Dynamic Expression of the Homeobox Factor PBX1 during Mouse Testis Development

Members of the pre-B-cell leukemia transcription factor (PBX) family of homeoproteins are mainly known for their involvement in hematopoietic cell differentiation and in the development of leukemia. The four PBX proteins, PBX1, PBX2, PBX3 and PBX4, belong to the three amino acid loop extension (TALE) superfamily of homeoproteins which are important transcriptional cofactors in several developmental processes involving homeobox (HOX) factors. Mutations in the human PBX1 gene are responsible for cases of gonadal dysgenesis with absence of male sex differentiation while Pbx1 inactivation in the mouse causes a failure in Leydig cell differentiation and function. However, no data is available regarding the expression profile of this transcription factor in the testis. To fill this knowledge gap, we have characterized PBX1 expression during mouse testicular development. Real time PCRs and Western blots confirmed the presence Pbx1 mRNA and PBX1 protein in different Leydig and Sertoli cell lines. The cellular localization of the PBX1 protein was determined by immunohistochemistry and immunofluorescence on mouse testis sections at different embryonic and postnatal developmental stages. PBX1 was detected in interstitial cells and in peritubular myoid cells from embryonic life until puberty. Most interstitial cells expressing PBX1 do not express the Leydig cell marker CYP17A1, indicating that they are not differentiated and steroidogenically active Leydig cells. In adults, PBX1 was mainly detected in Sertoli cells. The presence of PBX1 in different somatic cell populations during testicular development further supports a direct role for this transcription factor in testis cell differentiation and in male reproductive function.

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The development of rat Leydig cell progenitors in vitro: how essential is luteinising hormone?

Journal of Endocrinology ◽

10.1677/joe-06-0084 ◽

2007 ◽

Vol 194 (3) ◽

pp. 579-593 ◽

Cited By ~ 40

Author(s):

Katja J Teerds ◽

Eddy Rijntjes ◽

Margarita B Veldhuizen-Tsoerkan ◽

Focko F G Rommerts ◽

Mieke de Boer-Brouwer

Keyword(s):

Cell Differentiation ◽

Progenitor Cells ◽

Leydig Cell ◽

Leydig Cells ◽

Luteinising Hormone ◽

Interstitial Cells ◽

Precursor Cells ◽

Precursor Cell ◽

Old Rats

Luteinising hormone (LH) appears to be important for the establishment of the adult-type Leydig cell population. The role of LH in the initial steps of stem Leydig cell/precursor cell differentiation is less clear. The aim of the present study was to elucidate the role of LH in the differentiation of spindle-shaped mesenchymal-like cells into Leydig cell progenitors. Interstitial cells were isolated from rat testes at three different ages reflecting different phases in development, and cultured in the presence of increasing concentrations of LH (ranging from 0.01 to 10 ng/ml). Cells were isolated from 10-day-old rats when stem Leydig cells/precursor cells are abundant; 13-day-old rats when the first 3β-hydroxysteroid dehydrogenase (3β-HSD)-positive Leydig cell progenitors have developed in the strain of rats used in this study; and 18-day-old rats just prior to the wave of progenitor proliferation. Immunohistochemistry revealed that before stem Leydig cells differentiate into progenitor cells, they acquire functional LH receptors and become precursor cells. This was confirmed by an in vivo immunohistochemical double-labelling experiment. Addition of LH to the cultures increased the percentage of LH/3β-HSD-labelled Leydig cell progenitors, while the percentage of cells solely expressing the LH receptor decreased. Cell proliferation was negligible, suggesting that the increase in 3β-HSD-positive cells is the result of precursor cell differentiation. When interstitial cells were isolated from 13-day-old rats and to a lesser extent from 10-day-old rats, a small proportion of the precursors could develop into progenitor cells independent of the presence of LH. In conclusion: before Leydig stem cells differentiate into 3β-HSD-positive progenitor cells, they acquire LH receptors and become precursor cells. LH appears to be essential, even at very low doses for the differentiation of these precursor cells into 3β-HSD-positive progenitors, although a subpopulation of precursor cells can develop into progenitors independently of LH.

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