accessibility programs showing both inter-sexual and inter-individual variation. Multi-omics analysis of gene regulatory networks identified cell type-specific regulons whose composition and function were shaped by the promoter accessibility state of target genes. Co-accessibility analysis comprehensively identified putative cis-regulatory regions, including a domain 17kb upstream of Fshb that overlapped the fertility-linked rs11031006 human polymorphism. In vitro CRISPR-deletion at this locus increased Fshb levels, supporting this domains inferred regulatory role. The sn pituitary multi-omics atlas (snpituitaryatlas.princeton.edu) is a public resource for elucidating cell type-specific gene regulatory mechanisms and principles of transcription circuit control.

cell biology↗