The human papillomavirus type 11 upstream regulatory region triggers hair-follicle-specific gene expression in transgenic mice

Why HPV16? Why, now, HPV42? How the discovery of HPV42 in rare cancers provides an opportunity to challenge our understanding about the transition between health and disease for common members of the healthy microbiota

In 2022, a bioinformatic, agnostic approach identified HPV42 as causative agent of a rare cancer, later confirmed experimentally. This unexpected association offers an opportunity to reconsider our understanding about papillomavirus infections and cancers. We have expanded our knowledge about the diversity of papillomaviruses and the diseases they cause. Yet, we still lack answers to fundamental questions, such as what makes HPV16 different from the closely related HPV31 or HPV33; or why the very divergent HPV13 and HPV32 cause focal epithelial hyperplasia, while HPV6 or HPV42 do not, despite their evolutionary relatedness. Certain members of the healthy skin microbiota are associated to rare clinical conditions. We propose that a focus on cellular phenotypes, most often transient and influenced by intrinsic and extrinsic factors, may help understand the continuum between health and disease. A conceptual switch is required towards an interpretation of biology as a diversity of states connected by transition probabilities, rather than quasi-deterministic programs. Under this perspective, papillomaviruses may only trigger malignant transformation when specific viral genotypes interact with precise cellular states. Drawing on Canguilhem's concepts of normal and pathological, we suggest that understanding the transition between fluid cellular states can illuminate how commensal-like infections transition from benign to malignant.

Transgenic HPV11-E2 protein modulates URR activity in vivo

In vitro experiments have shown that the E2 protein of human papillomaviruses (HPV) binds to the upstream regulatory region (URR) of the viral genome and modulates transcription. Additionally, it seems to be a necessary component for viral DNA replication together with E1. We have developed a transgenic mouse model containing the URR region of the low-risk virus HPV11 that regulates the expression of the lacZ reporter gene. Most interestingly, in these mice, the transgene was exclusively expressed in the bulge region of the hair follicle but not in any other tissues. Further experimental data indicate that in double transgenic mice that also express the HPV11-E2 protein under the control of the Ubiquitin C-promoter, the transcription of the reporter gene is modulated. When E2 is present, the expression of the reporter gene also occurs exclusively in the bulge region of the hair follicles as it does in the single transgenic mice, but the expression of the lacZ driven by the URR is increased and the statistical spread is greater. Even if the expression of the reporter gene occurs in the hair follicles of the dorsal skin of an animal uniform, E2 obviously has the capacity for both to induce and to repress the URR activity in vivo.

Expression of the HPV11 E2 gene in transgenic mice does not result in alterations of the phenotypic pattern

The E2 early protein of human papillomaviruses (HPV) has been found associated with the mitotic spindle therefore being implicated in the partition of the replicated viral DNA to daughter cells. In addition, E2 proteins bind to the upstream regulatory region of the virus and to cellular promoters modulating thereby cellular transcription and differentiation. In many cervical cancers, the E2 reading frame is interrupted upon incorporation of the viral genome into the host DNA. This results in the loss of the E2 mediated transcriptional repression and uncontrolled expression of the viral oncogenes. All these results have been obtained in transfected cells but no information is available on the E2 effects in the context of the entire organism. Transgenic mice were generated expressing the E2 protein of HPV11 under the control of the Ubiquitin C promoter. E2 mRNA is present in all mice tissues analysed and the E2 protein expressed in the skin (the target tissue of HPV11) was shown by Western blotting, albeit at a very low level. Analysis of the transgenic mice shows no major histological changes in the skin or all other tissues investigated. These data indicate that in transgenic mice the human papillomavirus type 11 E2 does not grossly modulate cellular proliferation or differentiation events.

Infarct volume after transient middle cerebral artery occlusion (MCAo) can be reduced by attenuation but not by inactivation of c-Jun action

Stroke therapy aims to save penumbral tissue from apoptosis that is activated in response to the ischemic injury. Since the c-Jun transcription factor plays a crucial role in promoting apoptosis, inhibition of its activation might reduce the final infarct size and thus increase functional outcome. To test this hypothesis we made use of four genetically modified mouse lines influencing the c-Jun pathway at various steps. Upon transient middle cerebral artery occlusion for 90 min and 24 h of reperfusion, infarct volume and number of ATF-2-, TUNEL- and cleaved Caspase-3-positive cells were determined in conditional c-Jun knock-out mice (cond. c-Jun), mice overexpressing JunB (JunBtg), mice lacking the phosphoacceptor serines 63 and 73 of c-Jun (JunAA) and in mice overexpressing Bcl-2 (Bcl-2tg). Cond. c-Jun as well as JunAA mice did not show significant differences in the infarct size when compared to their non-mutant controls. By contrast smaller infarct volumes were detected in transgenic mice merely attenuating c-Jun action (JunBtg and Bcl-2tg). ATF-2, TUNEL or cleaved Caspase-3 staining revealed no significant differences between the experimental groups. A complete lack of functional c-Jun might be compensated by other cellular mechanisms, in contrast to its reduced function. Thus, our data suggest that attenuation rather than a complete block of c-Jun action appears to be more promising for therapy of stroke.

What is the biological basis of pattern formation of skin lesions?

Pattern recognition is at the heart of clinical dermatology and dermatopathology. Yet, while every practitioner of the art of dermatological diagnosis recognizes the supreme value of diagnostic cues provided by defined patterns of 'efflorescences', few contemplate on the biological basis of pattern formation in and of skin lesions. Vice versa, developmental and theoretical biologists, who would be best prepared to study skin lesion patterns, are lamentably slow to discover this field as a uniquely instructive testing ground for probing theoretical concepts on pattern generation in the human system. As a result, we have at best scraped the surface of understanding the biological basis of pattern formation of skin lesions, and widely open questions dominate over definitive answer. As a symmetry-breaking force, pattern formation represents one of the most fundamental principles that nature enlists for system organization. Thus, the peculiar and often characteristic arrangements that skin lesions display provide a unique opportunity to reflect upon--and to experimentally dissect--the powerful organizing principles at the crossroads of developmental, skin and theoretical biology, genetics, and clinical dermatology that underlie these--increasingly less enigmatic--phenomena. The current 'Controversies' feature offers a range of different perspectives on how pattern formation of skin lesions can be approached. With this, we hope to encourage more systematic interdisciplinary research efforts geared at unraveling the many unsolved, yet utterly fascinating mysteries of dermatological pattern formation. In short: never a dull pattern!

Human papillomavirus and skin cancer

Human papillomavirus (HPV) appears to be the most ubiquitous of the human viruses. Over 100 HPV types have been identified. A minority of HPV cause cutaneous warts and mucosal condylomata. The HPV that cause mucosal condylomata put the patient at various degrees of risk for developing cancers, particularly cervical cancer. The majority of HPV infect the skin of normal and immunocompromised individuals. In normal people, most of these HPV appear to establish a latent infection of the skin, most likely as normal flora residing in hair follicles; however, in patients with various systemic and localized depressions of cell-mediated immunity, some HPV infections appear to be involved in the development of nonmelanotic skin cancer and its precursor lesions in skin, usually in sunlight-exposed areas. Circumstantial evidence suggests that these HPV may have a role in promoting proliferative lesions of the skin, although their sites of active infection and mode of transmission to susceptible individuals remain unknown.

Controls of hair follicle cycling

Nearly 50 years ago, Chase published a review of hair cycling in which he detailed hair growth in the mouse and integrated hair biology with the biology of his day. In this review we have used Chase as our model and tried to put the adult hair follicle growth cycle in perspective. We have tried to sketch the adult hair follicle cycle, as we know it today and what needs to be known. Above all, we hope that this work will serve as an introduction to basic biologists who are looking for a defined biological system that illustrates many of the challenges of modern biology: cell differentiation, epithelial-mesenchymal interactions, stem cell biology, pattern formation, apoptosis, cell and organ growth cycles, and pigmentation. The most important theme in studying the cycling hair follicle is that the follicle is a regenerating system. By traversing the phases of the cycle (growth, regression, resting, shedding, then growth again), the follicle demonstrates the unusual ability to completely regenerate itself. The basis for this regeneration rests in the unique follicular epithelial and mesenchymal components and their interactions. Recently, some of the molecular signals making up these interactions have been defined. They involve gene families also found in other regenerating systems such as fibroblast growth factor, transforming growth factor-beta, Wnt pathway, Sonic hedgehog, neurotrophins, and homeobox. For the immediate future, our challenge is to define the molecular basis for hair follicle growth control, to regenerate a mature hair follicle in vitro from defined populations, and to offer real solutions to our patients' problems.