Biology subjects

Klungland, A.

Publications and source records attributed to Klungland, A..

7 recordsLinked to original sources

bioRxiv2025

N6-Methyladenosine Safeguards Mouse and Human Germline Competence

N6-Methyladenosine (m6A) regulation of germline entry in post-implantation-like-pluripotent states remains poorly defined. We characterized m6A depletion by Mettl3 or Mettl14 knock-down or METTL3 inhibition in in vitro models enabling primordial germ-cell-like-cell and somatic differentiation. Upon m6A depletion, mouse epiblast-like cells upregulated embryonic Ras (Eras) and PI3K-pAKT, facilitating EZH2 repression and depletion of H3K27me3. Consequently, enhancer activation promoted global gene deregulation and impaired germline entry. In mouse formative stem cells, ERAS-PI3K-pAKT upregulation resulted in unscheduled Blimp1 and Otx2 co-expression, germline entry deficiency and enhanced mesodermal differentiation. Conversely, upon m6A depletion, germline competent human pluripotent stem cells upregulated OTX2 through FGF-pERK activation, resulting in germline entry deficiency and enhanced neuroectodermal differentiation. meRIP-seq revealed preferential m6A deposition on mouse mesodermal and human neuroectodermal transcripts, suggesting a basis for differentiation bias following m6A depletion. We illustrate how decreasing m6A abundances impact signaling, chromatin epigenetics and transcript stabilities, constituting a powerful cell intrinsic barrier for germline entry.

developmental biology↗

bioRxiv2023

CDK12/CDK13 inhibition disrupts a transcriptional program critical for glioblastoma survival

Glioblastoma is the most prevalent and aggressive malignant tumor of the central nervous system. With a median overall survival of only one year, glioblastoma patients have a particularly poor prognosis, highlighting a clear need for novel therapeutic strategies to target this disease. Transcriptional cyclin-dependent kinases (tCDK), which phosphorylate key residues of RNA polymerase II (RNAPII) c-terminal domain (CTD), play a major role in sustaining aberrant transcriptional programs that are key to development and maintenance of cancer cells. Here, we show that either pharmacological inhibition or genetic ablation of the tCDKs, CDK12 and CDK13, markedly reduces both the proliferation and migratory capacity of glioma cells and patient-derived organoids. Using a xenograft mouse model, we demonstrate that CDK12/13 inhibition not only reduces glioma growth in vivo. Mechanistically, inhibition of CDK12/CDK13 leads to a genome-wide abrogation of RNAPII CTD phosphorylation, which in turn disrupts transcription and cell cycle progression in glioma cells. In summary, the results provide proof-of-concept for the potential of CDK12 and CDK13 as therapeutic targets for glioblastoma. Significance statementGlioblastoma is a common, aggressive, and invasive type of brain tumor that is usually fatal. The standard treatment for glioblastoma patients is surgical resection, radiotherapy, and chemotherapy with DNA-alkylating agents, and unfortunately current treatments only extend overall survival by a few months. It is therefore critical to identify and target additional biological processes in this disease. Here, we reveal that targeting a specific transcriptional addiction for glioma cells by inhibition of CDK12/CDK13 disrupts glioma-specific transcription and cell cycle progression and has potential to provide a new therapeutic strategy for glioblastoma.

cancer biology↗

bioRxiv2021

Exit from quiescence couples epithelial stress amplification to fluidization

Cellular quiescence is a state of reversible cell cycle arrest that is associated with tissue dormancy. Timely regulated entry into and exit from quiescence is important for processes such as tissue homeostasis, tissue repair, stem cell maintenance, developmental processes and immunity. Here we show that quiescent human keratinocyte monolayers contain an actinomyosin-based system that facilitates global viscoelastic flow upon serum-stimulated exit from quiescence. Mechanistically, serum exposure causes rapid amplification of pre-existing contractile sites leading to a burst in monolayer stress that subsequently drives monolayer fluidization. The stress magnitude after quiescence exit correlates with quiescence depth, and a critical stress level must be reached to overcome the cell sheet displacement barrier. The study shows that static quiescent cell monolayers are mechanically poised for motility and identifies global stress amplification as a mechanism for tissue fluidization.

biophysics↗

bioRxiv2021

ALKBH5 regulates somatic cell reprogramming in a phase specific manner

Establishment of the pluripotency regulatory network in somatic cells by introducing four transcriptional factors, (Octamer binding transcription factor 4 (OCT4), SRY (sex determining region Y)-box 2 (SOX2), Kruppel - like factor 4 (KLF4), and cellular-Myelocytomatosis (c-MYC) provides a promising tool for cell-based therapies in regenerative medicine. Still, the mechanisms at play when generating induced pluripotent stem cells from somatic cells is only partly understood. Here we show that the RNA specific N6-methyladenosine (m6A) demethylase ALKBH5 regulates somatic cell reprogramming in a stage specific manner. Knockdown or knockout of Alkbh5 in the early reprogramming phase impairs the reprogramming efficiency by reducing the proliferation rate through arresting the cells at G2/M phase and decreasing the mesenchymal-to-epithelial transition (MET) rate. However, there is no significant change in reprogramming efficiency when Alkbh5 is depleted at the late phase of reprogramming. On the other hand, ALKBH5 overexpression at the earlyreprogramming phase has no significant impact on reprogramming efficiency, while overexpression at the late phase enhances the reprogramming by stabilizing Nanog transcripts resulting in upregulated Nanog expression. Our study provides mechanistic insight into the crucial dynamic role of ALKBH5 in regulating somatic cell reprogramming at the posttranscriptional level.

cell biology↗

bioRxiv2021

Waves of sumoylation support transcription dynamics during adipocyte differentiation

Tight control of gene expression networks required for adipose tissue formation and plasticity is essential for adaptation to energy needs and environmental cues. However, little is known about the mechanisms that orchestrate the dramatic transcriptional changes leading to adipocyte differentiation. We investigated the regulation of nascent transcription by the sumoylation pathway during adipocyte differentiation using SLAMseq and ChIPseq. We discovered that the sumoylation pathway has a dual function in differentiation; it supports the initial downregulation of pre-adipocyte-specific genes, while it promotes the establishment of the mature adipocyte transcriptional program. By characterizing sumoylome dynamics in differentiating adipocytes by mass spectrometry, we found that sumoylation of specific transcription factors like Ppar{gamma}/RXR and their co-factors is associated with the transcription of adipogenic genes. Our data demonstrate that the sumoylation pathway coordinates the rewiring of transcriptional networks required for formation of functional adipocytes. This study also provides an in-depth resource of gene transcription dynamics, SUMO-regulated genes and sumoylation sites during adipogenesis.

genomics↗

bioRxiv2021

NEIL1 and NEIL2 DNA glycosylases regulate anxiety and learning in a cooperative manner

Oxidative DNA damage in the brain has been implicated in neurodegeneration and cognitive decline. DNA glycosylases initiate base excision repair (BER), the main pathway for oxidative DNA base lesion repair. NEIL1 and NEIL3 DNA glycosylases alter cognition in mice, the role of NEIL2 remains unclear. Here, we investigate the impact of NEIL2 and its potential overlap with NEIL1 on behavior in single and double knock-out mouse models. Neil1-/-Neil2-/- mice displayed hyperactivity, reduced anxiety and improved learning. Hippocampal oxidative DNA base lesion levels were comparable between genotypes, no mutator phenotype was found. Impaired canonical repair was thus not the cause of altered behavior. Electrophysiology indicated reduced stratum oriens afferents in the hippocampal CA1 region in Neil1-/-Neil2-/-. Within CA1, NEIL1 and NEIL2 jointly regulated transcription in genes relevant for synaptic function. Thus, we postulate a cooperative function of NEIL1 and NEIL2 in genome regulation beyond canonical BER modulating memory formation and anxiety.

molecular biology↗

bioRxiv2019

N6-methyladenosine dynamics during early vertebrate embryogenesis

Early vertebrate embryogenesis is characterized by extensive post-transcriptional regulation during the maternal-to-zygotic transition. The N6-methyladenosine (m6A) modifications on mRNA have been shown to affect both translation and stability of transcripts. Here we investigate the m6A topology during early vertebrate embryogenesis and its association with polyadenylated mRNA levels. The majority (>70%) of maternal transcripts harbor m6A, and there is a substantial increase of m6A in the polyadenylated mRNA fraction between 0 and 2 hours post fertilization. Notably, we find strong associations between m6A, cytoplasmic polyadenylation and translational efficiency prior to zygotic genome activation (ZGA). Interestingly, the relationship between m6A and translation is strongest for peaks located in the 3UTR, but not overlapping stop codons. Sequence analyses revealed enrichment of motifs for RNA binding proteins involved in translational regulation and RNA degradation. After ZGA, m6A seem to diminish the effect of miR-430 mediated degradation. The reported results improve our understanding of the combinatorial code behind post-transcriptional mRNA regulation during embryonic reprogramming and early differentiation.

developmental biology↗