Induction of Smad6 mRNA by bone morphogenetic proteins

Members of the transforming growth factor-beta (TGF-beta) superfamily transduce signals via Smad proteins. Smad2 and Smad3 mediate TGF-beta signaling, whereas Smad1 and Smad5 transduce bone morphogenetic protein (BMP) signals. Smad4 is a common mediator required for both pathways. Smad6 and Smad7 are recently identified members in the Smad family; they inhibit the signaling activity of the other Smad proteins. Here we show that expression of the Smad6 mRNA is dramatically induced by BMP-2 or osteogenic protein-1 (OP-1)/BMP-7 in various cells. BMP-2 induced expression of Smad7 in one cell type, although much less potently than that of Smad6. Smad6 message was induced by TGF-beta 1 in TGF-beta 1-responsive Mv1Lu cells, but the induction was transient in contrast to the induction by BMPs. These results indicate that Smad6 may form a feedback loop to regulate the signaling activity of BMPs.

An autopsy case of peripheral neuroepithelioma in posterior mediastinum with p53 point mutation

An 18-year old male was admitted to our hospital complaining of back pain. His chest computed tomography showed a tumor in the posterior mediastinum. Open biopsy was performed, and a diagnosis of peripheral neuroepithelioma was made. No genetic abnormalities were detected in the DNA obtained from the biopsy specimen. He received chemotherapy and radiation several times. These treatment regimens were effective, but he relapsed 14 months later and died of respiratory failure due to tumor growth. Autopsy examination revealed a large tumor which occupied almost the entire right thoracic cavity, but there was no evidence of metastasis to other organs. Chromosomal translocation t(14;17) (q24;p12.2) and point mutation of exon 5 of the p53 gene were detected.

[A case of pleuritis caused by strongyloides in a carrier of T-cell lymphoma virus type I (HTLV-I)]

A 73-year-old woman was admitted to our hospital complaining of dyspnea, fever and general edema. Chest roentgenogram showed bilateral pleural effusion and cardiomegaly. Cardiovascular examination demonstrated atrial tachycardia and left ventricle dysfunction, suggesting congestive heart failure. She was sero-positive for human T-cell lymphoma virus I (HTLV-I). The dyspnea and general edema improved after therapy for heart failure. Because the pleural effusion persisted after therapy, thoracentesis was performed. The pleural effusion was an exudate, and Strongyloides sterocoralis was detected by microscopy. Two courses of thiabendazole (1,500 mg/day, 3 days) were given orally. After this therapy, the pleural effusion improved markedly. This case suggests that Strongyloides stercoralis may be a causative agent of pleuritis in HTLV-I endemic areas.

Signal transduction by bone morphogenetic proteins

Bone morphogenetic proteins (BMPs) are multifunctional cytokines, which are members of the transforming growth factor-beta (TGF-beta) superfamily. Activities of BMPs are extracellularly regulated by BMP-binding proteins, Noggin and Chordin. BMPs bind to two different types of serine-threonine kinase receptors, type I and type II. Two BMP type I receptors and a BMP type II receptor have been identified in mammals. Intracellular signals are transduced by Smad proteins. Smad1, Smad5 and probably MADH6, are activated by BMP receptors, form heteromeric complexes with Smad4, and translocate into the nucleus where they may activate transcription of various genes. Smad6 and Smad7 are inhibitory Smads, and may act as autocrine switch-off signals. In Drosophila melanogaster, Decapentaplegic (Dpp) is a homologue of mammalian BMPs. In this review, mechanism of action of Dpp will be discussed in comparison with that of BMPs.

[A case of pulmonary infiltration with eosinophilia caused by Ascaris suum]

A 46-year old man was admitted to our hospital with dry cough and diarrhea. His chest CT showed diffuse subpleural small nodular shadows. Eosinophilia and an increase of serum IgE were detected. Eosinophils were also increased in BALF. An antibody against Ascaris suum was positive in serum while other causes of eosinophilia (e. g., drugs, fungus, collagen disease) were absent. Ivermectin was administered and the diarrhea improved within 3 days. The abnormal chest shadows and dry cough disappeared 3 months later. Pulmonary infiltration with eosinophilia (PIE) syndrome caused by Ascaris suum was diagnosed because of the clinical course and serum examination results. Recently, zoonoses are increasing with the boom of oversea travel and "natural" foods. We report a case of PIE syndrome caused by Ascaris suum and describe the clinical features and the social significance including the origin of this disease.

Identification of receptors and Smad proteins involved in activin signalling in a human epidermal keratinocyte cell line

BACKGROUND

Activin A is a multifunctional protein, which is a member of the transforming growth factor-beta (TGF-beta) superfamily. Smad proteins have recently been shown to transduce signals for the TGF-beta superfamily of proteins, and Smad2 was implicated in activin signalling in Xenopus embryos.

RESULTS

We identified the receptors and Smad proteins activated by activin A in a human epidermal keratinocyte cell line, HaCaT. The major activin receptors expressed on HaCaT cells were activin type II receptor (ActR-II) and activin type IB receptor (ActR-IB). We have also shown that in HaCaT cells, activin A induced the phosphorylation of Smad3 and, to a lesser extent, of Smad2. On the other hand, TGF-beta induced an efficient phosphorylation of both Smad2 and Smad3. Activin A preferentially induced the nuclear translocation of Smad3 in HaCaT cells, whereas TGF-beta strongly induced the nuclear translocation of Smad2, as well as other Smads. Moreover, a constitutively active form of ActR-IB efficiently stimulated the formation of a heteromeric complex between Smad3 and Smad4 in COS cells transfected with Smad cDNAs.

CONCLUSIONS

These results suggest that activin A binds to a receptor complex of ActR-II and ActR-IB, and preferentially activates Smad3 in HaCaT human keratinocytes.

PCR- and ligation-mediated synthesis of marker cassettes with long flanking homology regions for gene disruption in Saccharomyces cerevisiae

We developed a novel method for synthesizing marker-disrupted alleles of yeast genes. The first step is PCR amplification of two sequences located upstream and downstream of the reading frame to be disrupted. Due to the addition of non-specific single A overhangs by Taq DNA polymerase, each PCR product can be ligated with a marker DNA which has T residues at its 3' ends. After amplification of individual ligation products through the second PCR, both products are mixed and annealed, and the single strand is converted to a double strand by an extension reaction. The final step is PCR amplification of the fragment composed of a selectable marker and two flanking sequences with the outermost primers. This method is rapid and needs only short oligonucleotides as primers.

Clinical predictors in the natural history of uterine leiomyoma: preliminary study

This study was conducted to examine the correlation between uterine vascularity and natural history of uterine leiomyoma. Seventy women with leiomyoma participated in this study. Measurements of uterine and leiomyoma volume, as well as blood flow characteristics of the main uterine artery and leiomyoma arteries, were made every 3 months for 1 year. Leiomyoma arteries could be detected in 52 (51.5%) of 101 leiomyomas. Leiomyoma volume increased in 24 (46.2%) of 52 leiomyomas with leiomyoma artery. However, the leiomyoma volume increased in only three (6.1%) of 49 leiomyomas without leiomyoma artery. No difference was found between the pulsatility index of the leiomyoma artery in the group with increased size and in the group with stable size. This study shows the vascularity of leiomyoma to be useful as a predictor of leiomyoma growth.

A DNA-topoisomerase-II-binding protein with eight repeating regions similar to DNA-repair enzymes and to a cell-cycle regulator

A two-hybrid system was used to isolate factors that interact with the C-terminal region of DNA topoisomerase IIbeta. A positive clone isolated from a HeLa cDNA library encoded 1522 amino acid residues (molecular mass 170670). The protein, designated topoisomerase-IIbeta-binding protein 1 (TopBP1), interacted with the C-terminal region of topoisomerase IIbeta synthesized in vitro. A database search indicated that TopBP1 possessed eight regions similar to regions of Rad4, Cut5, Ect2, Rev1 and X-ray repair cross-complementing 1 (XRCC1) proteins and a region similar to auto-modification sites of poly(ADP-ribose) polymerase, suggesting that TopBP1 supported catalytic reactions of topoisomerase II through transient breakages of DNA strands.

[Clinical investigation of three cases of pulmonary eosinophilic granuloma]

Patient 1: An 18-year-old woman was admitted to our hospital with pneumothorax. She had no history of smoking. Chest CT showed multiple cysts, and pulmonary eosinophilic granuloma was diagnosed by open lung biopsy. She recovered without therapy 3 months later and a chest CT taken at that time was normal. She began smoking, 3 years later, and bore two children. She is without recurrence after 8 years. Patient 2: A 23-year-old man was admitted to our hospital with pneumothorax. He had a smoking history (index = 180). Chest CT showed multiple cysts, and pulmonary eosinophilic granuloma was diagnosed by open lung biopsy. He stopped smoking and recovered without therapy one month later, and subsequently, his CT findings returned to normal. Two years later, he began smoking again, but has no relapse. Patient 3: A 21-year-old man was admitted to our hospital with pneumothorax. He had no history of smoking. A chest CT showed multiple cysts, and pulmonary eosinophilic granuloma was diagnosed by open lung biopsy. Diabetes insipidus was subsequently noted. Dyspnea persisted, and he recovered 4 months later after steroid treatment. He was without relapse 2 years later but the multiple cysts remained. We report three cases of pulmonary eosinophilic granuloma, and discuss their pertinent clinical features.

Continuous local injection of carboplatin into the uterine cervix for cervical and endometrial cancer: preliminary study

Platinum compounds are thought to be concentration- and time-dependent, but intravenous (i.v.) administration does not afford prolonged high platinum concentration in tumor tissue. In order to examine the influence of long-term local continuous (LC) injection of carboplatin, a pharmacokinetic study was performed. Twenty-six patients with uterine cancer were included. I.v. administration (11 patients): carboplatin (210 mg) was given i.v. and samples of target tissue were obtained at operation about 2 or 24 h after administration. LC administration (15 patients): the 21-gauge needle was implanted at the uterine cervix, and carboplatin was injected continuously (30 mg/day) for 3, 7 or 14 days using an external pump. The tissue platinum concentration was measured in the pelvic organs. The mean platinum levels at the cervix and vaginal wall in the LC (7 days) group were higher than those in the i.v. (2 h) group (p < 0.01). With LC injection, sustained platinum levels were maintained in the pelvic organs for a long time, with very few side effects. LC injection may be advantageous on the basis of pharmacokinetics.

Alteration of cytokine levels by fosfomycin and prednisolone in spontaneous proliferation of cultured lymphocytes from patients with HTLV-I-associated myelopathy (HAM/TSP)

Fosfomycin has recently been reported as an antibiotic with immunomodulatory activities. To evaluate the possibility of clinical administration of fosfomycin in patients with human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP), the effects of this agent on the HTLV-I-induced in vitro phenomenon were studied. The influence of fosfomycin on in vitro spontaneous proliferation (SP) of peripheral blood mononuclear cells (PBMCs) from four patients with HAM/TSP was measured by thymidine incorporation into the cells, and the concentration of several cytokines in the culture supernatants was examined in three HAM/TSP patients. Enzyme-linked immunosorbent assays (ELISAs) were employed to detect the concentrations of interleukin-4 (IL-4), IL-6, IL-10, interferon-gamma (IFN-gamma), transforming growth factor-beta1 (TGF-beta1), and macrophage inflammatory protein-1alpha (MIP-1alpha). The data were compared to the changes by prednisolone which is known to regulate the HTLV-I-associated in vitro phenomenon and to have a therapeutic benefit in patients with HAM/TSP. Production of IL-6, IFN-gamma and MIP-1alpha from the spontaneously proliferating cells were demonstrated. Fosfomycin could not suppress the HTLV-I-associated SP, but had the properties to decrease the levels of TGF-beta1 and MIP-1alpha. It was also demonstrated that the concentrations of IFN-gamma and MIP-1alpha in the cultures in the presence of prednisolone were apparently decreased, suggesting a possible involvement of these cytokines in the pathogenesis of HAM/TSP. These findings support the hypothesis that fosfomycin may have immunomodulatory potentials in HTLV-I-related cellular interactions in a different manner from ordinary immunomodulatory agents.

Presenilin 1 binds to amyloid precursor protein directly

Mutations in the presenilin genes are associated with early onset familial Alzheimer's disease and lead to accumulation of beta-amyloid peptide in the brain of patients, suggesting that presenilin abnormalities induce pathological processing of amyloid precursor protein (APP) in Alzheimer's disease. For the understanding of pathogenesis in this type of familal Alzheimer disease, it is important to know whether presenilins are directly involved in the metabolism of beta-amyloid or not. To test whether presenilin 1 (PS1) directly binds to APP, we performed two-hybrid interaction assays between these proteins in yeast cells by using bait plasmids for normal and mutant PS1 and prey plasmids for APP fragments corresponding to the different molecular portions. Positive interaction was observed in any combination between PS1 bait plasmids and APP prey plasmids. Therefore, our results show that PS1 binds to APP directly and suggest that the PS1 protein itself is involved in the metabolism of beta-amyloid peptide.

Smad6 inhibits signalling by the TGF-beta superfamily

SMAD proteins have been identified as signalling mediators of the TGF-beta superfamily, which is involved in a range of biological activities including cell growth, morphogenesis, development and immune responses. Smad1, Smad2, Smad3 and Smad5 are ligand-specific: Smadl and Smad5 transduce signals from bone morphogenetic proteins, and Smad2 and Smad3 mediate signalling by TGF-beta and activin, whereas Smad4 acts as a common signalling component. For example, Smad2 is phosphorylated by the TGF-beta type I receptor upon ligand binding, forms a heteromer with Smad4, and then translocates into the nucleus where it activates transcription. Here we report the isolation of Smad6 in the mouse. Smad6 is quite different in structure from the other SMAD proteins, and forms stable associations with type I receptors. Smad6 interferes with the phosphorylation of Smad2 and the subsequent heteromerization with Smad4, but does not inhibit the activity of Smad3. Smad6 also inhibits the phosphorylation of Smad1 that is induced by the bone morphogenetic protein type IB receptor. These data indicate that signals of the TGF-beta superfamily are regulated both positively and negatively by members of the SMAD family.

Identification of Smad7, a TGFbeta-inducible antagonist of TGF-beta signalling

TGF-beta signals from the membrane to the nucleus through serine/threonine kinase receptors and their downstream effectors, termed SMAD proteins. The activated TGF-beta receptor induces phosphorylation of two such proteins, Smad2 and Smad3, which form hetero-oligomeric complex(es) with Smad4/DPC4 that translocate to the nucleus, where they then regulate transcriptional responses. However, the mechanisms by which the intracellular signals of TGF-beta are switched off are unclear. Here we report the identification of Smad7, which is related to Smad6. Transfection of Smad7 blocks responses mediated by TGF-beta in mammalian cells, and injection of Smad7 RNA into Xenopus embryos blocks activin/TGF-beta signalling. Smad7 associates stably with the TGF-beta receptor complex, but is not phosphorylated upon TGF-beta stimulation. TGFbeta-mediated phosphorylation of Smad2 and Smad3 is inhibited by Smad7, indicating that the antagonistic effect of Smad7 is exerted at this important regulatory step. TGF-beta rapidly induces expression of Smad7 mRNA, suggesting that Smad7 may participate in a negative feedback loop to control TGF-beta responses.

Enzymatic properties, substrate specificities and pH-activity profiles of two kiwifruit proteases

Kiwifruit (Actinidia chinensis) contains abundant protease, actinidin, and two possible components which were named A1 and A2. However, a comparison of the two components has not been thoroughly conducted. We have previously shown the presence of six proteases named KP1, KP2, KP3, KP4, KP5 and KP6 in kiwifruit, and that each purified kiwifruit protease was chromatographically pure. It was also indicated that the two representative components, KP4 and KP6, must be A1 and A2. To establish whether or not the two proteases, KP4 and KP6, have the same specificity in proteolytic activity, their enzymatic properties were compared. Between the two proteases, differences in substrate specificity against several protein-substrates (casein, gelatin, collagen, ovalbumin and bovine serum albumin) were not observed by digestion-product analysis with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The kinetic parameters of KP4 against N-alpha-carbobenzoxyl-lysine p-nitrophenyl esters were different from those of KP6. The pH-activity profiles of KP4 and KP6 against S-3-trimethylaminopropyl-lysozyme, a wide-pH range soluble substrate, and N-alpha-carbobenzoxyl-lysine p-nitrophenyl esters were different.

TGF-beta receptor-mediated signalling through Smad2, Smad3 and Smad4

Smad family members are newly identified essential intracellular signalling components of the transforming growth factor-beta (TGF-beta) superfamily. Smad2 and Smad3 are structurally highly similar and mediate TGF-beta signals. Smad4 is distantly related to Smads 2 and 3, and forms a heteromeric complex with Smad2 after TGF-beta or activin stimulation. Here we show that Smad2 and Smad3 interacted with the kinase-deficient TGF-beta type I receptor (TbetaR)-I after it was phosphorylated by TbetaR-II kinase. TGF-beta1 induced phosphorylation of Smad2 and Smad3 in Mv1Lu mink lung epithelial cells. Smad4 was found to be constitutively phosphorylated in Mv1Lu cells, the phosphorylation level remaining unchanged upon TGF-beta1 stimulation. Similar results were obtained using HSC4 cells, which are also growth-inhibited by TGF-beta. Smads 2 and 3 interacted with Smad4 after TbetaR activation in transfected COS cells. In addition, we observed TbetaR-activation-dependent interaction between Smad2 and Smad3. Smads 2, 3 and 4 accumulated in the nucleus upon TGF-beta1 treatment in Mv1Lu cells, and showed a synergistic effect in a transcriptional reporter assay using the TGF-beta-inducible plasminogen activator inhibitor-1 promoter. Dominant-negative Smad3 inhibited the transcriptional synergistic response by Smad2 and Smad4. These data suggest that TGF-beta induces heteromeric complexes of Smads 2, 3 and 4, and their concomitant translocation to the nucleus, which is required for efficient TGF-beta signal transduction.

[A case of rapidly progressive HTLV-I-associated myelopathy (HAM)]

We report a 65-year-old woman with HAM who showed rapid progression of the clinical symptoms. The initial symptom was lumbago and she became unable to walk within 4 months after the onset of the lumbago. When seen on admission, she had flaccid paraplegia and areflexia was seen in the lower extremities with positive Babinski and Chaddock reflexes. She had numbness below the level of the navel, vibratory sensation was decreased in both lower limbs, and there was a hyperesthesic zone at the tenth thoracic vertebral level. She had a difficulty in urination and defecation. Laboratory examination revealed elevated anti-HTLV-I antibody titers both in serum (4,096x by PA method) and in cerebrospinal fluid (CSF) (4,096x). The levels of IgG and neopterin in CSF were also increased to 16.6 mg/dl (normal: < 5 mg/dl) and 360.3 pmol/ml (normal: < 30 pmol/ml), respectively. HTLV-I messenger RNA positive cells were detected in 0.1% to 0.01% of cells in CSF by in situ hybridization using an oligonucleotide probe labelled with alkaline phosphatase. Spinal cord MRI detected neither spinal cord compression nor vascular diseases. She was treated with 1,000 mg methylprednisolone for 3 days intravenously, followed by 60 mg oral prednisolone therapy. In several days after receiving the treatments, her muscle tonus became spastic and deep tendon reflexes in the legs became brisk. The hyperesthesia at the tenth thoracic vertebral level and numbness below the level of the navel were also gradually improved. Subsequently, her clinical features were consistant with those of the typical HAM. Therefore, the patient was diagnosed as rapidly progressive HAM. The initial phase of rapidly progressive HAM patients had been described only from clinical history. These patients had common characteristic clinical features, such as older age at onset, relatively severe motor dysfunction, high titers of anti-HTLV-I antibody in CSF, and increased levels of neopterin and IgG in CSF, when compared with those of other HAM patients. The clinical course and laboratory findings in the present patient were compatible with those in the previous cases reported as rapidly progressive HAM. This patient showed flaccid paraplegia and areflexia which have rarely been seen in HAM patients. However, these symptoms were changed to spastic and hyperactive after prednisolone therapy. We speculate that inflammation in the spinal cord in this patient was severe enough to spread to the dorsal root, and disturbed the afferent pathway from the peripheral to the central nervous system. This inflammatory reaction might be suppressed by prednisolone to facilitate the recovery of the afferent pathway, which led to the typical clinical symptoms of HAM.

[Flow cytometric analysis of P-glycoprotein function by rhodamine 123 dye-efflux assay in human leukemia cells]

Cells with multidrug resistance(MDR) phenotype express P-glycoprotein(P-gp) on cell membrane, which works as a drug-efflux pump with low selectivity. P-gp function can be determined microfluorometrically using the fluorescent dye rhodamine 123(Rh123), which is an artificial substrate for P-gp. In this study, we assessed P-gp function in human leukemia sublines of MOLT-3 with various magnitude of MDR phenotype using the Rh123-efflux assay. The MDR cells efficiently pumped out Rh123 outside cells in parallel with the magnitude of resistance to vincristine, while the parent MOLT-3 cells scarcely showed dye efflux. The P-gp function determined by the dye efflux assay was correlated with the degree of cell surface expression of P-gp measured by indirect flow cytometric analysis using MRK16 anti-P-gp antibody and with the amount of MDR1 mRNA (encoding P-gp) quantified by Northern blot analysis and by competitive reverse transcription-polymerase chain reaction (RT-PCR) assay. In the evaluation of 28 clinical samples obtained from patients with leukemias, 9 cases exhibited positive results Rh123-efflux. A good correlation of Rh123-efflux with MDR1 expression measured by competitive RT-PCR was observed in these samples. Since subpopulations of normal lymphocytes show low degree of P-gp function, the strict gating of leukemia cells was mandatory in the dye-efflux assay in clinical samples. Although leukemia cells could not be distinguished from normal lymphocytes in the conventional scattergram in some cases, additional staining of the former cells with specific monoclonal antibody such as CD34(labelled with PE-Cy5, a dye without interference with Rh123 fluorescence emission) enabled a selective analysis of a particular subpopulation. The Rh123 dye-efflux assay is a simple and sensitive method for the determination of P-gp expression and its function, and is particularly suitable for the analyses in the clinical laboratory.

[A case of tuberculous abscess in the chest wall close to the thickening pleural lesion following tuberculous pleuritis]

A 33-year-old woman with a history of right tuberculous pleuritis was successfully treated in December 1992 by administration of anti-tuberculous drugs, she demonstrated residual localized pleural thickening on chest computed tomography (CT) and gradually developed a subcutaneous mass in the right chest which became apparent in March 1993. In September, chest CT revealed a periocostal abscess in the right anterior chest wall close to the localized pleural thickening. The patient was diagnosed with tuberculous abscess in the right chest wall on confirmation of acid-fast bacilli in a needle aspiration material of the abscess, and was referred to our hospital. Anti-tuberculous chemotherapy was continued but the chest abscess grew, so on January 28, 1994 she underwent a resection of the abscess, the third costal cartilage and bone, and the parietal pleural lesion connected to the abscess. Histopathological examination showed that the abscess and parietal pleural lesion were compatible with tuberculosis, i.e. both lesions consisted of caseous necrosis and epitheloid cell granuloma, but acid-fast bacilli were not demonstrated in both lesions. After one year of postoperative anti-tuberculous chemotherapy, she was followed without any therapy for 3 years and there has been no recurrence to date. When a localized thickening pleural lesion remains after tuberculous pleuritis, complication of tuberculous abscess in the chest wall should be considered.

Preoperative assessment of myometrial invasion of endometrial cancer by MR imaging and intrauterine ultrasonography with a high-frequency probe: preliminary study

This study was undertaken to assess the capabilities of intrauterine ultrasonography performed while inflating the endometrial cavity with fluid and magnetic resonance imaging as a means to assess the depth of myometrial invasion by endometrial cancer preoperatively. Twenty women with endometrial disorders underwent preoperative intrauterine ultrasonography and magnetic resonance imaging. We introduced the probe and hysteroscope simultaneously into the uterine cavity and observed both the uterine cavity surface and cross-sectional uterine muscle. We classified the depth of myometrial invasion as none, superficial (less than half of the myometrium), or deep (more than half of the myometrium). The accuracy of magnetic resonance imaging and intrauterine ultrasonography in assessing the depth of myometrial invasion was 85%. In two cases, intrauterine sonography was able to demonstrate superficial myometrial invasion that could not be diagnosed by magnetic resonance imaging. In contrast, intrauterine ultrasonography was unable to diagnose myometrial invasion in two cases in which magnetic resonance imaging could diagnose it. Intrauterine sonography may be useful for estimation of myometrial invasion of endometrial cancer.

cDNA cloning and genomic organization of the mouse BMP type II receptor

The cDNA for the mouse bone morphogenetic protein type II receptor (BMPR-II) was isolated using the human counterpart as a probe and its genomic structure was determined. The cDNA encodes a protein of 1,038 amino acids with a single transmembrane domain, a serine/threonine kinase domain, and a long carboxy-terminal tail. The overall amino acid sequence identity between the mouse and the human BMPR-II is 96.6%. mRNA is widely distributed in various adult tissues. The gene is encoded by 13 exons spanning over 80 kb. Two large introns (intron 1 and 3) contribute to the majority of the gene size, as in the mouse activin type II receptor gene. The intron/exon boundaries were sequenced. The results suggest that alternative splicing can yield a shorter form of BMPR-II of 530 amino acids, as reported previously. Knowledge of the structure of the BMPR-II gene is essential for the understanding of the role of bone morphogenetic proteins in the developmental and physiological processes of animals.