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Wound healing is the physiologic response to a disruption in normal skin architecture and requires both spatial and temporal coordination of multiple cell types and cytokines. This complex process is prone to dysregulation secondary to local and systemic factors such as ischemia and diabetes that frequently lead to chronic wounds. Chronic wounds such as diabetic foot ulcers are epidemic with great cost to the healthcare system as they heal poorly and recur frequently, creating an urgent need for new and advanced therapies. Stem cell therapy is emerging as a potential treatment for chronic wounds, and adult-derived stem cells are currently employed in several commercially available products; however, stem cell therapy is limited by the need for invasive harvesting techniques, immunogenicity, and limited cell survival in vivo. Induced pluripotent stem cells (iPSC) are an exciting cell type with enhanced therapeutic and translational potential. iPSC are derived from adult cells by in vitro induction of pluripotency, obviating the ethical dilemmas surrounding the use of embryonic stem cells; they are harvested non-invasively and can be transplanted autologously, reducing immune rejection; and iPSC are the only cell type capable of being differentiated into all of the cell types in healthy skin. This review focuses on the use of iPSC in animal models of wound healing including limb ischemia, as well as their limitations and methods aimed at improving iPSC safety profile in an effort to hasten translation to human studies.

Wnt signaling is essential for many aspects of embryonic development including the formation of the primary embryonic axis. In addition, excessive Wnt signaling drives multiple diseases including cancer, highlighting its importance for disease pathogenesis. β-catenin is a key effector in this pathway that translocates into the nucleus and activates Wnt responsive genes. However, due to our lack of understanding of β-catenin nuclear transport, therapeutic modulation of Wnt signaling has been challenging. Here, we took an unconventional approach to address this long-standing question by exploiting a heterologous model system, the budding yeast Saccharomyces cerevisiae, which contains a conserved nuclear transport machinery. In contrast to prior work, we demonstrate that β-catenin accumulates in the nucleus in a Ran-dependent manner, suggesting the use of a nuclear transport receptor (NTR). Indeed, a systematic and conditional inhibition of NTRs revealed that only Kap104, the ortholog of Kap-β2/Transportin-1 (TNPO1), was required for β-catenin nuclear import. We further demonstrate direct binding between TNPO1 and β-catenin that is mediated by a conserved PY-NLS. Finally, using Xenopus secondary axis and TCF/LEF (T Cell factor/lymphoid enhancer factor family) reporter assays, we demonstrate that our results in yeast can be directly translated to vertebrates. By elucidating the nuclear localization signal in β-catenin and its cognate NTR, our study suggests new therapeutic targets for a host of human diseases caused by excessive Wnt signaling. Indeed, we demonstrate that a small chimeric peptide designed to target TNPO1 can reduce Wnt signaling as a first step toward therapeutics.

Transitioning from pluripotency to differentiated cell fates is fundamental to both embryonic development and adult tissue homeostasis. Improving our understanding of this transition would facilitate our ability to manipulate pluripotent cells into tissues for therapeutic use. Here, we show that membrane voltage (V m ) regulates the exit from pluripotency and the onset of germ layer differentiation in the embryo, a process that affects both gastrulation and left-right patterning. By examining candidate genes of congenital heart disease and heterotaxy, we identify KCNH6 , a member of the ether-a-go-go class of potassium channels that hyperpolarizes the V m and thus limits the activation of voltage gated calcium channels, lowering intracellular calcium. In pluripotent embryonic cells, depletion of kcnh6 leads to membrane depolarization, elevation of intracellular calcium levels, and the maintenance of a pluripotent state at the expense of differentiation into ectodermal and myogenic lineages. Using high-resolution temporal transcriptome analysis, we identify the gene regulatory networks downstream of membrane depolarization and calcium signaling and discover that inhibition of the mTOR pathway transitions the pluripotent cell to a differentiated fate. By manipulating V m using a suite of tools, we establish a bioelectric pathway that regulates pluripotency in vertebrates, including human embryonic stem cells. The plasma membrane’s electrical potential is maintained by ion channels, though the impact of this potential on cell fate has not been clearly elucidated. Here they show that changes in membrane potential can affect calcium levels and mTOR in pluripotent stem cells, altering their transition from pluripotency to differentiation.

Abdominal aortic aneurysm (AAA) rupture remains a significant cause of morbidity and mortality, but predictors of continued growth and rupture risk remain limited. The aim of this study was to investigate the relationship between abdominal aortic calcification and AAA growth via a secondary cohort analysis of the Non-Invasive Treatment of Abdominal Aortic Aneurysm Clinical Trial (N-TA3CT), a prospective multicenter randomized study. Arterial calcification Agatston scores and maximum transverse diameter were measured in non-contrast computed tomography (CT) scans in patients enrolled in N-TA3CT. Uni- and multi-variable linear regression were used to assess the association of anatomic calcium burden and comorbid conditions with rate of aneurysm growth. Of the 261 randomized patients in the trial, 136 patients met inclusion criteria for analysis. On univariable analysis, baseline calcium score at all assessed anatomic locations- the superior mesenteric artery (spearman correlation coefficient (SCC) -0.20, p  = 0.0176), renal artery (-0.22, p  = 0.0120, infrarenal aorta (-0.26, p  = 0.0020), common iliac artery (-0.19, p  = 0.024), external iliac artery (-0.26, p  = 0.003), and sum of all measured sites (-0.28, p  = 0.001)- was significantly associated with lower AAA diameter growth rates. Of individually measured sites, baseline infrarenal aortic calcification had the strongest negative association with aneurysm growth. Interestingly, infrarenal calcium score was not significantly associated with baseline aneurysm diameter (R 2 0.0001, spearman correlation p  = 0.94), or diabetes status ( p  = 0.59). In a multivariable regression model, factors significantly associated with faster diameter growth included baseline volume and current tobacco use. Factors associated with reduced growth rate included diabetes and baseline infrarenal aorta calcium score thereby establishing aneurysmal calcification as a marker for slower aneurysm growth.

Patients with common variable immunodeficiency associated with autoimmune cytopenia (CVID+AIC) generate few isotype-switched B cells with severely decreased frequencies of somatic hypermutations (SHMs), but their underlying molecular defects remain poorly characterized. We identified a CVID+AIC patient who displays a rare homozygous missense M466V mutation in β-catenin-like protein 1 (CTNNBL1). Because CTNNBL1 binds activation-induced cytidine deaminase (AID) that catalyzes SHM, we tested AID interactions with the CTNNBL1 M466V variant. We found that the M466V mutation interfered with the association of CTNNBL1 with AID, resulting in decreased AID in the nuclei of patient EBV-transformed B cell lines and of CTNNBL1 466V/V Ramos B cells engineered to express only CTNNBL1 M466V using CRISPR/Cas9 technology. As a consequence, the scarce IgG+ memory B cells from the CTNNBL1 466V/V patient showed a low SHM frequency that averaged 6.7 mutations compared with about 18 mutations per clone in healthy-donor counterparts. In addition, CTNNBL1 466V/V Ramos B cells displayed a decreased incidence of SHM that was reduced by half compared with parental WT Ramos B cells, demonstrating that the CTNNBL1 M466V mutation is responsible for defective SHM induction. We conclude that CTNNBL1 plays an important role in regulating AID-dependent antibody diversification in humans.

Congenital Heart Disease (CHD) is the most common congenital malformation and a leading cause of infant mortality. While advances in genomic sequencing technology have enabled a fast and inexpensive candidate gene identification, the molecular mechanisms of CHD remain mostly unknown. Both nup107 and cacna1g are novel CHD genes identified in CHD patients with no plausible mechanisms explaining their roles in cardiac development. Here, we show that nup107 plays a key role in early embryonic patterning and subsequent organ development. The loss of Nup107 has a direct impact on germ layer specification, Left-Right patterning and downstream cardiac looping. Specifically, Nup107 depletion affects multiple developmental events by regulating the key step during the maternal-zygotic transition. In particular, Nup107 enhances the nuclear retention of miR427 primary transcript (pri-miR427), where it can be processed by Drosha to facilitate the clearance of maternal transcripts. While cacna1g mutations were also found in patients with CHD, we show that Cacna1g affects organogenesis via a completely distinct mechanism. Specifically, our results indicate that cacna1g loss-of-function affects Left-Right patterning and subsequent cardiac development by reducing the number of cilia in the Left-Right Organizer. In summary, we describe two mechanisms of how novel candidate genes affect different stages of embryonic development and contribute to CHD.

Wnt signaling is essential for many aspects of embryonic development including the formation of the primary embryonic axis. In addition, excessive Wnt signaling drives multiple diseases including cancer, highlighting its importance for disease pathogenesis. [beta]-catenin is a key effector in this pathway that translocates into the nucleus and activates Wnt responsive genes. However, due to our lack of understanding of [beta]-catenin nuclear transport, therapeutic modulation of Wnt signaling has been challenging. Here, we took an unconventional approach to address this long-standing question by exploiting a heterologous model system, the budding yeast Saccharomyces cerevisiae, which contains a conserved nuclear transport machinery. In contrast to prior work, we demonstrate that [beta]-catenin accumulates in the nucleus in a Ran-dependent manner, suggesting the use of a nuclear transport receptor (NTR). Indeed, a systematic and conditional inhibition of NTRs revealed that only Kap104, the ortholog of Kap-[beta]2/Transportin-1 (TNPO1), was required for [beta]-catenin nuclear import. We further demonstrate direct binding between TNPO1 and [beta]-catenin that is mediated by a conserved PY-NLS. Finally, using Xenopus secondary axis and TCF/LEF (T Cell factor/lymphoid enhancer factor family) reporter assays, we demonstrate that our results in yeast can be directly translated to vertebrates. By elucidating the nuclear localization signal in [beta]-catenin and its cognate NTR, our study suggests new therapeutic targets for a host of human diseases caused by excessive Wnt signaling. Indeed, we demonstrate that a small chimeric peptide designed to target TNPO1 can reduce Wnt signaling as a first step toward therapeutics.

Wnt signaling is essential for many aspects of embryonic development including the formation of the primary embryonic axis. In addition, excessive Wnt signaling drives multiple diseases including cancer highlighting its importance for disease pathogenesis. β-catenin is a key effector in this pathway that translocates into the nucleus and activates Wnt responsive genes. However, due to our lack of understanding of β-catenin nuclear transport, therapeutic modulation of Wnt signaling has been challenging. Here, we took an unconventional approach to address this long-standing question by exploiting a heterologous model system, the budding yeast Saccharomyces cerevisiae, which contains a conserved nuclear transport machinery. In contrast to prior work, we demonstrate that β-catenin accumulates in the nucleus in a Ran dependent manner, suggesting the use of a nuclear transport receptor (NTR). Indeed, a systematic and conditional inhibition of NTRs revealed that only Kap104, the orthologue of Kap-β2/Transportin-1 (TNPO1), was required for β-catenin nuclear import. We further demonstrate direct binding between TNPO1 and β-catenin that is mediated by a conserved amino acid sequence that resembles a PY NLS. Finally, using Xenopus secondary axis and TCF/LEF reporter assays, we demonstrate that our results in yeast can be directly translated to vertebrates. By elucidating the NLS in β-catenin and its cognate NTR, our study provides new therapeutic targets for a host of human diseases caused by excessive Wnt signaling. Indeed, we demonstrate that a small chimeric peptide designed to target TNPO1 can reduce Wnt signaling as a first step towards therapeutics.