Ultrastructural analysis of whole glomeruli using array tomography

The renal glomerulus produces primary urine from blood plasma by ultrafiltration. The ultrastructure of the glomerulus is closely related to filtration function and disease development. The ultrastructure of glomeruli has mainly been evaluated using transmission electron microscopy; however, the volume that can be observed using transmission electron microscopy is extremely limited relative to the total volume of the glomerulus. Consequently, observing structures that exist in only one location in each glomerulus, such as the vascular pole, and evaluating low-density or localized lesions are challenging tasks. Array tomography (AT) is a technique used to analyze the ultrastructure of tissues and cells via scanning electron microscopy of serial sections. In this study, we present an AT workflow that is optimized for observing complete serial sections of the whole glomerulus, and we share several analytical examples that use the optimized AT workflow, demonstrating the usefulness of this approach. Overall, this AT workflow can be a powerful tool for structural and pathological evaluation of the glomerulus. This workflow is also expected to provide new insights into the ultrastructure of the glomerulus and its constituent cells.

Cell lineage- and expression-based inference of the roles of forkhead box transcription factor Foxc2 in craniofacial development

BACKGROUND

Foxc2 is a member of the winged helix/forkhead (Fox) box family of transcription factors. Loss of function of Foxc2 causes craniofacial abnormalities such as cleft palate and deformed cranial base, but its role during craniofacial development remains to be elucidated.

RESULTS

The contributions of Foxc2-positive and its descendant cells to the craniofacial structure at E18.5 were examined using a tamoxifen-inducible Cre driver mouse (Foxc2-CreERT2) crossed with the R26R-LacZ reporter mouse. Foxc2 expression at E8.5 is restricted to the cranial mesenchyme, contributing to specific components including the cranial base, sensory capsule, tongue, upper incisor, and middle ear. Expression at E10.5 was still positively regulated in most of those regions. In situ hybridization analysis of Foxc2 and its closely related gene, Foxc1, revealed that expression domains of these genes largely overlap in the cephalic mesenchyme. Meanwhile, the tongue expressed Foxc2 but not Foxc1, and its development was affected by the neural crest-specific deletion of Foxc2 in mice (Wnt1-Cre; Foxc2^fl/fl ).

CONCLUSIONS

Foxc2 is expressed in cranial mesenchyme that contributes to specific craniofacial tissue components from an early stage, and it seems to be involved in their development in cooperation with Foxc1. Foxc2 also has its own role in tongue development.

Sandstorm weather is a risk factor for mortality in ischemic heart disease patients in the Hexi Corridor, northwestern China

Ischemic heart disease (IHD) is one of the leading causes of mortality worldwide. Moreover, the effects of air pollution have been associated with several cardiovascular diseases (CVDs). The relationship between sandstorm weather and IHD is unknown. The Hexi Corridor is located in northwestern China and is a typical desert region comprising a large area of desert with a high incidence of sandstorms. This study aimed to explore the association between sandstorm weather and IHD-related mortality in this area. We acquired meteorological data of sandstorm weather from 2006 to 2015 from the Gansu Meteorological Bureau, and data regarding deaths due to IHD in five cities within the Hexi Corridor were collected from the death registration system of the Center for Disease Control of Gansu during the same period. Two other cities with few sandstorm events were selected as control regions. The time series method of the generalized additive model (GAM) was used to assess the association between sandstorm weather and IHD-related mortality in the Hexi Corridor. The results showed that the frequency of sandstorms in the Hexi Corridor was higher than that in the control regions (5.48% vs 1.64%, P < 0.01), and IHD-related mortality was correspondingly higher than that in the control regions (56.42/100,000 vs 45.62/100,000, P < 0.01). After stratification by gender, age, and urban/rural residence, a significant difference in IHD-related mortality was also noted (P < 0.05). Significant associations were found between sandstorm weather and IHD-related mortality, and the relative risk (RR) increased with an increasing number of days of sandstorm weather. According to the monthly and annual analyses, the mortality rate corresponded to sandstorm frequency. Our data suggest a positive association between sandstorm weather and IHD-related mortality in the Hexi Corridor of Gansu Province. The underlying mechanism requires further study.

Conditional inactivation of Foxc1 and Foxc2 in neural crest cells leads to cardiac abnormalities

Cardiac neural crest cells (cNCCs) are required for normal heart development. cNCCs are a multipotent and migratory cell lineage that differentiates into multiple cell types. cNCCs migrate into the developing heart to contribute to the septation of the cardiac outflow tract (OFT). Foxc1 and Foxc2 are closely related members of the FOX (Forkhead box) transcription factor family and are expressed in cNCC during heart development. However, the precise role of Foxc1 and Foxc2 in cNCCs has yet to be fully described. We found that compound NCC-specific Foxc1;Foxc2 mutant embryos exhibited persistent truncus arteriosus (PTA), ventricular septal defects (VSDs), and thinning of the ventricular myocardium. Loss of Foxc1/c2 expression in cNCCs resulted in abnormal patterns of cNCC migration into the OFT without the formation of the aorticopulmonary septum. Further, loss of Foxc1 expression in cNCCs resulted in normal OFT development but abnormal ventricular septal formation. In contrast, loss of Foxc2 expression in NCCs led to no obvious cardiac abnormalities. Together, we provide evidence that Foxc1 and Foxc2 in cNCCs are cooperatively required for proper cNCC migration, the formation of the OFT septation, and the development of the ventricles. Our data also suggests that Foxc1 expression may play a larger role in ventricular development compared to Foxc2.

Foxc2 is required for proper cardiac neural crest cell migration, outflow tract septation, and ventricle expansion

BACKGROUND

Proper development of the great vessels of the heart and septation of the cardiac outflow tract requires cardiac neural crest cells. These cells give rise to the parasympathetic cardiac ganglia, the smooth muscle layer of the great vessels, some cardiomyocytes, and the conotruncal cushions and aorticopulmonary septum of the outflow tract. Ablation of cardiac neural crest cells results in defective patterning of each of these structures. Previous studies have shown that targeted deletion of the forkhead transcription factor C2 (Foxc2), results in cardiac phenotypes similar to that derived from cardiac neural crest cell ablation.

RESULTS

We report that Foxc2^-/- embryos on the 129s6/SvEv inbred genetic background display persistent truncus arteriosus and hypoplastic ventricles before embryonic lethality. Foxc2 loss-of-function resulted in perturbed cardiac neural crest cell migration and their reduced contribution to the outflow tract as evidenced by lineage tracing analyses together with perturbed expression of the neural crest cell markers Sox10 and Crabp1. Foxc2 loss-of-function also resulted in alterations in PlexinD1, Twist1, PECAM1, and Hand1/2 expression in association with vascular and ventricular defects.

CONCLUSIONS

Our data indicate Foxc2 is required for proper migration of cardiac neural crest cells, septation of the outflow tract, and development of the ventricles. Developmental Dynamics 247:1286-1296, 2018. © 2018 Wiley Periodicals, Inc.

Integrative analysis of methylome and transcriptome variation of identified cardiac disease-specific genes in human cardiomyocytes after PM2.5 exposure

PM_2.5 exposure is strongly linked to cardiac disease. Subtle epigenetic or transcriptional alterations induced by PM_2.5 might contribute to pathogenesis and disease susceptibility of cardiac disease. It is still a major challenge to identify biological targets in human genetics. Human cardiomyocytes AC16 was chosen as cell model. Epigenetic effect of PM_2.5 in AC16 was analyzed using Illumina HumanMethylation 450 K BeadChip. Meanwhile the transcriptomic profiling was performed by Affymetrix^® microarray. PM_2.5 induced genome wide variation of DNA methylation pattern, including differentially methylated CpGs in promoter region. Then gene ontology analysis demonstrated differentially methylated genes were significantly clustered in pathways in regulation of apoptotic process, cell death and metabolic pathways, or associated with ion binding and shuttling. Correlation of the methylome and transcriptome revealed a clear bias toward transcriptional suppression by hypermethylation or activation by hypomethylation. Identified 386 genes which exhibited both differential methylation and expression were functionally associated with pathways including cardiovascular system development, regulation of blood vessel size, vasculature development, p53 pathway, AC-modulating/inhibiting GPCRs pathway and cellular response to metal ion/inorganic substance. Disease ontology demonstrated their prominent role in cardiac diseases and identified 14 cardiac-specific genes (ANK2, AQP1 et al.). PPI network analysis revealed 6 novel genes (POLR2I, LEP, BRIX1, ADCY6, INSL3, RARS). Those genes were then verified by qRT-PCR. Thus, in AC16, PM_2.5 alters the methylome and transcriptome of genes might be relevant for PM_2.5-/heart-associated diseases. Result gives additional insight in PM_2.5 relative cardiac diseases/associated genes and the potential mechanisms that contribute to PM_2.5 related cardiac disease.

Foxc2CreERT2 knock-in mice mark stage-specific Foxc2-expressing cells during mouse organogenesis

Foxc2, a member of the winged helix transcription factor family, is essential for eye, calvarial bone, cardiovascular and kidney development in mice. Nevertheless, how Foxc2-expressing cells and their descendent cells contribute to the development of these tissues and organs has not been elucidated. Here, we generated a Foxc2 knock-in (Foxc2^CreERT2 ) mouse, in which administration of estrogen receptor antagonist tamoxifen induces nuclear translocation of Cre recombinase in Foxc2-expressing cells. By crossing with ROSA-LacZ reporter mice (Foxc2^CreERT2 ; R26R), the fate of Foxc2 positive (Foxc2⁺ ) cells was analyzed through LacZ staining at various embryonic stages. We found Foxc2⁺ cell descendants in the supraoccipital and exoccipital bone in E18.5 embryos, when tamoxifen was administered at embryonic day (E) 8.5. Furthermore, Foxc2⁺ descendant cranial neural crest cells at E8-10 were restricted to the corneal mesenchyme, while Foxc2⁺ cell derived cardiac neural crest cells at E6-12 were found in the aorta, pulmonary trunk and valves, and endocardial cushions. Foxc2⁺ cell descendant contributions to the glomerular podocytes in the kidney were also observed following E6.5 tamoxifen treatment. Our results are consistent with previous reports of Foxc2 expression during early embryogenesis and the Foxc2^CreERT2 mouse provides a tool to investigate spatiotemporal roles of Foxc2 and contributions of Foxc2⁺ expressing cells during mouse embryogenesis.