Differential expressions of BMPR1α, ACTN4α and FABP7 in Hirschsprung disease

Hirschsprung disease (HSCR) is characterized by the absence of intramural ganglion cells in the nerve plexuses of the distal gut. Recent studies have shown that the bone morphogenetic protein receptor-type IA (BMPR1α), actinin-alpha 4 (ACTN4α) and fatty acid binding protein 7 (FABP7) play important roles in the differentiation and development of neurons. The aganglionic (stenotic) and the ganglionic (normal) colon segment tissues of 60 HSCR patients were collected to investigate the expression pattern of BMPR1α, ACTININ-4α and FABP7 using RT-PCR, quantitative real-time RT-PCR (qRT-PCR) and immunohistochemical staining. The mRNA and protein expressions of BMPR1α and ACTN4α were higher in the stenotic colon segment tissue than those in the normal colon segment tissue. However, the mRNA and protein expressions of FABP7 were lower in the stenotic colon segment tissue than those in the normal colon segment tissue. The study in HSCR patients, findings in mRNA and protein alterations to expecting provide more information to in order to find some clue for the pathomechanism of HSCR disease.     

Differential expression of FOXA1, DUSP6, and HA117 in colon segments of Hirschsprung’s disease

Objective: To describe the expression profiles of FOXA1, DUSP6, and HA117 in different portions of the colon of patients diagnosed with Hirschsprung’s disease (HSCR). Methods: Colon specimens were collected from34 HSCR patients and grouped into 3 segments: proximal anastomosis, dilated segment and stenotic segment. Levels of FOXA1, DUSP6, and HA117 RNA were evaluated by real-time PCR. Levels of FOXA1 and DUSP6 protein were analyzed by immunohistochemistry and Western blotting. Results: The levels of FOXA1 and DUSP6 RNA were significantly lower in the stenotic segment compared to proximal anastomosis (P < 0.05). The level of HA117 RNA was significantly higher in the stenotic segment compared to proximal anastomosis (P < 0.05). In proximal anastomosis, FOXA1 and DUSP6 were both expressed at the protein level in ganglion cells and nerve fibers between the circular and longitudinal muscles. In the stenotic segments, positive staining for FOXA1 and DUSP6 was diminished. The levels of FOXA1 and DUSP6 protein were significantly lower in the stenotic segment compared to proximal anastomosis (P < 0.05). Conclusion: Suppression of the FOXA1/DUSP6 signaling pathway may contribute to the development of HSCR. LncRNA HA117 may have an anti-differentiation function, and play a pivotal role in the progression of HSCR.     

Comparative study of Hsp27, GSK3β, Wnt1 and PRDX3 in Hirschsprung's disease

Hirschsprung's disease (HSCR) is a developmental disorder of the enteric nervous system characterized by aganglionosis in distal gut. In this study, we used two‐dimensional gel electrophoresis (2‐DE) technology coupled with matrix assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) analysis to identify differentially expressed proteins in the aganglionic (stenotic) and ganglionic (normal) colon segment tissues from patients with HSCR. We identified 15 proteins with different expression levels between the stenotic and the normal colon segment tissues from patients with HSCR. Nine proteins were upregulated and six proteins downregulated in the stenotic colon segment tissues compared to the normal colon segment tissues. Based on the biological functions, we selected the Hsp27 upregulated proteins and the PRDX3 downregulated proteins to confirm their expression in 20 patients. The protein and mRNA expressions of Hsp27 were statistically higher in the stenotic colon segment tissues than in the normal colon segment tissues, whereas the protein and mRNA expressions of PRDX3 were statistically lower in the stenotic colon segment tissues than in the normal colon segment tissues. These findings of changes in mRNA and protein in tissues from patients with HSCR provide information which may be helpful in understanding the pathomechanism that is implicated in the disease.     

Expression of dishevelled gene in Hirschsprung’s disease

Hirschsprung’s disease (HSCR) is a congenital disorder of the enteric nervous system and is characterized by an absence of enteric ganglion cells in terminal regions of the gut during development. Dishevelled (DVL) protein is a cytoplasmic protein which plays pivotal roles in the embryonic development. In this study, we explore the cause of HSCR by studying the expression of DVL-1 and DVL-3 genes and their proteins in the aganglionic segment and the ganglionic segment of colon in HSCR patients. Materials and Methods: Specimen of aganglionic segment and ganglionic segment of colon in 50 cases of HSCR patients. Expression levels of mRNA and proteins of DVL-1 and DVL-3 were confirmed by quantitative real-time PCR (qRT-PCR), western blot and immunohistochemistry staining between the aganglionic segment and the ganglionic segment of colon in HSCR patients. Results: The mRNA expression of DVL-1 and DVL-3 were 2.06 fold and 3.12 fold in the aganglionic segment colon tissues compared to the ganglionic segment, respectively. Similarly, the proteins expression of DVL-1 and DVL-3 were higher (39.71 ± 4.53 vs and 53.90 ± 6.79 vs) in the aganglionic segment colon tissues than in the ganglionic segment (15.01 ± 2.66 and 20.13 ± 3.63) by western blot. Besides, immunohistochemical staining showed that DVL-1 and DVL-3 have a significant increase in mucous and submucous layers from aganglionic colon segments compared with ganglionic segments. Conclusion: The study showed an association of DVL-1 and DVL-3 with HSCR, it may play an important role in the pathogenesis of HSCR.     

BMP10 as a potent inducer of trophoblast differentiation in human embryonic and induced pluripotent stem cells

Bone morphogenetic proteins (BMPs) are known to induce diverse differentiation fates in human embryonic stem cells (hESCs). In the present study, we compared the potency at which BMP5, BMP10 and BMP13, which are members of distinct BMP subgroups due to differences in sequential and structural homology, induce differentiation in hESCs and human induced pluripotent stem cells (hiPSCs). We observed, in agreement with previous BMP4 model studies, that all ligands induced differentiation to the trophoblast lineage in the absence of bFGF. However, distinct BMPs exerted differences in the kinetics of induced differentiation, with BMP10 being the most potent. hiPSCs and hESCs shared comparable expression patterns of BMP type-I and -II receptor subtypes, which might explain conserved properties with respect to ligand potency and activation of SMAD-dependent (via SMAD1/5/8) and -independent (via MAPK p38) signal transduction pathways. The tested BMPs had distinct and also conserved target genes such as CDX2, DLX3, DLX5, GATA2, GATA3, HAND1, ID2, MSX2 and TFAP2A, known to be associated with the emergence of trophoblast cells. hESCs induced expression of the BMP antagonist NOGGIN as a protection mechanism to constrict extensive BMP action. Unlike BMP4, BMP10 has been shown to be resistant to NOGGIN-induced inhibition which in part might explain its potency. BMPs, in particular BMP4, are commonly used cytokines in differentiation protocols to generate diverse mesoderm- and endoderm-derivates from human pluripotent stem cells. Our study has identified BMP10, a cardiac-specific protein, as a superior alternative to BMP4 for inducing trophoblast differentiation in human pluripotent stem cells.     

先天性肠无神经节细胞症患儿中血清维生素A及肠组织维甲酸受体α和HA117的表达特点

目的检测先天性肠无神经节细胞症(HD)患儿中血清维生素A及肠组织维甲酸受体α(RARα)、抗分化长链非编码RNA(LncRNA)HA117的表达特点,探讨其与HD发病机制的可能联系。方法收取17例临床诊断为HD的患儿术前外周血及手术结肠组织标本,结肠组织由近端至远端分为3组:吻合口组、扩张段组和痉挛段组。检测血清维生素A浓度,采用Real-time PCR、免疫组织化学染色、Western blotting方法检测RARα及HA117在各组结肠组织的表达水平。结果 17例HD患儿均有不同程度维生素A缺乏,血清维生素A平均浓度为(0.73±0.05)μmol/L。在吻合口段,RARα在肌间神经丛可见棕黄色的阳性染色,而在痉挛段几乎未见阳性神经丛染色;在吻合口组、扩张段组和痉挛段组,RARαmRNA相对表达量依次为3.62±1.12、1.81±0.69、0.65±0.32,与吻合口相比,痉挛段表达量降低(P0.05,n=17);HA117 mRNA相对表达量依次为0.47±0.15、1.25±0.40、2.57±0.70,与吻合口相比,痉挛段表达量增高(P0.001,n=17);RARα蛋白相对表达量依次为1.16±0.05、0.99±0.05、0.88±0.04,与吻合口相比,扩张段及痉挛段表达量降低(分别为P0.05、P0.001,n=17)。结论维生素A、RARα及HA117可能共同参与肠神经系统(ENS)的发育过程;其中,维生素A和RARα可能促进了ENS的正常分化发育,而高表达的HA117可能对抗了前者的促分化作用,阻碍了ENS正常分化发育过程,进而导致HD的发生。     

Up-regulated FHL1 Expression Maybe Involved in the Prognosis of Hirschsprung's Disease

Background: In a subset of patients with Hirschsprung''s disease (HSCR), gastrointestinal motor dysfunction persisted long after surgical correction. Gastrointestinal motility is achieved through the coordinated activity of the enteric nervous system, interstitial cells of Cajal, and smooth muscle (SMC) cells. Inhibition of four-and-a-half LIM protein-1 (Fhl1) expression by siRNA significantly decreases pulmonary artery SMCs migration and proliferation. Furthermore when up-expressing FHL1 in atrial myocytes, K (+) current density markedly increases, therefore changing myocytes'' response to an electrical stimulus. However whether FHL1 in colon SMCs (the final effector organ) influences intestinal motility in HSCR patients has not been clarified. Methods: FHL1 mRNA and protein expressions were analyzed in 32 HSCR colons and 4 normal colons. Results: Smooth muscle layers were thicken and disorganized in HSCR. FHL1 was expressed in the ganglion cells of the myenteric plexus, submucosa, as well as in the longitudinal and circular muscle layer of the ganglionic colon. FHL1 mRNA relative expression level in aganglionic colons was 1.06±0.49 (ganglionic colon relative expression level was 1) (P=0.44). FHL1 protein gray level relative to GAPDH in normal colons was 0.83±0.09. FHL1 expression level in ganglionic colon (1.66±0.30) or aganglionic colon (1.81±0.35) was significantly higher than that in normal colons (P=0.045 and P=0.041, respectively). Meanwhile, we found FHL1 expression in aganglionic colon was slightly stronger than that in ganglionic colon (P=0.036). Conclusion: These data suggested that up-regulated FHL1 in smooth muscle in HSCR might be associated with intestinal wall remodeling in HSCR and might be one of the risk factors for gastrointestinal motor dysfunction.     

Dynamic patterns of expression of BMP isoforms 2, 4, 5, 6, and 7 during chicken heart development

Bone morphogentic proteins (BMPs) play an important role in cardiac development. Using an in vitro explant analysis, we show that BMPs are crucial for myocardium formation. As a first approach to identify which BMP may be involved in myocardium formation in intra- and extracardiac mesenchyme in vivo, a survey of the expression patterns of BMP2, -4, -5, -6, and -7 mRNA is prepared by in situ hybridization in chicken embryonic hearts from HH5 to 44. During recruitment of mesodermal cells to the outflow tract myocardium (HH10-23), BMP2, -4, -5, and -7 mRNA are expressed in the distal myocardial border and the flanking mesenchyme. After completion, BMP2 and -4 mRNA become restricted to the mesenchyme and BMP5 and -7 mRNA to the myocardium. At the venous pole, BMP2, -5, and -7 mRNA are expressed in the distal myocardial border of the caval vein, while BMP2, -5, -6, and -7 mRNA are expressed in the distal myocardium around the pulmonary vein. BMP4 mRNA is expressed in the adjacent mesenchyme at both sides. During muscularization of the atrioventricular cushions and the tricuspid valve, the cardiomyocytes that protrude into the mesenchyme express BMP2, -4, -5, and -7 mRNA, whereas BMP6 mRNA is expressed in the cushion mesenchyme. The myocardial protrusions formed in the mesenchymal proximal outlet septum express BMP4, -5, and -7 mRNA, while BMP2 and -6 mRNA are expressed in the mesenchyme. The spatiotemporal expression patterns of these BMPs in relation to myocardium formation at the distal ends and within the heart suggest a role for BMPs in myocardium formation. During delamination of the valves, BMP4 and -6 mRNA are expressed at the ventricular side of the forming mitral valve, BMP4 mRNA at the ventricular side of the forming tricuspid valve, and BMP2, -4, and -6 mRNA at the vascular side of the forming semilunar valves.     

Expression of Regulatory T Cells in Jejunum,Colon, and Cervical and Mesenteric Lymph Nodes of Dogs Naturally Infected with Leishmania infantum

Using flow cytometry, we evaluated the frequencies of CD4⁺ and CD8⁺ T cells and Foxp3⁺ regulatory T cells (Tregs) in mononuclear cells in the jejunum, colon, and cervical and mesenteric lymph nodes of dogs naturally infected with Leishmania infantum and in uninfected controls. All infected dogs showed chronic lymphadenitis and enteritis. Despite persistent parasite loads, no erosion or ulcers were evident in the epithelial mucosa. The colon harbored more parasites than the jejunum. Frequencies of total CD4⁺, total Foxp3, and CD4⁺ Foxp3⁺ cells were higher in the jejunum than in the colon. Despite negative enzyme-linked immunosorbent assay (ELISA) serum results for cytokines, levels of interleukin-10 (IL-10), gamma interferon (IFN-γ), transforming growth factor beta (TGF-β), and tumor necrosis factor alpha (TNF-α) were higher in the jejunum than in the colon for infected dogs. However, IL-4 levels were higher in the colon than in the jejunum for infected dogs. There was no observed correlation between clinical signs and histopathological changes or immunological and parasitological findings in the gastrointestinal tract (GIT) of canines with visceral leishmaniasis. However, distinct segments of the GIT presented different immunological and parasitological responses. The jejunum showed a lower parasite load, with increased frequencies and expression of CD4, Foxp3, and CD8 receptors and IL-10, TGF-β, IFN-γ, and TNF-α cytokines. The colon showed a higher parasite load, with increasing expression of IL-4. Leishmania infantum infection increased expression of CD4, Foxp3, IL-10, TGF-β, IFN-γ, and TNF-α and reduced CD8 and IL-4 expression in both the jejunum and the colon.     

The Prodomain-Containing BMP9 Produced from a Stable Line Effectively Regulates the Differentiation of Mesenchymal Stem Cells

Background: BMPs play important roles in regulating stem cell proliferation and differentiation. Using adenovirus-mediated expression of the 14 types of BMPs we demonstrated that BMP9 is one of the most potent BMPs in inducing osteogenic differentiation of mesenchymal stem cells (MSCs), which was undetected in the early studies using recombinant BMP9 proteins. Endogenous BMPs are expressed as a precursor protein that contains an N-terminal signal peptide, a prodomain and a C-terminal mature peptide. Most commercially available recombinant BMP9 proteins are purified from the cells expressing the mature peptide. It is unclear how effectively these recombinant BMP9 proteins functionally recapitulate endogenous BMP9.Methods: A stable cell line expressing the full coding region of mouse BMP9 was established in HEK-293 cells by using the piggyBac transposon system. The biological activities and stability of the conditioned medium generated from the stable line were analyzed.Results: The stable HEK-293 line expresses a high level of mouse BMP9. BMP9 conditioned medium (BMP9-cm) was shown to effectively induce osteogenic differentiation of MSCs, to activate BMP-R specific Smad signaling, and to up-regulate downstream target genes in MSCs. The biological activity of BMP9-cm is at least comparable with that induced by AdBMP9 in vitro. Furthermore, BMP9-cm exhibits an excellent stability profile as its biological activity is not affected by long-term storage at -80ºC, repeated thawing cycles, and extended storage at 4ºC.Conclusions: We have established a producer line that stably expresses a high level of active BMP9 protein. Such producer line should be a valuable resource for generating biologically active BMP9 protein for studying BMP9 signaling mechanism and functions.     

BMP2/7 heterodimer can modulate all cellular events of the in vitro RANKL-mediated osteoclastogenesis, respectively, in different dose patterns

Bone morphogenetic protein (BMP) heterodimers can trigger and sustain osteoblastic bone regeneration in significantly lower dosages than BMP homodimers. However, their effects on osteoclastic activity-a paramount coupling process with ostoblastic activity-remain undocumented. In this study, we delineated the functional characteristics of BMP2/7 heterodimer in inducing the in vitro osteoclastogenesis. We compared the dose-dependent effects of BMP2/7 heterodimer on the osteoclastogenesis of a preosteoclast cell line (RAW264.7) with those of BMP2 and BMP7 homodimers under the stimulation of 50 ng/mL receptor activator of nuclear factor-κB ligand. We quantitatively monitored the following parameters: cell proliferation, osteoclastic genes expression, morphological characteristics of osteoclasts, and calcium phosphate (CaP) resorption. BMP2/7 heterodimer could dose dependently modulate each osteoclastogenic event with different concentration patterns from the BMP homodimers. All BMPs of 10-150 ng/mL could increase the numbers of osteoclasts. Not BMP7 but 50-200 ng/mL BMP2 homodimer and 100-200 ng/mL BMP2/7 heterodimer could significantly enlarge the average surface-area of an osteoclast. BMP2/7 of 5-150 ng/mL could significantly enhance the osteoclastic CaP resorption to a similar level as the two homodimers. BMP2/7 heterodimer affects every osteoclastogenic event in a complicated dose-dependent manner. Low-concentration BMP2/7 heterodimer may favor a rapid and spontaneous remodeling of its induced bone and, thus, bear a promising potential in cytokine-based tissue engineering.     

Enzymatic regulation of pattern: BMP4 binds CUB domains of Tolloids and inhibits proteinase activity

In Xenopus embryos, a dorsal–ventral patterning gradient is generated by diffusing Chordin/bone morphogenetic protein (BMP) complexes cleaved by BMP1/Tolloid metalloproteinases in the ventral side. We developed a new BMP1/Tolloid assay using a fluorogenic Chordin peptide substrate and identified an unexpected negative feedback loop for BMP4, in which BMP4 inhibits Tolloid enzyme activity noncompetitively. BMP4 binds directly to the CUB (Complement 1r/s, Uegf [a sea urchin embryonic protein] and BMP1) domains of BMP1 and Drosophila Tolloid with high affinity. Binding to CUB domains inhibits BMP4 signaling. These findings provide a molecular explanation for a long-standing genetical puzzle in which antimorphic Drosophila tolloid mutant alleles displayed anti-BMP effects. The extensive Drosophila genetics available supports the relevance of the interaction described here at endogenous physiological levels. Many extracellular proteins contain CUB domains; the binding of CUB domains to BMP4 suggests a possible general function in binding transforming growth factor-β (TGF-β) superfamily members. Mathematical modeling indicates that feedback inhibition by BMP ligands acts on the ventral side, while on the dorsal side the main regulator of BMP1/Tolloid enzymatic activity is the binding to its substrate, Chordin.     

Thymosin ß4 expression in colorectal polyps and adenomas

OBJECTIVE:

Thymosin beta 4 (Tβ4) is a ubiquitous peptide that plays pivotal roles in the cytoskeletal system and in cell differentiation. Recently, a role for Tβ4 has been proposed in experimental and human carcinogenesis, including gastrointestinal cancer. This study was aimed at evaluating the relationship between Tβ4 immunoreactivity and the initial steps of carcinogenesis.

METHODS:

In total, 60 intestinal biopsies, including 10 hyperplastic polyps, 10 sessile serrated adenomas/polyps, 15 colorectal adenomas with low-grade dysplasia, 15 adenomas with high-grade dysplasia, 15 adenocarcinomas and 10 samples of normal colon mucosa, were analyzed for Tβ4 expression by immunohistochemistry.

RESULTS:

Weak cytoplasmic reactivity for Tβ4 was detected in the normal colon mucosa. No reactivity for Tβ4 was found in hyperplastic and sessile serrated polyps/adenomas. Tβ4 expression was observed in 10/15 colorectal adenocarcinomas. In adenomas with low-grade dysplasia, Tβ4 immunoreactivity was mainly detected in dysplastic glands but was absent in hyperplastic glands. Tβ4 immunoreactivity was characterized by spot-like perinuclear staining. In high-grade dysplastic polyps, immunostaining for Tβ4 appeared diffuse throughout the entire cytoplasm of dysplastic cells. Spot-like perinuclear reactivity was detected in adenocarcinoma tumor cells.

CONCLUSIONS:

Our study shows for the first time that Tβ4 is expressed during different steps of colon carcinogenesis. The shift of Tβ4 immunolocalization from low-grade to high-grade dysplastic glands suggests a role for Tβ4 in colorectal carcinogenesis. However, the real meaning of Tβ4 reactivity in dysplastic intestinal epithelium remains unknown.     

Association of apoE gene polymorphisms with lipid metabolism in renal diseases

Background and ObjectivesApolipoprotein E (apoE) plays a central role in the metabolism and homeostasis of lipids. ApoE gene encodes three major isoforms: ε2, ε3 a nd ε4 forming six phenotypes: E2E2, E2E3, E2E4, E3E3, E3E3 and E4E4. Disorders of the lipid metabolism and the homeostasis are frequently coexist in renal diseases. The association between gene polymorphisms of apoE and lipid metabolism were not consistent. This meta-analysis was performed to assess the association between gene polymorphisms of apoE and lipid metabolism in renal diseases.MethodsA pre-defined literatures search and selection of eligible relevant investigations were performed to extract and collect data from electronic databases.ResultsSixteen articles were enrolled for the analysis of association between apoE gene polymorphisms and lipid metabolism. Subjects with E3E4 had a higher total cholesterol (TC) than those with E3E3, and subjects with E2E3 had a lower TC than those with E3E3. Subjects with ε2, had a lower TC than those with ε3 or ε4, and subjects with ε4 had a higher TC than those with, ε3. Subjects with E2E2, E2E3 or E4E4 had a higher triglyceride (TG) than those with E3E3. Subjects with ε4 had a higher TG than those with ε3. Subjects with ε2, had a higher level of TG than those with non-ε2. Subjects with E3E4 had a slightly lower high-density lipoprotein (HDL) than those with E3E3. E3E4 appeared to be associated with lower levels of HDL. Subjects with E2E2, E2E3 had a notably lower low-density lipoprotein (LDL) than those with E3E3. Subjects with ε2, had a lower LDL than those with ε3 or ε4 ApoE gene polymorphisms were not associated with very low-density lipoprotein, and lipoprotein (a) [Lp(a)]. Subjects with E2E3 or E2E4 had higher apoE levels than those with E3E3, and subjects with E4E4 had lower apoE levels than those with E3E3.ConclusionApoE gene polymorphisms are associated with the expression of TC, TG HDL, LDL, Lp(a) or apoE.     

WNT3A gene expression is associated with isolated Hirschsprung disease polymorphism and disease status

WNT3A has been regarded as an activator of the canonical Wnt signaling pathway. It has been found Wnt signaling pathway is closely related with embrionic development and Hirschsprung disease (HSCR). A common haplotype consisting of minor SNPs alleles located in the WNT3A gene has been described as a risk factor for various genetic disorders. However, whether WNT3A contributes to the onset of HSCR has not been identified. The present study aims to detect the interactions of genetic variations in the WNT3A gene and examine the biological expression levels with Hirschsprung disease (HSCR) in the Chinese people. We analyzed WNT3A gene (rs61743220, rs192966556 and rs145882986) variants in the whole blood samples from HSCR patients and normal children (control groups). WNT3A expression was also examined by quantitative real-time PCR (qRT-PCR), western blotting and immunostaining. Consequently, when rs192966556 and rs145882986 alleles of the WNT3A gene lack the SNPs, they are especially associated with a greater risk of HSCR (OR [95% confidence interval] = 1.791, p = 0.001; OR [95% confidence interval] = 1.556, p = 0.003, respectively). The mRNA and protein expressions of WNT3A were higher in the aganglionic colon segment tissues than in the normal ganglionic segments tissues. Immunostaining indicates that the staining of WNT3A was much stronger (brown) in the aganglionic colon segment tissues than that in the normal ganglionic colon segment tissues (colorless or light yellow) in the mucous layer and muscular layer. Although preliminary, these results suggest that WNT3A may play an important role in the pathogenesis of HSCR.     

Characterisation of the human GFRalpha-3 locus and investigation of the gene in Hirschsprung disease

BACKGROUND—The GDNF family receptor alpha (GFRα) proteins are extracellular cell surface bound molecules that act as adapters in binding of the GDNF family of soluble neurotrophic factors to the RET receptor. These molecules are essential for development of many neural crest derived cell types and the kidney. Mutations in RET and in two members of the GDNF ligand family are associated with Hirschsprung disease (HSCR), a congenital absence of the enteric ganglia. Members of the GFRα family are also candidates for HSCR mutations. One such gene is GFRα-3, which is expressed in the peripheral nervous system and developing nerves.
OBJECTIVE—We have characterised the structure of the human GFRα-3 locus and investigated the gene for sequence variants in a panel of HSCR patients.
METHODS—Long range PCR or subcloning of PAC clones was used to investigate GFRα-3 intron-exon boundaries. A combination of single strand conformation polymorphism (SSCP) analysis and direct sequencing was used to investigate GFRα-3 sequence variants.
RESULTS—GFRα-3 spans eight coding exons and has a gene structure and organisation similar to that of GFRα-1. We identified three polymorphic variants in GFRα-3 in a normal control population, a subset of which also occurred in HSCR patients. We did not detect any sequence variants within the coding sequence of GFRα-3. We found a base substitution in the 5' UTR of GFRα-3, 15 base pairs upstream of the translation start site. A second substitution was identified in intron 4 (IVS4-30G>A) between the splice branch site and the splice acceptor site. The final variant was a 2 base pair insertion within the splice donor consensus sequence of exon 7 (IVS7+4ins GG).
CONCLUSIONS—We did not detect any correlation between variants of GFRα-3 and the HSCR phenotype. Our data suggest that mutations of this gene are not a cause of HSCR.


Keywords: GFRα-3; Hirschsprung disease; RET     

BMP9 and BMP10: Two close vascular quiescence partners that stand out

Bone morphogenetic proteins (BMPs) are dimeric transforming growth factor ß (TGFß) family cytokines that were first described in bone and cartilage formation but have since been shown to be involved in many pleiotropic functions. In human, there are 15 BMP ligands, which initiate their cellular signaling by forming a complex with two copies of type I receptors and two copies of type II receptors, both of which are transmembrane receptors with an intracellular serine/threonine kinase domain. Within this receptor family, ALK1 (activin receptor-like kinase 1), which is a type I receptor mainly expressed on endothelial cells, and BMPRII (BMP Receptor type II), a type II receptor also highly expressed on endothelial cells, have been directly linked to two rare vascular diseases: hereditary hemorrhagic telangiectasia (HHT), and pulmonary arterial hypertension (PAH), respectively. BMP9 (gene name GDF2) and BMP10, two close members of the BMP family, are the only known ligands for the ALK1 receptor. This specificity gives them a unique role in physiological and pathological angiogenesis and tissue homeostasis. The aim of this current review is to present an overview of what is known about BMP9 and BMP10 on vascular regulation with a particular emphasis on recent results and the many questions that remain unanswered regarding the roles and specificities between BMP9 and BMP10.     

Distinct roles of type I bone morphogenetic protein receptors in the formation and differentiation of cartilage

The bone morphogenetic proteins (BMPs), TGFβ superfamily members, play diverse roles in embryogenesis, but how the BMPs exert their action is unclear and how different BMP receptors (BMPRs) contribute to this process is not known. Here we demonstrate that the two type I BMPRs, BMPR-IA and BMPR-IB, regulate distinct processes during chick limb development. BmpR-IB expression in the embryonic limb prefigures the future cartilage primordium, and its activity is necessary for the initial steps of chondrogenesis. During later chondrogenesis, BmpR-IA is specifically expressed in prehypertrophic chondrocytes. BMPR-IA regulates chondrocyte differentiation, serving as a downstream mediator of Indian Hedgehog (IHH) function in both a local signaling loop and a longer-range relay system to PTHrP. BMPR-IB also regulates apoptosis: Expression of activated BMPR-IB results in increased cell death, and we showed previously that dominant-negative BMPR-IB inhibits apoptosis. Our studies indicate that in TGFβ signaling systems, different type I receptor isoforms are dedicated to specific functions during embryogenesis.