The presence of PHOSPHO1 in matrix vesicles and its developmental expression prior to skeletal mineralization

PHOSPHO1 is a phosphoethanolamine/phosphocholine phosphatase that has previously been implicated in generating inorganic phosphate (Pi) for matrix mineralization. In this study, we have investigated PHOSPHO1 mRNA expression during embryonic development in the chick. Whole-mount in situ hybridization indicated that PHOSPHO1 expression occurred prior to E6.5 and was initially restricted to the bone collar within the mid-shaft of the diaphysis of long bones but by E11.5 expression was observed over the entire length of the diaphysis. Alcian blue/alizarin red staining revealed that PHOSPHO1 expression seen in the primary regions of ossification preceded the deposition of mineral, suggesting that it is involved in the initial events of mineral formation. We isolated MVs from growth plate chondrocytes and confirmed the presence of high levels of PHOSPHO1 by immunoblotting. Expression of PHOSPHO1, like TNAP activity, was found to be up-regulated in MVs isolated from chondrocytes induced to differentiate by the addition of ascorbic acid. This suggests that both enzymes may be regulated by similar mechanisms. These studies provide for the first time direct evidence that PHOSPHO1 is present in MVs, and its developmental expression pattern is consistent with a role in the early stages of matrix mineralization

Identification of genes downstream of the Shh signalling in the developing chick wing and syn-expressed with <i>Hoxd13</i> using microarray and 3D computational analysis

Sonic hedgehog (Shh) signalling by the polarizing region at the posterior margin of the chick wing bud is pivotal in patterning the digits but apart from a few key downstream genes, such as Hoxd13, which is expressed in the posterior region of the wing that gives rise to the digits, the genes that mediate the response to Shh signalling are not known. To find genes that are co-expressed with Hoxd13 in the posterior of chick wing buds and regulated in the same way, we used microarrays to compare gene expression between anterior and posterior thirds of wing buds from normal chick embryos and from polydactylous talpid mutant chick embryos, which have defective Shh signalling due to lack of primary cilia. We identified 1070 differentially expressed gene transcripts, which were then clustered. Two clusters contained genes predominantly expressed in posterior thirds of normal wing buds; in one cluster, genes including Hoxd13, were expressed at high levels in anterior and posterior thirds in talpid wing buds, in the other cluster, genes including Ptc1, were expressed at low levels in anterior and posterior thirds in talpid wing buds. Expression patterns of genes in these two clusters were validated in normal and talpid mutant wing buds by in situ hybridisation and demonstrated to be responsive to application of Shh. Expression of several genes in the Hoxd13 cluster was also shown to be responsive to manipulation of protein kinase A (PKA) activity, thus demonstrating regulation by Gli repression. Genes in the Hoxd13 cluster were then sub-clustered by computational comparison of 3D expression patterns in normal wing buds to produce syn-expression groups. Hoxd13 and Sall1 are syn-expressed in the posterior region of early chick wing buds together with 6 novel genes which are likely to be functionally related and represent secondary targets of Shh signalling. Other groups of syn-expressed genes were also identified, including a group of genes involved in vascularisation

Loss of cilia causes embryonic lung hypoplasia, liver fibrosis and cholestasis in the talpid3 ciliopathy mutant

Sonic hedgehog plays an essential role in maintaining hepatoblasts in a proliferative non-differentiating state during embryogenesis. Transduction of the Hedgehog signaling pathway is dependent on the presence of functional primary cilia and hepatoblasts, therefore, must require primary cilia for normal function. In congenital syndromes in which cilia are absent or non-functional (ciliopathies) hepatorenal fibrocystic disease is common and primarily characterized by ductal plate malformations which underlie the formation of liver cysts, as well as less commonly, by hepatic fibrosis, although a role for abnormal Hedgehog signal transduction has not been implicated in these phenotypes. We have examined liver, lung and rib development in the talpid(3) chicken mutant, a ciliopathy model in which abnormal Hedgehog signaling is well characterized. We find that the talpid(3) phenotype closely models that of human short-rib polydactyly syndromes which are caused by the loss of cilia, and exhibit hypoplastic lungs and liver failure. Through an analysis of liver and lung development in the talpid(3) chicken, we propose that cilia in the liver are essential for the transduction of Hedgehog signaling during hepatic development. The talpid(3) chicken represents a useful resource in furthering our understanding of the pathology of ciliopathies beyond the treatment of thoracic insufficiency as well as generating insights into the role Hedgehog signaling in hepatic development

Synthesis and Antiviral Activity of Fatty Acyl Conjugates of Remdesivir Against Severe Acute Respiratory Syndrome Coronavirus 2 and Ebola Virus

We report here the synthesis, purification, and characterization of mono- and di-fatty acyl conjugates of remdesivir (RDV) and their in vitro antiviral activity against SAR-CoV-2, an Ebola virus transcription- and replication-competent virus-like particle (trVLP) system, and infectious Ebola virus. The most potent monofatty acyl conjugate was 4b, containing a 4-oxatetradecanolyl at the 3′ position. Monofatty acyl conjugates, 3′-O-tetradecanoyl (4a) (IC50(VeroE6) = 2.3 μM; IC50(Calu3) = 0.24 μM), 3′-O-4-oxatetradodecanoyl (4b) (IC50(VeroE6) = 2.0 μM; IC50(Calu3) = 0.18 μM), and 3′-O-(12-ethylthiododecanoyl) (4e) (IC50(VeroE6) = 2.4 μM; IC50(Calu3) = 0.25 μM) derivatives exhibited less activity than RDV (IC50(VeroE6) = 0.85 μM; IC50(Calu3) = 0.06 μM) in both VeroE6 and Calu3 cells. Difatty acylation led to a significant reduction in the antiviral activity of RDV (as shown in conjugates 5a and 5b) against SARS-CoV-2 when compared with monofatty acylation (3a-e and 4a-e). About 77.9% of 4c remained intact after 4 h incubation with human plasma while only 47% of parent RDV was observed at the 2 h time point. The results clearly indicate the effectiveness of fatty acylation to improve the half-life of RDV. The antiviral activities of a number of monofatty acyl conjugates of RDV, such as 3b, 3e, and 4b, were comparable with RDV against the Ebola trVLP system. Meanwhile, the corresponding physical mixtures of RDV and fatty acids 6a and 6b showed 1.6 to 2.2 times less antiviral activity than the corresponding conjugates, 4a and 4c, respectively, against SARS-CoV-2 in VeroE6 cells. A significant reduction in viral RNA synthesis was observed for selected compounds 3a and 4b consistent with the IC50 results. These studies indicate the potential of these compounds as long-acting antiviral agents or prodrugs of RDV

The chicken talpid3 gene encodes a novel protein that is essential for hedgehog signaling

Talpid(3) is a classical chicken mutant with abnormal limb patterning and malformations in other regions of the embryo known to depend on Hedgehog signaling. We combined the ease of manipulating chicken embryos with emerging knowledge of the chicken genome to reveal directly the basis of defective Hedgehog signal transduction in talpid(3) embryos and to identify the talpid(3) gene. We show in several regions of the embryo that the talpid(3) phenotype is completely ligand independent and demonstrate for the first time that talpid(3) is absolutely required for the function of both Gli repressor and activator in the intracellular Hedgehog pathway. We map the talpid(3) locus to chromosome 5 and find a frameshift mutation in a KIAA0586 ortholog (ENSGALG00000012025), a gene not previously attributed with any known function. We show a direct causal link between KIAA0586 and the mutant phenotype by rescue experiments. KIAA0586 encodes a novel protein, apparently specific to vertebrates, that localizes to the cytoplasm. We show that Gli3 processing is abnormal in talpid(3) mutant cells but that Gli3 can still translocate to the nucleus. These results suggest that the talpid(3) protein operates in the cytoplasm to regulate the activity of both Gli repressor and activator proteins

A variant in LIN28B is associated with 2D:4D finger-length ratio, a putative retrospective biomarker of prenatal testosterone exposure

The ratio of the lengths of an individual's second to fourth digit (2D:4D) is commonly used as a noninvasive retrospective biomarker for prenatal androgen exposure. In order to identify the genetic determinants of 2D:4D, we applied a genome-wide association approach to 1507 11-year-old children from the Avon Longitudinal Study of Parents and Children (ALSPAC) in whom 2D:4D ratio had been measured, as well as a sample of 1382 12- to 16-year-olds from the Brisbane Adolescent Twin Study. A meta-analysis of the two scans identified a single variant in the LIN28B gene that was strongly associated with 2D:4D (rs314277: p = 4.1 108) and was subsequently independently replicated in an additional 3659 children from the ALSPAC cohort (p = 1.53 106). The minor allele of the rs314277 variant has previously been linked to increased height and delayed age at menarche, but in our study it was associated with increased 2D:4D in the direction opposite to that of previous reports on the correlation between 2D:4D and age at menarche. Our findings call into question the validity of 2D:4D as a simplistic retrospective biomarker for prenatal testosterone exposure

TALPID3/KIAA0586 Regulates Multiple Aspects of Neuromuscular Patterning During Gastrointestinal Development in Animal Models and Human

TALPID3/KIAA0586 is an evolutionary conserved protein, which plays an essential role in protein trafficking. Its role during gastrointestinal (GI) and enteric nervous system (ENS) development has not been studied previously. Here, we analyzed chicken, mouse and human embryonic GI tissues with TALPID3 mutations. The GI tract of TALPID3 chicken embryos was shortened and malformed. Histologically, the gut smooth muscle was mispatterned and enteric neural crest cells were scattered throughout the gut wall. Analysis of the Hedgehog pathway and gut extracellular matrix provided causative reasons for these defects. Interestingly, chicken intra-species grafting experiments and a conditional knockout mouse model showed that ENS formation did not require TALPID3, but was dependent on correct environmental cues. Surprisingly, the lack of TALPID3 in enteric neural crest cells (ENCC) affected smooth muscle and epithelial development in a non-cell-autonomous manner. Analysis of human gut fetal tissues with a KIAA0586 mutation showed strikingly similar findings compared to the animal models demonstrating conservation of TALPID3 and its necessary role in human GI tract development and patterning

Inhibition of PHOSPHO1 activity results in impaired skeletal mineralization during limb development of the chick

PHOSPHO1 is a bone specific phosphatase implicated in the initiation of inorganic phosphate generation for matrix mineralization. The control of mineralization is attributed to the actions of tissue-non specific alkaline phosphatase (TNAP). However, matrix vesicles (MVs) containing apatite crystals are present in patients with hypophosphatasia as well as TNAP null (Akp2(-/-)) mice. It is therefore likely that other phosphatases work with TNAP to regulate matrix mineralization. Although PHOSPHO1 and TNAP expression is associated with MVs, it is not known if PHOSPHO1 and TNAP are co-expressed during the early stages of limb development. Furthermore the functional in-vivo role of PHOSPHO1 in matrix mineralization has yet to be established. Here, we studied the temporal expression and functional role of PHOSPHO1 within chick limb bud mesenchymal micromass cultures and also in wild-type and talpid(3) chick mutants. These mutants are characterized by defective hedgehog signalling and the absence of endochondral mineralization. The ability of in-vitro micromass cultures to differentiate and mineralize their matrix was temporally associated with increased expression of PHOSPHO1 and TNAP. Comparable changes in expression were noted in developing embryonic legs (developmental stages 23–36HH). Micromass cultures treated with lansoprazole, a small-molecule inhibitor of PHOSPHO1 activity, or FGF2, an inhibitor of chondrocyte differentiation, resulted in reduced alizarin red staining (P<0.05). FGF2 treatment also caused a reduction in PHOSPHO1 (P<0.001) and TNAP (P<0.001) expression. Expression analysis by whole mount RNA in-situ hybridization, correlated with qPCR micromass data and demonstrated the existence of a tightly regulated pattern of Phospho1 and Tnap expression which precedes mineralization. Treatment of developing embryos for 5-days with lansoprazole completely inhibited mineralization of all leg and wing long bones as assessed by alcian blue/alizarin red staining. Furthermore, long bones of the talpid(3) chick mutant did not express Phospho1 or Tnap whereas flat bones mineralized normally and expressed both phosphatases. In conclusion, this study has disclosed that PHOSPHO1 expression mirrors that of TNAP during embryonic bone development and that PHOSPHO1 contributes to bone mineralization in developing chick long bones