<ORIGINAL ARTICLE>Histochemical Localization of Carbonic Anhydrase in the Taste Buds of the Mouse and Goldfish

The activity of carbonic anhydrase in the taste buds of the mouse and goldfish was examined by enzyme histochemistry. An intense reaction of carbonic anhydrase was observed in the middle and basal regions of the taste buds in the mouse circumvallate papillae. Under the electron microscope, the reaction product was found in the cytoplasm of type-I cells which are characterized by the presence of ribosomes and rough endoplasmic reticulum. In other cell types (type-II and type-Ill cells), no reaction was detected. In the fungiform papillae, the reactivity was similar to that in the circumvallate ones; however, only a few cells were positively stained. In the goldfish, the receptor cells, which are characterized by the presence of tubular system, showed strong carbonic anhydrase activity. The results suggest that the activity of carbonic anhydrase, which is usually associated with H^+ or HCOs transport, is present in a specific type of taste bud cells

マウス歯発生時におけるインシュリン様成長因子ファミリーの遺伝子発現(Gene expression of insulin-like growth factor family during tooth development of the mouse)

マウス臼歯発生時におけるインシュリン様成長因子(IGF)とIGF結合蛋白質(IGFBP)の発現の時間的・空間的パターンを調べた。IGFとIGFBP発現はin situハイブリダイゼーションにて決定した。E14マウス胚の帽状期、E15胚の帽状期後期、E17-P0の鐘状期、P0-P13のクラウン形成期、P5-P13のルート形成期につき、IGF-I、IGF-II、IGFBP-2、-3、-4、-5、IGF-I受容体(IGF-IR)の発現部位と時期を網羅した。IGFおよびその作用調節因子は歯の成長分化の局所仲介因子となり、歯胚の上皮と間充織で局所的に発現するIGFBP-2、-3、-4、-5は歯の成長分化に役割を果たす可能性が示唆された。マウス臼歯発生時におけるインシュリン様成長因子(IGF)とIGF結合蛋白質(IGFBP)の発現の時間的・空間的パターンを調べた。IGFとIGFBP発現はin situハイブリダイゼーションにて決定した。E14マウス胚の帽状期、E15胚の帽状期後期、E17-P0の鐘状期、P0-P13のクラウン形成期、P5-P13のルート形成期につき、IGF-I、IGF-II、IGFBP-2、-3、-4、-5、IGF-I受容体(IGF-IR)の発現部位と時期を網羅した。IGFおよびその作用調節因子は歯の成長分化の局所仲介因子となり、歯胚の上皮と間充織で局所的に発現するIGFBP-2、-3、-4、-5は歯の成長分化に役割を果たす可能性が示唆された

発生中および除神経された味蕾におけるβ-カテニンの発現と活性化(Expression and activation of β-catenin in developing and denervated taste buds)

出生後発育期間または神経除去後期間の味蕾における活性化β-カテニンの発現の発現機構を明らかにすることを目的として、マウス味蕾におけるβ-カテニン、Wnt10b、Wnt5aおよびWntのレセプターであるFrizzled(Fzd)の発現パターンを調べた。これらパターンはin situハイブリダイゼーションおよび免疫組織化学法を用いて測定した。活性化β-カテニンの細胞質内の蓄積および核内への移行をソニックヘッジホッグ(Shh)免疫反応性基底細胞および味蕾内細胞において観察し、WntおよびそのレセプターであるFzd-1および-3の細胞内挙動を追跡した。これらの結果から、発生および再生の初期段階におけるβ-カテニン転写増大が基底細胞および未熟細胞の味蕾細胞への分化を促進すること、およびマウス味蕾細胞におけるWnt10bおよびFzd-1および-3はWnt/β-カテニン経路を構成し、その経路がβ-カテニンを活性化して、発生および再生の初期段階におけるβ-カテニン遺伝子の発現を上方調節する役割を持つことが示唆された。出生後発育期間または神経除去後期間の味蕾における活性化β-カテニンの発現の発現機構を明らかにすることを目的として、マウス味蕾におけるβ-カテニン、Wnt10b、Wnt5aおよびWntのレセプターであるFrizzled(Fzd)の発現パターンを調べた。これらパターンはin situハイブリダイゼーションおよび免疫組織化学法を用いて測定した。活性化β-カテニンの細胞質内の蓄積および核内への移行をソニックヘッジホッグ(Shh)免疫反応性基底細胞および味蕾内細胞において観察し、WntおよびそのレセプターであるFzd-1および-3の細胞内挙動を追跡した。これらの結果から、発生および再生の初期段階におけるβ-カテニン転写増大が基底細胞および未熟細胞の味蕾細胞への分化を促進すること、およびマウス味蕾細胞におけるWnt10bおよびFzd-1および-3はWnt/β-カテニン経路を構成し、その経路がβ-カテニンを活性化して、発生および再生の初期段階におけるβ-カテニン遺伝子の発現を上方調節する役割を持つことが示唆された

Engulfing cells promote neuronal regeneration and remove neuronal debris through distinct biochemical functions of CED-1

Two important biological events happen coincidently soon after nerve injury in the peripheral nervous system in C. elegans: removal of axon debris and initiation of axon regeneration. But, it is not known how these two events are co-regulated. Mutants of ced-1, a homolog of Draper and MEGF10, display defects in both events. One model is that those events could be related. But our data suggest that they are actually separable. CED-1 functions in the muscle-type engulfing cells in both events and is enriched in muscle protrusions in close contact with axon debris and regenerating axons. Its two functions occur through distinct biochemical mechanisms; extracellular domain-mediated adhesion for regeneration and extracellular domain binding-induced intracellular domain signaling for debris removal. These studies identify CED-1 in engulfing cells as a receptor in debris removal but as an adhesion molecule in neuronal regeneration, and have important implications for understanding neural circuit repair after injury

Intrinsic Oncogenic Function of Intracellular Connexin26 Protein in Head and Neck Squamous Cell Carcinoma Cells

It has long been known that the gap junction is down-regulated in many tumours. One of the downregulation mechanisms is the translocation of connexin, a gap junction protein, from cell membrane into cytoplasm, nucleus, or Golgi apparatus. Interestingly, as tumours progress and reinforce their malignant phenotype, the amount of aberrantly-localised connexin increases in different malignant tumours including oesophageal squamous cell carcinoma, thus suggesting that such an aberrantly-localised connexin should be oncogenic, although gap junctional connexins are often tumour-suppressive. To define the dual roles of connexin in head and neck squamous cell carcinoma (HNSCC), we introduced the wild-type connexin26 (wtCx26) or the mutant Cx26 (icCx26) gene, the product of which carries the amino acid sequence AKKFF, an endoplasmic reticulum-Golgi retention signal, at the C-terminus and is not sorted to cell membrane, into the human FaDu hypopharyngeal cancer cell line that had severely impaired the expression of connexin during carcinogenesis. wtCx26 protein was trafficked to the cell membrane and formed gap junction, which successfully exerted cell-cell communication. On the other hand, the icCx26 protein was co-localised with a Golgi marker, as revealed by immunofluorescence, and thus was retained on the way to the cell membrane. While the forced expression of wtCx26 suppressed both cell proliferation in vitro and tumorigenicity in mice in vivo, icCx26 significantly enhanced both cell proliferation and tumorigenicity compared with the mock control clones, indicating that an excessive accumulation of connexin protein in intracellular domains should be involved in cancer progression and that restoration of proper subcellular sorting of connexin might be a therapeutic strategy to control HNSCC