Biology subjects

Mollenkopf, H.-J.

Publications and source records attributed to Mollenkopf, H.-J..

6 recordsLinked to original sources

bioRxiv2021

Spatial organisation and homeostasis of epithelial lineages at the gastroesophageal junction is regulated by the divergent Wnt mucosal microenvironment

The gastroesophageal junction (GEJ), where squamous and columnar epithelia meet, is a hotspot for Barretts metaplasia development, dysbiosis and carcinogenesis. However, the mechanisms regulating GEJ homeostasis remain unclear. Here, by employing organoids, bulk and single-cell transcriptomics, single-molecule RNA in situ hybridisations and lineage tracing, we identified the spatial organisation of the epithelial, stromal compartment and the regulators that maintain the normal GEJ homeostasis. During development, common KRT8 progenitors generate committed unilineage p63/KRT5-squamous and KRT8-columnar stem cells responsible for the regeneration of postnatal esophagus and gastric epithelium that meet at GEJ. A unique spatial distribution of Wnt regulators in the underlying stromal compartment of these stem cells creates diverging Wnt microenvironments at GEJ and supports their differential regeneration. Further, we show that these tissue-resident stem cells do not possess the plasticity to transdifferentiate to the other lineage with the altered Wnt signals. Our study provides invaluable insights into the fundamental process of GEJ homeostasis and is crucial for understanding disease development.

developmental biology↗

bioRxiv2021

Chlamydia coinfection inhibits HPV-induced safeguards of the cellular and genomic integrity in patient-derived ectocervical organoids

Cervical mucosa is continually confronted by coinfections with pathogenic microbes. In addition to human papillomavirus, coinfections with Chlamydia trachomatis have been associated with an increased risk of cervical cancer. However, the dynamics of coinfections, their impact on the epithelia, and their contribution to pathogenesis remain obscure. Using a novel human ectocervical squamous stratified epithelial organoids, we recapitulated the natural infections of the cervix by Chlamydia, HPV, and their coinfections. Towards this, we genetically manipulated the healthy organoids to mimic in vivo HPV persistence by introducing E6E7 oncogenes into the host genome. HPV persistent organoids show enhanced tissue regeneration, increased proliferation and differentiation of stem cells, and nuclear atypia resembling cervical intraepithelial neoplasia grade 1. We found that HPV interferes with normal Chlamydia development. Further, a unique transcriptional host response induced by Chlamydia and HPV leads to distinct reprogramming of host cell processes. Strikingly, in coinfections, Chlamydia impedes HPV-induced mechanisms that maintain cellular and genome integrity, including mismatch repair (MMR). Distinct post-translational proteasomal-degradation and E2F-mediated transcriptional regulation delineate the inverse regulation of MMR during coinfections. Our study employing organoids demonstrates the jeopardy of multiple sequential infection processes and the unique cellular microenvironment they create, accelerating neoplastic progression.

cancer biology↗

bioRxiv2020

Pleiotropic Roles for the Plasmodium berghei RNA Binding Protein UIS12 in Transmission and Oocyst Maturation

Colonization of the mosquito host by Plasmodium parasites is achieved by sexually differentiated gametocytes. Gametocytogenesis, gamete formation and fertilization are tightly regulated processes, and translational repression is a major regulatory mechanism for stage conversion. Here, we present a characterization of a Plasmodium berghei RNA binding protein, UIS12, that contains two conserved eukaryotic RNA recognition motifs (RRM). Targeted gene deletion resulted in viable parasites that replicate normally during blood infection, but form fewer gametocytes. Upon transmission to Anopheles stephensi mosquitoes, both numbers and size of midgut-associated oocysts were reduced and their development stopped at an early time point. As a consequence, no salivary gland sporozoites were formed indicative of a complete life cycle arrest in the mosquito vector. Comparative transcript profiling in mutant and wild-type infected red blood cells revealed a decrease in transcript abundance of mRNAs coding for signature gamete-, ookinete- and oocyst-specific proteins in uis12(-) parasites. Together, our findings indicate multiple roles for UIS12 in regulation of gene expression after blood infection in good agreement with the pleiotropic defects that terminate successful sporogony and onward transmission to a new vertebrate host.

molecular biology↗

bioRxiv2019

Preservation of stemness in high-grade serous ovarian cancer organoids requires low Wnt environment

High-grade serous ovarian cancer (HGSOC) likely originates from the fallopian tube (FT) epithelium. Here, we established 15 organoid lines from HGSOC primary tumor deposits that closely match the parental tumor mutational profile and phenotype. We found that Wnt pathway activation leads to growth arrest of these cancer organoids. Moreover, active BMP signaling is almost always required for generation of HGSOC organoids, while healthy FT organoids depend on BMP suppression by Noggin. Interestingly, FT organoids modified by stable shRNA knockdown (KD) of p53, PTEN, and Retinoblastoma (RB), also require a low Wnt environment for long-term growth, while FT organoid medium triggers growth arrest. Thus, early changes in the stem cell niche environment are needed to support outgrowth of these genetically altered cells. Indeed, comparative analysis of gene expression pattern and phenotype of normal and KD organoids confirmed that depletion of tumor suppressors triggers changes in the regulation of stemness and differentiation.

cancer biology↗

bioRxiv2018

The Aryl Hydrocarbon Receptor senses the Henna pigment Lawsone and mediates Yin-Yang effects on skin homeostasis

As a first host barrier, the skin is constantly exposed to environmental insults that perturb its integrity. Tight regulation of skin homeostasis is largely controlled by the aryl hydrocarbon receptor (AhR). Here, we demonstrate that Henna and its major pigment, the naphthoquinone Lawsone activate AhR, both in vitro and in vivo. In human keratinocytes and epidermis equivalents, Lawsone exposure enhances the production of late epidermal proteins, impacts keratinocyte differentiation and proliferation, and regulates skin inflammation. To determine the potential use of Lawsone for therapeutic application, we harnessed human, murine and zebrafish models. In skin regeneration models, Lawsone interferes with physiological tissue regeneration and inhibits wound healing. Conversely, in a human acute dermatitis model, topical application of a Lawsone-containing cream ameliorates skin irritation. Altogether, our study reveals how a widely used natural plant pigment is sensed by the host receptor AhR, and how the physiopathological context determines beneficial and detrimental outcomes.

cell biology↗

bioRxiv2018

Transition of Wnt signaling microenvironment delineates the squamo-columnar junction and emergence of squamous metaplasia of the cervix

The transition zones (TZ) between squamous and columnar epithelium constitute hotspots for the emergence of cancers. Carcinogenesis at these sites is often preceded by the development of metaplasia, where one epithelial type invades the neighboring one. It remains unclear how these niches are restrained at the boundary between the two epithelial types and what factors contribute to metaplasia. Here we show that the cervical squamo-columnar junction derives from two distinct stem cell lineages that meet at the TZ. In contrast to the prevailing notion, our analysis of cervical tissue showed that the TZ is devoid of any locally restricted, specialized stem cell population, which has been implicated as precursor of both cervical squamous cell carcinoma and adenocarcinoma. Instead, we reveal that these cancers originate from two separate stem cell lineages. We show that the switch in the underlying Wnt signaling milieu of the stroma is a key determinant of proliferation or quiescence of epithelial stem cell lineages at the TZ. Strikingly, while the columnar lineage of the endocervix is driven by Wnt signaling, the maintenance of squamous stratified epithelium of the ectocervix and emergence of squamous metaplasia requires inhibition of Wnt signaling via expression of Dickkopf2 (Dkk2) in the underlying stroma. Moreover, Notch signaling is required for squamous cell stratification. Thus, our results indicate that homeostasis at the TZ is not maintained by a transition from one epithelial type to another but rather results from alternative signals from the stromal compartment driving the differential proliferation of the respective cell lineages at the squamo-columnar junction.

cancer biology↗