Developmental energetics: Energy expenditure, budgets and metabolism during animal embryogenesis.

Developing embryos are metabolically active, open systems that constantly exchange matter and energy with their environment. They function out of thermodynamic equilibrium and continuously use metabolic pathways to obtain energy from maternal nutrients, in order to fulfill the energetic requirements of growth and development. While an increasing number of studies highlight the role of metabolism in different developmental contexts, the physicochemical basis of embryogenesis, or how cellular processes use energy and matter to act together and transform a zygote into an adult organism, remains unknown. As we obtain a better understanding of metabolism, and benefit from current technology development, it is a promising time to revisit the energetic cost of development and how energetic principles may govern embryogenesis. Here, we review recent advances in methodology to measure and infer energetic parameters in developing embryos. We highlight a potential common pattern in embryonic energy expenditure and metabolic strategy across animal embryogenesis, and discuss challenges and open questions in developmental energetics.

Tracheal tube fusion in Drosophila involves release of extracellular vesicles from multivesicular bodies.

Extracellular vesicles (EVs) comprise diverse types of cell-released membranous structures that are thought to play important roles in intercellular communication. While the formation and functions of EVs have been investigated extensively in cultured cells, studies of EVs in vivo have remained scarce. We report here that EVs are present in the developing lumen of tracheal tubes in Drosophila embryos. We define two distinct EV subpopulations, one of which contains the Munc13-4 (also known as UNC13D) homolog Staccato (Stac) and is spatially and temporally associated with tracheal tube fusion (anastomosis) events. The formation of Stac-positive luminal EVs depends on the tracheal tip-cell-specific GTPase Arl3 (also known as Dnd in Drosophila), which is also required for the formation of Stac-positive multivesicular bodies (MVBs), suggesting that Stac-positive EVs derive from fusion of Stac-positive MVBs with the luminal membrane in tip cells during anastomosis formation. The GTPases Rab27 and Rab35 cooperate downstream of Arl3 to promote Stac-positive MVB formation and tube fusion. We propose that Stac-positive MVBs act as membrane reservoirs that facilitate tracheal lumen fusion in a process regulated by Arl3, Rab27, Rab35 and Stac. This article has an associated First Person interview with the first author of the paper.

The endometrial stem cell markers notch-1 and numb are associated with endometriosis.

Previous studies reported increased expression of the notch pathway-associated protein Musashi-1 in endometriosis. This case-control study investigates an association of the endometrial stem cell markers notch-1 and numb with endometriosis. Fifty-one endometriosis patients and 76 controls were recruited in the IVF unit and tertiary endometriosis referral centre of a university hospital. All subjects underwent transcervical endometrial biopsy and diagnostic laparoscopy. Expression of endometrial notch-1 and numb was assessed by immunostaining and correlated with clinical data. Association of stem-cell-marker expression with the presence of endometriosis was evaluated. Numb expression in the luminal epithelium was significantly higher in eutopic endometrium of endometriosis patients compared with controls (20.5% versus 16.5%, P = 0.033). Numb-positive single stromal cells were less frequent in endometrioma patients compared with other forms of endometriosis (0.3 versus 0.5 cells/visual field; P = 0.028). Notch-1 expression in endometrial glands was significantly higher in patients with deep infiltrating endometriosis compared with controls (39.1% versus 21.8%; P = 0.045). We conclude that stem cell markers notch-1 and numb of eutopic endometrium are associated with endometriosis and its clinical presentations, supporting the stem cell hypothesis of endometriosis. These findings could help develop promising research strategies applying endometrial stem cells as novel tools.

Sudden cardiac arrest as a presentation of Brugada syndrome unmasked by thyroid storm.

An 18-year-old man suffered a sudden cardiac arrest with ventricular fibrillation and was successfully resuscitated. He had neither a medical nor family history of cardiac disease/sudden death, but was known to have Graves' disease, for which he was treated with radioactive iodine. Recently, block-and-replacement therapy had been discontinued to evaluate thyroid functioning. On admission, thyroid hormone levels were markedly elevated, suggesting thyroid storm due to residual Graves' disease. The patient was treated with propylthiouracil, hydrocortisone and Lugol solution. ECG showed repolarisation patterns suggestive of an underlying type 1 Brugada syndrome (BS). These findings were confirmed by an additional ajmaline test. An implantable cardioverter defibrillator was implanted to prevent future arrhythmias. The patient underwent total thyroidectomy 9 months later and recovered completely. To the best of our knowledge, this is the first reported case of a sudden cardiac arrest as a presentation of BS unmasked by thyroid storm.