Expression of Terminal Differentiation Proteins Defines Stages of Mouse Mammary Gland Development

Abstract

Abstract. Immunohistochemical analysis using paraffin-embedded specimens is the method of choice to evaluate protein expression at a cellular level while preserving tissue architecture in normal and neoplastic tissues. Current knowledge of the expression of terminal differentiation markers in the mouse mammary gland relies on the evaluation of frozen tissues by use of immunofluorescence. We assessed changes in patterns of expression of terminal differentiation markers throughout the development of the mouse mammary gland in paraffin-embedded tissues. The expression of a-smooth muscle actin (SMA) and keratins (K) 5, 8/18, and 14 was influenced by the development stage of the mammary gland. Expression of K5 and SMA was restricted to basal cells. Keratin 14 was consistently expressed by mammary basal cells, and was detected in scattered luminal cells from 13.5 days after conception through puberty. Labeling for K8/18 of luminal cells was heterogeneous at all times. Heterogeneous expression patterns in luminal cells suggest this layer has cells with a variety of biological functions. The absence of K6 expression at any stage of the development of the mammary gland was confirmed by use of reverse transcriptase-polymerase chain reaction analysis, which indicates that this intermediate filament is not a marker of the mammary gland stem cell. Finally, consistent with results of earlier studies, keratins 1, 10, 13, and 15, and filaggrin, involucrin, and loricrin were not detected at any stage of mammary gland development.

Transforming Growth Factor–β Regulates Mammary Carcinoma Cell Survival and Interaction with the Adjacent Microenvironment

“…In the normal mammary gland, a common progenitor cell can differentiate to produce lubolar alveolar and ductal epithelium in addition to basal myoepithelium (47). Each of these cell types expresses a different subset of proteins that are often used to identify its lineage (34,35,48). The basal and myoepithelial cell populations in mammary tissue are known to express K5.…”

“…However, we wanted to address this issue more directly using previously defined mammary cell lineage markers because it is known that the MMTV promoter/enhancer (used to drive expression of the PyVmT oncogene) can express in all mammary epithelial cell lineages including the basal cell population. As a marker for the basal and myoepithelial cell populations, we have examined K5 expression, which has previously been used to identify putative mammary progenitors, basal myoepithelium, and bona fide basaloid carcinoma cells in situ (32)(33)(34) 6A, a and b). In the ThRII ( fl/fl);PY control tissues, K5 expression was predominantly limited to small lobules (Supplementary Fig.…”

The gene dosage of class Ia PI3K dictates the development of PTEN hamartoma tumor syndrome

“…33 Since K14 is expressed in the mammary epithelial cells and K14-cre has been used to mediate gene deletion in the mammary gland, [34][35][36] we also examined mammary glands of female virgin mice with the K14Cre;Pten L/L genotype at the age of 12 weeks, when they have developed skin PHTS. Consistent with previous findings, we found that mammary ducts of mutant mice developed excessive side branches by whole-mount analysis and MIN as determined by pathology (Fig.…”

El citoesqueleto celular en la glándula mamaria y su aplicación diagnóstica

“…ción con los elementos empleados, el grado de marcaje de casi todas las citoqueratinas del estudio depende de la fase de desarrollo de la glándula mamaria y la naturaleza de las citoqueratinas expresadas en células de la luz y basales está conservada a través de todo el árbol mamario 34,35 , aunque los niveles de expresión dependen de su localización específica. La cantidad de marcadores de diferenciación expresados por las células de la luz de los conductos y las basales 36 fue incrementando paulatinamente durante la morfogénesis mamaria.…”

“…La citoqueratina 6 está confinada a una pequeña cantidad de cé-lulas epiteliales mamarias asociadas con el crecimiento de los brotes terminales y del epitelio de la luz de los conductos 41,42 . Esta citoqueratina no fue detectada en ninguna etapa del desarrollo de la glándu-la mamaria en el experimento de Mikaelian 35 , contrastando con las observaciones efectuadas por Smith 41 , que la identificó mediante inmunofluorescencia en brotes terminales y en algunas células de los conductos intralobulares, y que indujo a otros a considerarla como marcador de células pluripotentes mamarias 43 . Los resultados obtenidos para las citoqueratinas 6 y 16 se restringieron a algunas célu-las en reposo, así como a un pequeño número de células catalogadas como positivas durante la primera y tercera semana en lactación.…”