A novel method to isolate the common fraction of two DNA samples: hybrid specific amplification (HSA).
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Hybrid specific amplification (HSA) is a novel simple method elaborated in order to isolate the common fraction of two DNA samples while avoiding the background due to repeated sequences. The method is based on the suppressive PCR principle, associated with a Cot1 pre-hybridization step. In recent work we demonstrated that hyperprolificity observed in Booroola ewes is associated with a mutation in the bone morphogenetic protein receptor IB gene (BMPR-IB). We applied HSA between ovarian cDNA and DNA from four BAC clones containing BMPR-IB in order to test for the presence of other genes expressed in ovary and to isolate additional BMPR-IB exon sequences. Of the 460 clones obtained, none contained repeated sequences. We successfully obtained 37 clones representing the major part of BMPR-IB coding sequence, together with 5'- and 3'-UTR sequences. Here we have successfully applied HSA to a particular tissue, but it should be possible to trap the common fraction of two DNA samples, whatever their nature. (+info)
Germline mutations in BMPR1A/ALK3 cause a subset of cases of juvenile polyposis syndrome and of Cowden and Bannayan-Riley-Ruvalcaba syndromes.
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Juvenile polyposis syndrome (JPS) is an inherited hamartomatous-polyposis syndrome with a risk for colon cancer. JPS is a clinical diagnosis by exclusion, and, before susceptibility genes were identified, JPS could easily be confused with other inherited hamartoma syndromes, such as Bannayan-Riley-Ruvalcaba syndrome (BRRS) and Cowden syndrome (CS). Germline mutations of MADH4 (SMAD4) have been described in a variable number of probands with JPS. A series of familial and isolated European probands without MADH4 mutations were analyzed for germline mutations in BMPR1A, a member of the transforming growth-factor beta-receptor superfamily, upstream from the SMAD pathway. Overall, 10 (38%) probands were found to have germline BMPR1A mutations, 8 of which resulted in truncated receptors and 2 of which resulted in missense alterations (C124R and C376Y). Almost all available component tumors from mutation-positive cases showed loss of heterozygosity (LOH) in the BMPR1A region, whereas those from mutation-negative cases did not. One proband with CS/CS-like phenotype was also found to have a germline BMPR1A missense mutation (A338D). Thus, germline BMPR1A mutations cause a significant proportion of cases of JPS and might define a small subset of cases of CS/BRRS with specific colonic phenotype. (+info)
Proteasomal degradation of Smad1 induced by bone morphogenetic proteins.
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The bone morphogenetic proteins (BMPs) regulate early embryogenesis and morphogenesis of multiple organs, such as bone, kidney, limbs, and muscle. Smad1 is one of the key signal transducers of BMPs and is responsible for transducing receptor activation signals from the cytoplasm to the nucleus, where Smad1 serves as a transcriptional regulator of various BMP-responsive genes. Based upon the ability of Smad1 to bind multiple proteins involved in proteasome-mediated degradation pathway, we investigated whether Smad1 could be a substrate for proteasome. We found that Smad1 is targeted to proteasome for degradation in response to BMP type I receptor activation. The targeting of Smad1 to proteasome involves not only the receptor activation-induced Smad1 ubiquitination but also the targeting functions of the ornithine decarboxylase antizyme and the proteasome beta subunit HsN3. Our studies provide the first evidence for BMP-induced proteasomal targeting and degradation of Smad1 and also reveal new players and novel mechanisms involved in this important aspect of Smad1 regulation and function. (+info)
Noggin is required for induction of the hair follicle growth phase in postnatal skin.
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During postnatal development, the hair follicle (HF) shows cyclic activity with periods of relative resting, active growth (anagen), and regression. We demonstrate that similar to the HF induction in embryonic skin, initiation of a new hair growth phase in postnatal skin requires neutralization of the inhibitory activity of bone morphogenetic protein 4 (BMP4) by the BMP antagonist noggin. In the resting HF, BMP4 mRNA predominates over noggin in the epithelium and mesenchyme, and the BMP receptor IA is prominently expressed in the follicular germ. Anagen development is accompanied by down-regulation of the BMP4 and increased noggin mRNA in the HF. Furthermore, administration of noggin protein induces new hair growth phase in postnatal telogen skin in vivo. In contrast, BMP4 induces selective arrest of anagen development in the non-tylotrich (secondary) HF. As a hair growth inducer, noggin increases Shh mRNA in the HF whereas BMP4 down-regulates Shh. This suggests that modulation of BMP4 signaling by noggin is essential for hair growth phase induction in postnatal skin and that the hair growth-inducing effect of noggin is mediated, at least in part, by Shh. (+info)
Bone morphogenetic proteins, genetics and the pathophysiology of primary pulmonary hypertension.
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Several recent papers have shown that both familial primary pulmonary hypertension (FPPH) and sporadic primary pulmonary hypertension (PPH) may have a common etiology that is associated with the inheritance and/or spontaneous development of germline mutations in the bone morphogenetic protein receptor (BMPR) type II gene. Because BMPR-II is a ubiquitously expressed receptor for a family of secreted growth factors known as the bone morphogenetic proteins (BMPs), these findings suggest that BMPs play an important role in the maintenance of normal pulmonary vascular physiology. In the present commentary we discuss the implications of these findings in the context of BMP receptor biology, and relate these data to the genetics and pulmonary pathophysiology of patients with PPH. (+info)
BMPR-IA signaling is required for the formation of the apical ectodermal ridge and dorsal-ventral patterning of the limb.
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We demonstrate that signaling via the bone morphogenetic protein receptor IA (BMPR-IA) is required to establish two of the three cardinal axes of the limb: the proximal-distal axis and the dorsal-ventral axis. We generated a conditional knockout of the gene encoding BMPR-IA (Bmpr) that disrupted BMP signaling in the limb ectoderm. In the most severely affected embryos, this conditional mutation resulted in gross malformations of the limbs with complete agenesis of the hindlimbs. The proximal-distal axis is specified by the apical ectodermal ridge (AER), which forms from limb ectoderm at the distal tip of the embryonic limb bud. Analyses of the expression of molecular markers, such as Fgf8, demonstrate that formation of the AER was disrupted in the Bmpr mutants. Along the dorsal/ventral axis, loss of engrailed 1 (En1) expression in the non-ridge ectoderm of the mutants resulted in a dorsal transformation of the ventral limb structures. The expression pattern of Bmp4 and Bmp7 suggest that these growth factors play an instructive role in specifying dorsoventral pattern in the limb. This study demonstrates that BMPR-IA signaling plays a crucial role in AER formation and in the establishment of the dorsal/ventral patterning during limb development. (+info)
The BMP/BMPR/Smad pathway directs expression of the erythroid-specific EKLF and GATA1 transcription factors during embryoid body differentiation in serum-free media.
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Erythroid cell-specific gene regulation during terminal differentiation is controlled by transcriptional regulators, such as EKLF and GATA1, that themselves exhibit tissue-restricted expression patterns. Their early expression, already in evidence within multipotential hematopoietic cell lines, has made it difficult to determine what extracellular effectors and transduction mechanisms might be directing the onset of their own transcription during embryogenesis. To circumvent this problem, we have taken the novel approach of investigating whether the ability of embryonic stem (ES) cells to mimic early developmental patterns of cellular expression during embryoid body (EB) differentiation can address this issue. We first established conditions whereby EBs could form efficiently in the absence of serum. Surprisingly, in addition to mesoderm, these cells expressed hemangioblast and hematopoietic markers. However, they did not express the committed erythroid markers EKLF and GATA1, nor the terminally differentiated beta-like globin markers. Using this system, we determined that EB differentiation in BMP4 was necessary and sufficient to recover EKLF and GATA1 expression and could be further stimulated by the inclusion of VEGF, SCF, erythropoietin and thyroid hormone. EBs were competent to respond to BMP4 only until day 4 of differentiation, which coincides with the normal onset of EKLF expression. The direct involvement of the BMP/Smad pathway in this induction process was further verified by showing that erythroid expression of a dominant negative BMP1B receptor or of the inhibitory Smad6 protein prevented induction of EKLF or GATA1 even in the presence of serum. Although Smad1, Smad5 and Smad8 are all expressed in the EBs, BMP4 induction of EKLF and GATA1 transcription is not immediate. These data implicate the BMP/Smad induction system as being a crucial pathway to direct the onset of EKLF and GATA1 expression during hematopoietic differentiation and demonstrate that EB differentiation can be manipulated to study induction of specific genes that are expressed early within a lineage. (+info)
Derivation in culture of primordial germ cells from cells of the mouse epiblast: phenotypic induction and growth control by Bmp4 signalling.
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Primordial germ cells (PGCs) are the embryonic precursors of the gametes of the adult. PGCs derive from cells of the most proximal part of the cup-shaped epiblast corresponding to the presumptive region of the extraembryonic mesoderm. At 7.2 days post coitum (dpc) a small group of PGCs located at the base of the allantois can be recognised due to a strong alkaline phosphatase activity. Thus far, scant information was available on the mechanism(s) controlling the lineage of PGCs in the mouse embryo. However, results obtained in mice defective for bone morphogenetic protein-4 (Bmp4) secreted molecule revealed that this growth factor has important functions for the derivation of PGCs from extraembryonic mesoderm cells. In this paper, we have studied the effects in culture of Bmp4 on epiblast cells obtained from egg-cylinder stage mouse embryos (5.5-6.0 dpc) and PGCs from 11.5 dpc embryos. We found that Bmp4 treatment enables recruitment of pluripotent cells to a PGC phenotype by a multi-step process involving an initial pre-commitment of epiblast cells and a following stage of PGC phenotypic determination. We further provide evidences that Bmp4 may promote the growth of gonadal PGCs through a Smad1/4 signalling. (+info)