Biology subjects

Pastor, W. A.

Publications and source records attributed to Pastor, W. A..

8 recordsLinked to original sources

bioRxiv2026

Phosphorylation of CARM1 at Ser572 preserves muscle stem cell self-renewal by restricting premature myogenic commitment

Skeletal muscle regeneration depends on satellite cells, which must balance myogenic commitment with self-renewal to maintain regenerative capacity throughout life. The methyltransferase CARM1 is a key regulator of satellite cell fate, acting through methylation of PAX7 to promote Myf5 expression and myogenic commitment. The dystrophin glycoprotein complex regulates this pathway through p38{gamma}-mediated phosphorylation of CARM1 at Ser572, however the physiological role of this phosphorylation event in vivo remains unknown. Here, we generated a phosphorylation-deficient CARM1 knock-in mouse (CARM1 SA) to determine how CARM1 Ser572 phosphorylation regulates satellite cell fate during regenerative myogenesis. Satellite cell-derived myoblasts from CARM1 SA mice exhibited reduced PAX7 expression, impaired fusion, and abnormal myotube formation despite transcriptional signatures consistent with accelerated myogenic progression. Ex vivo single-myofiber assays revealed precocious acquisition of a committed progenitor identity accompanied by a reduction in the self-renewing satellite cell population. While muscle development and regeneration following a single injury were largely preserved, repeated regenerative challenge resulted in progressive depletion of the satellite cell pool in CARM1 SA mice. Transcriptomic analysis demonstrated minimal effects under homeostatic conditions but identified substantial alterations during regeneration, including reduced expression of extracellular matrix-associated genes, impaired TGF{beta}-SMAD signaling, decreased Tgfbr3 expression, and increased MYC activity, consistent with a loss of self-renewal programs and enhanced activation. Collectively, these findings demonstrate that phosphorylation of CARM1 at Ser572 is a critical mechanism to delay satellite cell commitment, thereby maintaining a balance between self-renewal and commitment to ensure long-term maintenance of the muscle stem cell compartment.

cell biology↗

bioRxiv2025

Divergent roles of DNA methylation, TRIM28, and p53 surveillance in human embryonic and trophoblast stem cells

Transcriptional regulation of transposons and genes by TRIM28 and 5mC is critical for proper mammalian embryonic development, but the specific roles for these mediators in human embryonic and placental lineage remain unclear. We find that loss of TRIM28 has a limited effect on global transposon expression and instead results in upregulation of genes proximal to TRIM28-bound Long Terminal Repeats (LTRs) in both human trophoblast stem cells (hTSCs) and human embryonic stem cells (hESCs). MER11A elements show especially strong regulatory importance in hTSCs: these elements are bound by both TRIM28 and placental transcription factors and show both heterochromatic and euchromatic features. Some genes are positively regulated by MER11A elements in hTSC basal state, while other MER11A-proximal genes show upregulation only upon TRIM28 deletion. By contrast, loss of DNA methylation in hESCs or hTSCs leads to a global increase in transposon expression. While many genic 5mC targets are shared in hESCs and hTSCs, we also observe evidence that a handful of genes important for somatic development are repressed by 5mC in trophoblast, while a small parallel set of placental genes are repressed by methylation in embryonic tissue. Interestingly, loss of DNMT1 causes hESCs to be rapidly lost from culture in a TP53 and mitotic surveillance checkpoint-dependent manner, while hTSCs show little p53 response to DNMT1 loss or DNA damage generally, instead showing gradual mitotic defects and aneuploidy and slow loss from culture. This discrepancy may explain the higher frequency of karyotypic abnormality found in human placental cells. Together, this study charts the role of TRIM28 and DNA methylation in regulating embryonic and placental transcription and demonstrates divergent p53-dependent responses to genomic instability.

molecular biology↗

bioRxiv2025

Engulfing to Adapt: Efferocytosis by Epithelial Cells Triggers Cell State Transitions During Tissue Remodeling

Hormone deprivation treatments are a leading approach in prostate cancer treatment. Following deprivation, the organ regresses from a fully differentiated secretory organ to one less than 50% of the original size, that has been reprogrammed to a state primed for regeneration. Despite widespread use of hormone treatments, the events linking cellular apoptotic responses following prostate hormone deprivation and cell state reprogramming are not fully understood. We report that the absence of hormones creates a microenvironment rich in apoptotic cells that are engulfed by neighboring prostate epithelial cells. Mechanistically, we found that epithelial cells alter their metabolism and gene expression during efferocytosis. Efferocytic epithelial cells adopt a more glycolytic metabolism, resulting in elevated levels of lactate production. This correlates with increased histone Lactylation over gene regulatory elements for genes regulating autophagy and catabolism. To further demonstrate that efferocytosis is necessary to remodel tissue during regression, we expressed a mutant of the receptor protein MFGE8, MFGE8-D89E to "mask" PtdSer in the prostate epithelium and reduce efferocytosis. This effectively prevented the cell and lumen size changes hormone-deprived prostates usually go through. Our findings suggest new perspectives on how epithelial cell efferocytosis can impact tissue remodeling and altered cellular states.

developmental biology↗

bioRxiv2024

Reducing CETP activity prevents memory decline in an Alzheimer's disease mouse model

Epidemiological studies have shown that lower activity of the cholesteryl ester transfer protein (CETP) correlates with reduced Alzheimers disease (AD) risk. While small molecule CETP inhibitors like evacetrapib have previously been assessed for cardiovascular diseases, their involvement in AD has not been investigated. Here, we establish CETP as a novel pharmacological target for AD treatment. Using CETP transgenic mice crossed to a mouse model of amyloidosis and administering evacetrapib, we provide evidence that CETP inhibition maintained memory independent of classic AD markers, increased hippocampal cholesterol, altered plasma lipoproteins, and changed transcription of genes linked to brain barriers. Using proteomic data of cerebrospinal fluid from cognitively unimpaired individuals at risk for AD (the PREVENT-AD cohort), we confirm that our mouse model reflects physiological changes in pre-symptomatic human subjects. We propose the repurposing of CETP inhibitors as an effective therapeutic strategy to delay or prevent cognitive impairment in AD.

neuroscience↗

bioRxiv2024

Hypoxia and loss of GCM1 expression prevents differentiation and contact inhibition in human trophoblast stem cells

The placenta develops alongside the embryo and nurtures fetal development to term. During the first stages of embryonic development, due to low blood circulation, the blood and ambient oxygen supply is very low ([~]1-2% O2) and gradually increases upon placental invasion. While a hypoxic environment is associated with stem cell self-renewal and proliferation, persistent hypoxia may have severe effects on differentiating cells and could be the underlying cause of placental disorders. We find that human trophoblast stem cells (hTSC) thrive in low oxygen, whereas differentiation of hTSC to trophoblast to syncytiotrophoblast (STB) and extravillous trophoblast (EVT) is negatively affected by hypoxic conditions. The pro-differentiation factor GCM1 (human Glial Cell Missing-1) is downregulated in low oxygen, and concordantly there is substantial reduction of GCM1-regulated genes in hypoxic conditions. Knockout of GCM1 in hTSC caused impaired EVT and STB formation and function, reduced expression of differentiation-responsive genes, and resulted in maintenance of self-renewal genes. Treatment with a PI3K inhibitor reported to reduce GCM1 protein levels likewise counteracts spontaneous or directed differentiation. Additionally, chromatin immunoprecipitation of GCM1 showed enrichment of GCM1-specific binding near key transcription factors upregulated upon differentiation including the contact inhibition factor CDKN1C. Loss of GCM1 resulted in downregulation of CDKN1C and corresponding loss of contact inhibition, implicating GCM1 in regulation of this critical process.

cell biology↗

bioRxiv2024

Loss of the APP regulator RHBDL4 preserves memory in an Alzheimer's disease mouse model.

Characteristic cerebral pathological changes of Alzheimers disease (AD) such as glucose hypometabolism or the accumulation of cleavage products of the amyloid precursor protein (APP), known as A{beta} peptides, lead to sustained endoplasmic reticulum (ER) stress and neurodegeneration. To preserve ER homeostasis, cells activate their unfolded protein response (UPR). The rhomboid-like-protease 4 (RHBDL4) is an enzyme that participates in the UPR by targeting proteins for proteasomal degradation. We demonstrated previously that RHBLD4 cleaves APP in HEK293T cells, leading to decreased total APP and A{beta}. More recently, we showed that RHBDL4 processes APP in mouse primary mixed cortical cultures as well. Here, we aim to examine the physiological relevance of RHBDL4 in the brain. We first found that brain samples from AD patients and an AD mouse model (APPtg) showed increased RHBDL4 mRNA and protein expression. To determine the effects of RHBDL4s absence on APP physiology in vivo, we crossed APPtg mice to a RHBDL4 knockout (R4-/-) model. RHBDL4 deficiency in APPtg mice led to increased total cerebral APP and amyloidogenic processing when compared to APPtg controls. Contrary to expectations, as assessed by cognitive tests, RHBDL4 absence rescued cognition in 5-month-old female APPtg mice. Informed by unbiased RNAseq data, we demonstrated in vitro and in vivo that RHBDL4 absence leads to greater levels of active {beta}-catenin due to decreased proteasomal clearance. Decreased {beta}-catenin activity is known to underlie cognitive defects in APPtg mice and AD. Our work suggests that RHBDL4s increased expression in AD, in addition to regulating APP levels, leads to aberrant degradation of {beta}-catenin, contributing to cognitive impairment.

animal behavior and cognition↗

bioRxiv2022

ZMYM2 is essential for methylation of germline genes and active transposons in embryogenesis

ZMYM2 is a transcriptional repressor whose role in development is largely unexplored. We found that Zmym2-/- mice show embryonic lethality by E10.5. Molecular characterization of Zmym2-/- embryos revealed two distinct defects. First, they fail to undergo DNA methylation and silencing of germline gene promoters, resulting in widespread upregulation of germline genes. Second, they fail to methylate and silence the evolutionarily youngest and most active LINE element subclasses in mice. Zmym2-/- embryos show ubiquitous overexpression of LINE-1 protein as well as aberrant expression of transposon-gene fusion transcripts. Interaction and colocalization data indicate that ZMYM2 homes to germline genes via binding to the non-canonical polycomb complex PRC1.6 and to transposons via the TRIM28 complex. In the absence of ZMYM2, hypermethylation of histone 3 lysine 4 occurs at target sites, creating a chromatin landscape unfavourable for establishment of DNA methylation. ZMYM2-/- human embryonic stem cells also show aberrant upregulation and demethylation of young LINE elements, indicating a conserved role in repression of active transposons. ZMYM2 is thus an important new factor in DNA methylation patterning in early embryonic development.

molecular biology↗

bioRxiv2021

The DNMT1 inhibitor GSK-3484862 mediates global demethylation in murine embryonic stem cells

BackgroundDNA methylation plays an important role in regulating gene expression in mammals. The covalent DNMT1 inhibitors 5-azacytidine and decitabine are widely used in research to reduce DNA methylation levels, but they impart severe cytotoxicity which limits their demethylation capability and confounds interpretation of experiments. Recently, a non-covalent inhibitor of DNMT1 called GSK-3484862 was developed by GlaxoSmithKline. We sought to determine whether GSK-3484862 can induce demethylation more effectively than 5-azanucleosides. Murine embryonic stem cells (mESC) are an ideal cell type in which to conduct such experiments, as they have a high degree of DNA methylation but tolerate dramatic methylation loss. ResultsWe determined the cytotoxicity and optimal concentration of GSK-3484862 by treating wild-type (WT) or Dnmt1/3a/3b triple knockout (TKO) mESC with different concentrations of the compound, which was obtained from two commercial sources. Concentrations of 10 {micro}M or below were readily tolerated for 14 days of culture. Known DNA methylation targets such as germline genes and GLN-family transposons were upregulated within two days of the start of GSK-3484862 treatment. By contrast, 5-azacytidine and decitabine induced weaker upregulation of methylated genes and extensive cell death. Whole genome bisulfite sequencing (WGBS) showed that treatment with GSK-3484862 induced dramatic DNA methylation loss, with global CpG methylation levels falling from near 70% in WT mESC to less than 18% after 6 days of treatment with GSK-3484862, similar to the methylation level observed in Dnmt1 deficient mESCs. ConclusionsGSK-3484862 mediates striking demethylation in mESCs with minimal non-specific toxicity.

molecular biology↗