Multiple roles of Notch signaling in cochlear development

Notch signaling inhibits hair cell differentiation, based on studies on mice deficient in Notch signaling-related genes and its downstream genes. However, the precise mechanisms of this inhibition are unknown because it is difficult to control the timing and duration of the suppression of Notch signaling. Here, we developed a novel in vitro culture and analysis method for mouse fetal cochleae and examined the roles of Notch signaling by its reversible inhibition through the use of Notch signaling inhibitors of gamma-secretase and TNF-alpha-converting enzyme. Notch inhibition with Notch signaling inhibitor treatment increases the number of cochlear hair cells, as observed in gene deletion experiments. We elucidated that this increase is regulated by the dichotomy between hair cells and supporting cells from common progenitors. We also propose other roles of Notch signaling in cochlear development. First, Notch signaling arrests the cell cycle of the cochlear epithelium containing putative hair cells and supporting cell progenitors because Notch inhibition with inhibitor treatment increases the number of 5-bromo-2'-deoxyuridine (BrdU)-positive cells that can differentiate into hair cells or supporting cells. Second, Notch signaling is required for the induction of Prox1-positive supporting cells. Third, Notch signaling is required for the maintenance of supporting cells.     

Imaging the interaction of αv integrin-GFP in osteosarcoma cells with RFP-expressing host stromal cells and tumor-scaffold collagen in the primary and metastatic tumor microenvironment

Human osteosarcoma 143B cells were previously stably transfected with an α_v integrin green flourescent protein (GFP) vector. 143B cells expressing α_v integrin-GFP were transplanted orthotopically in the tibia of transgenic nude mice ubiquitously expressing red fluorescent protein (RFP). The primary tumors acquired RFP-expressing stroma and were passaged orthotopically in the tibia in noncolored nude mice, which maintained the RFP stroma. The interaction of α_v integrin-GFP expression in 143B cells with RFP-expressing host stromal cells was observed by confocal microscopy using the Olympus FV1000. Collagen fibers were imaged simultaneously in reflectance mode. The RFP-expressing stroma included cancer-associated fibroblasts (CAFs) and tumor-associated macrophages (TAMs) which persisted even 3 weeks after passage to nontransgenic nude mice. CAFs expressing RFP were aligned between collagen fibers and cancer cells expressing α_v integrin-GFP. Six weeks after transplantation, pulmonary metastases expressing α_v integrin-GFP could be identified. TAMs expressing RFP accompanied metastasized osteosarcoma cells expressing α_v integrin-GFP in the lung. The current study demonstrates the importance of α_v integrin interaction with stromal elements in osteosarcoma.     

HLA class II alleles in Ainu living in Hidaka district,Hokkaido, northern Japan

The Ainu people are considered to be the descendants of preagricultural native populations of northern Japan, while the majority of the population of contemporary Japan (Wajin) is descended mainly from postneolithic migrants. Polymorphisms of the HLA-DRB1, DRB3, and DQB1 alleles were investigated in DNA samples of 50 Ainu living in Hidaka district, Hokkaido. Unique features of the Ainu in this study were high incidences of DRB1*1401, DRB1*1406, and a newly described allele, DRB1*1106 (20%, 17%, and 5%, respectively). On the other hand, several common alleles in Wajin (DRB1*1502, 1302, 0803, and 1501) were found at relatively low frequencies (1–2%) in Ainu. Previously DRB1*1406 was described as a characteristic allele of some Native American or northeast Asian ethnic groups, and DRB1*1106 had been found in only two Singapore Chinese and one Korean. Principal component analysis of various populations based on HLA class II allele frequencies places the Ainu population midway between other east Asian populations, including Wajin, and Native Americans. These observations may support the hypothesis that the Ainu people are the descendants of some Upper Paleolithic populations of northeast Asia from which Native Americans are also descended. © 1996 Wiley-Liss, Inc.     

Functional assessment of self-renewal activity of male germline stem cells following cytotoxic damage and serial transplantation

Spermatogenesis is dependent on a small population of stem cells. Although stem cells are believed to expand infinitely, there is little functional evidence regarding whether spermatogonial stem cells can increase in their number. Using the spermatogonial transplantation technique, we evaluated the proliferative potential of spermatogonial stem cells in two models of regeneration. After busulfan injection to deplete stem cells, the surviving stem cells were able to expand by at least 15.8-fold within 2 mo. On the other hand, a serial transplantation study indicated that one transplanted stem cell was able to expand by 3.8- and 12-fold within 2 and 4 mo, respectively. These results provide direct functional evidence for the expansion of stem cells and establish the basis for further characterization of the stem cell self-renewal process.     

Allogeneic offspring produced by male germ line stem cell transplantation into infertile mouse testis

The testis is one of several immune-privileged organs and is known for its unique ability to support allogeneic or xenogeneic tissue transplants. We investigated the possibility of deriving offspring from mice that underwent transplantation with allogeneic male germ line stem cells in the testis. Although mature adult mice rejected allogeneic germ cells and were infertile, offspring were obtained by intracytoplasmic germ cell injection using partially differentiated donor cells. In contrast, complete spermatogenesis occurred when allogeneic germ cells were transplanted into immature pup testes. Tolerance induction by monoclonal antibody administration allowed the pup transplant recipients to produce allogeneic offspring by natural mating, whereas no spermatozoa were found in the epididymis of untreated recipients. Thus, these results indicate that a histoincompatible recipient can serve as a "surrogate father" to propagate the genetic information of heterologous male donors.     

Expression of Hex homeobox gene during skin development: Increase in epidermal cell proliferation by transfecting the Hex to the dermis

A number of homeobox genes have been found to be expressed in skin and its appendages, such as scale and feather, and appear to be candidates for the regulation of the development of these tissues. We report that the proline-rich divergent homeobox gene Hex is expressed during development of chick embryonic skin and its appendages (scale and feather). In situ hybridization analysis revealed that, during development of the skin, a transient expression of the Hex gene was observed. While the expression of Hex in the dermis was closely correlated with proliferation activity of epidermal basal cells, that in the epidermis was related to a suppression of epidermal differentiation. When dermal fibroblasts were transfected with Hex, stimulation of both DNA synthesis and proliferation of the epidermal cells followed by two-fold scale ridge elongation and increase in epidermal area was observed during culture of the skin, whereas epidemal keratinization was not affected. This is the first study to demonstrate that Hex is expressed during development of the skin and its appendages and that its expression in the dermal cells regulates epidermal cell proliferation through epithelial mesenchymal interaction.     

Primate limb bones and locomotor types in arboreal or terrestrial environments

Postcranial limb bones were compared among primates of different locomotor types. Seventy-one primate species, in which all families of primates were included, were grouped into nine locomotor types. Osteometrical data on long bones and data on the cross-sectional geometry of the humerus and the femur were studied by means of allometric analysis and principal component analysis. Relatively robust forelimb bones were observed in the primate group which adopted the relatively terrestrial locomotor type compared with the group that adopted the arboreal locomotor type. The difference resembled the previously reported comparison between terrestrial and arboreal groups among all quadrupedal mammals. The degree of arboreality in daily life is connected with the degree of hindlimb dominance, or the ratio of force applied to the fore- and hindlimb in positional behaviour and also with the shape, size and robusticity of limb bones.     

Autoantibodies against cardiac troponin I are responsible for dilated cardiomyopathy in PD-1-deficient mice

We recently reported that mice deficient in the programmed cell death-1 (PD-1) immunoinhibitory coreceptor develop autoimmune dilated cardiomyopathy (DCM), with production of high-titer autoantibodies against a heart-specific, 30-kDa protein. In this study, we purified the 30-kDa protein from heart extract and identified it as cardiac troponin I (cTnI), encoded by a gene in which mutations can cause familial hypertrophic cardiomyopathy (HCM). Administration of monoclonal antibodies to cTnI induced dilatation and dysfunction of hearts in wild-type mice. Monoclonal antibodies to cTnI stained the surface of cardiomyocytes and augmented the voltage-dependent L-type Ca2+ current of normal cardiomyocytes. These findings suggest that antibodies to cTnI induce heart dysfunction and dilatation by chronic stimulation of Ca2+ influx in cardiomyocytes.