Rank signaling regulates mammary gland development and epithelial differentiation. While Rank is expressed in both basal and luminal cells, its basal-specific role is unclear. Here, using inducible basal-specific Rank expression and lineage tracing, we show that Rank signaling regulates basal cell identity in postnatal mammary glands. Increased basal Rank activity disrupts basal and luminal identities, causing aberrant luminal-like differentiation, lactation defects, and premalignant lesions composed of hybrid basal-derived cells that progress to basal and luminal adenocarcinomas. Conversely, Rank loss reduces tumor formation and also impairs cell identity. Mechanistically, proteomic, transcriptomic, and chromatin analyses reveal that Rank activation drives epigenetic remodeling, leading to basal identity loss and tumor initiation. A basal Rank gene signature correlates with ductal carcinoma in situ recurrence, as well as poor outcomes in luminal breast cancers. Thus, basal Rank-driven lineage infidelity promotes pre-invasive lesions and transition to invasive breast cancer in females.

Background & Aims: Mouse models of lineage tracing have helped to describe the important subpopulations of hepatocytes responsible for liver regeneration. However, conflicting results have been obtained from different models. Herein, we aimed to reconcile these conflicting reports by repeating a key lineage-tracing study from pericentral hepatocytes and characterising this Axin2CreERT2 model in detail.Methods: We performed detailed characterisation of the labelled population in the Axin2CreERT2 model. We lineage traced this cell population, quantifying the labelled population over 1 year and performed in-depth phenotypic comparisons, including transcriptomics, metabolomics and analysis of proteins through immunohistochemistry, of Axin2CreERT2 mice to WT counterparts. Results: We found that after careful definition of a baseline population, there are marked differences in labelling between male and female mice. Upon induced lineage tracing there was no expansion of the labelled hepatocyte population in Axin2CreERT2 mice. We found substantial evidence of disrupted homeostasis in Axin2CreERT2 mice. Offspring are born with sub-Mendelian ratios and adult mice have perturbations of hepatic Wnt/b-catenin signalling and related metabolomic disturbance.Conclusions: We find no evidence of predominant expansion of the pericentral hepatocyte population during liver homeostatic regeneration. Our data highlight the importance of detailed preclinical model characterisation and the pitfalls which may occur when comparing across sexes and backgrounds of mice and the effects of genetic insertion into native loci.(c) 2023 The Author(s). Published by Elsevier B.V. on behalf of European Association for the Study of the Liver. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

Rank signaling pathway regulates mammary gland homeostasis and epithelial cell differentiation. Although Rank receptor is expressed by basal cells and luminal progenitors, its role in each individual cell lineage remains unclear. By combining temporal/lineage specific Rank genetic deletion with lineage tracing techniques, we found that loss of luminal Rank reduces the luminal progenitor pool and leads to aberrant alveolar-like differentiation with high protein translation capacity in virgin mammary glands. These Rank-deleted luminal cells are unable to expand during the first pregnancy, leading to lactation failure and impairment of protein synthesis potential in the parous stage. The unfit parous Rank-deleted luminal cells in the alveoli are progressively replaced by Rank-proficient cells early during the second pregnancy, thereby restoring lactation. Transcriptomic analysis and functional assays point to the awakening of basal bipotency after pregnancy by the induction of Rank/NF-κB signaling in basal parous cell to restore lactation and tissue homeostasis.

Objective To provide a survey of relevant literature on umbilical artery Doppler ultrasound use in clinical practice, technical considerations and limitations, and future perspectives. Methods Literature searches were conducted in PubMed and Medline, restricted to articles written in English. Additionally, the references of all analyzed studies were searched to obtain necessary information. Results The use of this technique as a routine surveillance method is only recommended for high-risk pregnancies with impaired placentation. Meta-analyses of randomized trials have established that obstetric management guided by umbilical artery Doppler findings can improve perinatal mortality and morbidity. The values of the indices of Umbilical artery Doppler decrease with advancing gestational age; however, a lack of consensus on reference ranges prevails. Conclusion Important clinical decisions are based on the information obtained with umbilical artery Doppler ultrasound. Future efforts in research are imperative to overcome the current limitations of the technique.

Rank signaling enhances stemness in mouse and human mammary epithelial cells (MECs) and mediates mammary tumor initiation. Mammary tumors initiated by oncogenes or carcinogen exposure display high levels of Rank and Rank pathway inhibitors have emerged as a new strategy for breast cancer prevention and treatment. Here, we show that ectopic Rank expression in the mammary epithelia unexpectedly delays tumor onset and reduces tumor incidence in the oncogene-driven Neu and PyMT models. Mechanistically, we have found that ectopic expression of Rank or exposure to Rankl induces senescence, even in the absence of other oncogenic mutations. Rank leads to DNA damage and senescence through p16/p19. Moreover, RANK-induced senescence is essential for Rank-driven stemness, and although initially translates into delayed tumor growth, eventually promotes tumor progression and metastasis. We uncover a dual role for Rank in the mammary epithelia: Rank induces senescence and stemness, delaying tumor initiation but increasing tumor aggressiveness.

Understanding how the liver regenerates is a key biological question. Hepatocytes are the principle regenerative population in the liver. Recently, numerous lineage tracing studies (which apply genetic tagging to a restricted population and track its descendants over time) have reported conflicting results using a variety of hepatocyte based reporting systems in mice[1][1],[2][2]. The first significant lineage tracing from a distinct subpopulation of hepatocytes in homeostasis reported hyper-proliferation of self-renewing pericentral hepatocytes with their subsequent expansion across the liver lobule[3][3]. This study used a CreERT2 construct knocked into the endogenous Axin2 locus; here termed Axin2CreERT2. Subsequent studies, using either a different pericentral marker (Lgr5[4][4]) or a different AxinCreERT2 transgene[5][5], did not show lineage tracing. Here we aim to reconcile these discrepancies by re-evaluating lineage tracing in the Axin2CreERT2 knock-in model and explore the physiological consequences of this mutant allele. We were unable to find evidence of expansion of an Axin2CreERT2 labelled population and show that this population, whilst zonated, is spread throughout the lobule rather than being zonally restricted. Finally, we report that this allele results in profound perturbation of the Wnt pathway and physiology in the mouse.### Competing Interest StatementThe authors have declared no competing interest. [1]: #ref-1 [2]: #ref-2 [3]: #ref-3 [4]: #ref-4 [5]: #ref-5

ABSTRACT The X-linked WTX/AMER1 protein constitutes an important component of the β-catenin destruction complex that can both enhance and suppress canonical β-catenin signaling. Somatic mutations in WTX/AMER1 have been found in a proportion of the pediatric kidney cancer Wilms’ tumor. By contrast, germline mutations cause the severe sclerosing bone dysplasia osteopathia striata congenita with cranial sclerosis (OSCS), a condition usually associated with fetal or perinatal lethality in male patients. Here we address the developmental and molecular function of WTX by generating two novel mouse alleles. We show that in addition to the previously reported skeletal abnormalities, loss of Wtx causes severe midline fusion defects including cleft palate and ectopic synostosis at the base of the skull. By contrast, deletion of the C-terminal part of the protein results in only mild developmental abnormalities permitting survival beyond birth. Adult analysis, however, revealed skeletal defects including changed skull morphology and an increased whole-body bone density, resembling a subgroup of male patients carrying a milder, survivable phenotype. Molecular analysis in vitro showed that while β-catenin fails to co-immunoprecipitate with the truncated protein, partial recruitment appears to be achieved in an indirect manner using AXIN/AXIN2 as a molecular bridge. Taken together our analysis provides a novel model for WTX-caused bone diseases and explains on the molecular level how truncation mutations in this gene may retain some of WTX-protein functions. © 2018 American Society for Bone and Mineral Research.

Coronary artery anomalies are common congenital disorders with serious consequences in adult life. Coronary circulation begins when the coronary stems form connections between the aorta and the developing vascular plexus. We recently identified the WNT signaling modulator R-spondin 3 (Rspo3), as a crucial regulator of coronary stem proliferation. Using expression analysis and tissue-specific deletion we now demonstrate that Rspo3 is primarily produced by cardiomyocytes. Moreover, we have employed CRISPR/Cas9 technology to generate novel Lgr4-null alleles that showed a significant decrease in coronary stem proliferation and thus phenocopied the coronary artery defects seen in Rspo3 mutants. Interestingly, Lgr4 mutants displayed slightly hypomorphic right ventricles, an observation also made after myocardial specific deletion of Rspo3. These results shed new light on the role of Rspo3 in heart development and demonstrate that LGR4 is the principal R-spondin 3 receptor in the heart.

Coronary arteries are essential to support the heart with oxygen, and coronary heart disease is one of the leading causes of death worldwide. The coronary arteries form at highly stereotyped locations and are derived from the primitive vascular plexus of the heart. How coronary arteries are remodeled and the signaling molecules that govern this process are poorly understood. Here, we have identified the Wnt-signaling modulator Rspo3 as a crucial regulator of coronary artery formation in the developing heart. Rspo3 is specifically expressed around the coronary stems at critical time points in their development. Temporal ablation of Rspo3 at E11.5 leads to decreased β-catenin signaling and a reduction in arterial-specific proliferation. As a result, the coronary stems are defective and the arterial tree does not form properly. These results identify a mechanism through which localized expression of RSPO3 induces proliferation of the coronary arteries at their stems and permits their formation.

Adrenal glands are zonated endocrine organs that are essential in controlling body homeostasis. How zonation is induced and maintained and how renewal of the adrenal cortex is ensured remain a mystery. Here we show that capsular RSPO3 signals to the underlying steroidogenic compartment to induce β-catenin signaling and imprint glomerulosa cell fate. Deletion of RSPO3 leads to loss of SHH signaling and impaired organ growth. Importantly, Rspo3 function remains essential in adult life to ensure replenishment of lost cells and maintain the properties of the zona glomerulosa. Thus, the adrenal capsule acts as a central signaling center that ensures replacement of damaged cells and is required to maintain zonation throughout life.

Liver zonation, the spatial separation of different metabolic pathways along the liver sinusoids, is fundamental for proper functioning of this organ, and its disruption can lead to the development of metabolic disorders such as hyperammonemia. Metabolic zonation involves the induction of β-catenin signaling around the central veins, but how this patterned activity is established and maintained is unclear. Here, we show that the signaling molecule Rspondin3 is specifically expressed within the endothelial compartment of the central vein. Conditional deletion of Rspo3 in mice disrupts activation of central fate, demonstrating its crucial role in determining and maintaining β-catenin-dependent zonation. Moreover, ectopic expression of Rspo1, a close family member of Rspo3, induces the expression of pericentral markers, demonstrating Rspondins to be sufficient to imprint a more central fate. Thus, Rspo3 is a key angiocrine factor that controls metabolic zonation of liver hepatocytes.

NET family members have recently emerged as important players in the development of multiple structures, from the trachea of fly larvae to the vertebrate eye and human breast cancers. However, their mechanisms of action are still poorly understood, and we lack a detailed characterization of their functional domains, as well as gene expression patterns—particularly in adult mammals. Here, we present a characterization of human NLZ1/ZNF703 (NocA‐like zinc finger 1/Zinc finger 703), one of the two human NET family member genes. We show that the gene is ubiquitously expressed in adult human and mouse tissues, that three mRNA species with the same coding sequence are generated by alternative polyadenylation, and that the encoded protein contains six evolutionarily conserved domains, three of which are specific to NET proteins. Finally, we present functional evidence that these domains are necessary for proper subcellular distribution of and transcription repression by the NLZ1 protein, but not for its interaction with Groucho family co‐repressors. J. Cell. Biochem. 114: 120–133, 2012. © 2012 Wiley Periodicals, Inc.

The accurate maintenance of genomic integrity is essential for tissue homeostasis. Deregulation of this process leads to cancer and aging. BRCA1 is a critical mediator of this process. Here, we performed conditional deletion of Brca1 during epidermal development and found that BRCA1 is specifically required for hair follicle (HF) formation and for development of adult HF stem cells (SCs). Mice deficient for Brca1 in the epidermis are hairless and display a reduced number of HFs that degenerate progressively. Surprisingly, the interfollicular epidermis and the sebaceous glands remain unaffected by Brca1 deletion. Interestingly, HF matrix transient amplifying progenitors present increased DNA damage, p53 stabilization, and caspase-dependent apoptosis compared with the interfollicular and sebaceous progenitors, leading to hyperproliferation, apoptosis, and subsequent depletion of the prospective adult HF SCs. Concomitant deletion of p53 and Brca1 rescues the defect of HF morphogenesis and loss of HF SCs. During adult homeostasis, BRCA1 is dispensable for quiescent bulge SCs, but upon their activation during HF regeneration, Brca1 deletion causes apoptosis and depletion of Brca1-deficient bulge SCs. Our data reveal a major difference in the requirement of BRCA1 between different types of epidermal SCs and progenitors and during the different activation stages of adult HF SCs.

Sweat glands are abundant in the body and essential for thermoregulation. Like mammary glands, they originate from epidermal progenitors. However, they display few signs of cellular turnover, and whether they have stem cells and tissue-regenerative capacity remains largely unexplored. Using lineage tracing, we here identify in sweat ducts multipotent progenitors that transition to unipotency after developing the sweat gland. In characterizing four adult stem cell populations of glandular skin, we show that they display distinct regenerative capabilities and remain unipotent when healing epidermal, myoepithelial-specific, and lumenal-specific injuries. We devise purification schemes and isolate and transcriptionally profile progenitors. Exploiting molecular differences between sweat and mammary glands, we show that only some progenitors regain multipotency to produce de novo ductal and glandular structures, but that these can retain their identity even within certain foreign microenvironments. Our findings provide insight into glandular stem cells and a framework for the further study of sweat gland biology.

Context: There are several genetic and molecular evidences suggesting dysregulation of the mammalian target of rapamycin (mTOR) pathway in thyroid neoplasia. Activation of the phosphatidylinositol-3-kinase/AKT pathway by RET/PTC and mutant RAS has already been demonstrated, but no data have been reported for the BRAFV600E mutation. Objective: The aim of this study was to evaluate the activation pattern of the mTOR pathway in malignant thyroid lesions and whether it may be correlated with known genetic alterations, as well as to explore the mechanisms underlying mTOR pathway activation in these neoplasias. Results: We observed, by immunohistochemical evaluation, an up-regulation/activation of the mTOR pathway proteins in thyroid cancer, particularly in conventional papillary thyroid carcinoma (cPTC). Overactivation of the mTOR signaling was particularly evident in cPTC samples harboring the BRAFV600E mutation. Transfection assays with BRAF expression vectors as well as BRAF knockdown by small interfering RNA revealed a positive association between BRAF expression and mTOR pathway activation, which appears to be mediated by pLKB1 Ser428, and emerged as a possible mechanism contributing to the association between BRAF mutation and mTOR pathway up-regulation. When we evaluated the rapamycin in the growth of thyroid cancer cell lines, we detected that cell lines with activating mutations in the MAPK pathway show a higher sensitivity to this drug. Conclusions: We determined that the AKT/mTOR pathway is particularly overactivated in human cPTC harboring the BRAFV600E mutation. Moreover, our results suggest that the mTOR pathway could be a good target to enhance therapy effects in certain types of thyroid carcinoma, namely in those harboring the BRAFV600E mutation.

The mammary epithelium is composed of several cell lineages including luminal, alveolar and myoepithelial cells. Transplantation studies have suggested that the mammary epithelium is maintained by the presence of multipotent mammary stem cells. To define the cellular hierarchy of the mammary gland during physiological conditions, we performed genetic lineage-tracing experiments and clonal analysis of the mouse mammary gland during development, adulthood and pregnancy. We found that in postnatal unperturbed mammary gland, both luminal and myoepithelial lineages contain long-lived unipotent stem cells that display extensive renewing capacities, as demonstrated by their ability to clonally expand during morphogenesis and adult life as well as undergo massive expansion during several cycles of pregnancy. The demonstration that the mammary gland contains different types of long-lived stem cells has profound implications for our understanding of mammary gland physiology and will be instrumental in unravelling the cells at the origin of breast cancers.

Ocular melanoma is the most common eye malignancy in adults. It usually arises in the uvea, mostly in the choroid and less frequently in the conjunctiva. There is no curative therapy available when it becomes metastatic. The etiopathogenesis of uvea and conjunctiva melanomas is still poorly understood. The mammalian target of rapamycin (mTOR) pathway is involved in many biological processes and has been implicated in the development of cutaneous melanoma tumours. The mTOR pathway is an important target for anticancer drug development, and an inhibitor of this pathway has already been approved for use in humans to treat advanced renal cell carcinoma. The aim of this study was to evaluate the contribution of the mTOR pathway in uvea and conjunctiva melanomas. We analysed specific mTOR pathway effectors using immunohistochemical analysis of 30 uvea and eight conjunctiva melanoma samples. We assessed the association with prognostic clinical-pathological features, and performed mutational analysis on the BRAF and NRAS genes. None of the cases had mutations in either BRAF or NRAS. Expression of phospho-AKT Thr308 was associated with metastatic uvea melanomas. In conjunctiva melanomas, overactivation of the mTOR pathway, as confirmed by high phospho-AKT Ser473 and Thr308, S6 and p4EBP1 Thr37/46 levels, was associated with adverse prognostic parameters (mitotic index and tumour thickness). Conjunctiva melanomas displayed high expression of phospho-mTOR effectors in contrast with uvea melanomas, in which PTEN seemed to downregulate the mTOR pathway. Characterizing the expression of PTEN, AKT and pS6 Ser235/236 might be a useful predictive tool for deciding whether to use mTOR inhibitors to treat conjunctiva melanomas.

The current ligaments treatment injuries has several drawbacks that prompted attempts to use synthetic materials in ligament replacements. Although fibroblasts do not comprise a large volume of ligament tissue, they have an important role in ligament tissue regeneration as they are able to model ECM and angiogenesis, therefore affecting the healing process.The aim is to appraise the biocompatibility of different biodegrable ligament composites (PGA‐PCL, PLA‐PCL, PDO, PGA) with the fibroblast‐mediated angiogenic process in vitro.HFF1 fibroblast cells were cultured on plates coated with each of the composite and cell viability was examined. Media from HFF1 cells incubated with composite material was removed and used to appraise the effect on angiogenesis (aortic ring assay and capillary‐like structures formation assay).No significant difference in cell viability was found for any composite tested. Aortic ring results suggested no disturbance of the angiogenic process. These findings were corroborated by the formation of cord‐like structures assay, as no significant difference in the number of structures was found in comparison to controls.Overall, our preliminary findings indicate that the composites do not promote nor prevent angiogenesis, being thus a good tool for the development of ligament composites. Supported by FCT (PTDC/EME‐PME/70155/2006)