Role of p57KIP2 in developing Leydig cells of mouse testis

Abstract

ABSTRACT

Kyung Noh Yoon Department of Life Science The Graduate School Hanyang University

p57KIP2 inhibit cyclin-dependent kinases (Cdks) and cyclins, and inhibit the cell cycle at the G1 stage. Unlike the Cdks inhibitor family p21CIP1 and p27KIP1, p57KIP2 is tissue-specifically expressed and expressed in cells at the terminally differentiated cells. It is also involved in cell survival and differentiation as well as cell cycle inhibitory function. Expression of p57KIP2 was confirmed in mouse testis Leydig cells. However, the function of p57KIP2 has not been studied in Leydig cells. In this study, interstitial p57kip2 mRNA levels gradually decreased from birth to puberty and re-increased markedly thereafter. p57KIP2 was found in the cytoplasm and nucleus of fetal Leydig cells (FLC) and in the cytoplasm and nucleus of spindle shaped HSD3β-negative stem Leydig cells (SLC). In the spindle shaped HSD3β-positive progenitor Leydig cells (PLC) p57KIP2 was primarily found in the cytoplasm. At puberty, p57KIP2 was primarily found in the cytoplasm of the immature Leydig cells (ILC), and which markedly increased in the adult Leydig cells (ALC). As a result of immunofluorescence analysis, it was confirmed that the cells expressing p57KIP2 of spindle-shaped cells at PND1, PND7, and PND14 were Leydig cells because they were not expressed α-SMA. In SLC isolated at PND7, p57kip2 siRNA increased the expression of ki67, pcna, ptch2 and pdgfrα mRNA and decreased the expression of nestin mRNA. This indicates that p57KIP2 suppresses cell proliferation of SLC and has a stemness maintenance function. In PLC isolated at PND14, p57kip2 siRNA increased the expression of pcna, ptch2, bcl2l11 and bax mRNA and decreased the expression of lhr, cyp17a1 and hsd3β6 mRNA. This means that p57KIP2 suppresses cell proliferation and apoptosis of PLC and regulates functional differentiation for steroidogenesis. In ALC isolated at PND56, p57kip2 siRNA increased the expression of bcl2l11 and bak1 mRNA and decreased the expression of sf1, star, cyp11a1, cyp17a1, hsd3β6 and hsd17β3 mRNA. This means that p57KIP2 suppresses apoptosis of ALC and regulates steroidogenesis. Through immunofluorescence analysis, p57KIP2 was not co-localized with markers of cell proliferation in PND1, PND7 and PND14 Leydig cells, it means that p57KIP2 functions as a cell cycle inhibitor of Leydig cells. It is considered that p57KIP2 suppresses cell proliferation and apoptosis of Leydig cells, regulate cell stemness maintains, differentiation and steroidogenesis.