Katsumasa Takahashi

Six4, a putative myogenin gene regulator, is not essential for mouse embryonal development.

ABSTRACT Six4 is a member of the Six family genes, homologues of Drosophila melanogaster sine oculis. The gene is thought to be involved in neurogenesis, myogenesis, and development of other organs, based on its specific expression in certain neuronal cells of the developing embryo and in adult skeletal muscles. To elucidate the biological roles of Six4, we generatedSix4-deficient mice by replacing the Sixhomologous region and homeobox by the β-galactosidase gene. 5-Bromo-4-chloro-3-indolyl-β-d-galactopyranoside staining of the heterozygous mutant embryos revealed expression ofSix4 in cranial and dorsal root ganglia, somites, otic and nasal placodes, branchial arches, Rathkes pouch, apical ectodermal ridges of limb buds, and mesonephros. The expression pattern was similar to that of Six1 except at the early stage of embryonic day 8.5. Six4-deficient mice were born according to the Mendelian rule with normal gross appearance and were fertile. No hearing defects were detected. Six4-deficient embryos showed no morphological abnormalities, and the expression patterns of several molecular markers, e.g., myogenin andNeuroD3 (neurogenin1), were normal. Our results indicate that Six4 is not essential for mouse embryogenesis and suggest that other members of the Six family seem to compensate for the loss of Six4.

Immunosuppressive activity of CD14+ HLA-DR- cells in squamous cell carcinoma of the head and neck.

Myeloid‐derived suppressor cells (MDSC) represent a heterogeneous population and have the potential to suppress immune responses via diverse mechanisms. In recent studies, a new subset of MDSC was identified by the markers CD14+ and HLA‐DR− in the peripheral blood from cancer patients. In this study, we investigated the proportions and characteristics of CD14+ HLA‐DR− cells in patients with squamous cell carcinoma of the head and neck (SCCHN). As expected, the percentage of CD14+ HLA‐DR− cells was significantly elevated in patients relative to healthy donors and the sorted CD14+ HLA‐DR− cells were able to suppress effectively both the proliferation and IFN‐γ production of anti‐CD3/anti‐CD28 stimulated T cells, suggesting that CD14+ HLA‐DR− cells in patients with SCCHN contribute to the immune suppressive status. Furthermore, CD14+ HLA‐DR− cells revealed a higher level of CD86 and PD‐L1 expression and transforming growth factor (TGF)‐β production than CD14+ HLA‐DR+ cells. Addition of anti‐CD86 mAb, anti‐PD‐L1 mAb and anti‐TGF‐β mAb partially restored T‐cell proliferation and IFN‐γ production, respectively, indicating that the suppressive effects of CD14+ HLA‐DR− cells appear to be mediated by various molecules, including coinhibitory molecules and cytokines. Our data suggest that CD14+ HLA‐DR− cells act as potent immunosuppressive cells and particularly contribute to tumor escape from the host immune system in patients with SCCHN. (Cancer Sci 2012; 103: 976–983)

Caspase-3-deficiency induces hyperplasia of supporting cells and degeneration of sensory cells resulting in the hearing loss ☆

Caspase-3 is one of the cystein proteases that play essential roles in programmed cell death. As such, brain development is profoundly affected by caspase-3-deficiency, resulting in hyperplasia and abnormal cell organization (Kuida et al., Nature 1996;384:368-372). In the present study, we used caspase-3 (-/-) mice to show that caspase-3 deficiency results in severe hearing loss, hyperplasia of supporting cells and degeneration of sensory hair cells. The greater epithelial ridge, a remnant of the primordial organ of Corti, persists throughout all of the turns of cochlea in 2-week-old caspase-3 (-/-) mice, which indicates that the morphology of the cochlea is immature. The number of border cells, that develop from the greater epithelial ridge and are one of the supporting cells of the inner hair cell, increase significantly in both 2- and 5-week-old caspase-3 (-/-) mice. On the other hand, abnormal fused stereocilia can be seen in both 2- and 5-week-old caspase-3 (-/-) mice, and disarrangement and loss of sensory hair cells are observed in 5-week-old caspase-3 (-/-) mice. Taken together, both hyperplasia and degeneration occur simultaneously in the inner ear of the caspase-3 (-/-) mice, suggesting that caspase-3-dependent apoptosis is necessary for the development and formation of a properly functioning auditory system in mammals.

Maturation of circulating dendritic cells and imbalance of T-cell subsets in patients with squamous cell carcinoma of the head and neck

Interactions between dendritic cells (DCs) and T cells play a pivotal role in the regulation and maintenance of immune responses. In cancer patients, various immunological abnormalities have been observed in these immune cells. Here, we investigated proportions and the phenotype of DCs and the cytokine profile of T-cell subsets in the peripheral blood of patients with squamous cell carcinoma of the head and neck (SCCHN), using multicolor flow cytometry. The percentage of myeloid (CD11c+), but not plasmacytoid (CD123+) DCs, was significantly lower (P<0.05) and expression of HLA-DR was significantly decreased in total and myeloid DCs of cancer patients compared to healthy donors. Simultaneous analyses of T-cell subsets in the patients’ circulation showed significantly increased proportions of CD4+ T cells expressing Th1 and Th2 cytokines after ex vivo stimulation without any skewing in the Th1/Th2 ratio. The relative level of HLA-DR expression on myeloid or total DCs positively correlated with the Th1/Th2 ratio (P<0.01), and the proportion of total circulating DCs was inversely correlated with that of regulatory CD4+CD25+ T cells (P<0.01). These results suggest that the decreased proportion of circulating DCs and decreased HLA-DR expression in DCs may have a major impact on systemic immune responses in patients with SCCHN.

Mitosis and apoptosis in postnatal auditory system of the C3H/He strain

The mouse auditory neurons, hair cells and their supporting cells in the cochlea are considered to be generated mainly in the embryonic days and to be sustained throughout the whole life. In the present study, however, we observed that auditory ganglion cells in the spiral ganglia undergo apoptosis and mitosis in the suckling mouse (1- to 2-week-old C3H/HeJ mice) with a normal auditory system. In spiral ganglia at postnatal days 7 (P7) and 10 (P10), TUNEL (TdT-mediated dUTP nick-end labeling)-positive and morphologically apoptotic ganglion cells were found. Furthermore, by bromodeoxyuridine labeling, mitosis of auditory ganglion cells was found at P10 to P14. In a functional study of auditory brainstem response, we demonstrated that the C3H/HeJ mouse acquires the ability to hear airborne sound at P12 and this is the same time as the opening of their external acoustic meatus (EAM). These results indicate that C3H/HeJ auditory ganglion cells have the ability to proliferate even after opening of the EAM and the initial input of airborne sound. We found that postnatal apoptosis and mitosis after P7 also occurred in the greater epithelial ridge (GER) which is an important organ for maturation of the organ of Corti and is located around the inner hair cells. This indicates that GER cells are not only degenerated but also regenerated until their disappearance around P12. This is the first report on mammals to demonstrate that neuronal mitosis of spiral ganglion cells and that of GER cells occur not only in embryonic and neonatal development but also in postnatal development of the normal auditory system.

Nonsyndromic hearing loss caused by a mitochondrial T7511C mutation

Objectives The aims of the present study were to identify a mutation in a Japanese family showing nonsyndromic sensorineural hearing loss and to relate the mutation to characteristics of patients, including audiovestibular findings.

Temporal bone histopathological and quantitative analysis of mitochondrial DNA in MELAS.

Objectives/Hypothesis Although hearing loss is common in MELAS (syndrome of mitochondrial encephalopathy, lactic acidosis and stroke‐like episodes), the histopathology of the temporal bone has not been reported. The majority of cases of MELAS are linked to a mitochondrial DNA (mtDNA) mutation at nucleotide 3243. In MELAS, normal mtDNA and mutant mtDNA coexist in a heteroplasmic manner. The purpose of the study was to report the otopathological findings from two patients with MELAS and quantitative mtDNA analysis in the inner ear of one of these patients.

Mutations of the Pendred syndrome gene (PDS) in patients with large vestibular aqueduct

A recent report demonstrated the presence of a mutation in the Pendred syndrome gene (PDS) of patients with large vestibular aqueducts but without goitre. We studied PDS mutations in members of four Japanese families, among which five affected members showed bilateral enlarged vestibular aqueducts. All affected members exhibited moderate to severe bilateral fluctuating sensorineural hearing loss and the absence of goitre. Three members also suffered from recurrent episodic vertiginous spells. Analysis of PDS mutation revealed two single base changes (mis-sense mutations) in exons 19 and 10. The first was an A-->G transition at nucleotide position 2168, resulting in a predicted His-->Arg substitution at position 723 (H723R), whereas the second was a C-->T transition at nucleotide position 1229, resulting in a predicted Thr-->Met substitution at position 410 (T410M). Both mutations are situated in the extracellular domain close to the C terminal. It thus appears that PDS mutations can lead not only to classic Pendred syndrome, but also to large vestibular aqueduct syndrome.A recent report demonstrated the presence of a mutation in the Pendred syndrome gene (PDS) of patients with large vestibular aqueducts but without goitre. We studied PDS mutations in members of four Japanese families, among which five affected members showed bilateral enlarged vestibular aqueducts. All affected members exhibited moderate to severe bilateral fluctuating sensorineural hearing loss and the absence of goitre. Three members also suffered from recurrent episodic vertiginous spells. Analysis of PDS

Sexually Dimorphic Expression of the Novel Germ Cell Antigen TEX101 During Mouse Gonad Development

Abstract Prospermatogonia, or gonocytes, are the cells that differentiate from primordial germ cells to the first mature type of spermatogonia in the developing testis. Although prospermatogonia play a central role in this stage (i.e., prespermatogenesis), the details regarding their characterization have not been fully elucidated. Recently, we identified a novel mouse testicular germ cell-specific antigen, TES101 reactive protein (TES101RP), in the adult mouse testis. The protein TES101RP is also designated as protein TEX101. In the present study, we investigated the expression of TEX101 on germ cells in developing mouse gonads using histochemical techniques (i.e., immunohistochemistry, BrdU labeling, and TUNEL staining) and reverse transcription-polymerase chain reaction. TEX101 appeared on germ cells in both male and female gonads after the pregonadal period. In the testis, TEX101 was expressed constitutively on surviving prospermatogonia during prespermatogenesis. After the initiation of spermatogenesis, the prospermatogonia differentiated into spermatogonia. TEX101 expression disappeared from the spermatogonia, but reappeared on spermatocytes and spermatids. In the ovary, TEX101 was expressed on germ cells until the start of folliculogenesis; TEX101 was not detected on oocytes that were surrounded by follicular cells. These findings indicate that TEX101 is a specific marker for both male and female germ cells during gonadal development. Because the on and off switching of TEX101 expression in germ cells almost parallels the kinetics of gametogenesis, TEX101 may play an important physiological role in germ cell development.

A preliminary study on sentinel lymph node biopsy: feasibility and predictive ability in oral cavity cancer.

The main factor that affects the prognosis of patients with head and neck cancer (HNC) is regional lymph node metastases. For this reason, the accurate evaluation of neck metastases is required for neck management. This study investigates the sentinel lymph node identification and the accuracy of the histopathology of the sentinel lymph node in patients with HNC. Eleven patients with histologically proven oral squamous cell carcinoma accessible to radiocolloid injection were enrolled in this study. Using both lymphoscintigraphy and a handheld gamma probe, the sentinel lymph node could be identified in all 11 patients. Subsequently, the sentinel lymph nodes and the neck dissection specimen were examined for lymph node involvement due to tumor. The histopathology of sentinel lymph nodes was consistent with the pathological N classification in all 11 patients. Furthermore, the histopathology of sentinel lymph nodes was superior to physical examination, computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET) scan. The results of this study indicate that sentinel lymph node identi-fication is technically feasible and predicts cervical metastases in patients with oral cavity cancer. This may be a useful diagnostic technique for identifying lymph node disease in staging lymph node dissection.