BMP-5 expression increases during chondrocyte differentiation in vivo and in vitro and promotes proliferation and cartilage matrix synthesis in primary chondrocyte cultures

Bone morphogenetic proteins (BMPs) play pivotal roles in bone and cartilage growth and repair. Through phenotypes of short-ear (se) mice, which have BMP-5 mutations, a role for BMP-5 in some specific aspects of skeletogenesis and cartilage growth is known. This report examines BMP-5 expression in the growth plate and in differentiating cultures of primary chondrocytes, and the effects of addition of BMP-5 or its inhibition by anti-BMP-5 antibody in chondrocyte cultures. By laser capture microdissection and immunohistochemistry, we found that BMP-5 is expressed in proliferating zone (PZ) chondrocytes and that the expression increases sharply with hypertrophic differentiation. A similar pattern was observed in differentiating cultures of primary chondrocytes, with BMP-5 expression increasing as cells differentiated, in contrast to other BMPs. BMP-5 added to cultures increased cell proliferation early in the culture period and also stimulated cartilage matrix synthesis. Also, BMP-5 addition to the cultures activated phosphorylation of Smad 1/5/8 and p38 MAP kinase and caused increased nuclear accumulation of phospho-Smads. Anti-BMP-5 antibody inhibited the endogenous BMP-5, reducing cell proliferation and phospho-Smad nuclear accumulation. Together, the results demonstrate that BMP-5 is normally an important regulator of chondrocyte proliferation and differentiation. Whether other BMPs may compensate in BMP-5 loss-of-function mutations is discussed.

Over-expression of BMP4 and BMP5 in a child with axial skeletal malformations and heterotopic ossification: a new syndrome

Bone morphogenetic proteins (BMPs) are a highly conserved class of signaling molecules that induce ectopic cartilage and bone formation in vivo. Dysregulated expression of bone morphogenetic protein 4 (BMP4) is found in the cells of patients who have fibrodysplasia ossificans progressiva (FOP), a genetic disorder of axial and appendicular skeletal malformation and progressive heterotopic ossification. Loss of function mutations in the bone morphogenetic protein 5 (bmp5) gene leading to under-expression of BMP5 cause the murine short ear syndrome, characterized by small malformed ears and a broad range of axial skeletal malformations. We found features reminiscent of both the short ear mouse and FOP in a child with malformed external ears, multiple malformations of the axial skeleton, and progressive heterotopic ossification in the neck and back. We examined BMP mRNA expression in transformed lymphocytes by semi-quantitative RT-PCR and protein expression by ELISA assays and immunohistochemistry. Elevated levels of BMP4 and BMP5 mRNA and protein were detected in the patient's cells while levels of BMP2 mRNA were unchanged. Our data suggest that dysregulated expression of BMP4 and BMP5 genes is associated with an array of human axial skeletal abnormalities similar to the short ear mouse and FOP.

Bone morphogenic factor gene dosage abnormalities in prostatic intraepithelial neoplasia and prostate cancer

Abnormal expression of bone morphogenic proteins (BMP) has been reported in prostate cancer as compared to benign prostatic tissue. Since aberrations in gene expression often result from alterations in gene copy number, we have investigated this possibility in patients with early prostate cancer. Probes for fluorescence in situ hybridization for the BMP, BMP5, BMP7, and UC28 gene loci were developed and applied to archival sections with areas of adjacent benign epithelium, high-grade prostatic intraepithelial neoplasia, and prostate carcinoma. Two hundred nuclei from each region were evaluated. No deletions of the gene loci examined were observed, but gain of BMP2, BMP5, BMP7, and UC28 occurred in 58, 50, 50, and 67% of tumor foci, respectively. These aberrations in copy number may be caused by early events in tumor development because they were also present in 10-30% of high-grade prostatic intraepithelial hyperplasia foci. In addition, one tumor demonstrated a tandem amplification of the UC28 gene locus. Approximately half of the prostate tumors displayed increased copy numbers of the BMP2, BMP5, BMP7, and UC28 gene loci, which may account for their abnormal gene expression patterns in neoplastic prostate tissue.

Histological development and dynamic expression of Bmp2-6 mRNAs in the embryonic and postnatal mouse cranial base

The cranial base is formed by endochondral ossification and is characterized by the presence of the synchondrosis growth centers. The aim of this study was to describe the histological development of the mouse midsagittal cranial base area from embryonic day 10 (E10) to the postnatal age of 2 months. The Bmp family of signaling molecules serves important functions in embryo and bone development and may therefore play a significant role in the early formation of the cranial base. To investigate this, we analyzed the mRNA pattern of expression of Bmp2-6 in the mouse cranial base from E10 to 5 days postnatally using radioactive in situ hybridization. We found that the formation of the mouse cranial base corresponds to that of rat and proceeds in a caudorostral sequence. Moreover, all Bmps studied showed distinct and overlapping developmentally regulated expression domains. Bmp2, Bmp5, and Bmp6 were expressed in the early mesenchymal condensations. Later, Bmp2, Bmp3, Bmp4, and Bmp5 were detected in the perichondrium and in the adjacent mesenchyme. Subsequently, Bmp2 and Bmp6 expressions were confined to hypertrophic chondrocytes, while Bmp3, Bmp4, and Bmp5 were expressed in the osteoblasts of the trabecular bone and bone collar. Interestingly, Bmp3 was uniquely expressed postnatally in the resting zone of the synchondrosis growth center, suggesting a role in the regulation of cranial base growth. These results suggest that Bmp signaling may serve specific and synergistic functions at different key stages of cranial base development and growth.

Extreme context specificity in differential allelic expression

Variability in cis-regulation of gene expression has been implicated in the phenotypic manifestation of complex traits including common, multifactorial diseases. The differential expression of alleles due to polymorphism in cis-regulatory elements is common in the human genome, but there is a paucity of information about the context specificity of these control elements. In this study, we examined the differential allelic expression (DAE) of BMP5 in human mesenchymal tissues obtained from 16 donors undergoing joint replacement for treatment of osteoarthritis. We observed significant differences in BMP5 allelic output, with allelic ratios greater than 4:1 (P < 10(-20)) in the tissues of some donors. We also discovered a significant variability in allelic expression within the different tissues of donors. For 12 of our donors, we examined the allelic expression of BMP5 in two different regions of cartilage: cartilage adjacent to the site of the osteoarthritic lesion and cartilage distal from the lesion. Five of these 12 donors demonstrated highly significant differences (P < or = 10(-8)) in allelic expression between the different regions of their cartilage. Using DAE as a phenotype, we attempted to map tissue-specific cis-regulatory polymorphisms, and we identified a single nucleotide polymorphism located downstream of BMP5, which was significantly associated with DAE in some but not all of the examined tissues. These findings suggest that allelic expression can be highly context specific and that when interrogating the cis-regulatory control of a particular gene, one cannot necessarily assume that allelic expression is conserved across different tissues or even across different regions of the same tissue.

Bone morphogenetic protein down-regulation of neuronal pituitary adenylate cyclase-activating polypeptide and reciprocal effects on vasoactive intestinal peptide expression

Among bone morphogenetic proteins (BMPs), the decapentaplegic (Dpp; BMP2, BMP4) and glass bottom boat (Gbb/60A; BMP5, BMP6, BMP7) subgroups have well-described functions guiding autonomic and sensory neuronal development, fiber formation and neurophenotypic identities. Evaluation of rat superior cervical ganglia (SCG) post-ganglionic sympathetic neuron developmental regulators identified that selected BMPs of the transforming growth factor beta superfamily have reciprocal effects on neuronal pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) expression. Dpp and Gbb/60A BMPs rapidly down-regulated PACAP expression, while up-regulating other sympathetic neuropeptides, including PACAP-related VIP. The suppressive effects of BMP on PACAP mRNA and peptide expression were potent, efficacious and phosphorylated mothers against decapentaplegic homolog (Smad) signaling-dependent. Axotomy of SCG dramatically increases PACAP expression, and the possibility that abrogation of inhibitory retrograde target tissue BMP signaling may contribute to this up-regulation of sympathetic neuron PACAP was investigated. Replacement of BMP6 to SCG explant preparations significantly blunted the injury-induced elevated PACAP expression, with a concomitant decrease in sympathetic PACAP-immunoreactive neuron numbers. These studies suggested that BMPs modulate neuropeptide identity and diversity by stimulating or restricting the expression of specific peptidergic systems. Furthermore, the liberation of SCG neurons from target-derived BMP inhibition following axotomy may be one participating mechanism associated with injury-induced neuropeptidergic plasticity.

BMP signaling regulates PGC numbers and motility in organ culture

Members of the bone morphogenetic protein (BMP) family play diverse roles in multiple developmental processes. However, in the mouse, mutations in many BMPs, BMP receptors and signaling components result in early embryonic lethality making it difficult to analyze the role of these factors during organogenesis or tissue homeostasis in the adult. To bypass this early lethality, we used an organ culture system to study the role of BMPs during primordial germ cell (PGC) migration. PGCs are the embryonic precursors of the sperm and eggs. BMPs induce formation of primordial germ cells within the proximal epiblast of embryonic day 7.5 (E7.5) mouse embryos. PGCs then migrate via the gut to arrive at the developing gonads by E10.5. Addition of BMP4 or the BMP-antagonist Noggin to transverse slices dissected from E9.5 embryos elevated PGC numbers or reduced PGC numbers, respectively. Noggin treatment also slowed and randomized PGC movements, resulting in a failure of PGCs to colonize the urogenital ridges (UGRs). Based on p-Smad1/5/8 staining, migratory PGCs do not respond to endogenous BMPs. Instead, the somatic cells of the urogenital ridges exhibit elevated p-Smad1/5/8 staining revealing active BMP signaling within the UGRs. Noggin treatment abrogated p-Smad staining within the UGRs and blocked localized expression of Kitl, a cytokine known to regulate the survival and motility of PGCs and Id1, a transcription factor expressed within the UGRs. We propose that BMP signaling regulates PGC migration by controlling gene expression within the somatic cells along the migration route and within the genital ridges.

Decrease in expression of bone morphogenetic proteins 4 and 5 in synovial tissue of patients with osteoarthritis and rheumatoid arthritis

Bone morphogenetic proteins (BMPs) have been identified as important morphogens with pleiotropic functions in regulating the development, homeostasis and repair of various tissues. The aim of this study was to characterize the expression of BMPs in synovial tissues under normal and arthritic conditions. Synovial tissue from normal donors (ND) and from patients with osteoarthritis (OA) and rheumatoid arthritis (RA) were analyzed for BMP expression by using microarray hybridization. Differential expression of BMP-4 and BMP-5 was validated by semiquantitative RT-PCR, in situ hybridization and immunohistochemistry. Activity of arthritis was determined by routine parameters for systemic inflammation, by histological scoring of synovitis and by semiquantitative RT-PCR of IL-1β, TNF-α, stromelysin and collagenase I in synovial tissue. Expression of BMP-4 and BMP-5 mRNA was found to be significantly decreased in synovial tissue of patients with RA in comparison with ND by microarray analysis (p < 0.0083 and p < 0.0091). Validation by PCR confirmed these data in RA (p < 0.002) and also revealed a significant decrease in BMP-4 and BMP-5 expression in OA compared with ND (p < 0.015). Furthermore, histomorphological distribution of both morphogens as determined by in situ hybridization and immunohistochemistry showed a dominance in the lining layer of normal tissues, whereas chronically inflamed tissue from patients with RA revealed BMP expression mainly scattered across deeper layers. In OA, these changes were less pronounced with variable distribution of BMPs in the lining and sublining layer. BMP-4 and BMP-5 are expressed in normal synovial tissue and were found decreased in OA and RA. This may suggest a role of distinct BMPs in joint homeostasis that is disturbed in inflammatory and degenerative joint diseases. In comparison with previous reports, these data underline the complex impact of these factors on homeostasis and remodeling in joint physiology and pathology.

Role of Smad- and Wnt-Dependent Pathways in Embryonic Cardiac Development

The development of the heart is essential for embryogenesis and precedes development of other organs. However, the mechanisms involved in embryonic cardiac development are ill-defined. Recent evidence suggests that Smad and Wnt signaling pathways are important in stem cell fate determination and their commitment to cardiovascular differentiation. We have previously reported that bone morphogenetic proteins (BMP)-2, -5, and -7 and fibroblast growth factors (FGF)-2 and -4 secreted from the adjoining endodermal cells favor cardiac differentiation in murine embryonic stem (ES) cells. Here, we demonstrate that BMP-2, -5, and -7 stimulate receptor-activated Smad1, 5, and 8, which in turn causes oligomerization of Smad4 in the nucleus. We further delineate the role of Wnt signaling pathway as evidenced by induction of Wnt3 and Wnt8b, stimulation of FRP-1, inhibition of GSK-B, accumulation of cytosolic beta-catenin, and transcription of target genes, including c-myc and cyclin-D1. We also ascertained the specificity of BMP- and Wnt-evoked activation of signaling cascades. Our data are consistent with the hypothesis that BMP-dependent activation of transcription factors including GATA-4, Nkx2.5, and MEF-2C augments cardiac differentiation mediated by cooperative control of Smad and Wnt signaling pathways. Our results provide a solid foundation for further study of the biochemistry of cardiac differentiation from stem cells.

Bone morphogenetic proteins 5 and 6 stimulate osteoclast generation

Bone regeneration is required for fracture-healing, and different procedures have been used to promote osteogenesis. Recently, BMP-2 has been shown to induce bone formation in vivo and has been tested in clinical trials. A recent in vitro study evaluated the osteogenic activity of 14 BMPs on osteoblastic progenitor cells with an osteogenic hierarchical model in which BMP-2 and BMP-6 may play an important role in inducing osteoblast differentiation. Although the relative osteoinductive activity of each BMP is important, bone regeneration is a process consisting of bone formation and bone resorption. Therefore, it remains unclear which effects BMP-5 and -6 have on the generation of osteoclasts and by which mechanism osteoclastogenesis is stimulated. To compare osteoclastic potency of each BMP, primary murine bone marrow cells were treated with human recombinant BMP-2, BMP-5, or BMP-6 and 1,25-(OH)2 vitamin D3 and stained for the TRAP enzyme. Osteogenic activity of BMP-5 was determined by measuring induction of ALP-activity and proliferation after incubation with primary murine osteoblasts. For elucidating the molecular mechanism, primary bone marrow cells with various concentrations of OPG were added to the TRAP assay and mRNA levels of RANKL and OPG were measured after stimulation with BMP-5. The presented data show that BMP-5 and BMP-6, unlike BMP-2, enhanced the formation of murine TRAP+/MNCs in a biphasic curve. BMP-5 and -6 were less potent in stimulating osteoclastogenesis compared to BMP-2. Concerning the effects of BMP-5 on osteoblasts, there was a dose-dependent increase of ALP activity and proliferation up to a maximum dose of 300 ng/mL. At the mRNA level, BMP-5 increased the RANKL/OPG ratio. In conclusion, this study demonstrates that in contrast to BMP-2, BMP-5 and -6 influences the generation of osteoclasts in a biphasic mode. Both proteins might be very important regulators of bone homeostasis, and therefore, potent candidates for future treatment strategies of bone regeneration.

Bone Morphogenetic Protein 5 Expression in the Rat Ovary: Biological Effects on Granulosa Cell Proliferation and Steroidogenesis1

Recently, the role of several elements of the bone morphogenetic protein (BMP) family has been studied in the ovary, some of them being crucial for ovarian function. In the present work, we have studied bone morphogenetic protein 5 (BMP5) expression and its biological role in the rat ovary. BMP5 is expressed by rat granulosa cells (GCs) and exerts specific biological effects on proliferation and steroidogenesis of these cells in an autocrine manner. These effects were shown to be associated with an increase in cyclin D2 protein level and a decrease in steroidogenic acute regulatory (StAR) protein expression in GCs in vitro. Ultimately, BMP5 actions were inhibited by follistatin. Overall, these data show that BMP5 is a novel element of the BMP family that might play a fully paracrine role in rodent ovarian folliculogenesis.

Requirements for endoderm and BMP signaling in sensory neurogenesis in zebrafish

Cranial sensory neurons largely derive from neurogenic placodes (epibranchial and dorsolateral), which are ectodermal thickenings that form the sensory ganglia associated with cranial nerves, but the molecular mechanisms of placodal development are unclear. Here, we show that the pharyngeal endoderm induces epibranchial neurogenesis in zebrafish, and that BMP signaling plays a crucial role in this process. Using a her5:egfp transgenic line to follow endodermal movements in living embryos, we show that contact between pharyngeal pouches and the surface ectoderm coincides with the onset of neurogenesis in epibranchial placodes. By genetic ablation and reintroduction of endoderm by cell transplantation, we show that these contacts promote neurogenesis. Using a genetic interference approach we further identify bmp2b and bmp5 as crucial components of the endodermal signals that induce epibranchial neurogenesis. Dorsolateral placodes (trigeminal, auditory, vestibular, lateral line) develop independently of the endoderm and BMP signaling, suggesting that these two sets of placodes are under separate genetic control. Our results show that the endoderm regulates the differentiation of cranial sensory ganglia, which coordinates the cranial nerves with the segments that they innervate.

Human chondrocytes differentially express matrix modulators during in vitro expansion for tissue engineering

Cartilage tissue engineering plays an important role in the generation of grafts for reconstructive surgery. In cultured chondrocytes, the dedifferentiation of cells seems unavoidable for multiplication. Dedifferentiated cells produce matrix of less quality, and the molecular basis is still not well understood. Therefore, the aim of our study was to investigate the expression of matrix modulators in human chondrocytes during expansion. Human chondrocytes were isolated from septal cartilage (n=32) and held in primary cell culture. Cells were harvested after 1, 6 and 21 days. The differentiation of cells using light microscopy, the expression patterns of various proteins (MMPs, BMPs, and TIMPs) using immunohistochemistry, and the expression of distinct genes using microarray technique, were investigated. The chondrocytes showed strong in vitro proliferation. After 6 and 21 days, BMP-5 and -8 were up-regulated, BMP-2 was down-regulated and BMP-6 was inactivated. Other BMPs were not expressed. The expression of MMP-2, -3 and -13 was up-regulated from day 1 to 21, and MMP-12 and -20 were down-regulated. Other MMPs were not expressed. TIMP-1 was up-regulated and TIMP-3 was down-regulated during expansion. Differential expression of matrix modulators might influence the matrix composition of engineered cartilage. Improving the basic knowledge in this area may ultimately help clinicians to identify and proactively intervene in an attempt to prevent bioartificial cartilage from losing stability.

The 2002 Marshall Urist Young Investigator Award Paper. Lumbar arthrodesis gene expression: a comparison of autograft with osteogenic protein-1

Data from animals have revealed that osteogenic protein-1 induces solid intertransverse process fusion more reliably than autograft, and has motivated the question: What is the difference in the fusion bed environment engendered by the addition of osteogenic protein-1? To address this question, an established New Zealand White rabbit model of spinal arthrodesis was used to evaluate the effect of iliac crest autograft, and alternatively osteogenic protein-1, on cytokine gene expression in the developing spinal fusion mass. The autograft group and the osteogenic protein-1 group had a similar pattern of gene expression for most of the cytokines investigated, highlighting the finding that the application of one bone morphogenetic protein to the fusion bed results in nearly the same gene expression as that resulting from application of autologous bone. Some differences in cytokine expression were observed at the fusion bed with the addition of osteogenic protein-1. The increased level of expression of particular osteogenic, chondrogenic, and angiogenic growth factors at the later stages of fusion may be responsible for the improved rate of solid fusion with osteogenic protein-1 as compared with autograft alone. Sequences for bone morphogenetic protein-5 and bone morphogenetic protein-7 were determined, and their respective expression in the developing spinal fusion mass was observed for the first time.

Differential expression of bone morphogenetic protein 4-6 (BMP-4, -5, and -6) and growth differentiation factor-9 (GDF-9) during ovarian development in neonatal pigs

Growth differentiation factor-9 (GDF-9) and bone morphogenetic proteins (BMPs), comprise the largest subgroups of ligands in the TGF-beta superfamily, and have been shown to be involved in follicle development in mammals. However, whether these factors are involved in folliculogenesis in pigs is still unknown. The present study was performed to determine the relationships between early folliculogenesis and the expression of GDF-9 and BMP (BMP-4, -5 and -6) mRNAs in neonatal pigs. Ovaries were removed at 5, 16, 28 and 39 days after birth to examine the follicular population (the right ovary of each animal) and to detect mRNA expression (the left ovary of each animal). Primordial follicles accounted for >80% of the ovarian follicles from 5 days until 39 days after birth. A marked increase in primary follicles and the appearance of secondary follicles were observed in the ovaries at 28 days after birth. BMP-4, -5, and -6 and GDF-9 mRNAs were expressed by ovaries at 5-, 16-, 28- and 39-day-old pigs. The peak expression of BMP-4, -5, and -6 and GDF-9 mRNAs was observed in the ovaries at 5, 39, 28 and 16 days, respectively, after birth. These data demonstrate that folliculogenesis in piglets might be controlled by the interaction with these factors. We conclude that BMPs and GDF-9 may have distinct functions in several stages of follicle development in neonatal pig ovaries.

Effect of bone morphogenetic proteins-4, -5 and -6 on DNA synthesis and expression of bone-related proteins in cultured human periodontal ligament cells

Bone morphogenetic proteins (BMPs) have multiple functions in the development and growth of skeletal and extraskeletal tissues. Therefore, BMPs may regulate the regeneration of periodontal tissue. To investigate this issue, we examined the effects of BMP-4, -5 and -6 on DNA synthesis and the expression of bone-related proteins in cultures of human periodontal ligament (HPL) cells. The expression of bone-related proteins was determined by Real-time polymerase chain reaction and enzyme linked immunosorbent assay in cultures of HPL cells. DNA synthesis was estimated by measuring bromoderoxyuridine incorporation. It was found that BMP-4, -5 and -6 enhanced DNA synthesis dose-dependently. BMP-4 and -5 increased the levels of osteopontin, BMP-2, alkaline phosphatase and core binding factor alpha 1 mRNAs. BMP-6 stimulated the expression of osteopontin, BMP-2, ALPase and osteoprotegerin. These findings show that BMP-4, -5 and -6 have different actions on the expression of bone-related proteins and may play a role in the regeneration of periodontal tissue by promoting cell proliferation and protein expression.

A new role for BMP5 during limb development acting through the synergic activation of Smad and MAPK pathways

In an attempt to identify new genes implicated in the control of programmed cell death during limb development, we have generated a cDNA library from the regressing interdigital tissue of chicken embryos. We have analyzed 804 sequences from this library and identified 23 genes involved in apoptosis in different models. One of the genes that came up in the screening was the Bone Morphogenetic Protein family member, Bmp5, that has not been previously involved in the control of apoptosis during limb development. In agreement with a possible role in the control of cell death, Bmp5 exhibited a regulated pattern of expression in the interdigital tissue. Transcripts of Bmp5 and BMP5 protein were abundant within the cytoplasm of the fragmenting apoptotic interdigital cells in a way suggesting that delivery of BMPs into the tissue is potentiated during apoptosis. Gain-of-function experiments demonstrated that BMP5 has the same effect as other interdigital BMPs inducing apoptosis in the undifferentiated mesoderm and growth in the prechondrogenic mesenchyme. We have characterized both Smad proteins and MAPK p38 as intracellular effectors for the action of BMPs in the developing limb autopod. Activation of Smad signaling involves the receptor-regulated genes Smad1 and -8, and the inhibitory Smad6, and results in both the upregulation of gene transcription and protein phosphorylation with subsequent nuclear translocation. MAPK p38 is also quickly phosphorylated after BMP stimulation in the limb mesoderm. Treatment with the inhibitor of p38, SB203580, revealed that there are interdigital genes induced by BMPs in a p38-dependent manner (DKK, Snail and FGFr3), and genes induced in a p38-independent manner (BAMBI, Msx2 and Smads). Together, our results suggest that Smad and MAPK pathways act synergistically in the BMP pathway controlling limb development.

Bone morphogenetic protein-5, -6 and -7 inhibit growth and induce apoptosis in human myeloma cells

Previously, bone morphogenetic protein (BMP)-2 and -4 have been shown to inhibit proliferation and induce apoptosis in human myeloma cells. BMP-2 and -4 belong to a subgroup of BMPs using the BMP receptors Alk-3 or -6. In this study, we examined the effects on human myeloma cells of BMP-6 and -7, members of a different BMP subgroup, which mainly utilize Alk-2 as their receptor. All cell lines examined expressed mRNA for the BMP-6 and -7 receptor Alk-2. We did not detect transcripts for the BMP-2 and -4 receptors Alk-3 or Alk-6 in INA-6 and RPMI-8226 cells by RT-PCR. Accordingly, the intracellular signalling molecules Smad-1, -5 and -8 were not phosphorylated by BMP-4 in INA-6 and RPMI-8226 cells. The expression patterns of various BMP receptors in the myeloma cell lines explained the differences in responses to the various BMPs. Alk-2-expressing cell lines responded with growth inhibition and apoptosis to BMP-6 and -7, whereas cell lines lacking both Alk-3 and -6 were resistant to BMP-4. Soluble Alk-3 and -6 were able to neutralize the BMP-4 effects in BMP-4-responsive cell lines. All BMPs reduced viability in more than 70% of purified primary myeloma cell samples. BMPs have intriguing antitumor effects in vitro. Importantly, myeloma cells not responsive to BMP-2 and -4 may still be sensitive to BMP-6 or -7. It is possible that therapeutic use of BMP or BMP analogues could have an impact on both myeloma bone disease and myeloma cell growth.

HyBMP5-8b, a BMP5-8 orthologue, acts during axial patterning and tentacle formation in hydra

Developmental gradients play a central role in axial patterning in hydra. As part of the effort towards elucidating the molecular basis of these gradients as well as investigating the evolution of the mechanisms underlying axial patterning, genes encoding signaling molecules are under investigation. We report the isolation and characterization of HyBMP5-8b, a BMP5-8 orthologue, from hydra. Processes governing axial patterning are continuously active in adult hydra. Expression patterns of HyBMP5-8b in normal animals and during bud formation, hydra's asexual form of reproduction, were examined. These patterns, coupled with changes in patterns of expression in manipulated tissues during head regeneration, foot regeneration as well as under conditions that alter the positional value gradient indicate that the gene is active in two different processes. The gene plays a role in tentacle formation and in patterning the lower end of the body axis.

Defect Repair in the Rat Mandible With Bone Morphogenic Protein 5 and Prostaglandin E1

OBJECTIVE

To compare the osteogenic abilities of 2 growth factors (bone morphogenic protein 5 [BMP-5] and prostaglandin E1 [PGE1]) and 2 carriers (collagen/polylactic acid [PLA] and collagen/calcium hydroxyapatite cement [HAC]) in the repair of a rat mandibular body defect.

DESIGN

Prospective controlled trial. Subjects Twenty-nine Sprague-Dawley rats.

INTERVENTIONS

Critical size defects were created in the bilateral mandibular bodies of the rats. Each hemimandible was assigned to an experimental group. The defects were filled with PLA (group 1), PLA with BMP-5 (group 2), PLA with PGE1 (group 3), HAC (group 4), HAC with BMP-5 (group 5), or HAC with PGE1 (group 6). The control group (group 7) had unfilled defects. The animals were killed after 12 weeks, and the nondemineralized specimens were processed histologically. Stereologic techniques were used to determine the volume fractions of new bone, osteoid, marrow, remaining implant, and fibrous tissue in each defect.

RESULTS

The HAC/BMP-5 group (group 5) contained significantly more new bone than the PLA/BMP-5 group (group 2) (P =.02), the HAC and HAC/PGE1 groups (groups 4 and 6) (P =.002), and the control group (group 7) (P<.01). The HAC/BMP-5 group also had less fibrous tissue than the HAC group and the HAC/PGE1 group (P<.001). Groups 5 and 6 had less fibrous tissue than group 7 (P<.01). The groups containing PGE1 demonstrated significantly more osteoid development than the other experimental groups (P<.001).

CONCLUSIONS

Inclusion of BMP-5 in an implant with calcium hydroxyapatite cement resulted in the formation of significantly larger fractions of new bone and less fibrous tissue ingrowth than occurred in the other experimental groups. The presence of PGE1 resulted in larger amounts of osteoid deposition, suggesting the potential for delayed bone healing.

Expression of bone morphogenetic proteins during mandibular distraction osteogenesis in rabbits

PURPOSE

We examined the expression pattern of bone morphogenetic proteins (BMPs) during mandibular distraction osteogenesis in rabbits and also investigated the mechanism of membranous bone distraction.

MATERIALS AND METHODS

Twenty-three rabbits underwent mandibular distraction (protocol; no latency period, a 1-week distraction at 0.5 mm/d, and a 2-week consolidation period). Samples were collected at 3, 5, and 7 days of distraction and at 1-week and 2-week consolidation. We prepared undecalcified fresh-frozen sections and immunohistochemically evaluated the expression of BMPs 2 through 8.

RESULTS

Both endochondral ossification and intramembranous ossification were observed. The expression of BMPs 2, 4, 5, and 6 was observed continuously from the beginning of distraction. BMP-7 was expressed weakly. The expression of BMP-3 was not observed conspicuously during distraction but was strongly expressed at 1- and 2-week consolidation.

CONCLUSION

The expression pattern of BMPs during membranous bone distraction was similar to that during long bone distraction, but it differed from the expression pattern of long bone distraction in that the expression of BMPs was maintained for 2 weeks after the completion of distraction.

Regulation of motor neuron subtype identity by repressor activity of Mnx class homeodomain proteins

In the developing spinal cord, motor neurons acquire columnar subtype identities that can be recognized by distinct profiles of homeodomain transcription factor expression. The mechanisms that direct the differentiation of motor neuron columnar subtype from an apparently uniform group of motor neuron progenitors remain poorly defined. In the chick embryo, the Mnx class homeodomain protein MNR2 is expressed selectively by motor neuron progenitors, and has been implicated in the specification of motor neuron fate. We show here that MNR2 expression persists in postmitotic motor neurons that populate the median motor column (MMC), whereas its expression is rapidly extinguished from lateral motor column (LMC) neurons and from preganglionic autonomic neurons of the Column of Terni (CT). The extinction of expression of MNR2, and the related Mnx protein HB9, from postmitotic motor neurons appears to be required for the generation of CT neurons but not for LMC generation. In addition, MNR2 and HB9 are likely to mediate the suppression of CT neuron generation that is induced by the LIM HD protein Lim3. Finally, MNR2 appears to regulate motor neuron identity by acting as a transcriptional repressor, providing further evidence for the key role of transcriptional repression in motor neuron specification.

Expression of bone morphogenetic proteins and cartilage-derived morphogenetic proteins during osteophyte formation in humans

Bone- and cartilage-derived morphogenetic proteins (BMPs and CDMPs), which are TGFbeta superfamily members, are growth and differentiation factors that have been recently isolated, cloned and biologically characterized. They are important regulators of key events in the processes of bone formation during embryogenesis, postnatal growth, remodelling and regeneration of the skeleton. In the present study, we used immunohistochemical methods to investigate the distribution of BMP-2, -3, -5, -6, -7 and CDMP-1, -2, -3 in human osteophytes (abnormal bony outgrowths) isolated from osteoarthritic hip and knee joints from patients undergoing total joint replacement surgery. All osteophytes consisted of three different areas of active bone formation: (1) endochondral bone formation within cartilage residues; (2) intramembranous bone formation within the fibrous tissue cover and (3) bone formation within bone marrow spaces. The immunohistochemistry of certain BMPs and CDMPs in each of these three different bone formation sites was determined. The results indicate that each BMP has a distinct pattern of distribution. Immunoreactivity for BMP-2 was observed in fibrous tissue matrix as well as in osteoblasts; BMP-3 was mainly present in osteoblasts; BMP-6 was restricted to young osteocytes and bone matrix; BMP-7 was observed in hypertrophic chondrocytes, osteoblasts and young osteocytes of both endochondral and intramembranous bone formation sites. CDMP-1, -2 and -3 were strongly expressed in all cartilage cells. Surprisingly, BMP-3 and -6 were found in osteoclasts at the sites of bone resorption. Since a similar distribution pattern of bone morphogenetic proteins was observed during embryonal bone development, it is suggested that osteophyte formation is regulated by the same molecular mechanism as normal bone during embryogenesis.

Molecular control of ciliary neuron development: BMPs and downstream transcriptional control in the parasympathetic lineage

The generation of noradrenergic sympathetic neurons is controlled by BMPs and the downstream transcription factors Mash1, Phox2b, Phox2a and dHand. We examined the role of these signals in developing cholinergic parasympathetic neurons. The expression of Mash1 (Cash1), Phox2b and Phox2a in the chick ciliary ganglion is followed by the sequential expression of panneuronal, noradrenergic and cholinergic marker genes. BMPs are expressed at the site where ciliary ganglia form and are essential and sufficient for ciliary neuron development. Unlike sympathetic neurons, ciliary neurons do not express dHand; noradrenergic gene expression is eventually lost but can be maintained by ectopic dHand expression. Together, these results demonstrate a common BMP dependence of sympathetic neurons and parasympathetic ciliary neurons and implicate dHand in the maintenance of noradrenergic gene expression in the autonomic nervous system.

Bone morphogenetic proteins promote development of fetal pancreas epithelial colonies containing insulin-positive cells

Extracellular signals that guide pancreas cell development are not well characterized. In an in vitro culture system of dissociated pancreas cells from the E15.5 mouse fetus we show that, in the presence of the extracellular matrix protein laminin-1, bone morphogenetic proteins (BMPs-4, -5 and -6)promote the development of cystic epithelial colonies. Transforming growth factor β1 (TGF-β1) and activin A antagonise this effect of BMP-6 and inhibit colony formation. Histological analysis revealed that the colonies are composed of E-cadherin-positive epithelial cells, which in localised areas are insulin positive. The colonies also contain occasional glucagon-positive cells, but no somatostatin- or α-amylase-positive cells. These findings indicate that members of the TGF-β superfamily regulate pancreas epithelial cell development and can promote the formation of islet-like structures in vitro.

The specification of noradrenergic locus coeruleus (LC) neurones depends on bone morphogenetic proteins (BMPs)

The role of BMPs in the development of the major noradrenergic centre of the brain, the locus coeruleus (LC), was investigated. LC generation is reflected by initial expression of the transcription factors Phox2a and Phox2b in dorsal rhombomere1 (r1), followed by expression of dopamine-β-hydroxylase and tyrosine hydroxylase. Bmp5 is expressed in the dorsal neuroepithelium in proximity to Phox2-expressing cells. BMP inhibition in stage 10 chick embryos resulted in the lack of LC neurones or in their generation at the dorsal midline, and loss of roof plate and rhombic lip, but it did not affect neural crest development. These results reveal late essential BMP functions in the specification of dorsal neuronal phenotypes in r1, including LC neurones, and in the development of dorsal midline structures.

Bone morphogenetic proteins promote cartilage differentiation and protect engineered artificial cartilage from fibroblast invasion and destruction

OBJECTIVE

An important role in joint and cartilage homeostasis in adults has been demonstrated recently for morphogenetic factors of the transforming growth factor beta family. Therefore, this study was undertaken to investigate the potential of bone morphogenetic proteins (BMPs) in chondrocyte differentiation using current technologies of tissue engineering.

METHODS

Complementary DNAs of recombinant human BMPs 2, 4, 5, 6, and 7 were transfected into primary bovine articular chondrocytes. Transgenic chondrocytes were assembled 3-dimensionally in alginate or in bioresorbable co-polymer fleeces of vicryl and polydioxanon embedded in low-melting-point agarose. Redifferentiation and formation of cartilage tissue in vitro or after subcutaneous transplantation into nude mice were assayed by semiquantitative reverse transcriptase-polymerase chain reaction, histology, and in situ hybridization, and findings were compared with those in unmodified or control-transfected primary chondrocytes.

RESULTS

Compared with other BMPs and control vector, BMP-7 induced a decrease in type I collagen expression in artificial cartilage, while transcription of the cartilage-specific type II collagen remained stable. In transplantation experiments, BMP-7 transgenic cartilage revealed the greatest amount of matrix synthesis, and BMP-7 was the only morphogen to suppress the infiltrative response of mouse fibroblastic cells into engineered cartilage, thereby preventing transplant destruction.

CONCLUSION

Cartilage differentiation and matrix maturation are promoted by BMPs in cartilage engineering. The inhibitory effect of BMP-7 on a nonspecific infiltrative response in immunocompromised nude mice further suggests that individual morphogens not only may contribute to cartilage maturation, but also may protect it from nonspecific inflammation and invasive destruction. These properties advance BMPs as promising tools for engineering of cartilaginous joint bioprostheses and as candidate biologic agents or genes for cartilage stabilization in arthritis.

Meier-Gorlin syndrome (ear-patella-short stature syndrome) in an Italian patient: clinical evaluation and analysis of possible candidate genes

We report on an Italian boy with the Meier-Gorlin syndrome (ear-patella-short stature syndrome). This rare autosomal recessive disorder comprises the triad of microtia, absent patellae, and growth retardation with prenatal onset. The patient had also an acute torsion of his left spermatic cord, a condition related to a congenital defect of the tunica vaginalis. Because this syndrome had been suggested as the human equivalent of the short ear mouse [Lacombe et al., 1994: Ann. Genet. 37:184-191], a mutation analysis of the BMP5 gene was performed and found normal. The LMX1B and the SHOX genes were also evaluated considering the absent patellae and short stature, respectively, and were found normal as well.

Expression of bone morphogenetic protein-5 gene during chick heart development: possible roles in valvuloseptal endocardial cushion formation

The bone morphogenetic protein (BMP) family, comprising multifunctional peptide growth factors, regulates many developmental processes in a variety of tissues. We examined the spatiotemporal expression of BMP5 by in situ hybridization in chick embryonic hearts from stages 5 to 33. The BMP5 gene was first expressed in the endoderm underlying the precardiac mesoderm at stages 5 to 8. Thereafter, BMP5 expression was restricted to the myocardium of the atrioventricular (AV) canal and outflow tract (OT) regions, where the valvuloseptal endocardial cushion tissue is induced. These results suggest that BMP5 may play important roles not only in myocardial differentiation, but also in the formation and maintenance of endocardial cushion tissue.

Bone morphogenetic protein-5 (BMP-5) promotes dendritic growth in cultured sympathetic neurons

BACKGROUND

BMP-5 is expressed in the nervous system throughout development and into adulthood. However its effects on neural tissues are not well defined. BMP-5 is a member of the 60A subgroup of BMPs, other members of which have been shown to stimulate dendritic growth in central and peripheral neurons. We therefore examined the possibility that BMP-5 similarly enhances dendritic growth in cultured sympathetic neurons.

RESULTS

Sympathetic neurons cultured in the absence of serum or glial cells do not form dendrites; however, addition of BMP-5 causes these neurons to extend multiple dendritic processes, which is preceded by an increase in phosphorylation of the Smad-1 transcription factor. The dendrite-promoting activity of BMP-5 is significantly inhibited by the BMP antagonists noggin and follistatin and by a BMPR-IA-Fc chimeric protein. RT-PCR and immunocytochemical analyses indicate that BMP-5 mRNA and protein are expressed in the superior cervical ganglia (SCG) during times of initial growth and rapid expansion of the dendritic arbor.

CONCLUSIONS

These data suggest a role for BMP-5 in regulating dendritic growth in sympathetic neurons. The signaling pathway that mediates the dendrite-promoting activity of BMP-5 may involve binding to BMPR-IA and activation of Smad-1, and relative levels of BMP antagonists such as noggin and follistatin may modulate BMP-5 signaling. Since BMP-5 is expressed at relatively high levels not only in the developing but also the adult nervous system, these findings suggest the possibility that BMP-5 regulates dendritic morphology not only in the developing, but also the adult nervous system.

Overexpression of BMP-2/4, -5 and BMPR-IA associated with malignancy of oral epithelium

The aim of the present study was to determine the relationships between bone morphogenetic proteins (BMPs), BMP receptor type IA and carcinogenesis of oral epithelium. A retrospective study was performed on material obtained from oral mucosa, including nine cases of normal mucosa (NB), eight cases of nonspecific chronic inflammation (NCI), seven cases of hyperkeratosis (HK), five cases of squamous cell papilloma (SCP), 29 cases of squamous cell carcinoma (SCC) with various grades of differentiation and 10 cases of epithelium adjacent to carcinoma (EAC). Six cases of NB from hard palate (NHP) were chosen as a control group. The benign groups consisted of NCI, HK and SCP. The antibodies against BMP-2/4, -5, receptor BMPR-IA and purified bovine BMP (bBMP-McAb) were utilised using an immunocytochemical method. The results demonstrated that the immunostaining of BMP-2/4, BMP-5, BMPR-IA and bBMP-McAb was weak and not consistent in normal and benign groups. The immunoreactivity level was independent of the clinical and pathological grading of SCC. All cases of SCC showed positive staining for BMP-2/4, BMP-5, BMPR-IA and bBMP-McAb except for three cases and one case of SCC which negatively stained for BMP-2/4 and BMP-5, respectively. The staining intensity and proportion of the positively stained cells were markedly increased in SCC when compared with that of the normal and benign groups except for EAC. The metastatic carcinoma cells in lymph nodes were strongly and positively stained for BMP-2/4 and BMP-5 when compared with the primary lesions. Our results indicate that there was an overexpression of BMP-2/4, BMP-5, bBMP-McAb and BMPR-IA in the high-risk premalignant and malignant lesions of oral epithelium. Our findings suggest that BMP-2/4 and BMP-5 but not BMPR-IA might be involved in the metastasis of oral carcinoma cells.

Developmental expression patterns of bone morphogenetic proteins, receptors, and binding proteins in the chick retina

Bone morphogenetic proteins (BMPs), a large subfamily of the transforming growth factor-beta (TGF-beta) superfamily of growth factors, have been implicated in patterning of the central nervous system, but their role in the retina is much less well known. As an initial step in addressing this issue, we have investigated by in situ hybridization the expression patterns of BMP-2, -4, -5, -6, and -7, BMP receptor kinases (BRKs) -1, -2, and -3, and BMP binding proteins noggin and chordin, in the chick embryonic eye at embryonic day 3 (E3), and in isolated retinas at E6, E8, and E18. Strikingly, all mRNAs examined had spatially restricted patterns of expression in the early eye, with the receptors found primarily in the ventral portion of the retina and in the optic stalk, and the ligands and binding proteins localized to other regions of the retina and/or retinal pigment epithelium. Dorso-ventrally restricted patterns of expression persisted at E8, but were no longer apparent at E18, whereas layer-specific patterns of expression were detectable at both E8 and E18. This distribution of BMP family members, receptors, and binding proteins within the retina appears consistent with a possible role in patterning and/or differentiation of this tissue.

Transcriptional mRNA of bone morphogenetic proteins 2, 3, 4, and 5 in trigeminal nerve, benign and malignant peripheral nerve sheath tumors

Bone morphogenetic proteins (BMPs) have been shown to play an important role in cell growth and differentiation. BMPs, a rapidly expanding family closely related to transforming growth factor-beta (TGF-beta) superfamily, have been proven recently to possess a regulatory role and neurotrophic capacity in neurogenesis. The aim of the present study is to reveal the relationship among BMPs, peripheral nerve and neoplastic lesions of nerve sheath tumors. The mRNA transcriptions of BMP 2, 3, 4 and 5 in 12 cases of schwannoma, four cases of malignant schwannoma and three cases of trigeminal neuralgia were detected using an in situ hybridization technique. Our results demonstrated that the myelin sheaths of schwann cell from the peripheral neuroectomy of trigeminal neuralgia were positively expressing mRNA of BMP-2, 3, 4 and 5. However, the nerve fibers of trigeminal nerve showed only BMP-2 positive staining. All of the neoplastic lesions of nerve sheath showed a consistent but variant expression of BMP-2, 3, 4, and 5. Except for the BMP-4 mRNA, the expression signals of BMP-2, 3 and 5 mRNA in malignant schwannoma were relatively lower than in benign lesions. On the basis of the findings, we concluded that selected members of BMPs existed in the peripheral nerves and might contribute to the health maintenance, proliferation, regeneration and neoplastic transformation of the peripheral nerve system. Moreover, the effects of BMP-2, 3, 4 and 5 on peripheral nerve system and its neoplastic transformation might be widespread, diverse and antagonistic.

Nodal and bone morphogenetic protein 5 interact in murine mesoderm formation and implantation

Mice mutant for the TGF-beta family member, nodal, lack mesoderm and die between E8.5 and E9.5. The short ear-lethal (se(l) ) mutation, a deletion that eliminates Bmp-5, causes a strikingly similar gastrulation defect. Here we analyze se(l);nodal compound mutants and find a dosage effect. Embryos homozygous for one mutation show distinct gastrulation stage defects that depend on whether they are heterozygous or homozygous for the other mutation. Embryos mutant for nodal or se(l);nodal compound mutants fail to execute an antigenic shift indicative of mesoderm differentiation and ectoderm cells are shunted into an apoptotic pathway. Furthermore, we find a novel phenotype in se(l);nodal double mutant litters, in which two to four genetically different embryos are contained within the same deciduum. Both the gastrulation and implantation phenotypes can also arise in short ear-viable (se(v) ) and se(v); nodal mutant mice. These data indicate that loss of Bmp-5 may underlie the se(l) gastrulation phenotype and suggest that nodal and Bmp-5 interact during murine mesoderm formation. Our data also reveal an unsuspected role for Bmp-5 in implantation and the decidual response in the mouse.

Skeletal abnormalities in doubly heterozygous Bmp4 and Bmp7 mice

Analysis of the skeletal phenotypes caused by the genetic inactivation of individual Bmps, along with the study of their expression patterns, suggest possible functional redundancy of these molecules. To investigate the effect on skeleton development of the combined absence of some Bmp genes expressed in the same areas, we have intercrossed heterozygous Bmp7 mice with Bmp2 +/-, Bmp4 +/-, or Bmp5 +/- animals. Bmp2/7 and Bmp5/7 double heterozygous animals do not present with any abnormalities. In contrast, Bmp4/7 double heterozygotes develop minor defects in two restricted areas of the skeleton, the rib cage, and the distal part of the limbs. In the ribs, Bmp4 and Bmp7 seem to act in the same pathway to assure proper guidance of mesenchymal condensations of the ribs extending toward the sternum. In the limbs, these molecules appear to play a similar role in controlling digit number, possibly through induction of apoptosis in the interdigital and anterior mesenchyme.

Efficient studies of long-distance Bmp5 gene regulation using bacterial artificial chromosomes

The regulatory regions surrounding many genes may be large and difficult to study using standard transgenic approaches. Here we describe the use of bacterial artificial chromosome clones to rapidly survey hundreds of kilobases of DNA for potential regulatory sequences surrounding the mouse bone morphogenetic protein-5 (Bmp5) gene. Simple coinjection of large insert clones with lacZ reporter constructs recapitulates all of the sites of expression observed previously with numerous small constructs covering a large, complex regulatory region. The coinjection approach has made it possible to rapidly survey other regions of the Bmp5 gene for potential control elements, to confirm the location of several elements predicted from previous expression studies using regulatory mutations at the Bmp5 locus, to test whether Bmp5 control regions act similarly on endogenous and foreign promoters, and to show that Bmp5 control elements are capable of rescuing phenotypic effects of a Bmp5 deficiency. This rapid approach has identified new Bmp5 control regions responsible for controlling the development of specific anatomical structures in the vertebrate skeleton. A similar approach may be useful for studying complex control regions surrounding many other genes important in embryonic development and human disease.

Alteration in the expression of bone morphogenetic protein-2,3,4,5 mRNA during pathogenesis of cleft palate in BALB/c mice

To identify the function of these bone morphogenetic proteins (BMP) during pathogenesis of cleft palate, an experimental model was established in BALB/c mice. Cleft palate was induced by exposure to retinoic acid on embryonic day (E)12. The expression of BMP-2,3,4,5 mRNA in normal and abnormal embryonic palatal shelves was then examined from E13 to E16 by in situ hybridization. The results showed that BMP-4 mRNA was expressed strongly and uniformly in normal epithelial cells and dispersed mesenchymal cells on E13. BMP-2,5 mRNA expression appeared only in dispersed mesenchymal cells. With the development of shelves, the staining density of BMP-2,4,5 decreased gradually in mesenchymal cells outside of the condensation and increased inside the condensation. After shelves had fused on E16, no positive signals for BMP-2,4,5 were detected in dispersed mesenchymal cells, but their expression persisted in the condensation. Exposure to retinoic acid delayed the formation of the condensation and decreased BMP-2,4,5 mRNA dramatically in mesenchyme from E13 to E15. BMP-3 mRNA expression were almost negative in either control or retinoic acid-treated groups during all stages. It was concluded that spatial and temporal expression of BMP-2,4,5 was required during normal palatogenesis, and that a deficiency of their mRNA expression may contribute to the pathogenesis of cleft palate.

Expression of bone morphogenetic proteins and rat distal-less homolog genes following rat femoral fracture

Expression of the genes encoding bone morphogenetic proteins (BMPs), BMP type IA receptor (BMPR-1A), and rat distal-less homolog (rDlx) was studied in bone, callus, and the surrounding soft tissue following rat femoral closed fracture, using RT-PCR-based techniques. Before fracture, the genes encoding BMP-5, BMP-6, and BMPR-1A were found to be expressed in both bone and the surrounding soft tissue, whereas the BMP-2 gene was expressed only in bone and BMP-7 was not expressed in either tissue. Expression of these genes was unaffected by fracture. The gene encoding BMP-4 was also expressed in both bone and the surrounding soft tissue before fracture. Moreover, although unchanged in bone, 6 h after fracture BMP-4 expression was increased tenfold in the surrounding soft tissue. The increased BMP-4 expression was transient and returned to prefracture levels within 72 h. Expression of rDlx was also increased in bone after fracture, but at later times than were observed with BMP-4: elevated rDlx expression was detected after 48 h and persisted for 30 days or more. No expression of rDlx was observed in the surrounding soft tissue before or after fracture. These findings indicate that BMP-4 and rDlx are selectively expressed following femoral fracture in the rat, and also suggest that they are involved in the formation of the callus at an early point during the postfracture healing of bone.

Lineage-restricted expression of bone morphogenetic protein genes in human hematopoietic cell lines

To explore the possibility that bone morphogenetic proteins (BMPs) are autocrine/paracrine regulators of hematopoietic differentiation and function, we screened a panel of human cell lines encompassing the hematopoietic lineages for expression of members of this family of genes. Expression of BMP-2, BMP-4, BMP-6, BMP-7, Growth and Differentiation Factor-1 (GDF-1), Placental Bone Morphogenetic Protein (PLAB), and Transforming Growth Factor-beta3 (TGF-beta3) was detected in one or more cell lines. BMP-2, BMP-4, BMP-7, and TGF-beta3 expression was also found in normal hematopoietic tissue. Expression of BMP-5 and BMP-8 was not seen. Lineage-restricted patterns of expression were found for BMP-4 (T-lymphoid), BMP-7 (lymphoid), PLAB (macrophage/monocyte), and GDF-1 (myeloid). Expression of BMP-2, GDF-1, and PLAB could be modulated by treatment with differentiating agents. Marked variations in the levels of BMP-4, BMP-7, and PLAB expression were encountered, indicating that disorders in BMP signaling pathways may play a role in the development of hematopoietic neoplasia.

Molecular characterization and phylogenetic analysis of SpBMP5-7, a new member of the TGF-beta superfamily expressed in sea urchin embryos

TGF-beta ligands are probably pan-bilaterian in phylogenetic distribution. The family appears to have diversified greatly with the evolution of the vertebrates, but only a few invertebrate deuterostome TGF-beta molecules have so far been isolated. A search for members of this family expressed in sea urchin embryos, using canonical PCR primers, revealed a single-copy gene encoding a new TGF-beta protein. The sequence which it encodes is closely related to those of vertebrate bone morphogenetic proteins (BMPs) 5-7. No additional TGF-beta family members were uncovered other than univin, which had previously been reported.

Early embryonic lethality in Bmp5;Bmp7 double mutant mice suggests functional redundancy within the 60A subgroup

Members of the BMP family of signaling molecules display a high conservation of structure and function, and multiple BMPs are often coexpressed in a variety of tissues during development. Moreover, distinct BMP ligands are capable of activating common pathways. Here we describe the coexpression of two members of the 60A subfamily of BMPs, Bmp5 and Bmp7, at a number of different sites in the embryo from gastrulation onwards. Previous studies demonstrate that loss of either Bmp5 or Bmp7 has negligible effects on development, suggesting these molecules functionally compensate for each other at early stages of embryonic development. Here we show this is indeed the case. Thus we find that Bmp5;Bmp7 double mutants die at 10.5 dpc and display striking defects primarily affecting the tissues where these factors are coexpressed. The present analysis also uncovers novel roles for BMP signaling during the development of the allantois, heart, branchial arches, somites and forebrain. Bmp5 and Bmp7 do not appear to be involved in establishing pattern in these tissues, but are instead necessary for the proliferation and maintenance of specific cell populations. These findings are discussed with respect to potential mechanisms underlying cooperative signaling by multiple members of the TGF-beta superfamily.

Ectopic bone morphogenetic proteins 5 and 4 in the chicken forebrain lead to cyclopia and holoprosencephaly

Proper dorsal-ventral patterning in the developing central nervous system requires signals from both the dorsal and ventral portions of the neural tube. Data from multiple studies have demonstrated that bone morphogenetic proteins (BMPs) and Sonic hedgehog protein are secreted factors that regulate dorsal and ventral specification, respectively, within the caudal neural tube. In the developing rostral central nervous system Sonic hedgehog protein also participates in ventral regionalization; however, the roles of BMPs in the developing brain are less clear. We hypothesized that BMPs also play a role in dorsal specification of the vertebrate forebrain. To test our hypothesis we implanted beads soaked in recombinant BMP5 or BMP4 into the neural tube of the chicken forebrain. Experimental embryos showed a loss of the basal telencephalon that resulted in holoprosencephaly (a single cerebral hemisphere), cyclopia (a single midline eye), and loss of ventral midline structures. In situ hybridization using a panel of probes to genes expressed in the dorsal and ventral forebrain revealed the loss of ventral markers with the maintenance of dorsal markers. Furthermore, we found that the loss of the basal telencephalon was the result of excessive cell death and not a change in cell fates. These data provide evidence that BMP signaling participates in dorsal-ventral patterning of the developing brain in vivo, and disturbances in dorsal-ventral signaling result in specific malformations of the forebrain.

BMP-5 deficiency alters chondrocytic activity in the mouse proximal tibial growth plate

The role of bone morphogenetic protein-5 (BMP-5) in regulating chondrocytic activity during endochondral ossification was examined in the mouse proximal tibial growth plate. Short ear mice homozygous for the SEA/Gn point mutation in the coding region for BMP-5 (King, J. A. et al. Dev Biol 166:112122; 1994) and heterozygous long ear littermates were examined at 5 and 9 weeks of age (n = 9/group, four groups). Animals were injected with oxytetracycline to estimate the rate of growth and with bromodeoxyuridine to identify proliferative chondrocytes. Age-related changes in chondrocytic stereological and kinetic parameters were compared by image analysis of 1-microm-thick growth plate sections. The number of proliferative chondrocytes did not vary with age in either genotype, but proliferative phase duration increased significantly (approximately 67%) with age in the long ear mice, whereas no change was detected in the short ear mice. The number of hypertrophic chondrocytes increased significantly (approximately 27%) in the short ears, whereas this number decreased significantly (approximately 40%) in the long ears. There was a small, but significant, increase in hypertrophic phase duration (approximately 45%) in short ear mice, but no change was detected in the long ears. These results indicate that BMP-5 deficiency prevents age-related decelerations in chondrocytic proliferation and initiation of hypertrophic differentiation, suggesting a role of BMP-5 in inhibiting these processes.

Loss of heterozygosity at the dilute-short ear (Myo5a-Bmp5) region of the mouse: mitotic recombination or double non-disjunction?

The occurrence of homozygous-viable dilute-short ear (Myo5a-Bmp5) double mutants in mouse specific locus mutation experiments has generally been assumed to be the result of double non-disjunction such that the mutant inherits two copies of chromosome 9 carrying the recessive alleles from the test-stock. A homozygous viable Myo5a-Bmp5 double mutant was recovered recently in our laboratory. We were able to genetically analyse both the Myo5a-Bmp5 region and proximal and distal markers in the original mutant as well as in offspring of the original mutant. Our results indicate the mutational event to be due to mitotic recombination and not double non-disjunction.

An extensive 3' regulatory region controls expression of Bmp5 in specific anatomical structures of the mouse embryo

Bone morphogenetic proteins (BMPs) are secreted signaling molecules that control important developmental events in many different organisms. Previous studies have shown that BMPs are expressed at the earliest stages of skeletal development, and are required for formation of specific skeletal features, strongly suggesting that they are endogenous signals used to control formation of skeletal tissue. Despite the importance of BMP signaling in normal development, very little is known about the mechanisms that control the synthesis and distribution of BMP signals in vertebrates. Here, we identify a large array of cis-acting control sequences that lay out expression of the mouse Bmp5 gene in specific skeletal structures and soft tissues. Some of these elements show striking specificity for particular anatomical features within the skeleton, rather than for cartilage and bone in general. These data suggest that the vertebrate skeleton is built from the sum of many independent domains of BMP expression, each of which may be controlled by separate regulatory elements driving expression at specific anatomical locations. Surprisingly, some of the regulatory sequences in the Bmp5 gene map over 270 kb from the Bmp5 promoter, making them among the most distant elements yet identified in studies of eukaryotic gene expression.

Mechanical and geometric changes in the growing femora of BMP-5 deficient mice

We examined the growth-related changes in femoral geometry and torsional strength in BMP-5 deficient short-ear mice over a 22-week time interval ("long-term" changes). Four groups of female mice (n = 6 per group) were examined: short-ear animals and their heterozygous control littermates at 4 and 26 weeks of age. In agreement with findings previously observed in a mixed-gender group of adult mice (26 weeks), the femora of short-ear animals were significantly smaller in length and cross section at both ages. The magnitudes of the differences between genotypes were comparable at each age, indicating that the overall rates of appositional and endochondral growth were similar for both genotypes over the 22-week period. In the adult animals, short-ear femora were 27 +/- 7% weaker in torsional strength due to their smaller cross-sectional geometry. However, bone strength in adult short-ear mice appeared to be adequate for animal size: No significant difference was detected in maximum femoral torque when normalized by body mass. In 4-week old animals, BMP-5 deficiency was associated with a 27 +/- 6% lower body mass, but the torsional strength of the femur was not significantly different from that of controls. Cross-sectional geometry was smaller in 4-week old short-ear mice, but the apparent bone material ultimate shear stress was elevated by 33 +/- 10%, thereby resulting in a whole bone torsional strength equivalent to that of the larger control mice. While the data suggest a higher material strength in the 4-week-old short-ear animals, no significant difference in the level of bone mineralization was detectable between genotypes at either age.

Long bone geometry and strength in adult BMP-5 deficient mice

Bone morphogenetic proteins (BMPs) play a critical role in early skeletal development. BMPs are also potential mediators of bone response to mechanical loading, but their role in later stages of bone growth and adaptation has yet to be studied. We characterized the postcranial skeletal defects in mature mice with BMP deficiency by measuring hind-limb muscle mass and long bone geometric, material, and torsional mechanical properties. The animals studied were 26-week-old short ear mice (n = 10) with a homozygous deletion of the BMP-5 gene and their heterozygous control litter mates (n = 15). Gender-related effects, which were found to be independent of genotype, were also examined. The femora of short ear mice were 3% shorter than in controls and had significantly lower values of many cross-sectional geometric and structural strength parameters (p < 0.05). No significant differences in ash content or material properties were detected. Lower femoral whole bone torsional strength was due to the smaller cross-sectional geometry (16% smaller section modulus) in the short ear mice. The diminished cross-sectional geometry may be commensurate with lower levels of in vivo loading, as reflected by body mass (-8%) and quadriceps mass (-11%). While no significant gender differences were found in whole bone strength or cross-sectional geometry, males had significantly greater body mass (+18%) and quadriceps mass (+15%) and lower tibio-fibular ash content (-3%). The data suggest that adult female mice have a more robust skeleton than males, relative to in vivo mechanical demands. Furthermore, although the bones of short ear mice are smaller and weaker than in control animals, they appear to be biomechanically appropriate for the in vivo mechanical loads that they experience.