NEW WORK IN STEM CELLS

Stem Cells. 2012 Mar 21. doi: 10.1002/stem.1090. [Epub ahead of print]

The Proto-Oncogene Myc is Essential for Mammary Stem Cell Function.

Moumen M, Chiche A, Deugnier MA, Petit V, Gandarillas A, Glukhova MA, Faraldo MM.

Source

Institut Curie, Centre de Recherche, Paris, F-75248 France; CNRS, UMR144, Paris, F-75248, France.

Abstract

The mammary epithelium comprises two major cell lineages: basal and luminal. Basal cells (BCs) isolated from the mammary epithelium and transplanted into the mouse mammary fat pad cleared from the endogenous epithelium regenerate the mammary gland, strongly suggesting that the basal epithelial compartment harbors a long-lived cell population with multipotent stem cell potential. The luminal cell layer is devoid of the regenerative potential but it contains cells with clonogenic capacity, the luminal progenitors. Mammary BCs and luminal progenitors express high levels of the transcription factor Myc. Here we show that deletion of Myc from mammary basal epithelial cells led to impaired stem cell self-renewal as evaluated by limiting dilution and serial transplantation assays. Luminal progenitor population was significantly diminished in mutant epithelium suggesting control by the basal cell layer. Colony formation assay performed with isolated basal cells showed that clonogenic capacity was abolished by Myc deletion. Moreover, transplanted BCs depleted of Myc failed to produce epithelial outgrowths. Stimulation with ovarian hormones estrogen (E) and progesterone (P) partially rescued the repopulation capacity of Myc-depleted BCs, however, the Myc-deficient mammary epithelium developed in response to E/P treatment lacked stem and progenitor cells. This study provides the first evidence that in the mammary gland, Myc has an essential non-redundant function in the maintenance of the self-renewing multipotent stem cell population responsible for the regenerative capacity of the mammary epithelium and is required downstream from ovarian hormones, for the control of mammary stem and progenitor cell functions.

Copyright © 2012 AlphaMed Press.
PMID:
22438054
[PubMed - as supplied by publisher]

THE BEAUTIFUL ORGAN



A human skin section fluorescence-labelled for differentiation cytoskeleton keratin 1 (K1; green) and the precursor of the cornified envelope, involucrin (red). Photo: Alberto Gandarillas, Biopsy processing: Ana Freije and Laura Ceballos. Skin provided by Ernesto De Diego at the Valdecilla Hospital of Santander.

WORK ACCEPTED FOR PUBLICATION IN ONCOGENE

This work, now in press:

-links cell cycle activation with epidermal differentiation.

An In Vitro Colony of human keratinocytes isolated from a skin biopsy
obtained by Dr. E. de Diego at the Paediatric Surgery Department
of the Valdecilla Hospital in Santander.

-proposes a model for the coordination between proliferation and terminal differentiation in epidermis.
-reports a skin anti-oncogenic mechanism.
-provides evidence for an oncogene-induced differentiation checkpoint.

Soon in Oncogene and Pubmed.



Oncogene. 2012 Feb 20. doi: 10.1038/onc.2012.22. [Epub ahead of print]
Cyclin E drives human keratinocyte growth into differentiation. Freije A, Ceballos L, Coisy M, Barnes L, Rosa M, De Diego E, Blanchard JM, Gandarillas A.
Source
1] Cell Cycle, Stem Cell Fate and Cancer Laboratory. Institute for Training and Research of the Fundación Marqués de Valdecilla (IFIMAV-FMDV), Santander, Spain [2] Molecular Biology Department of Universidad de Cantabria (UC), Santander, Spain.
Abstract
Human epidermis is continuously exposed to environmental mutagenic hazard and is the most frequent target of human cancer. How the epidermis coordinates proliferation with differentiation to maintain homeostasis, even in hyperproliferative conditions, is unclear. For instance, overactivation of the proto-oncogene MYC in keratinocytes stimulates differentiation. Here we explore the cell cycle regulation as proliferating human keratinocytes commit to terminal differentiation upon loss of anchorage or overactivation of MYC. The S-phase of the cell cycle is deregulated as mitotic regulators are inhibited in the onset of differentiation. Experimental inhibition of mitotic kinase cdk1 or kinases of the mitosis spindle checkpoint Aurora B or Polo-like Kinase, triggered keratinocyte terminal differentiation. Furthermore, hyperactivation of the cell cycle by overexpressing the DNA replication regulator Cyclin E induced mitosis failure and differentiation. Inhibition of Cyclin E by shRNAs attenuated the induction of differentiation by MYC. In addition, we present evidence that Cyclin E induces DNA damage and the p53 pathway. The results provide novel clues for the mechanisms committing proliferative keratinocytes to differentiate, with implications for tissue homeostasis maintenance, HPV amplification and tumorigenesis.Oncogene advance online publication, 20 February 2012; doi:10.1038/onc.2012.22.
PMID:
22349815
[PubMed - as supplied by publisher]

NEW WORK IN JOURNAL OF CELLULAR PHYSIOLOGY



J Cell Physiol. 2011 Jul 18. doi: 10.1002/jcp.22935. [Epub ahead of print]

MYC accelerates p21(CIP) -induced megakaryocytic differentiation involving early mitosis arrest in leukemia cells.

Muñoz-Alonso MJ, Ceballos L, Bretones G, Frade P, León J, Gandarillas A.

Source

Dpto. de Biología Molecular, Universidad de Cantabria.

Abstract

Supplementary Figure 3.
Muñoz-Alonso et al, 2011.



p21(CIP) is a potent cell cycle inhibitor often up-regulated in differentiation. Protooncogene MYC induces cell growth and proliferation, inhibits differentiation and represses p21(CIP) . However, both molecules are involved in processes of polyploidisation, cell size increase, differentiation and senescence. It is unclear why MYC has a dual role in differentiation. We have previously shown that overexpression of p21(CIP) in K562 myeloid cells induces megakaryocytic differentiation with polyploidy. We have now investigated the requirements for p21(CIP) to block mitosis and induce differentiation in the presence of overactivated MYC. Silencing and over-expression studies showed that p21(CIP) is required to induce differentiation. However, the expression of p21(CIP) needs to be transient to irreversibly inhibit mitosis but not DNA replication, what leads to polyploidy. Transient overexpression of p21(CIP) caused early down-regulation of mitotic Cyclins and up-regulation of G1/S Cyclins D and E, changes typical of endoreplication. Interestingly, over-activation of MYC did not release the proliferative block imposed by p21(CIP) and instead, accelerated cell size increase, megakaryocytic differentiation and polyploidisation. Our data suggests that in some systems p21(CIP) takes part in a mitosis control driving MYC-induced cellular growth into differentiation. J. Cell. Physiol. © 2011 Wiley-Liss, Inc.

Copyright © 2011 Wiley-Liss, Inc.

PMID: 21769863

OUR MODEL FOR CELL CYCLE AND DIFFERENTIATION IN HUMAN EPIDERMIS

Figure 10. Model for the relationship between cell cycle and differentiation in human epidermis.

Stem cells within the basal layer (SC; yellow) by division give rise to actively cycling cells that proliferate rapidly (ACC; pink). ACC lose adherence to the basement membrane, block mitosis, initiate terminal differentiation, migrate into suprabasal layers and continue DNA replication (red). Some of them undergo endomitosis in peribasal layers and become binucleate. Suprabasal keratinocytes lose mitotic cyclins A and B and reinitiate DNA replication in the absence of nuclear division (endoreduplication; punctuated red), the nuclei becoming polyploid. Endomitosis and endoreduplication are different forms of endoreplication.

doi:10.1371/journal.pone.0015701.g010




- WORKS ONGOING -  

                           

Cyclin B in normal human epidermis (red)  Keratin 1 (green)  DNA (blue)