The core SWI/SNF catalytic subunit Brg1 regulates nephron progenitor cell proliferation and differentiation.

Chromatin-remodeling complexes play critical roles in establishing gene expression patterns in response to developmental signals. How these epigenetic regulators determine the fate of progenitor cells during development of specific organs is not well understood. We found that genetic deletion of Brg1 (Smarca4), the core enzymatic protein in SWI/SNF, in nephron progenitor cells leads to severe renal hypoplasia. Nephron progenitor cells were depleted in Six2-Cre, Brg1flx/flx mice due to reduced cell proliferation. This defect in self-renewal, together with impaired differentiation resulted in a profound nephron deficit in Brg1 mutant kidneys. Sall1, a transcription factor that is required for expansion and maintenance of nephron progenitors, associates with SWI/SNF. Brg1 and Sall1 bind promoters of many progenitor cell genes and regulate expression of key targets that promote their proliferation.

Increased Risk for Ipsilateral Breast Tumor Recurrence in Invasive Lobular Carcinoma after Accelerated Partial Breast Irradiation Brachytherapy.

BACKGROUND: The suitability criteria for accelerated partial breast irradiation (APBI) from the American Brachytherapy Society (ABS), American Society for Radiation Oncology (ASTRO), and The Groupe Européende Curiethérapie European SocieTy for Radiotherapy & Oncology (GEC-ESTRO) have significant differences. MATERIALS AND METHODS: This is a single institution retrospective review of 946 consecutive patients with invasive breast cancer who underwent lumpectomy and APBI intracavitary brachytherapy from 2003 to 2018. Overall survival (OS), breast cancer-specific survival (BCSS), relapse-free survival (RFS), and ipsilateral breast tumor recurrence (IBTR) were estimated with Kaplan-Meier method. RESULTS: Median follow-up time was 60.2 months. Median age was 68 years (46-94 years). The majority of patients had estrogen receptor (ER)-positive disease (94%). There were 821 (87%) cases of invasive ductal carcinoma and 68 cases (7%) of invasive lobular carcinoma (ILC). The 5-year OS, BCSS, RFS, and IBTR were 93%, 99%, 90%, and 1.5%, respectively. Upon univariate analysis, ILC (hazard ratio [HR], 4.6; p = .008) and lack of nodal evaluation (HR, 6.9; p = .01) were risk factors for IBTR. The 10-year IBTR was 2.5% for IDC and 14% for ILC. While the ABS and ASTRO criteria could not predict IBTR, the GEC-ESTRO intermediate risk group was associated with inferior IBTR (p = .04) when compared to both low risk and high risk groups. None of the suitability criteria was able to predict RFS. CONCLUSION: These results show that APBI is an effective treatment for patients with invasive breast cancer. Expansion of the current eligibility criteria should be considered, although prospective validation is needed. Caution is required when considering APBI for patients with ILC. IMPLICATIONS FOR PRACTICE: In a large retrospective review of 946 patients with early breast cancer treated with partial mastectomy and accelerated partial breast irradiation (APBI) intracavitary brachytherapy, this study demonstrates durable local control. Patients deemed unsuitable or high risk by the American Brachytherapy Society, American Society for Radiation Oncology, and European Society for Radiotherapy and Oncology guidelines were not at increased risk for ipsilateral breast tumor recurrence (IBTR), suggesting that expansion of the current criteria should be considered. Importantly, however, these results demonstrate that caution should be taken when considering APBI for patients with invasive lobular carcinoma, as these patients had relatively high risk for IBTR (10-year IBTR, 14%).

Analysis of FGF20-regulated genes in organ of Corti progenitors by translating ribosome affinity purification.

BACKGROUND: Understanding the mechanisms that regulate hair cell (HC) differentiation in the organ of Corti (OC) is essential to designing genetic therapies for hearing loss due to HC loss or damage. We have previously identified Fibroblast Growth Factor 20 (FGF20) as having a key role in HC and supporting cell differentiation in the mouse OC. To investigate the genetic landscape regulated by FGF20 signaling in OC progenitors, we employ Translating Ribosome Affinity Purification combined with Next Generation RNA Sequencing (TRAPseq) in the Fgf20 lineage. RESULTS: We show that TRAPseq targeting OC progenitors effectively enriched for RNA from this rare cell population. TRAPseq identified differentially expressed genes (DEGs) downstream of FGF20, including Etv4, Etv5, Etv1, Dusp6, Hey1, Hey2, Heyl, Tectb, Fat3, Cpxm2, Sall1, Sall3, and cell cycle regulators such as Cdc20. Analysis of Cdc20 conditional-null mice identified decreased cochlea length, while analysis of Sall1-null and Sall1-ΔZn2-10 mice, which harbor a mutation that causes Townes-Brocks syndrome, identified a decrease in outer hair cell number. CONCLUSIONS: We present two datasets: genes with enriched expression in OC progenitors, and DEGs downstream of FGF20 in the embryonic day 14.5 cochlea. We validate select DEGs via in situ hybridization and in vivo functional studies in mice.

The chromatin landscape of healthy and injured cell types in the human kidney.

There is a need to define regions of gene activation or repression that control human kidney cells in states of health, injury, and repair to understand the molecular pathogenesis of kidney disease and design therapeutic strategies. Comprehensive integration of gene expression with epigenetic features that define regulatory elements remains a significant challenge. We measure dual single nucleus RNA expression and chromatin accessibility, DNA methylation, and H3K27ac, H3K4me1, H3K4me3, and H3K27me3 histone modifications to decipher the chromatin landscape and gene regulation of the kidney in reference and adaptive injury states. We establish a spatially-anchored epigenomic atlas to define the kidney's active, silent, and regulatory accessible chromatin regions across the genome. Using this atlas, we note distinct control of adaptive injury in different epithelial cell types. A proximal tubule cell transcription factor network of ELF3, KLF6, and KLF10 regulates the transition between health and injury, while in thick ascending limb cells this transition is regulated by NR2F1. Further, combined perturbation of ELF3, KLF6, and KLF10 distinguishes two adaptive proximal tubular cell subtypes, one of which manifested a repair trajectory after knockout. This atlas will serve as a foundation to facilitate targeted cell-specific therapeutics by reprogramming gene regulatory networks.

Deletion of NuRD component Mta2 in nephron progenitor cells causes developmentally programmed FSGS.

Low nephron endowment at birth is a risk factor for chronic kidney disease. The prevalence of this condition is increasing due to higher survival rates of preterm infants and children with multi- organ birth defect syndromes that affect the kidney and urinary tract. We created a mouse model of congenital low nephron number due to deletion of Mta2 in nephron progenitor cells. Mta2 is a core component of the Nucleosome Remodeling and Deacetylase (NuRD) chromatin remodeling complex. These mice developed albuminuria at 4 weeks of age followed by focal segmental glomerulosclerosis (FSGS) at 8 weeks, with progressive kidney injury and fibrosis. Our studies reveal that altered mitochondrial metabolism in the post-natal period leads to accumulation of neutral lipids in glomeruli at 4 weeks of age followed by reduced mitochondrial oxygen consumption. We found that NuRD cooperated with Zbtb7a/7b to regulate a large number of metabolic genes required for fatty acid oxidation and oxidative phosphorylation. Analysis of human kidney tissue also supported a role for reduced mitochondrial lipid metabolism and ZBTB7A/7B in FSGS and CKD. We propose that an inability to meet the physiological and metabolic demands of post-natal somatic growth of the kidney promotes the transition to CKD in the setting of glomerular hypertrophy due to low nephron endowment.

Biotic and abiotic pathways of phosphorus cycling in minerals and sediments: insights from oxygen isotope ratios in phosphate.

A key question to address in the development of oxygen isotope ratios in phosphate (δ(18)O(p)) as a tracer of biogeochemical cycling of phosphorus in ancient and modern environments is the nature of isotopic signatures associated with uptake and cycling of mineral-bound phosphate by microorganisms. Here, we present experimental results aimed at understanding the biotic and abiotic pathways of P cycling during biological uptake of phosphate sorbed to ferrihydrite and the selective uptake of sedimentary phosphate phases by Escherichia coli and Marinobacter aquaeolei. Results indicate that a significant fraction of ferrihydrite-bound phosphate is biologically available. The fraction of phosphate taken up by E. coli attained an equilibrium isotopic composition in a short time (<50 h) due to efficient O-isotope exchange (between O in PO(4) and O in water; that is, actual breaking and reforming of P-O bonds) (biotic pathway). The difference in isotopic composition between newly equilibrated aqueous and residual sorbed phosphate groups promoted the ion exchange (analogous to isotopic mixing) of intact phosphate ions (abiotic pathway) so that this difference gradually became negligible. In sediment containing different P phases, E. coli extracted loosely sorbed phosphate first, whereas M. aquaeolei preferred Fe-oxide-bound phosphate. The presence of bacteria always imprinted a biotic isotopic signature on the P phase that was taken up and cycled. For example, the δ(18)O(p) value of loosely sorbed phosphate shifted gradually toward equilibrium isotopic composition. The δ(18)O(p) value of Fe-oxide-bound phosphate, however, showed only slight changes initially but, when new Fe-oxides were formed, coprecipitated/occluded phosphate retained δ(18)O values of the aqueous phosphate at the time of formation of new Fe oxides. Concentrations and isotopic compositions of authigenic and detrital phosphates did not change, suggesting that these phosphate phases were not utilized by bacteria. These findings support burgeoning applications of δ(18)O(p) as a tracer of phosphorus cycling in sediments, soils, and aquatic environments and as an indicator of paleo- environmental conditions.

Management of ductal carcinoma in situ with accelerated partial breast irradiation brachytherapy: Implications for guideline expansion.

PURPOSE: Accelerated partial breast irradiation (APBI) for patients with ductal carcinoma in situ (DCIS) is controversial, and the suitability criteria from the American Brachytherapy Society (ABS), American Society of Therapeutic Radiology and Oncology (ASTRO), and the European Society for Radiotherapy and Oncology (GEC-ESTRO) have important differences. METHODS AND MATERIALS: This is a single-institution retrospective review of 169 consecutive patients with DCIS who underwent lumpectomy followed by APBI intracavitary brachytherapy from 2003 to 2018. Outcomes, including overall survival, recurrence-free survival (RFS), ipsilateral breast tumor recurrence, and distant metastasis, were estimated with the Kaplan-Meier method. RESULTS: The median followup time was 62.5 months. Median age was 66 years (47-89 years). The majority of patients had estrogen receptor-positive disease (89%). Fifty patients (30%) had Grade 3 disease. Of the 142 patients with adequate pathology interpretation, 91 and 108 cases had margins ≥ 3 mm and ≥2 mm, respectively. Most patients (72%) were prescribed and started endocrine therapy. Of the patients evaluable for ABS criteria (N = 130), 97 met the suitability criteria. Of the patients evaluable for ASTRO criteria (N = 129), 42 were deemed cautionary and 33 were deemed unsuitable. Of the patients evaluable for GEC-ESTRO criteria (N = 143), 141 cases were at intermediate risk and two were at high risk. Five-year ipsilateral breast tumor recurrence, RFS, and overall survival were 0.6%, 97.7%, and 97.2%, respectively. The ABS, ASTRO, and GEC-ESTRO criteria failed to significantly predict for RFS. CONCLUSIONS: These results, although limited by short-term followup, indicate that expansion of the eligibility criteria of APBI for patients with DCIS should be considered.

Pharmacologic inhibition of RGD-binding integrins ameliorates fibrosis and improves function following kidney injury.

Fibrosis is a final common pathway for many causes of progressive chronic kidney disease (CKD). Arginine-glycine-aspartic acid (RGD)-binding integrins are important mediators of the pro-fibrotic response by activating latent TGF-ß at sites of injury and by providing myofibroblasts information about the composition and stiffness of the extracellular matrix. Therefore, blockade of RGD-binding integrins may have therapeutic potential for CKD. To test this idea, we used small-molecule peptidomimetics that potently inhibit a subset of RGD-binding integrins in a murine model of kidney fibrosis. Acute kidney injury leading to fibrosis was induced by administration of aristolochic acid. Continuous subcutaneous administration of CWHM-12, an RGD integrin antagonist, for 28 days improved kidney function as measured by serum creatinine. CWHM-12 significantly reduced Collagen 1 (Col1a1) mRNA expression and scar collagen deposition in the kidney. Protein and gene expression markers of activated myofibroblasts, a major source of extracellular matrix deposition in kidney fibrosis, were diminished by treatment. RNA sequencing revealed that inhibition of RGD integrins influenced multiple pathways that determine the outcome of the response to injury and of repair processes. A second RGD integrin antagonist, CWHM-680, administered once daily by oral gavage was also effective in ameliorating fibrosis. We conclude that targeting RGD integrins with such small-molecule antagonists is a promising therapeutic approach in fibrotic kidney disease.

Modeling of biotic and abiotic processes affecting phosphate oxygen isotope ratios in a mineral-water-biota system.

Abiotic and biotic reactions operate side by side in the cycling of phosphorus (P) in the environment, but the relative roles of these two reactions vary both spatially and temporally. In biotic reactions, the uptake and release of P are catalyzed by enzymes and thus change phosphate oxygen isotope ratios, while in abiotic reactions, the absence of hydrolysis-condensation reactions results in no apparent changes in isotope composition, except short-term kinetic isotope effect due solely to preferential ion exchange. Therefore, isotope method could be a promising tool to differentiate relative roles of these two reactions in the environment but the relationship of the dynamic concentration and isotope exchange at the biota-water interface is largely unknown. In this study, we aimed to develop a process-based isotope model underpinning the competition of abiotic (sorption, desorption, and ion exchange) and biotic (uptake, metabolism, and release) reactions during uptake and recycling of ferrihydrite-bound P by E. coli. Our model comprises equations describing the partitioning relationship among different P pools and their corresponding oxygen isotope compositions and is based exclusively on oxygen isotope exchange at multiple sites including mineral surface, aqueous phase, and bacterial cells. The process-based model adequately reproduced the measured concentration and isotope compositions over time. Furthermore, parametric and sensitivity analyses using the model indicated that the rate of biological uptake of P was the major factor controlling the changes of phosphate isotope composition. In conclusion, our model provides new insights into a mechanistic aspect of isotope exchange and could be potentially useful for future efforts to understand the interplay of biotic and abiotic factors on phosphorus cycling in natural environments.

Phytoprotective influence of bacteria on growth and cadmium accumulation in the aquatic plant Lemna minor.

Certain plants are known to accumulate heavy metals, and can be used in remediation of polluted soil or water. Plant-associated bacteria, especially those that are metal tolerant, may enhance the total amount of metal accumulated by the plant, but this process is still unclear. In this study, we investigated metal enhancement vs. exclusion by plants, and the phytoprotective role plant-associated bacteria might provide to plants exposed to heavy metal. We isolated cadmium-tolerant bacteria from the roots of the aquatic plant Lemna minor grown in heavy metal-polluted waters, and tested these isolates for tolerance to cadmium. The efficiency of plants to accumulate heavy metal from their surrounding environment was then tested by comparing L. minor plants grown with added metal tolerant bacteria to plants grown axenically to determine, whether bacteria associated with these plants increase metal accumulation in the plant. Unexpectedly, cadmium tolerance was not seen in all bacterial isolates that had been exposed to cadmium. Axenic plants accumulated slightly more cadmium than plants inoculated with bacterial isolates. Certain isolates promoted root growth, but overall, addition of bacterial strains did not enhance plant cadmium uptake, and in some cases, inhibited cadmium accumulation by plants. This suggests that bacteria serve a phytoprotective role in their relationship with Lemna minor, preventing toxic cadmium from entering plants.

Microbial diversity of boron-rich volcanic hot springs of St. Lucia, Lesser Antilles.

The volcanic Sulphur Springs, St. Lucia, present an extreme environment due to high temperatures, low pH values, and high concentrations of sulfate and boron. St. Lucia offers some unique geochemical characteristics that may shape the microbial communities within the Sulphur Springs area. We chose six pools representing a range of geochemical characteristics for detailed microbial community analyses. Chemical concentrations varied greatly between sites. Microbial diversity was analyzed using 16S rRNA gene clone library analyses. With the exception of one pool with relatively low concentrations of dissolved ions, microbial diversity was very low, with Aquificales sequences dominating bacterial communities at most pools. The archaeal component of all pools was almost exclusively Acidianus spp. and did not vary between sites with different chemical characteristics. In the pool with the highest boron and sulfate concentrations, only archaeal sequences were detected. Compared with other sulfur springs such as those at Yellowstone, the microbial diversity at St. Lucia is very different, but it is similar to that at the nearby Lesser Antilles island of Montserrat. While high elemental concentrations seem to be related to differences in bacterial diversity here, similarities with other Lesser Antilles sites suggest that there may be a biogeographical component as well.

Shifts in rhizoplane communities of aquatic plants after cadmium exposure.

In this study we present the comparative molecular analysis of bacterial communities of the aquatic plant Lemna minor from a contaminated site (RCP) and from a laboratory culture (EPA), as well as each of these with the addition of cadmium. Plants were identified as L. minor by analysis of the rpl16 chloroplast region. Comparative bacterial community studies were based on the analyses of 16S rRNA clone libraries, each containing about 100 clones from the root surfaces of plants. Bacterial communities were compared at three phylogenetic levels of resolution. At the level of bacterial divisions, differences in diversity index scores between treatments, with and without cadmium within the same plant type (EPA or RCP), were small, indicating that cadmium had little effect. When we compared genera within the most dominant group, the beta-proteobacteria, differences between unamended and cadmium-amended libraries were much larger. Bacterial diversity increased upon cadmium addition for both EPA and RCP libraries. Analyses of diversity at the phylotype level showed parallel shifts to more even communities upon cadmium addition; that is, percentage changes in diversity indices due to cadmium addition were the same for either plant type, indicating that contamination history might be independent of disturbance-induced diversity shifts. At finer phylogenetic levels of resolution, the effects of cadmium addition on bacterial communities were very noticeable. This study is a first step in understanding the role of aquatic plant-associated microbial communities in phytoremediation of heavy metals.