The MexTAg collaborative cross: host genetics affects asbestos related disease latency, but has little influence once tumours develop.

Objectives: This study combines two innovative mouse models in a major gene discovery project to assess the influence of host genetics on asbestos related disease (ARD). Conventional genetics studies provided evidence that some susceptibility to mesothelioma is genetic. However, the identification of host modifier genes, the roles they may play, and whether they contribute to disease susceptibility remain unknown. Here we report a study designed to rapidly identify genes associated with mesothelioma susceptibility by combining the Collaborative Cross (CC) resource with the well-characterised MexTAg mesothelioma mouse model. Methods: The CC is a powerful mouse resource that harnesses over 90% of common genetic variation in the mouse species, allowing rapid identification of genes mediating complex traits. MexTAg mice rapidly, uniformly, and predictably develop mesothelioma, but only after asbestos exposure. To assess the influence of host genetics on ARD, we crossed 72 genetically distinct CC mouse strains with MexTAg mice and exposed the resulting CC-MexTAg (CCMT) progeny to asbestos and monitored them for traits including overall survival, the time to ARD onset (latency), the time between ARD onset and euthanasia (disease progression) and ascites volume. We identified phenotype-specific modifier genes associated with these traits and we validated the role of human orthologues in asbestos-induced carcinogenesis using human mesothelioma datasets. Results: We generated 72 genetically distinct CCMT strains and exposed their progeny (2,562 in total) to asbestos. Reflecting the genetic diversity of the CC, there was considerable variation in overall survival and disease latency. Surprisingly, however, there was no variation in disease progression, demonstrating that host genetic factors do have a significant influence during disease latency but have a limited role once disease is established. Quantitative trait loci (QTL) affecting ARD survival/latency were identified on chromosomes 6, 12 and X. Of the 97-protein coding candidate modifier genes that spanned these QTL, eight genes (CPED1, ORS1, NDUFA1, HS1BP3, IL13RA1, LSM8, TES and TSPAN12) were found to significantly affect outcome in both CCMT and human mesothelioma datasets. Conclusion: Host genetic factors affect susceptibility to development of asbestos associated disease. However, following mesothelioma establishment, genetic variation in molecular or immunological mechanisms did not affect disease progression. Identification of multiple candidate modifier genes and their human homologues with known associations in other advanced stage or metastatic cancers highlights the complexity of ARD and may provide a pathway to identify novel therapeutic targets.

N-glycosylation of serum proteins in adult type 1 diabetes mellitus exposes further changes compared to children at the disease onset.

OBJECTIVE: Previously we have shown that plasma protein N-glycosylation is changed in children at the onset of type 1 diabetes. In this study, we aim to identify N-glycan changes in adults with T1DM, compare them to those in children, and investigate their associations with disease duration, complications, glycaemic status, and smoking. METHODS: Serum protein N-glycans from 200 adults with type 1 diabetes and 298 healthy controls were analysed using ultra-high performance liquid chromatography and divided into 39 directly measured glycan groups from which 16 derived traits were calculated. RESULTS: Compared to healthy controls, subjects with type 1 diabetes showed differences in 19 glycan groups and a decrease in monogalactosylated, an increase in digalactosylated, monosialylated, and antennary fucosylated derived traits, from which changes in monogalactosylation and seven directly measured traits overlapped with previously reported in children. Changes in four directly measured and two derived traits previously seen in children were not detected in adults. HbA1c was positively associated with sialylated and highly branched structures, whereas N-glycome was not influenced by disease duration or diabetic complications. CONCLUSIONS: Our results suggest potential N-glycome involvement in different stages of type 1 diabetes, including processes underlying its development, the disease itself, as well as those occurring after disease establishment.

The first comprehensive database of germline pathogenic variants in East Asian cancer patients.

Pathogenic germline variants in cancer-associated genes are risk factors for cancer predisposition. However, systematic mining and summarizing of cancer pathogenic or likely pathogenic variants has not been performed for people of East Asian descent. This study aimed to investigate publicly available data to identify germline variants in East Asian cancer cohorts and compare them to variants in Caucasian cancer cohorts. Based on the data we retrieved, we built a comprehensive database, named COGVIC (Catalog of Germline Variants in Cancer). A total of 233 variants in the East Asian population were identified. The majority (87%) of genes with cancer-associated variants were not shared between the East Asian and Caucasian cohorts. This included pathogenic variants in BRCA2. Our study summarized the prevalence of germline variants in East Asian cancer cohorts and provides an easy-to-use online tool to explore germline mutations related to cancer susceptibility. DATABASE URL: http://www.cogvic.vip/.

Identification of Genetic Variants Associated with Sex-Specific Lung-Cancer Risk.

BACKGROUND: The incidence of lung cancer differs between men and women, suggesting the potential role of sex-specific influences in susceptibility to this cancer. While behavioural differences may account for some of the risk, another possibility is that X chromosome susceptibility genes may have an effect. Little is known about genetic variants on the X chromosome that contribute to sex-specific lung-cancer risk, so we investigated this in a previously characterized cohort. METHODS: We conducted a genetic association reanalysis of 518 lung cancer patients and 844 controls to test for lung cancer susceptibility variants on the X chromosome. Annotated gene expression, co-expression analysis, pathway, and immune infiltration analyses were also performed. RESULTS: 24 SNPs were identified as significantly associated with male, but not female, lung cancer cases. These resided in blocks near the annotated genes DMD, PTCHD1-AS, and AL008633.1. Of these, DMD was differentially expressed in lung cancer cases curated in The Cancer Genome Atlas. A functional enrichment and a KEGG pathway analysis of co-expressed genes revealed that differences in immune function could play a role in sex-specific susceptibility. CONCLUSIONS: Our analyses identified potential genetic variants associated with sex-specific lung cancer risk. Integrating GWAS and RNA-sequencing data revealed potential targets for lung cancer prevention.

How to Better Understand the Influence of Host Genetics on Developing an Effective Immune Response to Thoracic Cancers.

Thoracic cancers pose a significant global health burden. Immune checkpoint blockade therapies have improved treatment outcomes, but durable responses remain limited. Understanding how the host immune system interacts with a developing tumor is essential for the rational development of improved treatments for thoracic malignancies. Recent technical advances have improved our understanding of the mutational burden of cancer cells and changes in cancer-specific gene expression, providing a detailed understanding of the complex biology underpinning tumor-host interactions. While there has been much focus on the genetic alterations associated with cancer cells and how they may impact treatment outcomes, how host genetics affects cancer development is also critical and will greatly determine treatment response. Genome-wide association studies (GWAS) have identified genetic variants associated with cancer predisposition. This approach has successfully identified host genetic risk factors associated with common thoracic cancers like lung cancer, but is less effective for rare cancers like malignant mesothelioma. To assess how host genetics impacts rare thoracic cancers, we used the Collaborative Cross (CC); a powerful murine genetic resource designed to maximize genetic diversity and rapidly identify genes associated with any biological trait. We are using the CC in conjunction with our asbestos-induced MexTAg mouse model, to identify host genes associated with mesothelioma development. Once genes that moderate tumor development and progression are known, human homologues can be identified and human datasets interrogated to validate their association with disease outcome. Furthermore, our CC-MexTAg animal model enables in-depth study of the tumor microenvironment, allowing the correlation of immune cell infiltration and gene expression signatures with disease development. This strategy provides a detailed picture of the underlying biological pathways associated with mesothelioma susceptibility and progression; knowledge that is crucial for the rational development of new diagnostic and therapeutic strategies. Here we discuss the influence of host genetics on developing an effective immune response to thoracic cancers. We highlight current knowledge gaps, and with a focus on mesothelioma, describe the development and application of the CC-MexTAg to overcome limitations and illustrate how the knowledge gained from this unique study will inform the rational design of future treatments of mesothelioma.

Novel spontaneous myelodysplastic syndrome mouse model.

Background: Myelodysplastic syndrome (MDS) is a group of disorders involving hemopoietic dysfunction leading to leukemia. Although recently progress has been made in identifying underlying genetic mutations, many questions still remain. Animal models of MDS have been produced by introduction of specific mutations. However, there is no spontaneous mouse model of MDS, and an animal model to simulate natural MDS pathogenesis is urgently needed. Methods: In characterizing the genetically diverse mouse strains of the Collaborative Cross (CC) we observed that one, designated JUN, had abnormal hematological traits. This strain was thus further analyzed for phenotypic and pathological identification, comparing the changes in each cell population in peripheral blood and in bone marrow. Results: In a specific-pathogen free environment, mice of the JUN strain are relatively thin, with healthy appearance. However, in a conventional environment, they become lethargic, develop wrinkled yellow hair, have loose and light stools, and are prone to infections. We found that the mice were cytopenic, which was due to abnormal differentiation of multipotent bone marrow progenitor cells. These are common characteristics of MDS. Conclusions: A mouse strain, JUN, was found displaying spontaneous myelodysplastic syndrome. This strain has the advantage over existing models in that it develops MDS spontaneously and is more similar to human MDS than genetically modified mouse models. JUN mice will be an important tool for pathogenesis research of MDS and for evaluation of new drugs and treatments.

Higher frequency of vertebrate-infecting viruses in the gut of infants born to mothers with type 1 diabetes.

BACKGROUND: Microbial exposures in utero and early life shape the infant microbiome, which can profoundly impact on health. Compared to the bacterial microbiome, very little is known about the virome. We set out to characterize longitudinal changes in the gut virome of healthy infants born to mothers with or without type 1 diabetes using comprehensive virome capture sequencing. METHODS: Healthy infants were selected from Environmental Determinants of Islet Autoimmunity (ENDIA), a prospective cohort of Australian children with a first-degree relative with type 1 diabetes, followed from pregnancy. Fecal specimens were collected three-monthly in the first year of life. RESULTS: Among 25 infants (44% born to mothers with type 1 diabetes) at least one virus was detected in 65% (65/100) of samples and 96% (24/25) of infants during the first year of life. In total, 26 genera of viruses were identified and >150 viruses were differentially abundant between the gut of infants with a mother with type 1 diabetes vs without. Positivity for any virus was associated with maternal type 1 diabetes and older infant age. Enterovirus was associated with older infant age and maternal smoking. CONCLUSIONS: We demonstrate a distinct gut virome profile in infants of mothers with type 1 diabetes, which may influence health outcomes later in life. Higher prevalence and greater number of viruses observed compared to previous studies suggests significant underrepresentation in existing virome datasets, arising most likely from less sensitive techniques used in data acquisition.

The impact of angiogenesis inhibitors on survival of patients with small cell lung cancer.

BACKGROUND: Small cell lung cancer (SCLC) is a highly invasive and lethal neuroendocrine tumor. Antiangiogenic drugs have been reported in the treatment of SCLC. We aimed to provide a comprehensive evaluation of the impact of angiogenic inhibitors on SCLC survival using network meta-analysis. METHODS: The impact of five angiogenesis inhibitors, that is, vandetanib (Van), bevacizumab (Bev), Rh-endostatin (End), sunitinib (Sun), and thalidomide (Tha), on progression-free survival (PFS) and overall survival (OS) was evaluated by conducting a network meta-analysis. RNA sequencing data were downloaded from publicly available databases. RESULTS: Nine phase II and III randomized controlled trials (RCTs), that involved 1599 participants, that investigated angiogenesis inhibitors in the treatment of SCLC were included in this meta-analysis. Sun and Bev achieved better PFS than Tha (Bev VS. Tha, HR = 0.88, 95% CI: 0.79-0.98, Sun VS. Tha, HR = 0.80, 95% CI: 0.65-1.00). Moreover, Sun and Bev were superior to placebo in terms of PFS (Bev VS. Placebo, HR = 0.89, 95%CI: 0.81-0.97, Sun VS. Placebo, HR = 0.81, 95% CI: 0.66-1.00). Based on this study, we found no significant difference of OS of SCLC. The angiogenesis pathway and expression of target genes were globally deactivated in SCLC tissue. CONCLUSION: Results of this network meta-analysis indicate that the PFS outcome of SCLC with Sun or Bev drugs is superior to that of Tha. The improved therapeutic impact of angiogenesis inhibitors on SCLC needs more evidence, such as long-term observation in clinical trials, to be validated.

Different genetic mechanisms mediate spontaneous versus UVR-induced malignant melanoma.

Genetic variation conferring resistance and susceptibility to carcinogen-induced tumorigenesis is frequently studied in mice. We have now turned this idea to melanoma using the collaborative cross (CC), a resource of mouse strains designed to discover genes for complex diseases. We studied melanoma-prone transgenic progeny across seventy CC genetic backgrounds. We mapped a strong quantitative trait locus for rapid onset spontaneous melanoma onset to Prkdc, a gene involved in detection and repair of DNA damage. In contrast, rapid onset UVR-induced melanoma was linked to the ribosomal subunit gene Rrp15. Ribosome biogenesis was upregulated in skin shortly after UVR exposure. Mechanistically, variation in the 'usual suspects' by which UVR may exacerbate melanoma, defective DNA repair, melanocyte proliferation, or inflammatory cell infiltration, did not explain melanoma susceptibility or resistance across the CC. Instead, events occurring soon after exposure, such as dysregulation of ribosome function, which alters many aspects of cellular metabolism, may be important.

Profiling and genetic control of the murine immunoglobulin G glycome.

Immunoglobulin G (IgG) glycosylation is essential for function of the immune system, but the genetic and environmental factors that underlie its inter-individual variability are not well defined. The Collaborative Cross (CC) genetic resource harnesses over 90% of the common genetic variation of the mouse. By analyzing the IgG glycome composition of 95 CC strains, we made several important observations: (i) glycome variation between mouse strains was higher than between individual humans, despite all mice having the same environmental influences; (ii) five genetic loci were found to be associated with murine IgG glycosylation; (iii) variants outside traditional glycosylation site motifs affected glycome variation; (iv) bisecting N-acetylglucosamine (GlcNAc) was produced by several strains although most previous studies have reported the absence of glycans containing the bisecting GlcNAc on murine IgGs; and (v) common laboratory mouse strains are not optimal animal models for studying effects of glycosylation on IgG function.

Electrokinetic potential-stabilization by bile acid-microencapsulating formulation of pancreatic ß-cells cultured in high ratio poly-L-ornithine-gel hydrogel colloidal dispersion: applications in cell-biomaterials, tissue engineering and biotechnological applications.

INTRODUCTION: Current trials for ß-cell transplantation have been hindered by poor cell viability and function post-transplantation. Recently, electric charges of the microencapsulating formulation carrying ß-cells have shown significant effects on cell survival and function. Thus, this study aimed at investigating the effects of electric charge, of novel colloidal formulation containing ß-cells, on cell viability, biological activity and insulin release. METHODS: A new formulation, containing high ratios of poly-L-ornithine, suspending electrical-stimulation hydrogel and polystyrene sulphone (1:1:0.1 ratio), was used to form microcapsules utilizing 800 V and 2000 Hz encapsulating conditions. The bile acid, ursodeoxycholic acid, was added into the microcapsules to measure its effects on electric charges. RESULTS: The electric charge of the microencapsulating formulation was enhanced by bile acid addition, and resulted in better cell viability and function. CONCLUSION: Ursodeoxycholic acid microencapsulated with poly-L-ornithine, suspending electrical-stimulation hydrogel and polystyrene sulphone at 1:1:0.1 ratio, using 800 V and 2000 Hz microencapsulating conditions, produced enhanced electrokinetic parameters of microcapsules with optimized cell functions. This suggests that electric charge of formulations containing pancreatic ß-cell may have significant effects on cell mass and functions, post-transplantation.

Keratinocyte Sonic Hedgehog Upregulation Drives the Development of Giant Congenital Nevi via Paracrine Endothelin-1 Secretion.

Giant congenital nevi are associated with clinical complications such as neurocutaneous melanosis and melanoma. Virtually nothing is known about why some individuals develop these lesions. We previously identified the sonic hedgehog (Shh) pathway regulator Cdon as a candidate nevus modifier gene. Here we validate this by studying Cdon knockout mice, and go on to establishing the mechanism by which Shh exacerbates nevogenesis. Cdon knockout mice develop blue nevi without the need for somatic melanocyte oncogenic mutation. In a mouse model carrying melanocyte NRASQ61K, we found that strain backgrounds that carry genetic variants that cause increased keratinocyte Shh pathway activity, as measured by Gli1 and Gli2 expression, develop giant congenital nevi. Shh components are also active adjacent to human congenital nevi. Mechanistically, this exacerbation of nevogenesis is driven via the release of the melanocyte mitogen endothelin-1 from keratinocytes. We then suppressed nevus development in mice using Shh and endothelin antagonists. Our work suggests an aspect of nevus development whereby keratinocyte cytokines such as endothelin-1 can exacerbate nevogenesis, and provides potential therapeutic approaches for giant congenital nevi. Furthermore, it highlights the notion that germline genetic variation, in addition to somatic melanocyte mutation, can strongly influence the histopathological features of melanocytic nevi.

Analysis of early mesothelial cell responses to Staphylococcus epidermidis isolated from patients with peritoneal dialysis-associated peritonitis.

The major complication of peritoneal dialysis (PD) is the development of peritonitis, an infection within the abdominal cavity, primarily caused by bacteria. PD peritonitis is associated with significant morbidity, mortality and health care costs. Staphylococcus epidermidis is the most frequently isolated cause of PD-associated peritonitis. Mesothelial cells are integral to the host response to peritonitis, and subsequent clinical outcomes, yet the effects of infection on mesothelial cells are not well characterised. We systematically investigated the early mesothelial cell response to clinical and reference isolates of S. epidermidis using primary mesothelial cells and the mesothelial cell line Met-5A. Using an unbiased whole genome microarray, followed by a targeted panel of genes known to be involved in the human antibacterial response, we identified 38 differentially regulated genes (adj. p-value < 0.05) representing 35 canonical pathways after 1 hour exposure to S. epidermidis. The top 3 canonical pathways were TNFR2 signaling, IL-17A signaling, and TNFR1 signaling (adj. p-values of 0.0012, 0.0012 and 0.0019, respectively). Subsequent qPCR validation confirmed significant differences in gene expression in a number of genes not previously described in mesothelial cell responses to infection, with heterogeneity observed between clinical isolates of S. epidermidis, and between Met-5A and primary mesothelial cells. Heterogeneity between different S. epidermidis isolates suggests that specific virulence factors may play critical roles in influencing outcomes from peritonitis. This study provides new insights into early mesothelial cell responses to infection with S. epidermidis, and confirms the importance of validating findings in primary mesothelial cells.

Innovative Microcapsules for Pancreatic ß-Cells Harvested from Mature Double-Transgenic Mice: Cell Imaging, Viability, Induced Glucose-Stimulated Insulin Measurements and Proinflammatory Cytokines Analysis.

PURPOSE: Recently we demonstrated that microencapsulation of a murine pancreatic ß-cell line using an alginate-ursodeoxycholic acid (UDCA) matrix produced microcapsules with good stability and cell viability. In this study, we investigated if translation of this formulation to microencapsulation of primary ß-cells harvested from mature double-transgenic healthy mice would also generate stable microcapsules with good cell viability. METHODS: Islets of Langerhans were isolated from Ngn3-GFP/RIP-DsRED mice by intraductal collagenase P digestion and density gradient centrifugation, dissociated into single cells and the ß-cell population purified by Fluorescence Activated Cell Sorting. ß-cells were microencapsulated using either alginate-poly-l-ornithine (F1; control) or alginate-poly-l-ornithine-UDCA (F2; test) formulations. Microcapsules were microscopically examined and microencapsulated cells were analyzed for viability, insulin and cytokine release, 2 days post-microencapsulation. RESULTS: Microcapsules showed good uniformity and morphological characteristics and even cell distribution within microcapsules with or without UDCA. Two days post microencapsulation cell viability, mitochondrial ATP and insulin production were shown to be optimized in the presence of UDCA whilst production of the proinflammatory cytokine IL-1ß was reduced. Contradictory to our previous studies, UDCA did not reduce production of any other pro-inflammatory biomarkers. CONCLUSIONS: These results suggest that UDCA incorporation improves microcapsules' physical and morphological characteristics and improves the viability and function of encapsulated mature primary pancreatic ß-cells.

A comprehensive draft genome sequence for lupin (Lupinus angustifolius), an emerging health food: insights into plant-microbe interactions and legume evolution.

Lupins are important grain legume crops that form a critical part of sustainable farming systems, reducing fertilizer use and providing disease breaks. It has a basal phylogenetic position relative to other crop and model legumes and a high speciation rate. Narrow-leafed lupin (NLL; Lupinus angustifolius L.) is gaining popularity as a health food, which is high in protein and dietary fibre but low in starch and gluten-free. We report the draft genome assembly (609 Mb) of NLL cultivar Tanjil, which has captured >98% of the gene content, sequences of additional lines and a dense genetic map. Lupins are unique among legumes and differ from most other land plants in that they do not form mycorrhizal associations. Remarkably, we find that NLL has lost all mycorrhiza-specific genes, but has retained genes commonly required for mycorrhization and nodulation. In addition, the genome also provided candidate genes for key disease resistance and domestication traits. We also find evidence of a whole-genome triplication at around 25 million years ago in the genistoid lineage leading to Lupinus. Our results will support detailed studies of legume evolution and accelerate lupin breeding programmes.

A mutation in the Cdon gene potentiates congenital nevus development mediated by NRAS(Q61K).

Congenital nevi develop before birth and sometimes cover large areas of the body. They are presumed to arise from the acquisition of a gene mutation in an embryonic melanocyte that becomes trapped in the dermis during development. Mice bearing the Cdk4(R24C) ::Tyr-NRAS(Q) (61K) transgenes develop congenital nevus-like lesions by post-natal day 10, from melanocytes escaping the confines of hair follicles. We interbred these mice with the collaborative cross (CC), a resource that enables identification of modifier genes for complex diseases (those where multiple genes are involved). We examined variation in nevus cell density in 66 CC strains and mapped a large-effect quantitative trait locus (QTL) controlling nevus cell density to murine chromosome 9. The best candidate for a gene that exacerbates congenital nevus development in the context of an NRAS mutation is Cdon, a positive regulator of sonic hedgehog (Shh) that is expressed mainly in keratinocytes.

Pancreatic stem cells remain unresolved.

Diabetes mellitus is caused by absolute (type 1) or relative (type 2) deficiency of insulin-secreting islet ß cells. An ideal treatment of diabetes would, therefore, be to replace the lost or deficient ß cells, by transplantation of donated islets or differentiated endocrine cells or by regeneration of endogenous islet cells. Due to their ability of unlimited proliferation and differentiation into all functional lineages in our body, including ß cells, embryonic stem cells and induced pluripotent stem cells are ideally placed as cell sources for a diabetic transplantation therapy. Unfortunately, the inability to generate functional differentiated islet cells from pluripotent stem cells and the poor availability of donor islets have severely restricted the broad clinical use of the replacement therapy. Therefore, endogenous sources that can be directed to becoming insulin-secreting cells are actively sought after. In particular, any cell types in the developing or adult pancreas that may act as pancreatic stem cells (PSC) would provide an alternative renewable source for endogenous regeneration. In this review, we will summarize the latest progress and knowledge of such PSC, and discuss ways that facilitate the future development of this often controversial, but crucial research.

Andrographolide inhibits tumor angiogenesis via blocking VEGFA/VEGFR2-MAPKs signaling cascade.

Traditional medicinal herb Andrographis paniculata is known to possess anti-tumor activity, and its potential active compound is the diterpenoid lactone andrographolide (ANGL). In this study, we have found that ANGL inhibits tumor growth in nude mice bearing xenografted Hep3B cancer cells, concomitant with a reduction in tumor vessel counts. ANGL inhibits vascular endothelial growth factor A (VEGFA)-induced angiogenic responses in vitro and neoangiogenesis in vivo. We also found that ANGL inhibits VEGFA-induced phosphorylation of vascular endothelial growth factor receptor 2 (VEGFR2) and its downstream targets such as the mitogen-activated protein kinases (MAPKs). ANGL interferes with the binding of VEGFA to VEGFR2, but has no effect on VEGFR2 kinase activity in vitro. Taken together, our results indicate that ANGL possesses anti-angiogenic activity which is mediated by preventing VEGFA-induced phosphorylation and activation of VEGFR2 and MAPKs. The present study indicates that ANGL can block tumor angiogenesis and therefore represents therapeutic potential for cancer treatment.

Functionally distinct PI 3-kinase pathways regulate myelination in the peripheral nervous system.

The PI 3-kinase (PI 3-K) signaling pathway is essential for Schwann cell myelination. Here we have characterized PI 3-K effectors activated during myelination by probing myelinating cultures and developing nerves with an antibody that recognizes phosphorylated substrates for this pathway. We identified a discrete number of phospho-proteins including the S6 ribosomal protein (S6rp), which is down-regulated at the onset of myelination, and N-myc downstream-regulated gene-1 (NDRG1), which is up-regulated strikingly with myelination. We show that type III Neuregulin1 on the axon is the primary activator of S6rp, an effector of mTORC1. In contrast, laminin-2 in the extracellular matrix (ECM), signaling through the α6ß4 integrin and Sgk1 (serum and glucocorticoid-induced kinase 1), drives phosphorylation of NDRG1 in the Cajal bands of the abaxonal compartment. Unexpectedly, mice deficient in α6ß4 integrin signaling or Sgk1 exhibit hypermyelination during development. These results identify functionally and spatially distinct PI 3-K pathways: an early, pro-myelinating pathway driven by axonal Neuregulin1 and a later-acting, laminin-integrin-dependent pathway that negatively regulates myelination.