Lack of IRF6 Disrupts Human Epithelial Homeostasis by Altering Colony Morphology, Migration Pattern, and Differentiation Potential of Keratinocytes.

Variants within the gene encoding for the transcription factor Interferon Regulatory Factor 6 (IRF6) are associated with syndromic and non-syndromic Cleft Lip/Palate (CLP) cases. IRF6 plays a vital role in the regulation of the proliferation/differentiation balance in keratinocytes and is involved in wound healing and migration. Since a fraction of CLP patients undergoing corrective cleft surgery experience wound healing complications, IRF6 represents an interesting candidate gene linking the two processes. However, Irf6 function has been mainly studied in mice and knowledge on IRF6 in human cells remains sparse. Here, we aimed to elucidate the role of IRF6 in human postnatal skin- and oral mucosa-derived keratinocytes. To do so, we applied CRISPR/Cas9 to ablate IRF6 in two TERT-immortalized keratinocyte cultures, which we used as model cell lines. We show that IRF6 controls the appearance of single cells and colonies, with the latter being less cohesive in its absence. Consequently, IRF6 knockout keratinocytes often moved as single cells instead of a collective epithelial sheet migration but maintained their epithelial character. Lack of IRF6 triggered severe keratinocyte differentiation defects, which were already apparent in the stratum spinosum and extended to the stratum corneum in 3D organotypic skin cultures, while it did not alter their growth rate. Finally, proteomics revealed that most of the differentially expressed proteins in the absence of IRF6 could be associated with differentiation, cell-cell adhesion as well as immune response. Our data expand the knowledge on IRF6 in human postnatal keratinocytes, which will help to better understand IRF6-related pathologies

A Living Cell Repository of the Cranio-/Orofacial Region to Advance Research and Promote Personalized Medicine

The prevalence of congenital anomalies in newborns is estimated to be as high as 6%, many of which involving the cranio-/orofacial region. Such malformations, including several syndromes, are usually identified prenatally, at birth, or rarely later in life. The lack of clinically relevant human cell models of these often very rare conditions, the societal pressure to avoid the use of animal models and the fact that the biological mechanisms between rodents and human are not necessarily identical, makes studying cranio-/orofacial anomalies challenging. To overcome these limitations, we are developing a living cell repository of healthy and diseased cells derived from the cranio-/orofacial region. Ultimately, we aim to make patient-derived cells, which retain the molecular and genetic characteristics of the original anomaly or disease in vitro, available for the scientific community. We report our efforts in establishing a human living cell bank derived from the cranio-/orofacial region of otherwise discarded tissue samples, detail our strategy, processes and quality checks. Such specific cell models have a great potential for discovery and translational research and might lead to a better understanding and management of craniofacial anomalies for the benefit of all affected individuals

A Novel Van der Woude Syndrome-Causing IRF6 Variant Is Subject to Incomplete Non-sense-Mediated mRNA Decay Affecting the Phenotype of Keratinocytes

Van der Woude syndrome (VWS) is a genetic syndrome that leads to typical phenotypic traits, including lower lip pits and cleft lip/palate (CLP). The majority of VWS-affected patients harbor a pathogenic variant in the gene encoding for the transcription factor interferon regulatory factor 6 (IRF6), a crucial regulator of orofacial development, epidermal differentiation and tissue repair. However, most of the underlying mechanisms leading from pathogenic IRF6 gene variants to phenotypes observed in VWS remain poorly understood and elusive. The availability of one VWS individual within our cohort of CLP patients allowed us to identify a novel VWS-causing IRF6 variant and to functionally characterize it. Using VWS patient-derived keratinocytes, we reveal that most of the mutated IRF6_VWS transcripts are subject to a non-sense-mediated mRNA decay mechanism, resulting in IRF6 haploinsufficiency. While moderate levels of IRF6_VWS remain detectable in the VWS keratinocytes, our data illustrate that the IRF6_VWS protein, which lacks part of its protein-binding domain and its whole C-terminus, is noticeably less stable than its wild-type counterpart. Still, it maintains transcription factor function. As we report and characterize a so far undescribed VWS-causing IRF6 variant, our results shed light on the physiological as well as pathological role of IRF6 in keratinocytes. This acquired knowledge is essential for a better understanding of the molecular mechanisms leading to VWS and CLP

Evaluation of polyvinylpyrrolidone and block copolymer micelle encapsulation of serine chlorin e6 and chlorin e4 on their reactivity towards albumin and transferrin and their cell uptake.

Encapsulation of porphyrinic photosensitizers (PSs) into polymeric carriers plays an important role in enhancing their efficiency as drugs in photodynamic therapy (PDT). Porphyrin aggregation and low solubility as well as the preservation of the advantageous photophysical properties pose a challenge on the design of efficient PS-carrier systems. Block copolymer micelles (BCMs) and polyvinylpyrrolidone (PVP) are promising drug delivery vehicles for physical entrapment of PSs. BCMs exhibit enhanced dynamics as compared to the less flexible PVP network. In the current work the question is addressed how these different dynamics affect PS encapsulation, release from the carrier, reaction with serum proteins, and cellular uptake. The porphyrinic compounds serine-amide of chlorin e6 (SerCE) and chlorin e4 (CE4) were used as model PSs with different lipophilicity and aggregation properties. 1H NMR and fluorescence spectroscopy were applied to study their interactions with PVP and BCMs consisting of Kolliphor P188 (KP). Both chlorins were well encapsulated by the carriers and had improved photophysical properties. Compared to SerCE, the more lipophilic CE4 exhibited stronger hydrophobic interactions with the BCM core, stabilizing the system and preventing exchange with the surrounding medium as was shown by NMR NOESY and DOSY experiments. PVP and BCMs protected the encapsulated chlorins against interaction with human transferrin (Tf). However, SerCE and CE4 were released from BCMs in favor of binding to human serum albumin (HSA) while PVP prevented interaction with HSA. Fluorescence spectroscopic studies revealed that HSA binds to the surface of PVP forming a protein corona. PVP and BCMs reduced cellular uptake of the chlorins. However, encapsulation into BCMs resulted in more efficient cell internalization for CE4 than for SerCE. HSA significantly lowered both, free and carrier-mediated cell uptake for CE4 and SerCE. In conclusion, PVP appears as the more universal delivery system covering a broad range of host molecules with respect to polarity, whereas BCMs require a higher drug-carrier compatibility. Poorly soluble hydrophobic PSs benefit stronger from BCM-type carriers due to enhanced bioavailability through disaggregation and solubilization allowing for more efficient cell uptake. In addition, increased PS-carrier hydrophobic interactions have a stabilizing effect. For more hydrophilic PSs, the main advantage of polymeric carriers like PVP or poloxamer micelles lies in their protection during the transport through the bloodstream. HSA binding plays an important role for drug release and cell uptake in carrier-mediated delivery to the target tissue