Sex-linked genes are not silenced in fetal bovine testes expressing X-inactive specific transcript (XIST)

Tumor necrosis factor-alpha-induced TRPC1 expression amplifies store-operated Ca2+ influx and endothelial permeability

We determined the effects of TNF-alpha on the expression of transient receptor potential channel (TRPC) homologues in human vascular endothelial cells and the consequences of TRPC expression on the endothelial permeability response. We observed that TNF-alpha exposure increased TRPC1 expression without significantly altering expression of other TRPC isoforms in human pulmonary artery endothelial cells (HPAEC). Because TRPC1 belongs to the store-operated cation channel family, we measured the Ca(2+) store depletion-mediated Ca(2+) influx in response to thrombin exposure. We observed that thrombin-induced Ca(2+) influx in TNF-alpha-stimulated HPAEC was twofold greater than in control cells. To address the relationship between store-operated Ca(2+) influx and TRPC1 expression, we overexpressed TRPC1 by three- to fourfold in the human dermal microvascular endothelial cell line (HMEC) using the TRPC1 cDNA. Thrombin-induced store Ca(2+) depletion in these cells caused approximately twofold greater increase in Ca(2+) influx than in control cells. Furthermore, the inositol 1,4,5-trisphosphate-sensitive store-operated cationic current was increased greater than twofold in TRPC1-transfected cells compared with control. To address the role of Ca(2+) influx via TRPC1 in signaling endothelial permeability, we measured actin-stress fiber formation and transendothelial monolayer electrical resistance (TER) in the TRPC1 cDNA-transfected HMEC and TNF-alpha-challenged HPAEC. Both thrombin-induced actin-stress fiber formation and a decrease in TER were augmented in TRPC1-overexpressing HMEC compared with control cells. TNF-alpha-induced increased TRPC1 expression in HPAEC also resulted in marked endothelial barrier dysfunction in response to thrombin. These findings indicate the expression level of TRPC1 in endothelial cells is a critical determinant of Ca(2+) influx and signaling of the increase in endothelial permeability.

The monotreme genome: a patchwork of reptile, mammal and unique features?

The first specimen of platypus (Ornithorhynchus anatinus) that reached Britain in the late 18th century was regarded a scientific hoax. Over decades the anatomical characteristics of these unique mammals, such as egg laying and the existence of mammary glands, were hotly debated before they were accepted. Within the last 40 years, more and more details of monotreme physiology, histology, reproduction and genetics have been revealed. Some show similarities with birds or reptiles, some with therian mammals, but many are very specific to monotremes. The genome is no exception to monotreme uniqueness. An early opinion was that the karyotype, composed of a few large chromosomes and many small ones, resembled bird and reptile macro- and micro-chromosomes. However, the platypus genome also features characteristics that are not present in other mammals, such as a complex translocation system. The sex chromosome system is still not resolved. Nothing is known about dosage compensation and, unlike in therian mammals, there seems to be no genomic imprinting. In this article we will recount the mysteries of the monotreme genome and describe how we are using recently developed technology to identify chromosomes in mitosis, meiosis and sperm, to map genes to chromosomes, to unravel the sex chromosome system and the translocation chain and investigate X inactivation and genomic imprinting in monotremes.