Nkx2-5 and Sarcospan genetically interact in the development of the muscular ventricular septum of the heart.

The muscular ventricular septum separates the flow of oxygenated and de-oxygenated blood in air-breathing vertebrates. Defects within it, termed muscular ventricular septal defects (VSDs), are common, yet less is known about how they arise than rarer heart defects. Mutations of the cardiac transcription factor NKX2-5 cause cardiac malformations, including muscular VSDs. We describe here a genetic interaction between Nkx2-5 and Sarcospan (Sspn) that affects the risk of muscular VSD in mice. Sspn encodes a protein in the dystrophin-glycoprotein complex. Sspn knockout (SspnKO) mice do not have heart defects, but Nkx2-5+/-/SspnKO mutants have a higher incidence of muscular VSD than Nkx2-5+/- mice. Myofibers in the ventricular septum follow a stereotypical pattern that is disrupted around a muscular VSD. Subendocardial myofibers normally run in parallel along the left ventricular outflow tract, but in the Nkx2-5+/-/SspnKO mutant they commonly deviate into the septum even in the absence of a muscular VSD. Thus, Nkx2-5 and Sspn act in a pathway that affects the alignment of myofibers during the development of the ventricular septum. The malalignment may be a consequence of a defect in the coalescence of trabeculae into the developing ventricular septum, which has been hypothesized to be the mechanistic basis of muscular VSDs.

Temporal monitoring of perfluorooctane sulfonate accumulation in aquatic biota downstream of historical aqueous film forming foam use areas.

Perfluoroalkyl substances (PFAS) have recently received increased research attention, particularly concerning aquatic organisms and in regions of exposure to aqueous film forming foams (AFFFs). Air Force bases historically applied AFFFs in the interest of fire training exercises and have since expressed concern for PFAS contamination in biota from water bodies surrounding former fire training areas. Six PFAS were monitored, including perfluorooctane sulfonate (PFOS), in aquatic species from 8 bayou locations at Barksdale Air Force Base in Bossier City, Louisiana (USA) over the course of 1 yr. The focus was to evaluate temporal and spatial variability in PFAS concentrations from historic use of AFFF. The PFOS concentrations in fish peaked in early summer, and also increased significantly downstream of former fire training areas. Benthic organisms had lower PFOS concentrations than pelagic species, contrary to previous literature observations. Bioconcentration factors varied with time but were reduced compared with previously reported literature values. The highest concentration of PFOS in whole fish was 9349 ng/g dry weight, with 15% of samples exceeding what is believed to be the maximum whole fish concentration reported to date of 1500 ng/g wet weight. Further studies are ongoing, to measure PFAS in larger fish and tissue-specific partitioning data to compare with the current whole fish values. The high concentrations presently observed could have effects on higher trophic level organisms in this system or pose a potential risk to humans consuming contaminated fish. Environ Toxicol Chem 2017;36:2022-2029. © 2016 SETAC.

GLI1+ progenitor cells in the adrenal capsule of the adult mouse give rise to heterotopic gonadal-like tissue.

As certain strains of mice age, hyperplastic lesions resembling gonadal tissue accumulate beneath the adrenal capsule. Gonadectomy (GDX) accelerates this heterotopic differentiation, resulting in the formation of wedge-shaped adrenocortical neoplasms that produce sex steroids. Stem/progenitor cells that reside in the adrenal capsule and retain properties of the adrenogonadal primordium are thought to be the source of this heterotopic tissue. Here, we demonstrate that GLI1+ progenitors in the adrenal capsule give rise to gonadal-like cells that accumulate in the subcapsular region. A tamoxifen-inducible Cre driver (Gli1-creERT2) and two reporters (R26R-lacZ, R26R-confetti) were used to track the fate of GLI1+ cells in the adrenal glands of B6D2F2 mice, a strain that develops both GDX-induced adrenocortical neoplasms and age-dependent subcapsular cell hyperplasia. In gonadectomized B6D2F2 mice GLI1+ progenitors contributed to long-lived adrenal capsule cells and to adrenocortical neoplasms that expressed Gata4 and Foxl2, two prototypical gonadal markers. Pdgfra, a gene expressed in adrenocortical stromal cells, was upregulated in the GDX-induced neoplasms. In aged non-gonadectomized B6D2F2 mice GLI1+ progenitors gave rise to patches of subcapsular cell hyperplasia. Treatment with GANT61, a small-molecule GLI antagonist, attenuated the upregulation of gonadal-like markers (Gata4, Amhr2, Foxl2) in response to GDX. These findings support the premise that GLI1+ progenitor cells in the adrenal capsule of the adult mouse give rise to heterotopic tissue.

Adrenocortical zonation, renewal, and remodeling.

The adrenal cortex is divided into concentric zones. In humans the major cortical zones are the zona glomerulosa, zona fasciculata, and zona reticularis. The adrenal cortex is a dynamic organ in which senescent cells are replaced by newly differentiated ones. This constant renewal facilitates organ remodeling in response to physiological demand for steroids. Cortical zones can reversibly expand, contract, or alter their biochemical profiles to accommodate needs. Pools of stem/progenitor cells in the adrenal capsule, subcapsular region, and juxtamedullary region can differentiate to repopulate or expand zones. Some of these pools appear to be activated only during specific developmental windows or in response to extreme physiological demand. Senescent cells can also be replenished through direct lineage conversion; for example, cells in the zona glomerulosa can transform into cells of the zona fasciculata. Adrenocortical cell differentiation, renewal, and function are regulated by a variety of endocrine/paracrine factors including adrenocorticotropin, angiotensin II, insulin-related growth hormones, luteinizing hormone, activin, and inhibin. Additionally, zonation and regeneration of the adrenal cortex are controlled by developmental signaling pathways, such as the sonic hedgehog, delta-like homolog 1, fibroblast growth factor, and WNT/ß-catenin pathways. The mechanisms involved in adrenocortical remodeling are complex and redundant so as to fulfill the offsetting goals of organ homeostasis and stress adaptation.

Toying with fate: Redirecting the differentiation of adrenocortical progenitor cells into gonadal-like tissue.

Cell fate decisions are integral to zonation and remodeling of the adrenal cortex. Animal models exhibiting ectopic differentiation of gonadal-like cells in the adrenal cortex can shed light on the molecular mechanisms regulating steroidogenic cell fate. In one such model, prepubertal gonadectomy (GDX) of mice triggers the formation of adrenocortical neoplasms that resemble luteinized ovarian stroma. Transcriptomic analysis and genome-wide DNA methylation mapping have identified genetic and epigenetic markers of GDX-induced adrenocortical neoplasia. Members of the GATA transcription factor family have emerged as key regulators of cell fate in this model. Expression of Gata4 is pivotal for the accumulation of gonadal-like cells in the adrenal glands of gonadectomized mice, whereas expression of Gata6 limits the spontaneous and GDX-induced differentiation of gonadal-like cells in the adrenal cortex. Additionally, Gata6 is essential for proper development of the adrenal X-zone, a layer analogous to the fetal zone of the human adrenal cortex. The relevance of these observations to developmental signaling pathways in the adrenal cortex, to other animal models of altered adrenocortical cell fate, and to human diseases is discussed.