Biology subjects

Naumann, R.

Publications and source records attributed to Naumann, R..

13 recordsLinked to original sources

bioRxiv2025

Magnetically Controlled Microrobots for In Vivo Non-Invasive Embryo Transfer

Infertility affects millions worldwide and is often linked to factors such as poor sperm quality and female reproductive organ disorders. Despite significant advancements in in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI), implantation rates remain low, ranging from 17 to 21% after three days of incubation, mainly due to stress, lifestyle factors, and uterine conditions. Extended embryo culture techniques have shown promise in improving pregnancy rates. However, the availability of high-quality blastocysts remains a major challenge. Intrafallopian transfer techniques, such as gamete/zygote intrafallopian transfer (GIFT/ZIFT), were introduced to improve fertilization and early embryo development, particularly for patients with repeated embryo implantation failure (10-30% of assisted reproduction technology (ART) cases, particularly in women >35). However, these methods have declined due to advancements in IVF and the variability in laparoscopy procedures used for GIFT/ZIFT. To address these challenges, we propose a non-invasive microrobotic embryo transfer ({micro}ET) technique using remotely controlled microcarriers comparable in size to embryos. We demonstrate the capabilities of magnetically actuated spiral microrobots, fabricated using laser direct writing for capturing, transporting, and releasing embryos into murine uteri. Additionally, we characterize their motion performance and implement image-guided closed-loop control and dual ultrasound (US)/photoacoustic (PA) tracking for deep-tissue interventions. Recognizing the importance of clinical translation, we present preliminary studies on gelatin-based microrobots, a biodegradable alternative, and explore endometrial remodeling after the in vivo transfer of microrobots carrying embryo-like structures. Our findings show that these microrobots can effectively transport embryos, support their development, and enable minimally invasive delivery, providing a more natural, targeted, and non-invasive strategy for in vivo assisted reproduction. One-Sentence SummaryWe propose a non-invasive {micro}ET technique using magnetically actuated microcarriers to improve embryo cargo-delivery in assisted reproduction, addressing challenges in infertility treatments by enabling precise, image-guided embryo delivery with minimal invasiveness.

bioengineering↗

bioRxiv2025

Pathological meprin α expression associated with degradation of dermokine drives a psoriasis-like skin phenotype in a genetic mouse model

Keratinocyte proliferation and differentiation is regulated via proteolytic networks. Dysregulation of proteases within these networks can cause hyperproliferative and inflammatory skin disorders. In healthy skin the metalloprotease meprin is localized in the stratum basale. In contrast, in wound healing tissue and psoriatic lesions increased meprin levels are found in the upper epidermal layers. We developed a transgenic mouse model for inducible expression of pathological meprin levels (K5M) to investigate its epidermal degradome and identify molecular links to keratinocyte proliferation and skin inflammation. K5M mice developed a severe skin phenotype characterized by hyperkeratosis, acanthosis and parakeratosis accompanied by increased transepidermal water loss and a strong inflammatory response within six days after induction of meprin overexpression. Histological and molecular analyses showed that increasing meprin expression correlates with meprin activity and keratinocyte hyperproliferation. Proteomics analyses revealed massive changes in proteins associated with keratinocyte differentiation and epidermal barrier integrity already three days after induction. N-terminomics data indicated a dominant chymotryptic activity with elevated proteolytic turnover of proteins associated with the cytoskeleton, cellular stress responses and cell adhesion. By filtering for cleavage sites that match with the specificity of meprin , we identified highly elevated dermokine-derived peptides. Subsequent mass spectrometric analyses validated dermokine as a novel substrate of meprin and identified the cleavage site, which is highly conserved in mammals. Based on the striking similarities with the phenotype reported for dermokine {beta}{gamma}-/- mice, we propose meprin as a central regulator of keratinocyte proliferation and leukocyte recruitment by proteolytic inactivation of dermokine. Hence, pathological meprin activity could be a driver of hyperproliferative, inflammatory skin disorders like psoriasis vulgaris.

molecular biology↗

bioRxiv2023

A cytokinetic ring-driven cell rotation achieves Hertwig's rule in early development

Cells tend to divide along the direction in which they are longest, as famously stated by Oscar Hertwig in 1884 in his long axis rule1,2. The orientation of the mitotic spindle determines the cell division axis3, and Hertwigs long axis rule is usually ensured by forces stemming from microtubules4. Pulling on the spindle from the cell cortex can give rise to unstable behaviors5,6, and we here set out to understand how Hertwigs long axis rule is realized in early embryonic divisions where cortical pulling forces are prevalent. We focus on early C. elegans development, where we compressed embryos to reveal that cortical pulling forces favor an alignment of the spindle with the cells short axis. Strikingly, we find that this misalignment is corrected by an actomyosin-based mechanism that rotates the entire cell, including the mitotic spindle. We uncover that myosin-driven contractility in the cytokinetic ring generates inward forces that align it with the short axis, and thereby the spindle with the long axis. A theoretical model together with experiments using slightly compressed mouse zygotes suggest that a constricting cytokinetic ring can ensure Hertwigs long axis rule in cells that are free to rotate inside a confining structure, thereby generalizing the underlying principle.

developmental biology↗

bioRxiv2023

Targeting the TCA cycle can ameliorate widespread axonal energy deficiency in neuroinflammatory lesions

Inflammation in the central nervous system (CNS) can impair the function of neuronal mitochondria and contributes to axon degeneration in the common neuroinflammatory disease multiple sclerosis (MS). Here we combine cell type-specific mitochondrial proteomics with in vivo biosensor imaging to dissect how inflammation alters the molecular composition and functional capacity of neuronal mitochondria. We show that neuroinflammatory lesions in the mouse spinal cord cause widespread and persisting axonal ATP deficiency, which precedes mitochondrial oxidation and calcium overload. This axonal energy deficiency is associated with impaired electron transport chain function, but also an upstream imbalance of tricarboxylic acid (TCA) cycle enzymes, with several, including key rate-limiting, enzymes being depleted in neuronal mitochondria in experimental models and in MS lesions. Notably, viral overexpression of individual TCA enzymes can ameliorate the axonal energy deficits in neuroinflammatory lesions, suggesting that TCA cycle dysfunction in MS may be amendable to therapy.

neuroscience↗

bioRxiv2022

Human photoreceptor cell transplants integrate into human retina organoids

Cell transplantation is a promising therapeutic approach to recover loss of neurons and vision in patient retinas. So far, human photoreceptor transplants restored some visual function in degenerating mouse retina. Whether retinal cell transplants also integrate into human retina, and how to optimize this for different pathologies are still unknown. Here, we sought to determine if human retina organoids generated from pluripotent stem cells might assist cell replacement therapy development in a human-to-human setting. Models for intra- and subretinal cell transplantation strategies were explored: Photoreceptor donor cells carrying a transgenic fluorescent reporter were enriched from acutely dissociated human retinal organoids. Donor cells were precisely transplanted by microinjection into the retina of host organoids, but high cell numbers might require multiple injections posing potential damage. Alternatively, donor cells were transplanted in large numbers by placing them in subretinal-like contact to the apical organoid surface. Using postmitotic retinal organoids (age >170-days) as a source for donor cells and as hosts, we show that six weeks after subretinal-like transplantation, large clusters of photoreceptors reproducibly incorporate into the host retina. Transplanted clusters frequently are located within or across the host photoreceptor layer, include cone and rod photoreceptors, and become infiltrated by cell processes of host Muller glia, indicative of structural integration. Histological and ultrastructural data of virally-labeled photoreceptor transplants show characteristic morphological and structural features of polarized photoreceptors: inner segments and ribbon synapses, and donor-host cell contacts develop contributing to the retinal outer limiting membrane. These results demonstrate that human retinal organoids provide a preclinical research system for cell replacement therapies. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=193 SRC="FIGDIR/small/500037v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@3a405dorg.highwire.dtl.DTLVardef@57c4deorg.highwire.dtl.DTLVardef@3de9c5org.highwire.dtl.DTLVardef@be9820_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

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↗

bioRxiv2021

A conserved role of Parkinson-associated DJ-1 metabolites in sperm motility, mitosis, and embryonic development

Fertility rates in the developing world have dramatically dropped in the last decades. This drop is likely due to a decline in sperm quality and women having children at older ages. Loss of function mutations in DJ-1, a Parkinsons associated gene, are linked to alterations in multiple cellular processes such as mitochondrial activity, ROS production or sperm motility and lead to an early onset of Parkinsons disease and male infertility in humans and other species. Glycolate (GA) and D-lactate (DL), products of DJ-1 glyoxalase activity, sustain mitochondrial function and protect against environmental aggressions. We, therefore, tested whether these substances could also have a rescue effect on these phenotypes. Here, we show that DJ-1 loss of function not only affects sperm motility but also leads to defects in mitosis and an age-dependent increase in the abortion rate. Remarkably, whereas DL was only able to rescue embryonic lethality in C. elegans, GA rescued these phenotypes in all model systems tested and even increased sperm motility in wild-type sperm. These positive effects seem to be mediated through an increase in NAD(P)H production and the regulation of intracellular calcium. These findings not only strongly suggest GA as a new therapeutic candidate to improve male and female fertility but also show its potential to treat diseases associated with a decline in mitochondrial function or to improve mitochondrial function in aging.

developmental biology↗

bioRxiv2020

Reduced purine biosynthesis in humans after their divergence from Neandertals

We analyze the metabolomes of humans, chimpanzees and macaques in muscle, kidney and three different regions of the brain. Whereas several compounds in amino acid metabolism occur at either higher or lower concentrations in humans than in the other primates, metabolites in oxidative phosphorylation and purine biosynthesis are consistently present in lower concentrations in the brains of humans. In particular, metabolites downstream of adenylosuccinate lyase, which catalyzes two reactions in purine synthesis, occur at lower concentrations in humans. This enzyme carries an amino acid substitution that is present in all humans today but absent in Neandertals. By introducing the modern human substitution into the genomes of mice, as well as the ancestral, Neandertal-like substitution into the genomes of human cells, we show that this amino acid substitution is responsible for much or all of the reduction of de novo synthesis of purines in humans.

evolutionary biology↗

bioRxiv2020

Enhanced differentiation of functional human T cells in NSGW41 mice with tissue-specific expression of human interleukin-7.

Humanized mouse models have become increasingly valuable tools to study human hematopoiesis and infectious diseases. However, human T cell differentiation remains inefficient. We generated mice expressing human interleukin (IL-7), a critical growth and survival factor for T cells, under the control of murine IL-7 regulatory elements. After transfer of human cord blood-derived hematopoietic stem and progenitor cells, transgenic mice on the NSGW41 background, termed NSGW41hIL7, showed elevated and prolonged human cellularity in the thymus while maintaining physiological ratios of thymocyte subsets. As a consequence, numbers of functional human T cells in the periphery were increased without evidence for pathological lymphoproliferation or aberrant expansion of effector or memory-like T cells. We conclude that the novel NSGW41hIL7 strain represents an optimized mouse model for humanization to better understand human T cell differentiation in vivo and to generate a human immune system with a better approximation of human lymphocyte ratios.

immunology↗

bioRxiv2020

Recapitulating evolutionary divergence in a single regulatory element causes expression changes of the lens gene Tdrd7

Mutations in cis-regulatory elements play important roles for phenotypic changes during evolution. Eye degeneration in the blind mole rat (BMR) and other subterranean mammals is significantly associated with widespread divergence of eye regulatory elements, but the effect of these regulatory mutations on eye development and function has not been explored. Here, we investigate the effect of mutations observed in the BMR sequence of a conserved non-coding element upstream of Tdrd7, a pleiotropic gene required for lens development and spermatogenesis. We first show that this conserved element is a transcriptional repressor in lens cells and that the BMR sequence partially lost repressor activity. Next, we recapitulated the evolutionary changes by precisely replacing the endogenous regulatory element in a mouse line by the orthologous BMR sequence with CRISPR-Cas9. Strikingly, this repressor element has a large effect, causing a more than two-fold up-regulation of Tdrd7 in developing lens. Interestingly, the increased mRNA level does not result in a corresponding increase in TDRD7 protein nor an obvious lens phenotype, likely explained by buffering at the posttranscriptional level. Our results are consistent with eye degeneration in subterranean mammals having a polygenic basis where many small-effect mutations in different eye-regulatory elements collectively contribute to phenotypic differences.

evolutionary biology↗

bioRxiv2020

Optimization of mouse embryonic stem cell culture for organoid and chimeric mice production.

In vitro stem cell culture is demanding in terms of manpower and media supplements. In recent years, new protocols have been developed to expand pluripotent embryonic stem cells in suspension culture, which greatly simplifies cell handling and scalability. However, it is still unclear how suspension culture protocols with different supplements affect pluripotency, cell homogeneity and cell differentiation compared to established adherent culture methods. Here we tested four different culture conditions for mouse embryonic stem cells (mESC) and quantified chimerism and germ line transmission as well as in vitro differentiation into three-dimensional neuro-epithelia. We found that suspension culture supplemented with CHIR99021/LIF offers the best compromise between culturing effort, robust pluripotency and cell homogeneity. Our work provides a guideline for simplifying mESC culture and should encourage more cell biology labs to use stem cell-based organoids as model systems.

cell biology↗

bioRxiv2018

The genomic and molecular basis of response to selection for longer limbs in mice

Evolutionary studies are often limited by missing data that are critical to understanding the history of selection. Selection experiments, which reproduce rapid evolution under controlled conditions, are excellent tools to study how genomes evolve under strong selection. Here we present a genomic dissection of the Longshanks selection experiment, in which mice were selectively bred over 20 generations for longer tibiae relative to body mass, resulting in 13% longer tibiae in two replicate lines. We synthesized evolutionary theory, genome sequences and molecular genetics to understand the selection response and found that it involved both polygenic adaptation and discrete loci of major effect, with the strongest loci likely to be selected in parallel between replicates. We show that selection may favor de-repression of bone growth through inactivation of two limb enhancers of an inhibitor, Nkx3-2. Our integrative genomic analyses thus show that it is possible to connect individual base-pair changes to the overall selection response.

evolutionary biology↗

bioRxiv2017

Genetic mapping of species differences via "in vitro crosses" in mouse embryonic stem cells

Discovering the genetic changes underlying species differences is a central goal in evolutionary genetics. However, hybrid crosses between species in mammals often suffer from hybrid sterility, greatly complicating genetic dissection of trait variation. Here we describe a simple, robust and transgene-free technique to make \"in vitro crosses\" in hybrid mouse embryonic stem cells by inducing random mitotic crossovers with the drug ML216, which inhibits Bloom syndrome (BLM). Starting with an interspecific hybrid (between Mus musculus and Mus spretus) embryonic stem cell line spanning 1.5 million years of divergence, we demonstrate the feasibility of mapping enzymatic differences across species within weeks and the possibility of re-deriving whole mice. Our work shows how in vitro crosses can overcome major bottlenecks like hybrid sterility in traditional mouse breeding to address fundamental questions in evolutionary biology.\n\nImpact StatementBy mixing hybrid mouse genomes in stem cells via mitotic recombination, genetic mapping and hybrid mosaic mice can be achieved in weeks, even across species barriers.

genetics↗