Expression of Heparin/Heparan Sulfate Interacting Protein/Ribosomal Protein L29 During the Estrous Cycle and Early Pregnancy in the Mouse1

Abstract

Using a variety of approaches, we have examined the expression of the heparin/heparan sulfate (Hp/HS) interacting protein/ribosomal protein L29 (HIP/RPL29) in mouse uteri during the estrous cycle and early pregnancy. HIP/RPL29 selectively binds heparin and HS and may promote HS-dependent embryo adhesion. HIP/RPL29 was prominently expressed in both luminal and glandular epithelia under almost all conditions, including the phase of embryo attachment. In contrast, differences were noted in HIP/RPL29 expression in the stromal compartment both during the estrous cycle and during early pregnancy. Most notably, HIP/RPL29 accumulated in decidua, where it displayed a pattern complementary to that of pericellular deposition of the HS proteoglycan, perlecan. HIP/RPL29 protein was detected in implanted embryos at both initial and later stages of implantation; however, embryonic HIP/RPL29 mRNA accumulation was more pronounced at later stages (Day 7.5 postcoitum). In situ hybridization revealed similar spatial changes for HIP/RPL29 mRNA during these different physiological states. Whereas differences in the spatial pattern of HIP/RPL29 protein and mRNA expression were demonstrable, little change was detected in the level of HIP/RPL29 mRNA or protein in total endometrial extracts. Mouse blastocysts attached, but did not outgrow, on surfaces coated with recombinant murine HIP/RPL29. Surprisingly, soluble glycosaminoglycans including heparin, low molecular weight heparin, or chondroitin sulfate were not able to inhibit embryo attachment to HIP/RPL29-coated surfaces. These latter observations indicate that embryonic cell surface components other than HS proteoglycans can promote binding to HIP/RPL29 expressed by uterine cells.

Global growth deficiencies in mice lacking the ribosomal protein HIP/RPL29

“…PMEFs cells were collected by direct solubilization in SEB to which phosphatase inhibitor cocktail (Calbiochem) was added. Protein samples were quantified using a standard Lowry assay (Lowry et al, 1951), and protein lysates of equal amount (10 -20 g) were combined to an equal volume of 2ϫ Laemmli buffer and submitted to 10% (w/v) SDS-PAGE as described (Julian et al, 2001). After transfer to a nitrocellulose membrane, the blot was blocked in blocking buffer (5% [w/v] BSA, 0.1% [v/v] Tween-20 in PBS) for at least 6 hr and probed with specific antibodies raised in rabbit.…”

“…In contrast to adult tissues, HIP/ RPL29 displays a much more widespread pattern of expression throughout embryonic development, and high levels of HIP/RPL29 are found in all developing organs (Kirn-Safran et al, 2000;Julian et al, 2001). Of interest, several reports showed that HIP/ RPL29 expression is up-regulated in human carcinomas and constitutes a candidate marker for abnormal growth when overexpressed (de Nigris et al, 1998;Wang et al, 1999).…”

Heparan sulfate proteoglycans and their binding proteins in embryo implantation and placentation

“…HIP/RPL29 is prominently expressed in uterine luminal and glandular epithelia in both humans and mice at all stages of the cycle including during the window of receptivity [32,34]. During the post-implantation period in mice, HIP/RPL29 accumulates in decidualizing stroma and actively dividing embryonic structures [34]. These expression patterns suggest an important role for HIP/RPL29 in the establishment and maintenance of pregnancy.…”

“…HIP RL29 also can modulate blood coagulation processes [33] and inhibits heparanase activity (see below). HIP/RPL29 is prominently expressed in uterine luminal and glandular epithelia in both humans and mice at all stages of the cycle including during the window of receptivity [32,34]. During the post-implantation period in mice, HIP/RPL29 accumulates in decidualizing stroma and actively dividing embryonic structures [34].…”

“…Two naturally occurring inhibitors of HPSE have been identified: eosinophil major basic protein [59] and HIP/RPL29 [34]. Human placenta express eosinophil basic protein mRNA [60] and a precursor form of eosinophil major basic protein is secreted constitutively by human trophoblast cells isolated from the first to third trimester as well as decidualizing human uterine stroma cells [61].…”