Although the existence of mammary stem cells has been suggested by serial transplantation studies in mice, their identification has been hindered by the lack of specific surface markers, and by the absence of suitable in vitro assays for testing stem cell properties: self-renewal and ability to generate differentiated progeny. We have developed an in vitro cultivation system that allows for propagation of human mammary epithelial cells (HMECs) in an undifferentiated state, based on their ability to proliferate in suspension, as nonadherent mammospheres. We demonstrate that nonadherent mammospheres are enriched in early progenitor/stem cells and able to differentiate along all three mammary epithelial lineages and to clonally generate complex functional structures in reconstituted 3D culture systems. Gene expression analysis of cells isolated from nonadherent mammospheres revealed overlapping genetic programs with other stem and progenitor cells and identified new markers that may be useful in the identification of mammary stem cells. The isolation and characterization of these stem cells should help elucidate the molecular pathways that govern normal mammary development and carcinogenesis.

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In vitro propagation and transcriptional profiling of human mammary stem/progenitor cells

Deficient T cell fate specification in mice with an induced inactivation of Notch1.

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 Chas...

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Controls of hair follicle cycling.

Notch signaling dictates cell fate and critically influences cell proliferation, differentiation, and apoptosis in metazoans. Multiple factors at each step-ligands, receptors, signal transducers and effectors-play critical roles in executing the pleiotropic effects of Notch signaling. Ligand-binding results in proteolytic cleavage of Notch receptors to release the signal-transducing Notch intracellular domain (NICD). NICD migrates into the nucleus and associates with the nuclear proteins of the RBP-Jkappa family (also known as CSL or CBF1/Su(H)/Lag-1). RBP-Jkappa, when complexed with NICD, acts as a transcriptional activator, and the RBP-Jkappa-NICD complex activates expression of primary target genes of Notch signaling such as the HES and enhancer of split [E(spl)] families. HES/E(spl) is a basic helix-loop-helix (bHLH) type of transcriptional repressor, and suppresses expression of downstream target genes such as tissue-specific transcriptional activators. Thus, HES/E(spl) directly affects cell fate decisions as a primary Notch effector. HES/E(spl) had been the only known effector of Notch signaling until a recent discovery of a related but distinct bHLH protein family, termed HERP (HES-related repressor protein, also called Hey/Hesr/HRT/CHF/gridlock). In this review, we summarize the recent data supporting the idea of HERP being a new Notch effector, and provide an overview of the similarities and differences between HES and HERP in their biochemical properties as well as their tissue distribution. One key observation derived from identification of HERP is that HES and HERP form a heterodimer and cooperate for transcriptional repression. The identification of the HERP family as a Notch effector that cooperates with HES/E(spl) family has opened a new avenue to our understanding of the Notch signaling pathway.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/jcp.10208

HES and HERP families: multiple effectors of the Notch signaling pathway.

Alagille syndrome is an autosomal dominant disorder characterized by abnormal development of liver, heart, skeleton, eye, face and, less frequently, kidney Analyses of many patients with cytogenetic deletions or rearrangements have mapped the gene to chromosome 20p12, although deletions are found in a relatively small proportion of patients (< 7%) We have mapped the human Jagged1 gene (JAG1), encoding a ligand for the developmentally important Notch transmembrane receptor, to the Alagille syndrome critical region within 20p12 The Notch intercellular signalling pathway has been shown to mediate cell fate decisions during development in invertebrates and vertebrates We demonstrate four distinct coding mutations in JAG1 from four Alagille syndrome families, providing evidence that it is the causal gene for Alagille syndrome All four mutations lie within conserved regions of the gene and cause translational frameshifts, resulting in gross alterations of the protein product Patients with cytogenetically detectable deletions including JAG1 have Alagille syndrome, supporting the hypothesis that haploinsufficiency for this gene is one of the mechanisms causing the Alagille syndrome phenotype

Alagille syndrome is caused by mutations in human Jagged1, which encodes a ligand for Notch1

The int-3 oncogene was identified as a frequent target in Mouse Mammary Tumor Virus (MMTV)-induced mammary carcinomas and encodes the intracellular domain of a novel mouse Notch gene. To investigate the role of the int-3 proto-oncogene in mouse development and carcinogenesis, we isolated cDNA clones corresponding to the entire coding potential of the int-3 proto-oncogene. We propose to name this gene Notch4 and reserve the int-3 nomenclature for references to the oncogenic form. The deduced amino acid sequence of Notch4 contains conserved motifs found in Notch proteins; however Notch4 has fewer epidermal growth factor (EGF)-like repeats and a shorter intracellular domain than other mouse Notch homologues. Comparison of the coding potential of the int-3 gene to that of Notch4 suggests that loss of the extracellular domain of Notch4 leads to constitutive activation of this murine Notch protein. In situ hybridization revealed that Notch4 transcripts are primarily restricted to endothelial cells in embryonic and adult life. Truncated Notch4 transcripts were detected in post-meiotic male germ cells. The distinct Notch4 protein features and its restricted expression pattern suggests a specific role for Notch4 during development of vertebrate endothelium.

Notch4/int-3, a mammary proto-oncogene, is an endothelial cell-specific mammalian Notch gene

BACKGROUNDFollicular Unit Transplantation (FUT) is performed using large numbers of naturally occuring individual follicular units obtained by single-strip harvesting and stereo-microscopic dissection. Donor wound scarring from strip excision, although an infrequent complication, still concerns enou

/pdf/follicular-unit-extraction-minimally-invasive-surgery-for-4x8qzdnxhj.pdf

Follicular unit extraction: minimally invasive surgery for hair transplantation.

The recent discovery of the human counterpart of the hairless mouse phenotype1 has helped our understanding of the molecular genetics of hair growth. But there are no reports of a defect in the human homologue of the best known of the ‘bald’ mouse phenotypes, the nude mouse2. This may be because affected individuals are so gravely ill from the accompanying immunodeficiency that their baldness goes unnoticed. We have carried out a genetic analysis that reveals a human homologue of the nude mouse.

/pdf/exposing-the-human-nude-phenotype-384sb17pyq.pdf

Exposing the human nude phenotype

Notch4 and wnt-1 proteins function to regulate branching morphogenesis of mammary epithelial cells in an opposing fashion

The protein encoded by the Notch4 gene is a member of the Notch/lin-12 family of transmembrane receptor proteins, which have been shown to control cell fate determination and cell differentiation in a wide variety of organisms. Expression of Notch4(int-3), a truncated form of Notch4 having most of its extracellular domain deleted, as a transgene in mice induces the formation of poorly differentiated mammary carcinomas. To establish whether Notch4(int-3) has the capacity of subverting normal epithelial architecture, we assessed the effect of Notch4(int-3) expression on the in vitro morphogenetic properties of TAC-2 mammary epithelial cells. When grown in three-dimensional collagen gels in the presence of hydrocortisone, both wild-type and LacZ-transfected TAC-2 cells formed alveolar-like structures composed of polarized epithelial cells surrounding a central lumen. In contrast, TAC-2 cells programmed to express Notch4(int-3) formed compact cell aggregates devoid of tissue-specific organization. In addition, when grown on the surface of a collagen gel, Notch4(int-3)-expressing TAC-2 cells invaded the underlying matrix, whereas TAC-2 LacZ cells remained strictly confined to the gel surface. Expression of Notch4(int-3) in TAC-2 cells also disrupted contact-inhibition of cell proliferation, resulting in cell multilayering. Our results suggest that the ability of Notch4(int-3) to subvert normal epithelial morphogenesis and to promote invasion of the extracellular matrix contributes significantly to its tumorigenic potential.

Hendrik Uyttendaele

Papers

Notch4/int-3, a mammary proto-oncogene, is an endothelial cell-specific mammalian Notch gene

Follicular unit extraction: minimally invasive surgery for hair transplantation.

Exposing the human nude phenotype

Notch4 and wnt-1 proteins function to regulate branching morphogenesis of mammary epithelial cells in an opposing fashion

Expression of an activated Notch4(int-3) oncoprotein disrupts morphogenesis and induces an invasive phenotype in mammary epithelial cells in vitro.