A family of RAS proteins, originally designated RHO proteins, were identified and isolated from protein products expressed in the marine snail, Aplysia. In humans, the products of these genes, called ARH (Aplysia ras-related homologs), display striking homology to the products of the classic RAS genes. Madaule and Axel (1985) identified 3 classes of ARH genes, designated H6, H9, and H12. Chardin et al. (1988) reported the complete H6 coding sequence and renamed the gene RhoB. The predicted protein is 196 amino acids long.
The actin cytoskeleton undergoes extensive remodeling during cell morphogenesis and motility. The small guanosine triphosphatase Rho regulates such remodeling. In their Figure 3C, Maekawa et al. (1999) diagrammed proposed signaling pathways for Rho-induced remodeling of the actin cytoskeleton.
upstream of Hippo signaling
Luteinization, Oogenesis, Oocyte maturation
, First polar body extrusion
Comment
Small GTPases are involved in sprout formation in human granulosa lutein cells. Franz MB et al. INTRODUCTION: The corpus luteum (CL), develops from the ruptured follicle after gonadotropin stimulation. Based on intracellular reorganization of the cytoskeleton an human chorionic gonadotropin (hCG) dependent sprouting and migration of luteinizing granulosa cells (LGCs) and endothelial cells is observed. Rho-GTPases are shown to be key regulators of cytoskeletal restructuring. In the present study we analyzed the role of Rho-GTPases in the sprouting activity of LGCs. METHODS: We used the Rho-GTPase-inhibitors Toxin A and -B and the Cdc42-activator Bradykinin in a LGC-spheroid sprouting assay to determine the effect of these modulators in LGCs. RESULTS: Toxin A and Toxin B reduces sprout formation in LGC spheroids. However, the reduction is less than in hCG treated cells. The usage of Bradykinin demonstrates both, a reduction of sprouts in untreated spheroids and an increase of sprouting in previous hCG treated spheroids. CONCLUSIONS: The presented results let us suggest that small Rho-GTPases may regulate the sprouting activity of LGCs after stimulation by hCG and that this mechanism may play a role in CL formation.
Expression regulated by
LH
Comment
This gene was found in a rat ovarian cDNA library
Ovarian localization
Oocyte, Ovarian tumor
Comment
Expression Loss and Revivification of RhoB Gene in Ovary Carcinoma Carcinogenesis and Development. Liu Y 2013 et al.
RhoB, a member of small GTPases belonging to the Ras protein superfamily, might have a suppressive activity in cancer progression. Here, expression of RhoB gene was evaluated in human benign, borderline and malignant ovary tumors by immunostaining, with normal ovary tissue as control. Malignant tumors were assessed according to Federation Internationale de Gynecologie Obstetrique (FIGO) guidelines and classified in stage I-IV. Revivification of RhoB gene was investigated by analyzing the effect of histone deacetylase (HDAC) inhibitor trichostatin (TSA) and methyltransferase inhibitor 5-azacytidine (5-Aza) on ovarian cancer cells via RT-PCR and western blot. Apoptosis of ovary cancer cells was detected using flowcytometry and fluorescence microscopy. Subsequently, RhoB expression is detected in normal ovary epithelium, borderline tumors, and decreases significantly or lost in the majority of ovarian cancer specimen (P<0.05). RhoB expression decreases significantly from stage II (71.4%) to stage III (43.5%) to stage IV (18.2%, P<0.05). TSA can both significantly revive the RhoB gene and mediate apoptosis of ovarian cancer cells, but 5-Aza couldn't. Interference into Revivification of RhoB gene results in reduction of ovary carcinoma cell apoptosis. It is proposed that loss of RhoB expression occurs frequently in ovary carcinogenesis and progression and its expression could be regulated by histone deacetylation but not by promoter hypermethylation, which may serve as a prospective gene treatment target for the patients with ovarian malignancy not responding to standard therapies.
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Polar body cytokinesis. Maddox AS et al. Polar body cytokinesis is the physical separation of a small polar body from a larger oocyte or ovum. This maternal meiotic division shares many similarities with mitotic and spermatogenic cytokinesis, but there are several distinctions, which will be discussed in this review. We synthesize results from many different model species, including those popular for their genetics and several that are more obscure in modern cell biology. The site of polar body division is determined before anaphase, by the eccentric, cortically associated meiotic spindle. Depending on the species, either the actin and microtubule cytoskeleton is required for spindle anchoring. Chromatin is necessary and sufficient to elicit differentiation of the associated cortex, via Ran-based signaling. The midzone of the anaphase spindle serves as a hub for regulatory complexes that elicit Rho activation, and ultimately actomyosin contractile ring assembly and contraction. Polar body cytokinesis uniquely requires another Rho family GTPase, Cdc42, for dynamic reorganization of the polar cortex. This is perhaps due to the considerable asymmetry of this division, wherein the polar body and the oocyte/ovum have distinct fates and very different sizes. Thus, maternal meiotic cytokinesis appears to occur via simultaneous polar relaxation and equatorial contraction, since the polar body is extruded from the spherical oocyte through the nascent contractile ring. As such, polar body cytokinesis is an interesting and important variation on the theme of cell division. ? 2012 Wiley Periodicals, Inc.