Lhx2 regulates bone remodeling in mice by modulating RANKL signaling in osteoclasts.

The LIM homeobox 2 (Lhx2) transcription factor Lhx2 has a variety of functions, including neural induction, morphogenesis, and hematopoiesis. Here we show the involvement of Lhx2 in osteoclast differentiation. Lhx2 was strongly expressed in osteoclast precursor cells but its expression was significantly reduced during receptor activator of nuclear factor-κB ligand (RANKL)-mediated osteoclastogenesis. Overexpression of Lhx2 in bone marrow-derived monocyte/macrophage lineage cells (BMMs), which are osteoclast precursor cells, attenuated RANKL-induced osteoclast differentiation by inhibiting the induction of nuclear factor of activated T cells c1 (NFATc1). Interestingly, interaction of Lhx2 proteins with c-Fos attenuated the DNA-binding ability of c-Fos and thereby inhibited the transactivation of NFATc1. Furthermore, Lhx2 conditional knockout mice exhibited an osteoporotic bone phenotype, which was related with increased osteoclast formation in vivo. Taken together, our results suggest that Lhx2 acts as a negative regulator of osteoclast formation in vitro and in vivo. The anti-osteoclastogenic effect of Lhx2 may be useful for developing a therapeutic strategy for bone disease.

HOXB13 downregulates intracellular zinc and increases NF-κB signaling to promote prostate cancer metastasis.

Characteristically, prostate cancer (PCa) cells exhibit marked decrease in intracellular zinc; however, the mechanism responsible is not clearly understood. HOXB13 is involved in PCa progression and is overexpressed in castration-resistant PCa. DNA microarray analysis of LNCaP Pca cells showed that ZnT zinc output transporters were strikingly upregulated among androgen-independent HOXB13 target genes. Furthermore, exogenous HOXB13 caused intracellular zinc concentrations to fall in PCa cells, stimulated NF-κB-mediated signaling by reducing inhibitor of NF-κB alpha (IκBα) and enhanced the nuclear translocation of RelA/p65. Human prostate tumors also exhibited strong inverse correlation between the protein expressions of HOXB13 and IκBα. Consequently, HOXB13 stimulated PCa cell invasion, and this was inhibited by the suppression of ZnT4. In addition, studies in a PC3 orthotopic mouse model of PCa metastasis showed that HOXB13 is a strong metastatic stimulator. Taken together, these results show that HOXB13 promotes PCa invasion and metastasis by decreasing intracellular zinc levels, thus stimulating NF-κB signals, and suggest that HOXB13 acts as a modulator of intracellular zinc levels that promotes the malignant characteristics of PCa.

Ret finger protein inhibits muscle differentiation by modulating serum response factor and enhancer of polycomb1.

Skeletal myogenesis is precisely regulated by multiple transcription factors. Previously, we demonstrated that enhancer of polycomb 1 (Epc1) induces skeletal muscle differentiation by potentiating serum response factor (SRF)-dependent muscle gene activation. Here, we report that an interacting partner of Epc1, ret finger protein (RFP), blocks skeletal muscle differentiation. Our findings show that RFP was highly expressed in skeletal muscles and was downregulated during myoblast differentiation. Forced expression of RFP delayed myoblast differentiation, whereas knockdown enhanced it. Epc1-induced enhancements of SRF-dependent multinucleation, transactivation of the skeletal α-actin promoter, binding of SRF to the serum response element, and muscle-specific gene induction were blocked by RFP. RFP interfered with the physical interaction between Epc1 and SRF. Muscles from rfp knockout mice (Rfp(-/-)) mice were bigger than those from wild-type mice, and the expression of SRF-dependent muscle-specific genes was upregulated. Myotube formation and myoblast differentiation were enhanced in Rfp(-/-) mice. Taken together, our findings highlight RFP as a novel regulator of muscle differentiation that acts by modulating the expression of SRF-dependent skeletal muscle-specific genes.

Anatomic variations of the infraorbital fat compartment.

Resection of the infraorbital fat is performed in blepharoplasty of the lower eyelid, however, the previous anatomical reports on its compartmentalization have been in disagreement. The aim of this study was to classify the infraorbital fat based on the extent of compartmentalization, and to clarify its topographic relationship with the surrounding structures. Sixty orbits from 30 cadavers were dissected. The infraorbital fat was classified into four types based on its compartmentalization. In type I, which was the most common type (60.0%), the infraorbital fat was compartmentalised into three encapsulated medial, central, and lateral parts, which were side by side. In type II (11.7%), the medial or lateral compartment, or both compartments were under the central fat compartment. In type III (26.7%), there were two compartments, the medial and remaining part or the lateral and remaining part. In type IV (1.7%), the fat was not compartmentalised, but presented as a single pad. The average heights from the inferior orbital rim, the average widths, and the average distances from the fornix were 7.3, 17.2, and 7.1 mm in the medial compartment, 8.9, 24.2, and 8.0mm in the central compartment, and 8.1, 17.2, and 6.9 mm in the lateral compartment, respectively. The average distance from the end of the margin of the stretched lower eyelid to the most cephalic point in the compartments was 8.6 mm. These results are relevant to blepharoplasty with removal of the infraorbital fat.

Expression of differentiation markers during fetal skin development in humans: immunohistochemical studies on the precursor proteins forming the cornified cell envelope.

The cornified cell envelope is formed during the terminal differentiation of epidermis through cross-linking of specific proteins by transglutaminases. The specific arrangement of individual protein in the cornified cell envelope and participation of individual protein in the cornified cell envelope at different regions of skin, i.e., palm, foreskin, lips, etc. are not clearly understood. In order to understand the pattern and expression schedule of each individual precursor protein during the differentiation and formation of cornified cell envelope, the expression of precursor proteins in developing human fetal skins from the first to the third trimester were examined by immunohistochemical studies. Involucrin was found in the periderm and intermediate layer from 14 wk estimated gestational age, while loricrin and small proline-rich protein 1 were found in the periderm from 16 wk estimated gestational age. Filaggrin and trichohyalin that are absent in the adult cornified cell envelope were found in the granular and horny layers from 24 wk estimated gestational age. The precursor proteins except trichohyalin did not change their patterns after the onset of initial expression during development. Trichohyalin was transiently expressed in the granular and horny layers of the epidermis from 24 wk estimated gestational age with peak expression at 27 wk estimated gestational age, but was not detected in adult skin. In hair follicles, trichohyalin expression was stable without change from 20 wk estimated gestational age. These findings suggest that fetal skin may have different sets of barriers from the second trimester; the immature cornified cell envelope is formed in the early second trimester and the mature cornified cell envelope is formed in the late second or early third trimester when filaggrin and trichohyalin appear.