Biology subjects

Haffner, C.

Publications and source records attributed to Haffner, C..

4 recordsLinked to original sources

bioRxiv2026

KRAS-driven metabolic reprogramming of enhanced MFSD2A-mediated lysophosphatidylcholine scavenging promotes survival and progression of pancreatic ductal adenocarcinoma

Oncogenic KRAS drives lipid reprogramming in pancreatic ductal adenocarcinoma (PDAC) to promote disease progression, and these changes are manifest in circulation. Using mass spectrometry, we performed lipidomic analyses on plasmas from a cohort of 93 newly-diagnosed resectable PDAC cases, 43 patients with chronic pancreatitis, and 93 age- and sex-matched healthy controls, the results of which revealed pronounced reductions in circulating lysophosphatidylcholines (LysoPC) as a prominent feature associated with PDAC. Using stable-isotope resolved lipidomics, we further found that PDAC cells exhibit a lipid scavenging phenotype characterized by preferential uptake of extracellular unsaturated LysoPCs to sustain pro-growth signals. Restricting bioavailability of extracellular unsaturated LysoPCs shifted the metabolic phenotype of PDAC cells towards enhanced de novo lipogenesis and autophagy, which was accompanied by suppression of AKT signaling activities and increased susceptibility to apoptosis. Using bulk, single-cell, and spatial transcriptomic datasets together with functional experiments, we identified oncogenic KRAS-mediated upregulation of major facilitator superfamily domain-containing protein 2a (MFSD2A) as a key mediator that facilitates extracellular uptake of LysoPCs in PDAC cells. Loss of MFSD2A expression mimicked LysoPC restriction and resulted in inhibition of AKT signaling and increased propensity of PDAC cells to undergo apoptosis in vitro and suppressed tumor growth in vivo. Therapeutic targeting of the KRAS-MFSD2A-LysoPC axis via repurposing of the synthetic alkyl-lysophospholipid edelfosine promoted potent anti-cancer effects in vitro that were mechanistically attributed to reduced extracellular uptake of LysoPCs, and attenuation of AKT signaling. Collectively, our findings describe a previously unrecognized onco-metabolic program of enhanced LysoPC scavenging mediated by MFSD2A that promotes PDAC progression and that is therapeutically targetable via repurposing edelfosine.

cancer biology↗

bioRxiv2022

DOT1L activity affects cell lineage progression in the developing brain by controlling metabolic programs

Cortical neurogenesis depends on the tight balance between self-renewal and differentiation of apical progenitors (APs), the key progenitor type generating all other neural cells including neocortical neurons. We here report the activity of the histone methyltransferase DOT1L as a gatekeeper for AP cell identity. Combining lineage tracing with single-cell RNA sequencing of clonally related cells, we explore consequences of DOT1L inhibition on AP lineage progression during neurogenesis in the embryonic mouse neocortex. At the cellular level, DOT1L inhibition led to increased neurogenesis driven by a shift from asymmetric self-renewing to symmetric neurogenic divisions of APs. At the molecular level, we show that DOT1L activity preserved AP identity by promoting transcription of a gene set involved in AP metabolism. On a mechanistic level, DOT1L inhibition increased expression of metabolic genes, including microcephaly-associated Asparagine synthetase (Asns) and overexpression of ASNS in APs resulted in increased neuronal differentiation. Asns expression was predicted to be controlled through EZH2 and we show that DOT1L activity allows PRC2-mediated repression of Asns expression. Importantly, inhibition of ASNS activity rescued increased AP differentiation upon DOT1L inhibition. Our data show that DOT1L activity/PRC2 crosstalk controls AP lineage progression by regulating AP metabolism, and they provide a mechanistic view on how DOT1L activity might affect neocortical neurogenesis.

developmental biology↗

bioRxiv2022

Longer metaphase and fewer chromosome segregation errors in modern human than Neandertal brain development

Since the ancestors of modern humans separated from those of Neandertals, around one hundred amino acid substitutions spread to essentially all modern humans. The biological significance of these changes is largely unknown. Here, we examine all six such amino acid substitutions in the three proteins known to have key roles in kinetochore function and chromosome segregation and to be highly expressed in the stem cells of the developing neocortex. When we introduce these modern human-specific substitutions in the mouse, three substitutions in two of these proteins, KIF18a and KNL1, cause a prolongation of metaphase and a reduction in chromosome segregation errors in apical progenitors of the developing neocortex. Conversely, the ancestral substitutions cause a reduction in metaphase length and an increase in chromosome segregation errors in human brain organoids. Our data also show that, in these aspects, Neandertals were more similar to chimpanzees than to modern humans. Thus, the fidelity of chromosome segregation during neocortex development improved in modern humans after their divergence from Neandertals.

neuroscience↗

bioRxiv2018

Robotic platform for microinjection into single cells in intact tissue

Microinjection into single cells in intact tissue allows the delivery of membrane-impermeant molecules such as nucleic acids and proteins is a powerful technique to study and manipulate the behavior of these cells and, if applicable, their progeny. However, a high level of skill is required to perform such microinjection and is a low-throughput and low-yield process. The automation of microinjection into cells in intact tissue would empower an increasing number of researchers to perform these challenging experiments and could potentially open up new avenues of experimentation. We have developed the Autoinjector, a robot that utilizes images acquired from a microscope to guide a microinjection needle into tissue to deliver femtoliter volumes of liquids into single cells. The robotic operation enables microinjection of hundreds of cells within a single organotypic slice, resulting in an overall yield that is an order of magnitude greater than manual microinjection. We validated the performance of the Autoinjector by microinjecting both apical progenitors (APs) and newborn neurons in the embryonic mouse telencephalon, APs in the embryonic mouse hindbrain, and neurons in fetal human brain tissue. We demonstrate the capability of the Autoinjector to deliver exogenous mRNA into APs. Further, we used the Autoinjector to systematically study gap-junctional communication between neural progenitors in the embryonic mouse telencephalon and found that apical contact is a characteristic feature of the cells that are part of a gap junction-coupled cell cluster. The throughput and versatility of the Autoinjector will not only render microinjection a broadly accessible high-performance cell manipulation technique but will also provide a powerful new platform for bioengineering and biotechnology for performing single-cell analyses in intact tissue.

neuroscience↗