Role of axonal guidance factor netrin-1 in human placental vascular growth

Possible Role of Netrin-1/Deleted in Colorectal Cancer/Vascular Endothelial Growth Factor Signaling Pathway in the Pathogenesis of Placenta Accreta Spectrum: A Case-control Study

SUMMARY

Netrin-1, an epithelial-secreted protein, plays a key role in placental formation through the promotion of cytotrophoblast proliferation and placental vascular development. These effects are mediated through several receptors, including the deleted in colorectal cancer (DCC) receptor. Placenta accreta spectrum (PAS) is an exaggerated trophoblastic invasion into the uterine myometrium. The exact etiology is unknown, but it is believed that increased trophoblastic invasion, defect decidualization, and/or abnormal angiogenesis might play a role. Our study aimed to investigate the suggested role of macrophage-induced netrin-1/DCC/vascular endothelial growth factor (VEGF) signaling in PAS pathogenesis. A total of 29 women with PAS (as cases) and 29 women with normal pregnancies (as controls) were enrolled in the study. At delivery, placental tissues of both groups were collected and processed for the evaluation of placental netrin-1 level by enzyme-linked immunoassay technique and immunohistochemical analysis of tissue DCC receptor. Placental tissue netrin-1 level of PAS cases showed a statistically significantly higher value than those in the normal group. Significant overexpression of DCC receptors, VEGF, and enhanced macrophage recruitment was noted in PAS cases in comparison to the normal placenta. Macrophage-induced netrin-1/DCC/VEGF signaling might be involved in PAS pathogenesis through the enhancement of trophoblastic angiogenesis.

Fetal growth delay caused by loss of non-canonical imprinting is resolved late in pregnancy and culminates in offspring overgrowth

Germline epigenetic programming, including genomic imprinting, substantially influences offspring development. Polycomb Repressive Complex 2 (PRC2) plays an important role in Histone 3 Lysine 27 trimethylation (H3K27me3)-dependent imprinting, loss of which leads to growth and developmental changes in mouse offspring. In this study, we show that offspring from mouse oocytes lacking the PRC2 protein Embryonic Ectoderm Development (EED) were initially developmentally delayed, characterised by low blastocyst cell counts and substantial growth delay in mid-gestation embryos. This initial developmental delay was resolved as offspring underwent accelerated fetal development and growth in late gestation resulting in offspring that were similar stage and weight to controls at birth. The accelerated development and growth in offspring from Eed-null oocytes was associated with remodelling of the placenta, which involved an increase in fetal and maternal tissue size, conspicuous expansion of the glycogen-enriched cell population, and delayed parturition. Despite placental remodelling and accelerated offspring fetal growth and development, placental efficiency, and fetal blood glucose levels were low, and the fetal blood metabolome was unchanged. Moreover, while expression of the H3K27me3-imprinted gene and amino acid transporter Slc38a4 was increased, fetal blood levels of individual amino acids were similar to controls, indicating that placental amino acid transport was not enhanced. Genome-wide analyses identified extensive transcriptional dysregulation and DNA methylation changes in affected placentas, including a range of imprinted and non-imprinted genes. Together, while deletion of Eed in growing oocytes resulted in fetal growth and developmental delay and placental hyperplasia, our data indicate a remarkable capacity for offspring fetal growth to be normalised despite inefficient placental function and the loss of H3K27me3-dependent genomic imprinting.

A genome-wide single nucleotide polymorphism and copy number variation analysis for number of piglets born alive

Background

In this study we integrated the CNV (copy number variation) and WssGWAS (weighted single-step approach for genome-wide association) analyses to increase the knowledge about number of piglets born alive, an economically important reproductive trait with significant impact on production efficiency of pigs.

Results

A total of 3892 samples were genotyped with the Porcine SNP80 BeadChip. After quality control, a total of 57,962 high-quality SNPs from 3520 Duroc pigs were retained. The PennCNV algorithm identified 46,118 CNVs, which were aggregated by overlapping in 425 CNV regions (CNVRs) ranging from 2.5 Kb to 9718.4 Kb and covering 197 Mb (~ 7.01%) of the pig autosomal genome. The WssGWAS identified 16 genomic regions explaining more than 1% of the additive genetic variance for number of piglets born alive. The overlap between CNVR and WssGWAS analyses identified common regions on SSC2 (4.2–5.2 Mb), SSC3 (3.9–4.9 Mb), SSC12 (56.6–57.6 Mb), and SSC17 (17.3–18.3 Mb). Those regions are known for harboring important causative variants for pig reproductive traits based on their crucial functions in fertilization, development of gametes and embryos. Functional analysis by the Panther software identified 13 gene ontology biological processes significantly represented in this study such as reproduction, developmental process, cellular component organization or biogenesis, and immune system process, which plays relevant roles in swine reproductive traits.

Conclusion

Our research helps to improve the understanding of the genetic architecture of number of piglets born alive, given that the combination of GWAS and CNV analyses allows for a more efficient identification of the genomic regions and biological processes associated with this trait in Duroc pigs. Pig breeding programs could potentially benefit from a more accurate discovery of important genomic regions.

Electronic supplementary material

The online version of this article (10.1186/s12864-019-5687-0) contains supplementary material, which is available to authorized users.

Netrin-1 as a potential target for metastatic cancer: focus on colorectal cancer

Despite advanced screening technology and cancer treatments available today, metastasis remains an ongoing major cause of cancer-related deaths worldwide. Typically, colorectal cancer is one of the cancers treatable by surgery in conjunction with chemotherapy when it is detected at an early stage. However, it still ranks as the second highest modality and mortality of cancer types in western countries, and this is mostly due to a recurrence of metastatic colorectal cancer post-resection of the primary malignancy. Colorectal cancer metastases predominantly occur in the liver and lung, and yet the molecular mechanisms that regulate these organ-specific colorectal cancer metastases are largely unknown. Therefore, the identification of any critical molecule, which triggers malignancy in colorectal cancer, would be an excellent target for treatment. Netrin-1 was initially discovered as a chemotropic neuronal guidance molecule, and has been marked as a regulator for many cancers including colorectal cancer. Here, we summarise key findings of the role of netrin-1 intrinsic to colorectal cancer cells, extrinsic to the tumour microenvironment and angiogenesis, and consequently, we evaluate netrin-1 as a potential target molecule for metastasis.

Comparison of two in vitro angiogenesis assays for evaluating the effects of netrin-1 on tube formation

Netrin-1 is a neural guidance cue that also regulates vascular development. Controversial results, however, have been obtained concerning the roles of netrin-1 in vascular development both in vivo and in vitro. In the present study, two in vitro angiogenesis assays were compared to evaluate the effects of netrin-1 secreted by retrovirally transduced melanoma cells (Mel2a-netrin1) on tube formation. The results showed that there was no obvious difference in tube formation induced by conditioned media (CM) from the control, Mel2a-netrin1 and Mel2a cells in a matrigel assay. The results of another in vitro assay, in which endothelial cells were co-cultured with human fibroblasts, however, showed that Mel2a-netrin1 CM inhibited the tube formation, supposedly through blocking the elongation and coalescence of human umbilical vein endothelial cells (HUVECs). These results confirmed that the matrigel assay is not able to demonstrate the anti-angiogenic roles of netrin-1.

Netrins and their roles in placental angiogenesis

Netrins, a family of laminin-related proteins, were originally identified as axonal guidance molecules. Subsequently, netrins were found to modulate various biological processes including morphogenesis, tumorogenesis, adhesion, and, recently, angiogenesis. In human placenta, the most vascularized organ, the presence of netrins has also been reported. Recent studies demonstrated the involvement of netrins in the regulation of placental angiogenesis. In this review we focused on the role of netrins in human placental angiogenesis. Among all netrins examined, netrin-4 and netrin-1 have been found to be either pro- or antiangiogenic factors. These opposite effects appear to be related to the endothelial cell phenotype studied and seem also to depend on the receptor type to which netrin binds, that is, the canonical receptor member of the DCC family, the members of the UNC5 family, or the noncanonical receptor members of the integrin family or DSCAM.