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Biomedical subjects

Alea A Mills

Publications and source records attributed to Alea A Mills.

At least 19 recordsLinked to original sources
PubMed2007

p63, cellular senescence and tumor development.

Deficiency of p63, a p53-related protein, causes severe defects in epithelial morphogenesis. Studies of p63-compromised mouse models reveal that p63 deficiency induces cellular senescence both in cultured cells and in vivo, through regulation p19(Arf)/p53 and p16(Ink4a)/Rb pathways. An extensive tumor study of p63-compromised mice demonstrated that p63 deficiency does not predispose to, but rather protects from, tumor development. These findings further implicate p63 as a negative regulator of the tumor suppressive mechanism of cellular senescence.

Animals↗
PubMed2006

DeltaNp63 plays an anti-apoptotic role in ventral bladder development.

The bladder, the largest smooth-muscle organ in the human body, is responsible for urine storage and micturition. P63, a homolog of the p53 tumor-suppressor gene, is essential for the development of all stratified epithelia, including the bladder urothelium. The N-terminal truncated isoform of p63, DeltaNp63, is known to have anti-apoptotic characteristics. We have established that DeltaNp63 is not only the predominant isoform expressed throughout the bladder, but is also preferentially expressed in the ventral bladder urothelium during early development. We observed a host of ventral defects in p63-/- embryos, including the absence of the abdominal and ventral bladder walls. This number of ventral defects is identical to bladder exstrophy, a congenital anomaly exhibited in human neonates. In the absence of p63, the ventral urothelium was neither committed nor differentiated, whereas the dorsal urothelium was both committed and differentiated. Furthermore, in p63-/- bladders, apoptosis in the ventral urothelium was significantly increased. This was accompanied by the upregulation of mitochondrial apoptotic mediators Bax and Apaf1, and concurrent upregulation of p53. Overexpression of DeltaNp63gamma and DeltaNp63beta in p63-/- bladder primary cell cultures resulted in a rescue, evidenced by significantly reduced expressions of Bax and Apaf1. We conclude that DeltaNp63 plays a crucial anti-apoptotic role in normal bladder development.

Animals↗
PubMed2006

p63 regulates an adhesion programme and cell survival in epithelial cells.

p63 is critical for epithelial development yet little is known about the transcriptional programmes it regulates. By characterising transcriptional changes and cellular effects following modulation of p63 expression, we have defined a vital role for p63 in cellular adhesion. Knockdown of p63 expression caused downregulation of cell adhesion-associated genes, cell detachment and anoikis in mammary epithelial cells and keratinocytes. Conversely, overexpression of the TAp63gamma or deltaNp63alpha isoforms of p63 upregulated cell adhesion molecules, increased cellular adhesion and conferred resistance to anoikis. Apoptosis induced by loss of p63 was rescued by signalling downstream of beta4 integrin. Our results implicate p63 as a key regulator of cellular adhesion and survival in basal cells of the mammary gland and other stratified epithelial tissues.

Anoikis↗
PubMed2006

p63 heterozygous mutant mice are not prone to spontaneous or chemically induced tumors.

Homology between p63 and p53 has suggested that these proteins might function similarly. However, the majority of data from human tumors have not supported a similar role for p63 in tumor suppression. To investigate this issue, we studied spontaneous tumorigenesis in p63+/- mice in both WT and p53-compromised backgrounds. We found that p63+/- mice were not tumor prone and mice heterozygous for both p63 and p53 had fewer tumors than p53+/- mice. The rare tumors that developed in mice with compromised p63 were also distinct from those of p53+/- mice. Furthermore, p63+/- mice were not prone to chemically induced tumorigenesis, and p63 expression was maintained in carcinomas. These findings demonstrate that, in agreement with data from human tumors, p63 plays a markedly different biological role in cancer than p53.

Animals↗
PubMed2006

p63 regulates multiple signalling pathways required for ectodermal organogenesis and differentiation.

Heterozygous germline mutations in p63, a transcription factor of the p53 family, result in abnormal morphogenesis of the skin and its associated structures, including hair follicles and teeth. In mice lacking p63, all ectodermal organs fail to develop, and stratification of the epidermis is absent. We show that the ectodermal placodes that mark early tooth and hair follicle morphogenesis do not form in p63-deficient embryos, although the multilayered dental lamina that precedes tooth placode formation develops normally. The N-terminally truncated isoform of p63 (DeltaNp63) was expressed at high levels in embryonic ectoderm at all stages of tooth and hair development, and it was already dominant over the transactivating TAp63 isoform prior to epidermal stratification. Bmp7, Fgfr2b, Jag1 and Notch1 transcripts were co-expressed with DeltaNp63 in wild-type embryos, but were not detectable in the ectoderm of p63 mutants. In addition, beta-catenin and Edar transcripts were significantly reduced in skin ectoderm. We also demonstrate that BMP2, BMP7 and FGF10 are potent inducers of p63 in cultured tissue explants. Hence, we suggest that p63 regulates the morphogenesis of surface ectoderm and its derivatives via multiple signalling pathways.

Animals↗
PubMed2006

p63: a new link between senescence and aging.

Cellular senescence is a distinctive form of cell cycle arrest that has been suggested to modulate the processes of tumor suppression and aging. Though a detailed understanding of the cellular machinery regulating this process is emerging, a more thorough understanding of the key players linking senescence to organismal aging is needed. The recent discovery that loss of the p53-related protein p63 induces cellular senescence and causes features of accelerated aging provides further evidence that cellular senescence is intimately linked with organismal aging, and identifies p63 as a key regulator of both of these processes.

Aging↗
PubMed2005

p63: oncogene or tumor suppressor?

p53, the original member of the family of genes now known to include p63 and p73, was first heralded as an oncogene because of its potent transformation capabilities and its robust expression in human tumors. However, it was later discovered that only mutant p53 was oncogenic, and that wild type p53 functioned as a tumor suppressor. Decades later, p63, the newest member of this gene family, is involved in a similar controversy: is p63 an oncogene or a tumor suppressor? Recent progress on understanding the in vivo role of p63 in cancer has focused primarily on investigating its involvement in the tumor-suppressive mechanism of apoptosis, by analyzing mouse models to assess its tumor-suppressive capabilities, and by assessing its expression in human cancers.

Animals↗
PubMed2005

p63 is an essential proapoptotic protein during neural development.

The p53 family member p63 is required for nonneural development, but has no known role in the nervous system. Here, we define an essential proapoptotic role for p63 during naturally occurring neuronal death. Sympathetic neurons express full-length TAp63 during the developmental death period, and TAp63 levels increase following NGF withdrawal. Overexpression of TAp63 causes neuronal apoptosis in the presence of NGF, while cultured p63-/- neurons are resistant to apoptosis following NGF withdrawal. TAp63 is also essential in vivo, since embryonic p63-/- mice display a deficit in naturally occurring sympathetic neuron death. While both TAp63 and p53 induce similar apoptotic signaling proteins and require BAX expression and function for their effects, TAp63 induces neuronal death in the absence of p53, but p53 requires coincident p63 expression for its proapoptotic actions. Thus, p63 is essential for developmental neuronal death, likely functioning both on its own, and as an obligate proapoptotic partner for p53.

Aging↗
PubMed2005

p63 deficiency activates a program of cellular senescence and leads to accelerated aging.

The p53 tumor suppressor plays a key role in organismal aging. A cellular mechanism postulated to drive the aging process is cellular senescence, mediated in part by p53. Although senescent cells accumulate in elderly individuals, most studies have relied on correlating in vitro senescence assays with in vivo phenotypes of aging. Here, using two different mouse models in which the p53-related protein p63 is compromised, we demonstrate that cellular senescence and organismal aging are intimately linked and that these processes are mediated by p63 loss. We found that p63(+/-) mice have a shortened life span and display features of accelerated aging. Both germline and somatically induced p63 deficiency activates widespread cellular senescence with enhanced expression of senescent markers SA-beta-gal, PML, and p16(INK4a). Using an inducible tissue-specific p63 conditional model, we further show that p63 deficiency induces cellular senescence and causes accelerated aging phenotypes in the adult. Our results thus suggest a causative link between cellular senescence and aging in vivo, and demonstrate that p63 deficiency accelerates this process.

Aging↗
PubMed2005

Perp is a p63-regulated gene essential for epithelial integrity.

p63 is a master regulator of stratified epithelial development that is both necessary and sufficient for specifying this multifaceted program. We show here that Perp, a tetraspan membrane protein originally identified as an apoptosis-associated target of the p53 tumor suppressor, is the first direct target of p63 clearly involved in mediating this developmental program in vivo. During embryogenesis, Perp is expressed in an epithelial pattern, and its expression depends on p63. Perp-/- mice die postnatally, with dramatic blistering in stratified epithelia symptomatic of compromised adhesion. Perp localizes specifically to desmosomes, adhesion junctions important for tissue integrity, and numerous structural defects in desmosomes are observed in Perp-deficient skin, suggesting a role for Perp in promoting the stable assembly of desmosomal adhesive complexes. These findings demonstrate that Perp is a key effector in the p63 developmental program, playing an essential role in an adhesion subprogram central to epithelial integrity and homeostasis.

Animals↗
PubMed2005

Differential expression of p63 isoforms in female reproductive organs.

p63 is the identity switch for uterine/vaginal epithelial cell fate, and disruption of p63 expression by diethylstilbestrol (DES) induces cervical/vaginal adenosis in mice. In this article, we report the expression patterns of p63 isoforms (TA, DeltaN, alpha, beta and gamma) in mice, focusing on the reproductive tract. We also present the reproductive tract phenotype of female p63-/- mice. Finally, to better evaluate the potential role of p63 in human development of DES-induced cervical/vaginal adenosis, we describe the ontogeny of p63 in human female fetuses. In adult mice, the DeltaN isoforms of p63 were expressed only in squamous/basal/myoepithelial cells of epithelial tissues, while TA isoforms of p63 were highly expressed in germ cells of the ovary and testis. In fetal mice, the DeltaN and alpha forms of p63 were expressed in the cloacal and urogenital sinus epithelia. In the female p63-/- mice, the sinus vagina developed, but p63-/- sinus vaginal epithelium failed to undergo squamous differentiation confirming an essential role of p63 in squamous epithelial differentiation. Although TAp63 was highly expressed in developing primordial germ cells/oocytes, p63-/- ovaries and oocytes developed normally. The ontogeny of p63 in female reproductive organs was essentially identical in mouse and human. In the human fetus at the susceptible stage for DES-induced cervical/vaginal adenosis, most cervical/vaginal epithelial cells were columnar and negative for p63. Therefore, inhibition of p63 expression by DES should change the cell fate of human Müllerian duct epithelial cells and cause cervical/vaginal adenosis as previously demonstrated in mouse.

Animals↗
PubMed2004

Role of p63 and basal cells in the prostate.

The prostate contains two major epithelial cell types - luminal and basal cells - both of which develop from urogenital sinus epithelium. The cell linage relationship between these two epithelial types is not clear. Here we demonstrate that luminal cells can develop independently of basal cells, but that basal cells are essential for maintaining ductal integrity and the proper differentiation of luminal cells. Urogenital sinus (UGS) isolated from p63(+/+) and p63(-/-) embryos developed into prostate when grafted into adult male nude mice. Prostatic tissue that developed in p63(-/-) UGS grafts contained neuroendocrine and luminal cells, but basal cells were absent. Therefore, p63 is essential for differentiation of basal cells, but p63 and thus basal cells are not required for differentiation of prostatic neuroendocrine and luminal epithelial cells. p63(-/-) prostatic grafts also contained atypical mucinous cells, which appeared to differentiate from luminal cells via activation of Src. In the response to castration, regression of p63(-/-) prostate was inordinately severe with almost complete loss of ducts, resulting in the formation of residual cystic structures devoid of epithelium. Therefore, basal cells play critical roles in maintaining ductal integrity and survival of luminal cells. However, regressed p63(-/-) prostate did regenerate in response to androgen administration, indicating that basal cells were not essential for prostatic regeneration.

Androgens↗
PubMed2004

Roles of p63 in the diethylstilbestrol-induced cervicovaginal adenosis.

Women exposed to diethylstilbestrol (DES) in utero develop abnormalities, including cervicovaginal adenosis that can lead to cancer. We report that transient disruption of developmental signals by DES permanently changes expression of p63, thereby altering the developmental fate of Müllerian duct epithelium. The cell fate of Müllerian epithelium to be columnar (uterine) or squamous (cervicovaginal) is determined by mesenchymal induction during the perinatal period. Cervicovaginal mesenchyme induced p63 in Müllerian duct epithelium and subsequent squamous differentiation. In p63(-/-) mice, cervicovaginal epithelium differentiated into uterine epithelium. Thus, p63 is an identity switch for Müllerian duct epithelium to be cervicovaginal versus uterine. P63 was also essential for uterine squamous metaplasia induced by DES-exposure. DES-exposure from postnatal day 1 to 5 inhibited induction of p63 in cervicovaginal epithelium via epithelial ERalpha. The inhibitory effect of DES was transient, and most cervicovaginal epithelial cells recovered expression of p63 by 2 days after discontinuation of DES-treatment. However, some cervicovaginal epithelial cells failed to express p63, remained columnar and persisted into adulthood as adenosis.

Animals↗
PubMed2004

p63 is the molecular switch for initiation of an epithelial stratification program.

Development of stratified epithelia, such as the epidermis, requires p63 expression. The p63 gene encodes isoforms that contain (TA) or lack (DeltaN) a transactivation domain. We demonstrate that TAp63 isoforms are the first to be expressed during embryogenesis and are required for initiation of epithelial stratification. In addition, TAp63 isoforms inhibit terminal differentiation, suggesting that TAp63 isoforms must be counterbalanced by DeltaNp63 isoforms to allow cells to respond to signals required for maturation of embryonic epidermis. Our data demonstrate that p63 plays a dual role: initiating epithelial stratification during development and maintaining proliferative potential of basal keratinocytes in mature epidermis.

Animals↗
PubMed2003

Dicer is essential for mouse development.

To address the biological function of RNA interference (RNAi)-related pathways in mammals, we disrupted the gene Dicer1 in mice. Loss of Dicer1 lead to lethality early in development, with Dicer1-null embryos depleted of stem cells. Coupled with our inability to generate viable Dicer1-null embryonic stem (ES) cells, this suggests a role for Dicer, and, by implication, the RNAi machinery, in maintaining the stem cell population during early mouse development.

Amino Acid Sequence↗
PubMed2003

Inducible systems see the light.

Advances in our capacity to design and use novel strategies for achieving inducible gene expression will improve our ability to define gene function. An extremely efficient system designed by nature -- that of the regulatable phytochrome system in plants -- has provided the basis for developing a novel inducible gene expression system.

Gene Expression Regulation, Fungal↗