Recent studies have identified markers for germ stem cells (GSCs) in the testis, such as Nanos2, Ngn3, and c-kit. The differentiation-stage specific expression of these markers indicates a hierarchical relationship between GSC populations and their plasticity. However, the exact nature of most primitive fraction of Asingle GSCs is unclear because direct kinetic assay of Asingle GSCs have not been performed. Here we show that Bmi1 is a specific marker for Asingle GSCs. Bmi1-positive GSCs are a part of GFRα1-positive GSCs, furthermore its expression correlates with the seminiferous stages. Bmi1 expression is followed by proliferative stage of Asingle GSCs. Bmi1-positive GSCs maintain spermatogenesis. They are resistant to irradiation-induced injury, and they regenerate. Thus, the present study first indicates that Bmi1 is a novel marker for Asingle GSCs whose cyclic expression suggests a regulatory role in the seminiferous stages.
Latent TGF-β-binding protein-2 (LTBP-2) is an extracellular matrix protein associated with microfibrils, but its function in vivo has not been well understood. Homozygous mutations in LTBP2 have been found in humans with genetic eye diseases such as congenital glaucoma and lens dislocation, but pathogenic mechanism has been unknown. In this study, we explore the in vivo function of LTBP-2 by generating Ltbp2–/– mice. Ltbp2–/– mice developed lens luxation caused by compromised ciliary zonule formation, suggesting that LTBP-2 is an essential component for the development of bundled ciliary zonule. Addition of recombinant LTBP-2 in the organ culture of eyes from Ltbp2–/– mice restored ciliary zonule formation. The transfection study of human LTBP2 mutant cDNAs suggests that LTBP2 mutations cause structural alterations in the proteins, leading to secretion failure, and/or loss of binding with fibrillin-1. These data suggest an essential function of LTBP-2 in ciliary zonule microfibril development that could explain the pathological mechanism of human patients with LTBP2 mutations.
Multi-drug resistance (MDR) in cancer is known to decrease the therapeutic efficacy of chemotherapy. The effects of irradiation on MDR in cancer cells remain unclear. Tc-99m methoxyisobutylisonitrile (MIBI) exhibits the same ATP-binding cassette (ABC) transporter kinetics as the chemotherapeutic compounds doxorubicin and cisplatin. In this study, we investigated the synergistic effects of chemotherapeutics and irradiation in the non-small lung cancer cell line, H1299 exhibiting MDR, on MIBI and doxorubicin ABC transporter kinetics, in vitro and in vivo, respectively. The irradiation has an inhibitory effect on MDR while a cellular proliferation is suppressed. Furthermore it was necessary to consider the most suitable irradiation protocol in chemoradiotherapy because the radiation effect to restrain MDR is reversible change.
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