Impact of heterozygous ALK1 mutations on the transcriptomic response to BMP9 and BMP10 in endothelial cells from hereditary hemorrhagic telangiectasia and pulmonary arterial hypertension donors

Heterozygous activin receptor-like kinase 1 (ALK1) mutations are associated with two vascular diseases: hereditary hemorrhagic telangiectasia (HHT) and more rarely pulmonary arterial hypertension (PAH). Here, we aimed to understand the impact of ALK1 mutations on BMP9 and BMP10 transcriptomic responses in endothelial cells. Endothelial colony-forming cells (ECFCs) and microvascular endothelial cells (HMVECs) carrying loss of function ALK1 mutations were isolated from newborn HHT and adult PAH donors, respectively. RNA-sequencing was performed on each type of cells compared to controls following an 18 h stimulation with BMP9 or BMP10. In control ECFCs, BMP9 and BMP10 stimulations induced similar transcriptomic responses with around 800 differentially expressed genes (DEGs). ALK1-mutated ECFCs unexpectedly revealed highly similar transcriptomic profiles to controls, both at the baseline and upon stimulation, and normal activation of Smad1/5 that could not be explained by a compensation in cell-surface ALK1 level. Conversely, PAH HMVECs revealed strong transcriptional dysregulations compared to controls with > 1200 DEGs at the baseline. Consequently, because our study involved two variables, ALK1 genotype and BMP stimulation, we performed two-factor differential expression analysis and identified 44 BMP9-dysregulated genes in mutated HMVECs, but none in ECFCs. Yet, the impaired regulation of at least one hit, namely lunatic fringe (LFNG), was validated by RT-qPCR in three different ALK1-mutated endothelial models. In conclusion, ALK1 heterozygosity only modified the BMP9/BMP10 regulation of few genes, including LFNG involved in NOTCH signaling. Future studies will uncover whether dysregulations in such hits are enough to promote HHT/PAH pathogenesis, making them potential therapeutic targets, or if second hits are necessary.

Pulmonary vascular phenotype identified in patients with GDF2 (BMP9) or BMP10 variants: an international multicentre study

BACKGROUND

Bone morphogenetic proteins 9 and 10 (BMP9 and BMP10), encoded by GDF2 and BMP10, respectively, play a pivotal role in pulmonary vascular regulation. GDF2 variants have been reported in pulmonary arterial hypertension (PAH) and hereditary haemorrhagic telangiectasia (HHT). However, the phenotype of GDF2 and BMP10 carriers remains largely unexplored.

METHODS

We report the characteristics and outcomes of PAH patients in GDF2 and BMP10 carriers from the French and Dutch pulmonary hypertension registries. A literature review explored the phenotypic spectrum of these patients.

RESULTS

26 PAH patients were identified: 20 harbouring heterozygous GDF2 variants, one homozygous GDF2 variant, four heterozygous BMP10 variants, and one with both GDF2 and BMP10 variants. The prevalence of GDF2 and BMP10 variants was 1.3% and 0.4%, respectively. Median age at PAH diagnosis was 30 years, with a female/male ratio of 1.9. Congenital heart disease (CHD) was present in 15.4% of the patients. At diagnosis, most of the patients (61.5%) were in New York Heart Association Functional Class III or IV with severe haemodynamic compromise (median (range) pulmonary vascular resistance 9.0 (3.3-40.6) WU). Haemoptysis was reported in four patients; none met the HHT criteria. Two patients carrying BMP10 variants underwent lung transplantation, revealing typical PAH histopathology. The literature analysis showed that 7.6% of GDF2 carriers developed isolated HHT, and identified cardiomyopathy and developmental disorders in BMP10 carriers.

CONCLUSIONS

GDF2 and BMP10 pathogenic variants are rare among PAH patients, and occasionally associated with CHD. HHT cases among GDF2 carriers are limited according to the literature. BMP10 full phenotypic ramifications warrant further investigation.

GDF11: An emerging therapeutic target for liver diseases and fibrosis

Growth differentiation factor 11 (GDF11), also known as bone morphogenetic protein 11 (BMP11), has been identified as a key player in various biological processes, including embryonic development, aging, metabolic disorders and cancers. GDF11 has also emerged as a critical component in liver development, injury and fibrosis. However, the effects of GDF11 on liver physiology and pathology have been a subject of debate among researchers due to conflicting reported outcomes. While some studies suggest that GDF11 has anti-aging properties, others have documented its senescence-inducing effects. Similarly, while GDF11 has been implicated in exacerbating liver injury, it has also been shown to have the potential to reduce liver fibrosis. In this narrative review, we present a comprehensive report of recent evidence elucidating the diverse roles of GDF11 in liver development, hepatic injury, regeneration and associated diseases such as non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), liver fibrosis and hepatocellular carcinoma. We also explore the therapeutic potential of GDF11 in managing various liver pathologies.

Close negative correlation of local and circulating Dickkopf-1 and Sclerostin levels during human fracture healing

Wnt signaling is critically involved in fracture healing. Existing data predominantly relies on rodent models. Here, we explored local and circulating Dickkopf-1 (DKK1) levels in patients with respect to fracture healing and explore its association to sclerostin (SOST). 69 patients after surgical stabilization of long bone fractures of which six patients had impaired fracture healing were included in this study. Life-style and patient related factors with a known effect on DKK1 and SOST were recorded. DKK1 and SOST concentrations were measured using enzyme-linked immunosorbent assay (ELISA) at the fracture site and in circulation. DKK1 and SOST showed a close inverse correlation. In fracture hematoma and immediately after trauma DKK1 levels were significantly reduced while SOST levels were significantly increased, compared to healthy control. Postoperatively, DKK1 peaked at week 2 and SOST at week 8, again demonstrating a close negative correlation. Age and smoking status affected the balance of DKK1 and SOST, while type 2 diabetes and sex did not demonstrate a significant influence. Early postoperative elevation of SOST without compensatory DKK1 decrease was associated with fracture non-union in younger patients (< 50a). The close inverse correlation and very rapid dynamics of DKK1 and SOST locally as well as systemically suggest their critical involvement during human fracture healing. Importantly, as immediate compensatory feedback mechanism are apparent, we provide evidence that dual-blockade of DKK1 and SOST could be critical to allow for therapeutic efficiency of Wnt targeted therapies for fracture healing.

iMSC-mediated delivery of ACVR2B-Fc fusion protein reduces heterotopic ossification in a mouse model of fibrodysplasia ossificans progressiva

BACKGROUND

Fibrodysplasia ossificans progressiva (FOP) is a rare genetic disease caused by a gain-of-function mutation in ACVR1, which is a bone morphogenetic protein (BMP) type I receptor. Moreover, it causes progressive heterotopic ossification (HO) in connective tissues. Using FOP patient-derived induced pluripotent stem cells (FOP-iPSCs) and mouse models, we elucidated the underlying mechanisms of FOP pathogenesis and identified a candidate drug for FOP.

METHODS

In the current study, healthy mesenchymal stem/stromal cells derived from iPSCs (iMSCs) expressing ACVR2B-Fc (iMSCACVR2B-Fc), which is a neutralizing receptobody, were constructed. Furthermore, patient-derived iMSCs and FOP mouse model (ACVR1R206H, female) were used to confirm the inhibitory function of ACVR2B-Fc fusion protein secreted by iMSCACVR2B-Fc on BMP signaling pathways and HO development, respectively.

RESULTS

We found that secreted ACVR2B-Fc attenuated BMP signaling initiated by Activin-A and BMP-9 in both iMSCs and FOP-iMSCs in vitro. Transplantation of ACVR2B-Fc-expressing iMSCs reduced primary HO in a transgenic mouse model of FOP. Notably, a local injection of ACVR2B-Fc-expressing iMSCs and not an intraperitoneal injection improved the treadmill performance, suggesting compound effects of ACVR2B-Fc and iMSCs.

CONCLUSIONS

These results offer a new perspective for treating FOP through stem cell therapy.

Impaired bone morphogenetic protein (BMP) signaling pathways disrupt decidualization in endometriosis

Endometriosis is linked to increased infertility and pregnancy complications due to defective endometrial decidualization. We hypothesized that identification of altered signaling pathways during decidualization could identify the underlying cause of infertility and pregnancy complications. Our study reveals that transforming growth factor β (TGFβ) pathways are impaired in the endometrium of individuals with endometriosis, leading to defective decidualization. Through detailed transcriptomic analyses, we discovered abnormalities in TGFβ signaling pathways and key regulators, such as SMAD4, in the endometrium of affected individuals. We also observed compromised activity of bone morphogenetic proteins (BMP), a subset of the TGFβ family, that control endometrial receptivity. Using 3-dimensional models of endometrial stromal and epithelial assembloids, we showed that exogenous BMP2 improved decidual marker expression in individuals with endometriosis. Our findings reveal dysfunction of BMP/SMAD signaling in the endometrium of individuals with endometriosis, explaining decidualization defects and subsequent pregnancy complications in these individuals.

Genome-wide identification and structural analysis of the BMP gene family in Triplophysa dalaica

BACKGROUND

Bone morphogenetic proteins (BMPs) are part of the transforming growth factor beta (TGF-β) superfamily and play crucial roles in bone development, as well as in the formation and maintenance of various organs. Triplophysa dalaica, a small loach fish that primarily inhabits relatively high elevations and cooler water bodies, was the focus of this study. Understanding the function of BMP genes during the morphogenesis of T. dalaica helps to clarify the mechanisms of its evolution and serves as a reference for the study of BMP genes in other bony fishes. The data for the T. dalaica transcriptome and genome used in this investigation were derived from the outcomes of our laboratory sequencing.

RESULTS

This study identified a total of 26 BMP genes, all of which, except for BMP1, possess similar TGF-β structural domains. We conducted an analysis of these 26 BMP genes, examining their physicochemical properties, subcellular localization, phylogenetic relationships, covariance within and among species, chromosomal localization, gene structure, conserved motifs, conserved structural domains, and expression patterns. Our findings indicated that three BMP genes were associated with unstable proteins, while 11 BMP genes were located within the extracellular matrix. Furthermore, some BMP genes were duplicated, with the majority being enriched in the GO:0008083 pathway, which is related to growth factor activity. It was hypothesized that genes within the BMP1/3/11/15 subgroup (Group I) play a significant role in the growth and development of T. dalaica. By analyzing the expression patterns of proteins in nine tissues (gonad, kidney, gill, spleen, brain, liver, fin, heart, and muscle), we found that BMP genes play diverse regulatory roles during different stages of growth and development and exhibit characteristics of division of labor.

CONCLUSIONS

This study contributes to a deeper understanding of BMP gene family member expression patterns in high-altitude, high-salinity environments and provides valuable insights for future research on the BMP gene family in bony fishes.

ZSWIM4 regulates embryonic patterning and BMP signaling by promoting nuclear Smad1 degradation

The dorsoventral gradient of BMP signaling plays an essential role in embryonic patterning. Zinc Finger SWIM-Type Containing 4 (zswim4) is expressed in the Spemann-Mangold organizer at the onset of Xenopus gastrulation and is then enriched in the developing neuroectoderm at the mid-gastrula stages. Knockdown or knockout of zswim4 causes ventralization. Overexpression of zswim4 decreases, whereas knockdown of zswim4 increases the expression levels of ventrolateral mesoderm marker genes. Mechanistically, ZSWIM4 attenuates the BMP signal by reducing the protein stability of SMAD1 in the nucleus. Stable isotope labeling by amino acids in cell culture (SILAC) identifies Elongin B (ELOB) and Elongin C (ELOC) as the interaction partners of ZSWIM4. Accordingly, ZSWIM4 forms a complex with the Cul2-RING ubiquitin ligase and ELOB and ELOC, promoting the ubiquitination and degradation of SMAD1 in the nucleus. Our study identifies a novel mechanism that restricts BMP signaling in the nucleus.

The MuSK-BMP pathway maintains myofiber size in slow muscle through regulation of Akt-mTOR signaling

Myofiber size regulation is critical in health, disease, and aging. MuSK (muscle-specific kinase) is a BMP (bone morphogenetic protein) co-receptor that promotes and shapes BMP signaling. MuSK is expressed at all neuromuscular junctions and is also present extrasynaptically in the mouse soleus, whose predominantly oxidative fiber composition is akin to that of human muscle. To investigate the role of the MuSK-BMP pathway in vivo, we generated mice lacking the BMP-binding MuSK Ig3 domain. These ∆Ig3-MuSK mice are viable and fertile with innervation levels comparable to wild type. In 3-month-old mice, myofibers are smaller in the slow soleus, but not in the fast tibialis anterior (TA). Transcriptomic analysis revealed soleus-selective decreases in RNA metabolism and protein synthesis pathways as well as dysregulation of IGF1-Akt-mTOR pathway components. Biochemical analysis showed that Akt-mTOR signaling is reduced in soleus but not TA. We propose that the MuSK-BMP pathway acts extrasynaptically to maintain myofiber size in slow muscle by promoting protein synthetic pathways including IGF1-Akt-mTOR signaling. These results reveal a novel mechanism for regulating myofiber size in slow muscle and introduce the MuSK-BMP pathway as a target for promoting muscle growth and combatting atrophy.

Genome-wide analysis of BMP/GDF family and DAP-seq of YY1 suggest their roles in Cynoglossus semilaevis sexual size dimorphism

Sexual size dimorphism (SSD) characterized by different body size between females and males have been reported in various animals. Gonadectomy experiments have implied important regulatory roles of the gonad in SSD. Among multiple factors from the gonad, TGF-β superfamily (especially BMP/GDF family) attracted our interest due to its pleiotropy in growth and reproduction regulations. Thus, whether BMP/GDF family members serve as crucial regulators for SSD was studied in a typically female-biased SSD flatfish named Chinese tongue sole (Cynoglossus semilaevis). Firstly, a total of 26 BMP/GDF family members were identified. The PPI network analysis showed that they may interact with ACVR2a, ACVR2b, ACVR1, BMPR2, SMAD3, BMPR1a, and other proteins. Subsequently, DAP-seq was employed to reveal the binding sites for yin yang 1 (yy1), a transcription factor involved in gonad function and cell growth partly by regulating TGF-β superfamily. The results revealed that two yy1 homologues yy1a and yy1b in C. semilaevis could regulate Hippo signaling pathway, mTOR signaling pathway, and AMPK signaling pathway. Moreover, BMP/GDF family genes including bmp2, bmp4, bmp5, gdf6a, and gdf6b were important components of Hippo pathway. In future, the crosstalk among yy1a, yy1b, and TGF-β family would provide more insight into sexual size dimorphism in C. semilaevis.

Expression of bone morphogenetic protein 10 and its role in biomineralization in Hyriopsis cumingii

Shells and pearls are the products of biomineralization of shellfish after ingesting external mineral ions. Bone morphogenetic proteins (BMPs) play a role in a variety of biological function, and the genes that encode them, are considered important shell-forming genes in mollusks and are associated with shell and pearl formation, embryonic development, and other functions, but bone morphogenetic protein 10 (BMP10) is poorly understood in Hyriopsis cumingii. In this study, we cloned Hc-BMP10 and obtained a 2477 bp full-length sequence encoding 460 amino acids with a conserved TGF-β structural domain. During the embryonic developmental stages, the cleavage stage had the highest expression of Hc-BMP10, followed by juvenile clams; the expression in the mantle gradually decreased with increasing mussel age. A strong signal was detected on epidermal cells on the mantle edge by in situ hybridization. In both the shell notching and inserting operations of the pearl fragment assay, we found that the expression of Hc-BMP10 increased after the above treatments. RNA interference assays showed that the silencing of Hc-BMP10 resulted in a change in the morphology of the prismatic layer and nacreous layer, with the prismatic layer less closely aligned and the disordered aragonite flakes in the nacreous layer. These findings indicate that Hc-BMP10 is involved in the growth and development of H. cumingii, as well as the formation of shells and pearls. Therefore, this study provides some reference for selecting superior species for growth and pearl breeding of H. cumingii at a molecular level and further investigation of the molecular mechanism for biomineralization of Hc-BMP10.

[Recommendations for the healthcare of patients with FOP]

BACKGROUND

Fibrodysplasia ossificans progressiva (FOP) is a very rare, severe genetic disorder triggered by a gain-of-function mutation in the ACVR1 gene that codes for the type I bone morphogenetic protein (BMP) receptor ACVR1 (activin A receptor-type 1), also known as ALK2 (activin receptor-like kinase-2). It leads to the onset and progression of heterotopic ossification (HO) in soft and connective tissue. HO is often preceded by episodes of soft tissue swelling or flare-ups. Flare-ups, characteristic of FOP, may be induced by trauma, infection, vaccination, or other medications, as well as surgical procedures or may occur spontaneously. As patients age, they develop severe mobility limitations due to progressive HO formation, including immobility, causing a shortened life expectancy. FOP's first characteristic clinical sign is the congenital malformation of one or both big toes with valgus axis deviation, which is present in almost all patients. To confirm the diagnosis, molecular genetic analysis of the ACVR1 gene is possible.

AIM OF THE RECOMMENDATIONS

This white paper aims to provide an overview of the necessary prerequisites and conditions for the care of patients with FOP and positively contribute to patients with FOP by improving the overall availability of knowledge. To achieve this, relevant aspects of the care of the very rare disease FOP are presented, from the initial diagnosis to the care in regular care based on the authors' knowledge (German FOP network) and the international FOP Treatment Guidelines. The recommendations presented here are addressed to all actors and decision-makers in the health care system and are also intended to inform patients and the public.

Defining the clinical validity of genes reported to cause pulmonary arterial hypertension

PURPOSE

Pulmonary arterial hypertension (PAH) is a rare, progressive vasculopathy with significant cardiopulmonary morbidity and mortality. Genetic testing is currently recommended for adults diagnosed with heritable, idiopathic, anorexigen-, hereditary hemorrhagic telangiectasia-, and congenital heart disease-associated PAH, PAH with overt features of venous/capillary involvement, and all children diagnosed with PAH. Variants in at least 27 genes have putative evidence for PAH causality. Rigorous assessment of the evidence is needed to inform genetic testing.

METHODS

An international panel of experts in PAH applied a semi-quantitative scoring system developed by the NIH Clinical Genome Resource to classify the relative strength of evidence supporting PAH gene-disease relationships based on genetic and experimental evidence.

RESULTS

Twelve genes (BMPR2, ACVRL1, ATP13A3, CAV1, EIF2AK4, ENG, GDF2, KCNK3, KDR, SMAD9, SOX17, and TBX4) were classified as having definitive evidence and 3 genes (ABCC8, GGCX, and TET2) with moderate evidence. Six genes (AQP1, BMP10, FBLN2, KLF2, KLK1, and PDGFD) were classified as having limited evidence for causal effects of variants. TOPBP1 was classified as having no known PAH relationship. Five genes (BMPR1A, BMPR1B, NOTCH3, SMAD1, and SMAD4) were disputed because of a paucity of genetic evidence over time.

CONCLUSION

We recommend that genetic testing includes all genes with definitive evidence and that caution be taken in the interpretation of variants identified in genes with moderate or limited evidence. Genes with no known evidence for PAH or disputed genes should not be included in genetic testing.

Maternal RNA binding protein with multiple splicing 2 (RBPMS2) is involved in mouse blastocyst formation through the bone morphogenetic protein pathway

RESEARCH QUESTION

Is early embryo development in mice influenced by RNA binding protein with multiple splicing 2 (RBPMS2), a maternal factor that accumulates and is stored in the cytoplasm of mature oocytes?

DESIGN

The expression patterns of RBPMS2 in mouse were analysed using quantitative real-time PCR (qRT PCR) and immunofluorescence staining. The effect of knockdown of RBPMS2 on embryo development was evaluated through a microinjection of specific morpholino or small interfering RNA. RNA sequencing was performed for mechanistic analysis. The interaction between RBPMS2 and the bone morphogenetic protein (BMP) pathway was studied using BMP inhibitor and activator. The effect on the localization of E-cadherin was determined by immunofluorescence staining.

RESULTS

Maternal protein RBPMS2 is highly expressed in mouse oocytes, and knockdown of RBPMS2 inhibits embryo development from the morula to the blastocyst stage. Mechanistically, RNA sequencing showed that the differentially expressed genes were enriched in the transforming growth factor-β (TGF-β) signalling pathway. BMPs are members of the TGF-β superfamily of growth factors. It was found that the addition of BMP inhibitor to the culture medium led to a morula-stage arrest, similar to that seen in RBPMS2 knockdown embryos. This morula-stage arrest defect caused by RBPMS2 knockdown was partially rescued by BMP activator. Furthermore, the localization of E-cadherin to the membrane was impaired in response to a knockdown of RBPMS2 or inhibition of the BMP pathway.

CONCLUSION

This study suggests that RBPMS2 activates the BMP pathway and thus influences the localization of E-cadherin, which is important for early mouse embryo development during blastocyst formation.

Sclerostin and Cardiovascular Disease

PURPOSE OF REVIEW

The role of wnt signalling in atherogenesis raises the possibility that the wnt inhibitor, sclerostin, provides a natural defence to this process, and that anti-sclerostin antibodies might increase the risk of atherosclerosis and associated conditions such as CVD. This article aims to triangulate evidence concerning possible adverse effects of sclerostin inhibition on CVD risk.

RECENT FINDINGS

Randomised controlled trials of treatment with the anti-sclerostin antibody, romosozumab, have yielded conflicting evidence with respect to possible adverse effects of sclerostin inhibition on CVD risk. To further examine the causal relationship between sclerostin inhibition and CVD risk, three Mendelian randomisation (MR) studies have examined effects of sclerostin lowering on CVD outcomes, using common genetic variants in the SOST gene which produces sclerostin, to mimic effects of a randomised trial. Concordant findings were seen in two studies, comprising an effect of sclerostin lowering on increased risk of MI and type II diabetes mellitus. One study also suggested that sclerostin lowering increases coronary artery calcification. Triangulation of evidence from different sources provides some suggestion that sclerostin lowering increases MI risk, supporting the need for CVD risk assessment when considering treatment with romosozumab.

A novel variant in BMPR1B causes acromesomelic dysplasia Grebe type in a consanguineous Moroccan family: Expanding the phenotypic and mutational spectrum of acromesomelic dysplasias

Acromesomelic dysplasia Grebe type (AMD Grebe type) is an autosomal recessive trait characterized by short stature, shortened limbs and malformations of the hands and feet. It is caused by variants in the growth differentiation factor 5 (GDF5) or, in rare cases, its receptor, the bone morphogenetic protein receptor-1B (BMPR1B). Here, we report a novel homozygous BMPR1B variant causing AMD Grebe type in a consanguineous Moroccan family with two affected sibs from BRO Biobank. Remarkably, the affected individuals showed additional features including bilateral simian creases, lumbar hyperlordosis, as well as lower limb length inequality and dislocated hips in one of them, which were never reported previously for AMD Grebe type patients. The identified novel BMPR1B variant (c.1201C>T, p.R401*) is predicted to result in loss of function of the BMPR1B protein either by nonsense-mediated mRNA decay or production of a truncated BMPR1B protein. Thus, these findings expand the phenotypic and mutational spectrum of AMD, and may improve the diagnosis of AMD and enable appropriate genetic counselling to be offered to patients.

Identification of Bone Morphometric Protein-Related Hub Genes and Construction of a Transcriptional Regulatory Network in Patients With Ossification of the Ligamentum Flavum

STUDY DESIGN

Basic science laboratory study.

OBJECTIVE

To identify hub genes related to bone morphogenetic proteins (BMPs) in the ossification of the ligamentum flavum (OLF) and analyze their functional characteristics.

SUMMARY OF BACKGROUND DATA

The exact etiology and pathologic mechanism of OLF remain unclear. BMPs are pleiotropic osteoinductive proteins that may play a critical role in this condition.

MATERIALS AND METHODS

The GSE106253 and GSE106256 data sets were downloaded from the Gene Expression Omnibus database. The messenger RNA (mRNA) and long noncoding RNA expression profiles were obtained from GSE106253. The microRNA expression profiles were obtained from GSE106256. Differentially expressed genes were identified between OLF and non-OLF groups and then intersected with BMP-related genes to obtain differentially expressed BMP-related genes. The least absolute shrinkage selection operator and support vector machine recursive feature elimination were used to screen hub genes. Furthermore, a competing endogenous RNA network was constructed to explain the expression regulation of the hub genes in OLF. Finally, the protein and mRNA expression levels of the hub genes were verified using Western blot and real-time polymerase chain reaction, respectively.

RESULTS

We identified 671 Differentially expressed genes and 32 differentially expressed BMP-related genes. Hub genes ADIPOQ , SCD , SCX , RPS18 , WDR82 , and SPON1 , identified through the least absolute shrinkage selection operator and support vector machine recursive feature elimination analyses, showed high diagnostic values for OLF. Furthermore, the competing endogenous RNA network revealed the regulatory mechanisms of the hub genes. Real-time polymerase chain reaction showed that the mRNA expression of the hub genes was significantly downregulated in the OLF group compared with the non-OLF group. Western blot showed that the protein levels of ADIPOQ, SCD, WDR82 , and SPON1 were significantly downregulated, whereas those of SCX and RPS18 were significantly upregulated in the OLF group compared with the non-OLF group.

CONCLUSION

This study is the first to identify BMP-related genes in OLF pathogenesis through bioinformatics analysis. ADIPOQ , SCD , SCX , RPS18 , WDR82 , and SPON1 were identified as hub genes for OLF. The identified genes may serve as potential therapeutic targets for treating patients with OLF.

SMAD4 maintains the fluid shear stress set point to protect against arterial-venous malformations

Vascular networks form, remodel, and mature under the influence of both fluid shear stress (FSS) and soluble factors. Physiological FSS promotes and maintains vascular stability via synergy with bone morphogenic proteins 9 and 10 (BMP9 and BMP10). Conversely, mutation of the BMP receptors activin-like kinase 1 (ALK1), endoglin (ENG), or the downstream effector, SMAD family member 4 (SMAD4) leads to hereditary hemorrhagic telangiectasia (HHT), characterized by fragile and leaky arterial-venous malformations (AVMs). How endothelial cells (ECs) integrate FSS and BMP signals in vascular development and homeostasis and how mutations give rise to vascular malformations is not well understood. Here, we aimed to elucidate the mechanism of synergy between FSS and SMAD signaling in vascular stability and how disruption of this synergy leads to AVMs. We found that loss of Smad4 increased the sensitivity of ECs to flow by lowering the FSS set point, with resulting AVMs exhibiting features of excessive flow-mediated morphological responses. Mechanistically, loss of SMAD4 disinhibits flow-mediated KLF4-TIE2-PI3K/Akt signaling, leading to cell cycle progression-mediated loss of arterial identity due to KLF4-mediated repression of cyclin dependent Kinase (CDK) inhibitors CDKN2A and CDKN2B. Thus, AVMs caused by Smad4 deletion are characterized by chronic high flow remodeling with excessive EC proliferation and loss of arterial identity as triggering events.

Bmp8a deletion leads to obesity through regulation of lipid metabolism and adipocyte differentiation

The role of bone morphogenetic proteins (BMPs) in regulating adipose has recently become a field of interest. However, the underlying mechanism of this effect has not been elucidated. Here we show that the anti-fat effect of Bmp8a is mediated by promoting fatty acid oxidation and inhibiting adipocyte differentiation. Knocking out the bmp8a gene in zebrafish results in weight gain, fatty liver, and increased fat production. The bmp8a-/- zebrafish exhibits decreased phosphorylation levels of AMPK and ACC in the liver and adipose tissues, indicating reduced fatty acid oxidation. Also, Bmp8a inhibits the differentiation of 3T3-L1 preadipocytes into mature adipocytes by activating the Smad2/3 signaling pathway, in which Smad2/3 binds to the central adipogenic factor PPARγ promoter to inhibit its transcription. In addition, lentivirus-mediated overexpression of Bmp8a in 3T3-L1 cells significantly increases NOD-like receptor, TNF, and NF-κB signaling pathways. Furthermore, NF-κB interacts with PPARγ, blocking PPARγ's activation of its target gene Fabp4, thereby inhibiting adipocyte differentiation. These data bring a signal bridge between immune regulation and adipocyte differentiation. Collectively, our findings indicate that Bmp8a plays a critical role in regulating lipid metabolism and adipogenesis, potentially providing a therapeutic approach for obesity and its comorbidities.

Executive summary of the 14th HHT international scientific conference

Hereditary Hemorrhagic Telangiectasia (HHT) is an autosomal dominant vascular disorder characterized by small, dilated clustered vessels (telangiectasias) and by larger visceral arteriovenous malformations (AVMs), which directly connect the feeding arteries with the draining veins. These lesions are fragile, prone to rupture, and lead to recurrent epistaxis and/or internal hemorrhage among other complications. Germline heterozygous loss-of-function (LOF) mutations in Bone Morphogenic Protein 9 (BMP9) and BMP10 signaling pathway genes (endoglin-ENG, activin like kinase 1 ACVRL1 aka ALK1, and SMAD4) cause different subtypes of HHT (HHT1, HHT2 and HHT-juvenile polyposis (JP)) and have a worldwide combined incidence of about 1:5000. Expert clinicians and international scientists gathered in Cascais, Portugal from September 29th to October 2nd, 2022 to present the latest scientific research in the HHT field and novel treatment strategies for people living with HHT. During the largest HHT scientific conference yet, participants included 293 in person and 46 virtually. An impressive 209 abstracts were accepted to the meeting and 59 were selected for oral presentations. The remaining 150 abstracts were presented during judged poster sessions. This review article summarizes the basic and clinical abstracts selected as oral presentations with their new observations and discoveries as well as surrounding discussion and debate. Two discussion-based workshops were also held during the conference, each focusing on mechanisms and clinical perspectives in either AVM formation and progression or current and future therapies for HHT. Our hope is that this paper will represent the current progress and the remaining unanswered questions surrounding HHT, in order to serve as an update for those within the field and an invitation to those scientists and clinicians as yet outside of the field of HHT.

BMP-induced non-canonical signaling is upregulated during autophagy-mediated regeneration in inflamed mesothelial cells

Previously, we showed that after Freund's adjuvant-induced peritonitis, rat mesothelial cells regain their epithelial phenotype through mesenchymal-epithelial transition (MET) accompanied by autophagy. Since bone morphogenetic proteins (BMPs) are well-known MET-inducers, we were interested in the potential expression of BMPs and BMP-induced pathways. Although mesothelial cells expressed lower amounts of BMP7, its level in the peritoneal cavity and mesothelial synthesis of BMP4 were significantly increased during inflammation. BMPR1A and BMPR2 were also significantly expressed. Expression of transforming growth factor beta-activated kinase (TAK1) and c-Jun NH2-terminal kinases (JNK1-JNK2) were more intense than that of phosphorylated Mothers Against Decapentaplegic homolog 1/5 (p-SMAD1/5), confirming that the non-canonical pathway of BMPs prevailed in our model. JNK signaling through B-cell lymphoma-2 (Bcl-2) can contribute to Beclin-1 activation. We demonstrated that TAK1-JNK-Bcl-2 signaling was upregulated simultaneously with the autophagy-mediated regeneration. A further goal of our study was to prove the regenerative role of autophagy after inflammation. We used a specific inhibitor, bafilomycin A1 (BafA1), and found that BafA1 treatment decreased the expression of microtubule-associated protein 1A/1B-light chain 3 (LC3B) and resulted in morphological signs of cell death in inflamed mesothelial cells indicating that if autophagy is arrested, regeneration turns into cell death and consequently, mesothelial cells die.

Functional interaction of Clock genes and bone morphogenetic proteins in the adrenal cortex

The bone morphogenetic protein (BMP) system in the adrenal cortex plays modulatory roles in the control of adrenocortical steroidogenesis. BMP-6 enhances aldosterone production by modulating angiotensin (Ang) II-mitogen-activated protein kinase (MAPK) signaling, whereas activin regulates the adrenocorticotropin (ACTH)-cAMP cascade in adrenocortical cells. A peripheral clock system in the adrenal cortex was discovered and it has been shown to have functional roles in the adjustment of adrenocortical steroidogenesis by interacting with the BMP system. It was found that follistatin, a binding protein of activin, increased Clock mRNA levels, indicating an endogenous function of activin in the regulation of Clock mRNA expression. Elucidation of the interrelationships among the circadian clock system, the BMP system and adrenocortical steroidogenesis regulated by the hypothalamic-pituitary-adrenal (HPA) axis would lead to an understanding of the pathophysiology of adrenal disorders and metabolic disorders and the establishment of better medical treatment from the viewpoint of pharmacokinetics.

Neurological manifestations in patients and disease carriers in an Italian family with osteosclerosis

BACKGROUND

Hereditary cranial hyperostosis is a rare disease never described in Italy, so the neurological manifestations in patients and carriers of the disease have been little studied.

METHODS

We describe the neurological and neuroimaging features of patients and carriers of the gene from a large Italian family with sclerosteosis.

RESULTS

In this family, genetic testing detected the homozygous p.Gln24X (c.70C > T) mutation of the SOST gene in the proband and a heterozygous mutation in 9 siblings. In homozygous adults, severe craniofacial hyperostosis was manifested by cranial neuropathy in childhood, chronic headache secondary to intracranial hypertension, and an obstructive sleep apnea syndrome in adults. In one of the adult patients, there was a compressible subcutaneous swelling in the occipital region caused by transosseous intracranial-extracranial occipital venous drainage, a compensation mechanism of obstructed venous drainage secondary to cranial hyperostosis. Mild cranial hyperostosis causing frequent headache and snoring was evident in the nine heterozygous subjects.

CONCLUSIONS

Multiple cranial neuropathies and headache in children, while severe chronic headache and sleep disturbances in adults, are the neurological manifestations of the first Italian family with osteosclerosis. It is reasonable to extend neurological and neuroimaging evaluation to gene carriers as well.

Functional substitutions of amino acids that differ between GDF11 and GDF8 impact skeletal development and skeletal muscle

Growth differentiation factor 11 (GDF11) and GDF8 (MSTN) are closely related TGF-β family proteins that interact with nearly identical signaling receptors and antagonists. However, GDF11 appears to activate SMAD2/3 more potently than GDF8 in vitro and in vivo. The ligands possess divergent structural properties, whereby substituting unique GDF11 amino acids into GDF8 enhanced the activity of the resulting chimeric GDF8. We investigated potentially distinct endogenous activities of GDF11 and GDF8 in vivo by genetically modifying their mature signaling domains. Full recoding of GDF8 to that of GDF11 yielded mice lacking GDF8, with GDF11 levels ∼50-fold higher than normal, and exhibiting modestly decreased muscle mass, with no apparent negative impacts on health or survival. Substitution of two specific amino acids in the fingertip region of GDF11 with the corresponding GDF8 residues resulted in prenatal axial skeletal transformations, consistent with Gdf11-deficient mice, without apparent perturbation of skeletal or cardiac muscle development or homeostasis. These experiments uncover distinctive features between the GDF11 and GDF8 mature domains in vivo and identify a specific requirement for GDF11 in early-stage skeletal development.

MeCP2 regulates Gdf11, a dosage-sensitive gene critical for neurological function

Loss- and gain-of-function of MeCP2 causes Rett syndrome (RTT) and MECP2 duplication syndrome (MDS), respectively. MeCP2 binds methyl-cytosines to finely tune gene expression in the brain, but identifying genes robustly regulated by MeCP2 has been difficult. By integrating multiple transcriptomics datasets, we revealed that MeCP2 finely regulates growth differentiation factor 11 (Gdf11). Gdf11 is down-regulated in RTT mouse models and, conversely, up-regulated in MDS mouse models. Strikingly, genetically normalizing Gdf11 dosage levels improved several behavioral deficits in a mouse model of MDS. Next, we discovered that losing one copy of Gdf11 alone was sufficient to cause multiple neurobehavioral deficits in mice, most notably hyperactivity and decreased learning and memory. This decrease in learning and memory was not due to changes in proliferation or numbers of progenitor cells in the hippocampus. Lastly, loss of one copy of Gdf11 decreased survival in mice, corroborating its putative role in aging. Our data demonstrate that Gdf11 dosage is important for brain function.

Bone morphogenetic protein pathway responses and alterations of osteogenesis in metastatic prostate cancers

BACKGROUND

Prostate cancer is a common cancer in men that annually results in more than 33 000 US deaths. Mortality from prostate cancer is largely from metastatic disease, reflecting on the great strides in the last century of treatments in care for the localized disease. Metastatic castrate resistant prostate cancer (mCRPC) will commonly travel to the bone, creating unique bone pathology that requires nuanced treatments in those sites with surgical, radio and chemotherapeutic interventions. The bone morphogenetic protein (BMP) pathway has been historically studied in the capacity to regulate the osteogenic nature of new bone. New mineralized bone generation is a frequent and common observation in mCRPC and referred to as blastic bone lesions. Less common are bone destructive lesions that are termed lytic.

METHODS

We queried the cancer genome atlas (TCGA) prostate cancer databases for the expression of the BMP pathway and found that distinct gene expression of the ligands, soluble antagonists, receptors, and intracellular mediators were altered in localized versus metastatic disease. Human prostate cancer cell lines have an innate ability to promote blastic- or lytic-like bone lesions and we hypothesized that inhibiting BMP signaling in these cell lines would result in a distinct change in osteogenesis gene expression with BMP inhibition.

RESULTS

We found unique and common changes by comparing these cell lines response and unique BMP pathway alterations. We treated human PCa cell lines with distinct bone pathologic phenotypes with the BMP inhibitor DMH1 and found distinct osteogenesis responses. We analyzed distinct sites of metastatic PCa in the TCGA and found that BMP signaling was selectively altered in commons sites such as lymph node, bone and liver compared to primary tumors.

CONCLUSIONS

Overall we conclude that BMPs in metastatic prostate cancer are important signals and functional mediators of diverse processes that have potential for individualized precision oncology in mCRPC.

Systemic GDF11 attenuates depression-like phenotype in aged mice via stimulation of neuronal autophagy

Cognitive decline and mood disorders increase in frequency with age. Many efforts are focused on the identification of molecules and pathways to treat these conditions. Here, we demonstrate that systemic administration of growth differentiation factor 11 (GDF11) in aged mice improves memory and alleviates senescence and depression-like symptoms in a neurogenesis-independent manner. Mechanistically, GDF11 acts directly on hippocampal neurons to enhance neuronal activity via stimulation of autophagy. Transcriptomic and biochemical analyses of these neurons reveal that GDF11 reduces the activity of mammalian target of rapamycin (mTOR), a master regulator of autophagy. Using a murine model of corticosterone-induced depression-like phenotype, we also show that GDF11 attenuates the depressive-like behavior of young mice. Analysis of sera from young adults with major depressive disorder (MDD) reveals reduced GDF11 levels. These findings identify mechanistic pathways related to GDF11 action in the brain and uncover an unknown role for GDF11 as an antidepressant candidate and biomarker.

BMP10 functions independently from BMP9 for the development of a proper arteriovenous network

Hereditary hemorrhagic telangiectasia (HHT) is a genetic vascular disorder characterized by the presence of arteriovenous malformation (AVM) in multiple organs. HHT is caused by mutations in genes encoding major constituents for transforming growth factor-β (TGF-β) family signaling: endoglin (ENG), activin receptor-like kinase 1 (ALK1), and SMAD4. The identity of physiological ligands for this ENG-ALK1 signaling pertinent to AVM formation has yet to be clearly determined. To investigate whether bone morphogenetic protein 9 (BMP9), BMP10, or both are physiological ligands of ENG-ALK1 signaling involved in arteriovenous network formation, we generated a novel Bmp10 conditional knockout mouse strain. We examined whether global Bmp10-inducible knockout (iKO) mice develop AVMs at neonatal and adult stages in comparison with control, Bmp9-KO, and Bmp9/10-double KO (dKO) mice. Bmp10-iKO and Bmp9/10-dKO mice showed AVMs in developing retina, postnatal brain, and adult wounded skin, while Bmp9-KO did not display any noticeable vascular defects. Bmp10 deficiency resulted in increased proliferation and size of endothelial cells in AVM vessels. The impaired neurovascular integrity in the brain and retina of Bmp10-iKO and Bmp9/10-dKO mice was detected. Bmp9/10-dKO mice exhibited the lethality and vascular malformation similar to Bmp10-iKO mice, but their phenotypes were more pronounced. Administration of BMP10 protein, but not BMP9 protein, prevented retinal AVM in Bmp9/10-dKO and endothelial-specific Eng-iKO mice. These data indicate that BMP10 is indispensable for the development of a proper arteriovenous network, whereas BMP9 has limited compensatory functions for the loss of BMP10. We suggest that BMP10 is the most relevant physiological ligand of the ENG-ALK1 signaling pathway pertinent to HHT pathogenesis.

Novel bone Morphogenetic Protein (BMP)-2/4 Consensus Peptide (BCP) for the Osteogenic Differentiation of C2C12 Cells

BACKGROUND

Despite the promising clinical potential of bone morphogenetic protein (BMP)-related therapies for bone formation, their side effects warrant the need for alternative therapeutic peptides. BMP family members can aid in bone repair; however, peptides derived from BMP2/ 4 have not yet been investigated.

METHODS

In this study, three candidates BMP2/4 consensus peptide (BCP) 1, 2, and 3 were identified and their ability to induce osteogenesis in C2C12 cells was analyzed. First, an alkaline phosphatase (ALP) staining assay was performed to evaluate the osteogenic effects of BCPs. Next, the effects of BCPs on RNA expression levels and protein abundances of osteogenic markers were explored. Furthermore, the transcriptional activity of ALP by BCP1 and in silico molecular docking model on BMP type IA receptor (BRIA) were performed.

RESULTS

BCP1-3 induced higher RUNX2 expression than BMP2. Interestingly, among them, BCP1 significantly promoted osteoblast differentiation more than BMP2 in ALP staining with no cytotoxicity. BCP1 significantly induced the osteoblast markers, and the highest RUNX2 expression was observed at 100 ng/mL compared to other concentrations. In transfection experiments, BCP1 stimulated osteoblast differentiation via RUNX2 activation and the Smad signaling pathway. Finally, in silico molecular docking suggested the possible binding sites of BCP1 on BRIA.

CONCLUSION

These results show that BCP1 promotes osteogenicity in C2C12 cells. This study suggests that BCP1 is the most promising candidate peptide to replace BMP2 for osteoblast differentiation.

In Silico Study and Effects of BDMC33 on TNBS-Induced BMP Gene Expressions in Zebrafish Gut Inflammation-Associated Arthritis

The bone morphogenic protein (BMP) family is a member of the TGF-beta superfamily and plays a crucial role during the onset of gut inflammation and arthritis diseases. Recent studies have reported a connection with the gut-joint axis; however, the genetic players are still less explored. Meanwhile, BDMC33 is a newly synthesized anti-inflammatory drug candidate. Therefore, in our present study, we analysed the genome-wide features of the BMP family as well as the role of BMP members in gut-associated arthritis in an inflammatory state and the ability of BDMC33 to attenuate this inflammation. Firstly, genome-wide analyses were performed on the BMP family in the zebrafish genome, employing several in silico techniques. Afterwards, the effects of curcumin analogues on BMP gene expression in zebrafish larvae induced with TNBS (0.78 mg/mL) were determined using real time-qPCR. A total of 38 identified BMP proteins were revealed to be clustered in five major clades and contain TGF beta and TGF beta pro peptide domains. Furthermore, BDMC33 suppressed the expression of four selected BMP genes in the TNBS-induced larvae, where the highest gene suppression was in the BMP2a gene (an eight-fold decrement), followed by BMP7b (four-fold decrement), BMP4 (four-fold decrement), and BMP6 (three-fold decrement). Therefore, this study reveals the role of BMPs in gut-associated arthritis and proves the ability of BDMC33 to act as a potential anti-inflammatory drug for suppressing TNBS-induced BMP genes in zebrafish larvae.

Crosstalk between BMP signaling and KCNK3 in phenotypic switching of pulmonary vascular smooth muscle cells

Pulmonary arterial hypertension (PAH) is a progressive and devastating disease whose pathogenesis is associated with a phenotypic switch of pulmonary arterial vascular smooth muscle cells (PASMCs). Bone morphogenetic protein (BMP) signaling and potassium two pore domain channel subfamily K member 3 (KCNK3) play crucial roles in PAH pathogenesis. However, the relationship between BMP signaling and KCNK3 expression in the PASMC phenotypic switching process has not been studied. In this study, we explored the effect of BMPs on KCNK3 expression and the role of KCNK3 in the BMP-mediated PASMC phenotypic switch. Expression levels of BMP receptor 2 (BMPR2) and KCNK3 were downregulated in PASMCs of rats with PAH compared to those in normal controls, implying a possible association between BMP/BMPR2 signaling and KCNK3 expression in the pulmonary vasculature. Treatment with BMP2, BMP4, and BMP7 significantly increased KCNK3 expression in primary human PASMCs (HPASMCs). BMPR2 knockdown and treatment with Smad1/5 signaling inhibitor substantially abrogated the BMP-induced increase in KCNK3 expression, suggesting that KCNK3 expression in HPASMCs is regulated by the canonical BMP-BMPR2-Smad1/5 signaling pathway. Furthermore, KCNK3 knockdown and treatment with a KCNK3 channel blocker completely blocked BMP-mediated anti-proliferation and expression of contractile marker genes in HPAMSCs, suggesting that the expression and functional activity of KCNK3 are required for BMP-mediated acquisition of the quiescent PASMC phenotype. Overall, our findings show a crosstalk between BMP signaling and KCNK3 in regulating the PASMC phenotype, wherein BMPs upregulate KCNK3 expression and KCNK3 then mediates BMP-induced phenotypic switching of PASMCs. Our results indicate that the dysfunction and/or downregulation of BMPR2 and KCNK3 observed in PAH work together to induce aberrant changes in the PASMC phenotype, providing insights into the complex molecular pathogenesis of PAH. [BMB Reports 2022; 55(11): 565-570].

Crosstalk between BMP signaling and KCNK3 in phenotypic switching of pulmonary vascular smooth muscle cells

Pulmonary arterial hypertension (PAH) is a progressive and devastating disease whose pathogenesis is associated with a phenotypic switch of pulmonary arterial vascular smooth muscle cells (PASMCs). Bone morphogenetic protein (BMP) signaling and potassium two pore domain channel subfamily K member 3 (KCNK3) play crucial roles in PAH pathogenesis. However, the relationship between BMP signaling and KCNK3 expression in the PASMC phenotypic switching process has not been studied. In this study, we explored the effect of BMPs on KCNK3 expression and the role of KCNK3 in the BMP-mediated PASMC phenotypic switch. Expression levels of BMP receptor 2 (BMPR2) and KCNK3 were downregulated in PASMCs of rats with PAH compared to those in normal controls, implying a possible association between BMP/BMPR2 signaling and KCNK3 expression in the pulmonary vasculature. Treatment with BMP2, BMP4, and BMP7 significantly increased KCNK3 expression in primary human PASMCs (HPASMCs). BMPR2 knockdown and treatment with Smad1/5 signaling inhibitor substantially abrogated the BMP-induced increase in KCNK3 expression, suggesting that KCNK3 expression in HPASMCs is regulated by the canonical BMP-BMPR2-Smad1/5 signaling pathway. Furthermore, KCNK3 knockdown and treatment with a KCNK3 channel blocker completely blocked BMP-mediated anti-proliferation and expression of contractile marker genes in HPAMSCs, suggesting that the expression and functional activity of KCNK3 are required for BMP-mediated acquisition of the quiescent PASMC phenotype. Overall, our findings show a crosstalk between BMP signaling and KCNK3 in regulating the PASMC phenotype, wherein BMPs upregulate KCNK3 expression and KCNK3 then mediates BMP-induced phenotypic switching of PASMCs. Our results indicate that the dysfunction and/or downregulation of BMPR2 and KCNK3 observed in PAH work together to induce aberrant changes in the PASMC phenotype, providing insights into the complex molecular pathogenesis of PAH. [BMB Reports 2022; 55(11): 565-570].

Context-dependent tumor-suppressive BMP signaling in diffuse intrinsic pontine glioma regulates stemness through epigenetic regulation of CXXC5

The most lethal subtype of diffuse intrinsic pontine glioma (DIPG) is H3K27M. Although ACVR1 mutations have been implicated in the pathogenesis of this currently incurable disease, the impacts of bone morphogenetic protein (BMP) signaling on more than 60% of H3K27M DIPG carrying ACVR1 wild-type remain unknown. Here we show that BMP ligands exert potent tumor-suppressive effects against H3.3K27M and ACVR1 WT DIPG in a SMAD-dependent manner. Specifically, clinical data revealed that many DIPG tumors have exploited the capacity of CHRDL1 to hijack BMP ligands. We discovered that activation of BMP signaling promotes the exit of DIPG tumor cells from 'prolonged stem-cell-like' state to differentiation by epigenetically regulating CXXC5, which acts as a tumor suppressor and positive regulator of BMP signaling. Beyond showing how BMP signaling impacts DIPG, our study also identified the potent antitumor efficacy of Dacinostat for DIPG. Thus, our study delineates context-dependent features of the BMP signaling pathway in a DIPG subtype.

Selective role of the DNA helicase Mcm5 in BMP retrograde signaling during Drosophila neuronal differentiation

The MCM2-7 complex is a highly conserved hetero-hexameric protein complex, critical for DNA unwinding at the replicative fork during DNA replication. Overexpression or mutation in MCM2-7 genes is linked to and may drive several cancer types in humans. In mice, mutations in MCM2-7 genes result in growth retardation and mortality. All six MCM2-7 genes are also expressed in the developing mouse CNS, but their role in the CNS is not clear. Here, we use the central nervous system (CNS) of Drosophila melanogaster to begin addressing the role of the MCM complex during development, focusing on the specification of a well-studied neuropeptide expressing neuron: the Tv4/FMRFa neuron. In a search for genes involved in the specification of the Tv4/FMRFa neuron we identified Mcm5 and find that it plays a highly specific role in the specification of the Tv4/FMRFa neuron. We find that other components of the MCM2-7 complex phenocopies Mcm5, indicating that the role of Mcm5 in neuronal subtype specification involves the MCM2-7 complex. Surprisingly, we find no evidence of reduced progenitor proliferation, and instead find that Mcm5 is required for the expression of the type I BMP receptor Tkv, which is critical for the FMRFa expression. These results suggest that the MCM2-7 complex may play roles during CNS development outside of its well-established role during DNA replication.

The MCM2-7 complex plays a critical role in the DNA replication allowing cells to progress throughout the cell cycle and divide. Overexpression or mutation in MCM2-7 genes is linked to and may drive several cancer types in humans. While MCM2-7 complex is widely expressed in the central nervous system (CNS) during development, its role is not yet clear. Here, we use the CNS of Drosophila melanogaster to address the role of the MCM complex, focusing on the specification of a well-studied neuropeptide expressing neuron: the Tv4/FMRFa neuron. We identified that Mcm5 plays a highly specific role in the specification of this neuron, and it involves other components of the MCM2-7 complex. Despite the described importance of this complex on DNA replication, we find no evidence of reduced progenitor proliferation, and instead we find that Mcm5 is required for the expression of the type I BMP receptor Tkv, which is critical for the specification of the Tv4/FMRFa neuron. These results suggest that the MCM2-7 complex may play roles during CNS development outside of its well-established role during DNA replication.

Twists in the fibrodysplasia ossificans progressiva story challenge and expand our understanding of BMP biology

Fibrodysplasia ossificans progressiva (FOP) is an ultrarare, debilitating disease in which heterotopic bone is formed in certain soft tissues. A gain-of-function variant in the cytoplasmic domain of the activin A receptor type I (ACVR1) exists in all patients with FOP. Strikingly, these FOP-causing variants imbue a neofunction to ACVR1 — the ability to recognize activin A as an agonist with bone morphogenic protein–like signaling that leads to heterotopic ossification (HO). These findings are supported by the efficacy of anti–activin A antibodies in preventing HO in FOP mice. This surprising story continues in companion papers in this issue of the JCI. Aykul et al. and Lees-Shepard et al. independently found that antibodies against ACVR1, which were being developed as potential therapeutics for FOP, instead caused HO in FOP mice. While this unexpected finding may be the clinical final act for such antibodies, it provides another twist in the unique and evolving FOP story.

Decoding the PITX2-controlled genetic network in atrial fibrillation

Atrial fibrillation (AF), the most common sustained cardiac arrhythmia and a major risk factor for stroke, often arises through ectopic electrical impulses derived from the pulmonary veins (PVs). Sequence variants in enhancers controlling expression of the transcription factor PITX2, which is expressed in the cardiomyocytes (CMs) of the PV and left atrium (LA), have been implicated in AF predisposition. Single nuclei multiomic profiling of RNA and analysis of chromatin accessibility combined with spectral clustering uncovered distinct PV- and LA-enriched CM cell states. Pitx2-mutant PV and LA CMs exhibited gene expression changes consistent with cardiac dysfunction through cell type-distinct, PITX2-directed, cis-regulatory grammars controlling target gene expression. The perturbed network targets in each CM were enriched in distinct human AF predisposition genes, suggesting combinatorial risk for AF genesis. Our data further reveal that PV and LA Pitx2-mutant CMs signal to endothelial and endocardial cells through BMP10 signaling with pathogenic potential. This work provides a multiomic framework for interrogating the basis of AF predisposition in the PVs of humans.

Exome sequencing in multiplex families with left-sided cardiac defects has high yield for disease gene discovery

Congenital heart disease (CHD) is a common group of birth defects with a strong genetic contribution to their etiology, but historically the diagnostic yield from exome studies of isolated CHD has been low. Pleiotropy, variable expressivity, and the difficulty of accurately phenotyping newborns contribute to this problem. We hypothesized that performing exome sequencing on selected individuals in families with multiple members affected by left-sided CHD, then filtering variants by population frequency, in silico predictive algorithms, and phenotypic annotations from publicly available databases would increase this yield and generate a list of candidate disease-causing variants that would show a high validation rate. In eight of the nineteen families in our study (42%), we established a well-known gene/phenotype link for a candidate variant or performed confirmation of a candidate variant’s effect on protein function, including variants in genes not previously described or firmly established as disease genes in the body of CHD literature: BMP10, CASZ1, ROCK1 and SMYD1. Two plausible variants in different genes were found to segregate in the same family in two instances suggesting oligogenic inheritance. These results highlight the need for functional validation and demonstrate that in the era of next-generation sequencing, multiplex families with isolated CHD can still bring high yield to the discovery of novel disease genes.

Congenital heart disease is a common group of birth defects that are a leading cause of death in children under one year of age. There is strong evidence that genetics plays a role in causing congenital heart disease. While studies using individual cases have identified causative genes for those with a heart defect when accompanied by other birth defects or intellectual disabilities, for individuals who have only a heart defect without other problems, a genetic cause can be found in fewer than 10%. In this study, we enrolled families where there was more than one individual with a heart defect. This allowed us to take advantage of inheritance by searching for potential disease-causing genetic variants in common among all affected individuals in the family. Among 19 families studied, we were able to find a plausible disease-causing variant in eight of them and identified new genes that may cause or contribute to the presence of a heart defect. Two families had potential disease-causing variants in two different genes. We designed assays to test if the variants led to altered function of the protein coded by the gene, demonstrating a functional consequence that support the gene and variant as contributing to the heart defect. These findings show that studying families may be more effective than using individuals to find causes of heart defects. In addition, this family-based method suggests that changes in more than one gene may be required for a heart defect to occur.

Transcriptional regulation of cyclophilin D by BMP/Smad signaling and its role in osteogenic differentiation

Cyclophilin D (CypD) promotes opening of the mitochondrial permeability transition pore (MPTP) which plays a key role in both cell physiology and pathology. It is, therefore, beneficial for cells to tightly regulate CypD and MPTP but little is known about such regulation. We have reported before that CypD is downregulated and MPTP deactivated during differentiation in various tissues. Herein, we identify BMP/Smad signaling, a major driver of differentiation, as a transcriptional regulator of the CypD gene, Ppif. Using osteogenic induction of mesenchymal lineage cells as a BMP/Smad activation-dependent differentiation model, we show that CypD is in fact transcriptionally repressed during this process. The importance of such CypD downregulation is evidenced by the negative effect of CypD 'rescue' via gain-of-function on osteogenesis both in vitro and in a mouse model. In sum, we characterized BMP/Smad signaling as a regulator of CypD expression and elucidated the role of CypD downregulation during cell differentiation.

Mutation Detection and Functional Analysis of MSX1, PAX9, AXIN2, and BMP in Nonsyndromic Congenital Missing Teeth Based on Intelligent Image Detection

Due to the complexity of clinical manifestations and the lack of standardized diagnostic criteria, it is still difficult to distinguish the etiological types of congenital edentulousness corresponding to genetic defects. This paper studies the application of deep learning image processing and digital image processing in medical images in detail and analyzes the functions of congenital edentulous hotspot genes. The cases in the control group and the study group were collected, and the gene mutations of direct sequence MSX1, PAX9, AXIN2, and BMP were analyzed, and new pathogens were found. The experimental results suggest that PAX9 and MSX1 genes may have a synergistic effect in nonsyndromic congenital edentulous patients. In severely missing teeth, the role of PAX9 may be greater than that of MSX1. The experimental results will help us lay the foundation for further understanding of the disease in the future.

The role of the histone methyltransferase SET domain bifurcated 1 during palatal development

The histone methyltransferase SET domain bifurcated 1 (SETDB1) catalyzes the trimethylation of lysine 9 of histone H3, thereby regulating gene expression. In this study, we used conditional knockout mice, where Setdb1 was deleted only in neural crest cells (Setdb1fl/fl,Wnt1-Cre + mice), to clarify the role of SETDB1 in palatal development. Setdb1fl/fl,Wnt1-Cre + mice died shortly after birth due to a cleft palate with full penetration. Reduced palatal mesenchyme proliferation was seen in Setdb1fl/fl,Wnt1-Cre + mice, which might be a possible mechanism of cleft palate development. Quantitative RT-PCR and in situ hybridization showed that expression of the Pax9, Bmp4, Bmpr1a, Wnt5a, and Fgf10 genes, known to be important for palatal development, were markedly decreased in the palatal mesenchyme of Setdb1fl/fl,Wnt1-Cre + mice. Along with these phenomena, SMAD1/5/9 phosphorylation was decreased by the loss of Setdb1. Our results demonstrated that SETDB1 is indispensable for palatal development partially through its proliferative effect. Taken together with previous reports that PAX9 regulates BMP signaling during palatal development which implies that loss of Setdb1 may be involved in the cleft palate development by decreasing SMAD-dependent BMP signaling through Pax9.

Evolution of the dorsoventral axis in insects: the changing role of Bone Morphogenetic Proteins

Embryonic dorsal-ventral (DV) patterning by Bone Morphogenetic Proteins (BMPs) is a conserved feature of Bilateria, based on graded BMP activity set up by diffusible BMP ligands and Chordin/Sog antagonists. In the fly Drosophila melanogaster BMP function is secondary to patterning by the Toll pathway, suggesting a more restricted role for BMPs in insects. With widespread genome sequencing technologies allied to functional analysis in a growing number of species, recent work has shown that BMP's role in DV patterning relative to Toll varies among insect orders. Further, the role of BMP antagonists to set up BMP gradients is also greatly diversified. Here we review the recent findings concerning the role of BMP in the DV patterning of insects and address the potential aspects that may have co-evolved with BMPs to attain this functional divergence.

A Novel Mutation in a Gene Causes Sclerosteosis in a Family of Mediterranean Origin

Background and Objectives: Sclerostin is an SOST gene product that inhibits osteoblast activity and prevents excessive bone formation by antagonizing the Wnt signaling pathway. Sclerosteosis has been linked to loss of function mutations in the SOST gene. It is a rare autosomal recessive disorder characterized by craniotubular hyperostosis and can lead to fatal cerebellar herniation. Our aim is to describe the clinical and radiological features and the new underlying SOST mutation in a patient with sclerosteosis. Case: A 25-year-old female who was referred to the endocrine clinic for suspected excess growth hormone. The patient complained of headaches, progressive blurred vision, hearing disturbances, increased size of feet, proptosis, and protrusion of the chin. She had normal antenatal history except for syndactyly. Images showed diffuse osseous thickening and high bone mineral density. Biochemical and hormonal tests were normal. Due to progressive compressive optic neuropathy, optic nerve fenestration with decompression hemicraniotomy was performed. Sclerosteosis was suspected due to the predominant craniotubular hyperostosis with syndactyly. Using peripheral leucocyte DNA, genomic sequencing of the SOST gene was performed. This identified a novel deletion homozygous mutation in the SOST gene (c.387delG, p.Asp131ThrfsTer116) which disrupts sclerostin function, causing sclerosteosis. Conclusions: Discovery of the molecular basis of sclerosteosis represents an important advance in the diagnosis and management of this fatal disease.

Wnt signaling pathway inhibitors, sclerostin and DKK-1, correlate with pain and bone pathology in patients with Gaucher disease

Patients with Gaucher disease (GD) have progressive bone involvement that clinically presents with debilitating bone pain, structural bone changes, bone marrow infiltration (BMI), Erlenmeyer (EM) flask deformity, and osteoporosis. Pain is referred by the majority of GD patients and continues to persist despite the type of therapy. The pain in GD is described as chronic deep penetrating pain; however, sometimes, patients experience severe acute pain. The source of bone pain is mainly debated as nociceptive pain secondary to bone pathology or neuropathic or inflammatory origins. Osteocytes constitute a significant source of secreted molecules that coordinate bone remodeling. Osteocyte markers, sclerostin (SOST) and Dickkopf-1 (DKK-1), inactivate the canonical Wnt signaling pathway and lead to the inhibition of bone formation. Thus, circulated sclerostin and DKK-1 are potential biomarkers of skeletal abnormalities. This study aimed to assess the circulating levels of sclerostin and DKK-1 in patients with GD and their correlation with clinical bone pathology parameters: pain, bone mineral density (BMD), and EM deformity. Thirty-nine patients with GD were classified into cohorts based on the presence and severity of bone manifestations. The serum levels of sclerostin and DKK-1 were quantified by enzyme-linked immunosorbent assays. The highest level of sclerostin was measured in GD patients with pain, BMI, and EM deformity. The multiparameter analysis demonstrated that 95% of GD patients with pain, BMI, and EM deformity had increased levels of sclerostin. The majority of patients with elevated sclerostin also have osteopenia or osteoporosis. Moreover, circulating sclerostin level increase with age, and GD patients have elevated sclerostin levels when compared with healthy control from the same age group. Pearson's linear correlation analysis showed a positive correlation between serum DKK-1 and sclerostin in healthy controls and GD patients with normal bone mineral density. However, the balance between sclerostin and DKK-1 waned in GD patients with osteopenia or osteoporosis. In conclusion, the osteocyte marker, sclerostin, when elevated, is associated with bone pain, BMI, and EM flask deformity in GD patients. The altered sclerostin/DKK-1 ratio correlates with the reduction of bone mineral density. These data confirm that the Wnt signaling pathway plays a role in GD-associated bone disease. Sclerostin and bone pain could be used as biomarkers to assess patients with a high risk of BMI and EM flask deformities.

Free-fall landing and interval running have different effects on trabecular bone mass and microarchitecture, serum osteocalcin, biomechanical properties, SOST expression and on osteocyte-related characteristics

The effects of treadmill interval training (IT) and free-fall exercise were evaluated on bone parameters including osteocyte related characteristics. Thirty-eight 4-month-old male Wistar rats were randomly divided into a control (C) group and exercise groups: IT, 10 free-fall impacts/day with a 10-s (FF10) or 20-s interval between drops (FF20), 5 days/week, for 9 weeks. We assessed bone mineral density (BMD); microarchitecture by µCT; mechanical strength by a 3-point bending test; density and occupancy of the osteocyte lacunae by toluidine blue staining; osteocalcin and NTx systemic levels by ELISA; and bone tissue Sost messenger RNA (mRNA) expression by RT-PCR. NTx levels were significantly lower in exercise groups as compared with the C group. In exercise groups the Sost mRNA expression was significantly lower than in C. Tb.N was significantly higher for IT and FF20 compared with the C group. Tb.Sp was significantly lower in FF10 compared with the C group. Both IT and FF20 were associated with higher tibial lacunar density as compared with FF10. compared with FF10, IT fat mass was lower, while tibial osteocyte lacunae occupancy and systemic osteocalcin level were higher. All exercise modes were efficient in reducing bone resorption. Both IT and free-fall impact with appropriate recovery periods, which may be beneficial for bone health and osteocyte-related characteristics. Novelty: Interval training is beneficial for bone mineral density. Exercises decreased both bone resorption and inhibition of bone formation (Sost mRNA). Longer interval recovery time favors osteocyte lacunae density.

Roles of NR5A1 and NR5A2 in the regulation of steroidogenesis by Clock gene and bone morphogenetic proteins by human granulosa cells

The functional role of the transcription factors NR5A1 and NR5A2 and their interaction with Clock gene and bone morphogenetic proteins (BMPs) were investigated in human granulosa KGN cells. Treatment with BMP-15 and GDF-9 suppressed forskolin (FSK)-induced steroidogenesis as shown by the mRNA expression levels of StAR and P450scc but not the mRNA expression level of P450arom. Of interest, treatment with BMP-15 and GDF-9 also suppressed FSK-induced NR5A2 mRNA expression. Treatment with BMP-15 suppressed NR5A2 mRNA and protein expression but increased Clock mRNA and protein expression levels by granulosa cells. The mRNA expression levels of NR5A1, but not those of NR5A2, were positively correlated with the levels of Clock mRNA, while the mRNA levels of Id-1, the target gene of BMP signaling, were positively correlated with those of NR5A1 but not with those of NR5A2. It was also demonstrated that the mRNA expression levels of NR5A1 were positively correlated with those of P450arom and 3βHSD, whereas the mRNA expression level of NR5A2 was correlated with those of StAR and P450scc. Furthermore, inhibition of Clock gene expression by siRNA attenuated the expression of NR5A1, and the mRNA levels of Clock gene were significantly correlated with those of NR5A1. Collectively, the results suggested a novel mechanism by which Clock gene expression induced by BMP-15 is functionally linked to the expression of NR5A1, whereas NR5A2 expression is suppressed by BMP-15 in granulosa cells. The interaction between Clock NR5A1/NR5A2 and BMP-15 is likely to be involved in the fine-tuning of steroidogenesis by ovarian granulosa cells.

Asymmetric requirement of Dpp/BMP morphogen dispersal in the Drosophila wing disc

How morphogen gradients control patterning and growth in developing tissues remains largely unknown due to lack of tools manipulating morphogen gradients. Here, we generate two membrane-tethered protein binders that manipulate different aspects of Decapentaplegic (Dpp), a morphogen required for overall patterning and growth of the Drosophila wing. One is "HA trap" based on a single-chain variable fragment (scFv) against the HA tag that traps HA-Dpp to mainly block its dispersal, the other is "Dpp trap" based on a Designed Ankyrin Repeat Protein (DARPin) against Dpp that traps Dpp to block both its dispersal and signaling. Using these tools, we found that, while posterior patterning and growth require Dpp dispersal, anterior patterning and growth largely proceed without Dpp dispersal. We show that dpp transcriptional refinement from an initially uniform to a localized expression and persistent signaling in transient dpp source cells render the anterior compartment robust against the absence of Dpp dispersal. Furthermore, despite a critical requirement of dpp for the overall wing growth, neither Dpp dispersal nor direct signaling is critical for lateral wing growth after wing pouch specification. These results challenge the long-standing dogma that Dpp dispersal is strictly required to control and coordinate overall wing patterning and growth.

Biphasic Roles of Clock Genes and Bone Morphogenetic Proteins in Gonadotropin Expression by Mouse Gonadotrope Cells

Roles of Clock genes and the bone morphogenetic protein (BMP) system in the regulation of gonadotropin secretion by gonadotropin-releasing hormone (GnRH) were investigated using mouse gonadotropin LβT2 cells. It was found that luteinizing hormone (LH)β mRNA expression level in LβT2 cells changed gradually over time, with LHβ expression being suppressed in the early phase up to 12 h and then elevated in the late phase 24 h after GnRH stimulation. In addition, the mRNA expression levels of Clock genes, including Bmal1, Clock, Per2, and Cry1, also showed temporal changes mimicking the pattern of LHβ expression in the presence and absence of GnRH. Notably, the expression levels of Bmal1 and Clock showed strong positive correlations with LHβ mRNA expression levels. Moreover, a functional link of the ERK signaling of mitogen-activated protein kinases (MAPKs) in the suppression of LHβ mRNA expression, as well as Bmal1 and Clock mRNA expression by GnRH at the early phase, was revealed. Inhibition of Bmal1 and Clock expression using siRNA was involved in the reduction in LHβ mRNA levels in the late phase 24 h after GnRH stimulation. Furthermore, in the presence of BMP-6 and -7, late-phase Bmal1 and LHβ mRNA expression after GnRH stimulation was significantly attenuated. Collectively, the results indicated that LH expression in gonadotrope cells exhibits Bmal1/Clock-dependent fluctuations under the influence of GnRH and that the fluctuations are regulated by ERK and BMPs in the early and late stages, respectively, in a phase-dependent manner after GnRH stimulation.

Tracing the emergence of primordial germ cells from bilaminar disc rabbit embryos and pluripotent stem cells

Rabbit embryos develop as bilaminar discs at gastrulation as in humans and most other mammals, whereas rodents develop as egg cylinders. Primordial germ cells (PGCs) appear to originate during gastrulation according to many systematic studies on mammalian embryos. Here, we show that rabbit PGC (rbPGC) specification occurs at the posterior epiblast at the onset of gastrulation. Using newly derived rabbit pluripotent stem cells, we show robust and rapid induction of rbPGC-like cells in vitro with WNT and BMP morphogens, which reveals SOX17 as the critical regulator of rbPGC fate as in several non-rodent mammals. We posit that development as a bilaminar disc is a crucial determinant of the PGC regulators, regardless of the highly diverse development of extraembryonic tissues, including the amnion. We propose that investigations on rabbits with short gestation, large litters, and where gastrulation precedes implantation can contribute significantly to advances in early mammalian development.

Bone Morphogenetic Protein 2/4 in Mollusk, Haliotis diversicolor: Its Expression and Osteoinductive Function In Vitro

Bone morphogenetic proteins (BMPs), which are members of the superfamily of transforming growth factor-β (TGF-β), are known both in vitro and in vivo for their osteoinduction properties on the osteoblastic cells. Its role in the mollusk shell formation has also been gradually established. Using Haliotis diversicolor as a model, we characterized the HdBMP2/4 gene in the mantle tissue and showed its expression in the outer fold epithelium (particularly at the periostracal groove) the epithelial site which is involved in shell formation, both prismatic and nacreous layers. Shell notching experiments following gene analysis by qPCR revealed the upregulation of the HdBMP2/4 gene up to 3.2-fold than that of the control animals. In vitro treatments of the preosteoblastic cells, MC3T3-E1 with HdBMP2/4 synthetic peptide demonstrated the enhanced effect of many osteogenic genes that are known to regulate bone and shell biomineralization including ALP, Runx2, and OCN with 2-4 fold-change throughout 14 days of culture. In addition, the increased deposition of calcium-based mineral (as assessed by Alizarin red staining) of the treated cells was comparable to the ascorbic acid (Vit C) + glycerophosphate positive control which revealed the enhanced effect of HdBMP2/4 peptide on matrix biomineralization of the preosteoblastic cells. In conclusion, these results indicated the presence of the HdBMP2/4 gene in the mantle tissue at the site involved in shell formation and the effect of the HdBMP2/4 knuckle epitope peptide in osteoinduction in vitro.

Heterozygous loss-of-function variants significantly expand the phenotypes associated with loss of GDF11

PURPOSE

Growth differentiation factor 11 (GDF11) is a key signaling protein required for proper development of many organ systems. Only one prior study has associated an inherited GDF11 variant with a dominant human disease in a family with variable craniofacial and vertebral abnormalities. Here, we expand the phenotypic spectrum associated with GDF11 variants and document the nature of the variants.

METHODS

We present a cohort of six probands with de novo and inherited nonsense/frameshift (4/6 patients) and missense (2/6) variants in GDF11. We generated gdf11 mutant zebrafish to model loss of gdf11 phenotypes and used an overexpression screen in Drosophila to test variant functionality.

RESULTS

Patients with variants in GDF11 presented with craniofacial (5/6), vertebral (5/6), neurological (6/6), visual (4/6), cardiac (3/6), auditory (3/6), and connective tissue abnormalities (3/6). gdf11 mutant zebrafish show craniofacial abnormalities and body segmentation defects that match some patient phenotypes. Expression of the patients' variants in the fly showed that one nonsense variant in GDF11 is a severe loss-of-function (LOF) allele whereas the missense variants in our cohort are partial LOF variants.

CONCLUSION

GDF11 is needed for human development, particularly neuronal development, and LOF GDF11 alleles can affect the development of numerous organs and tissues.