Long-term (trophic) purinergic signalling: purinoceptors control cell proliferation, differentiation and death

The purinergic signalling system, which uses purines and pyrimidines as chemical transmitters, and purinoceptors as effectors, is deeply rooted in evolution and development and is a pivotal factor in cell communication. The ATP and its derivatives function as a 'danger signal' in the most primitive forms of life. Purinoceptors are extraordinarily widely distributed in all cell types and tissues and they are involved in the regulation of an even more extraordinary number of biological processes. In addition to fast purinergic signalling in neurotransmission, neuromodulation and secretion, there is long-term (trophic) purinergic signalling involving cell proliferation, differentiation, motility and death in the development and regeneration of most systems of the body. In this article, we focus on the latter in the immune/defence system, in stratified epithelia in visceral organs and skin, embryological development, bone formation and resorption, as well as in cancer. Cell Death and Disease (2010) 1, e9; doi:10.1038/cddis.2009.11; published online 14 January 201

Multiple Organ System Defects and Transcriptional Dysregulation in the Nipbl+/− Mouse, a Model of Cornelia de Lange Syndrome

Cornelia de Lange Syndrome (CdLS) is a multi-organ system birth defects disorder linked, in at least half of cases, to heterozygous mutations in the NIPBL gene. In animals and fungi, orthologs of NIPBL regulate cohesin, a complex of proteins that is essential for chromosome cohesion and is also implicated in DNA repair and transcriptional regulation. Mice heterozygous for a gene-trap mutation in Nipbl were produced and exhibited defects characteristic of CdLS, including small size, craniofacial anomalies, microbrachycephaly, heart defects, hearing abnormalities, delayed bone maturation, reduced body fat, behavioral disturbances, and high mortality (75–80%) during the first weeks of life. These phenotypes arose despite a decrease in Nipbl transcript levels of only ∼30%, implying extreme sensitivity of development to small changes in Nipbl activity. Gene expression profiling demonstrated that Nipbl deficiency leads to modest but significant transcriptional dysregulation of many genes. Expression changes at the protocadherin beta (Pcdhb) locus, as well as at other loci, support the view that NIPBL influences long-range chromosomal regulatory interactions. In addition, evidence is presented that reduced expression of genes involved in adipogenic differentiation may underlie the low amounts of body fat observed both in Nipbl+/− mice and in individuals with CdLS

The fate of received sperm in the reproductive tract of a hermaphroditic snail and its implications for fertilisation.

Multiple mating, sperm storage and internal fertilisation enhance sperm competition. The great pond snail can use stored sperm for over three months, and frequently mates with different partners. This hermaphrodite, Lymnaea stagnalis, can also self-fertilise and often produces egg masses containing both selfed and outcrossed eggs. Hence, a sperm recipient may exert considerable control over paternity. Using microsatellite markers, we show that when allosperm are present, all genotyped eggs are cross-fertilised. We also find that sperm have the opportunity to compete, because double matings lead on average to equal paternity for each sperm donor. This indicates that received sperm are randomly mixed in storage. To gain further insight into the mechanisms underlying the process of sperm storage, digestion and utilisation, we investigated the fate of donated sperm at different times after copulation. We find that within 3 h after transfer most sperm have been transported into the sperm-digesting organ. Fluorescent labelling of sperm in histological sections further reveals that allosperm are not stored in the fertilisation pouch, but upstream in either the hermaphroditic duct, seminal vesicles, or ovotestis. Besides contributing to the understanding of the mechanisms underlying sperm competition and/or cryptic sperm choice, this study shows that mixed mating cannot be treated as a separate issue in hermaphroditic animals. © Springer Science+Business Media B.V. 2008

Intermediate conductance Ca2+-activated K+ channels modulate human placental trophoblast syncytialization.

Regulation of human placental syncytiotrophoblast renewal by cytotrophoblast migration, aggregation/fusion and differentiation is essential for successful pregnancy. In several tissues, these events are regulated by intermediate conductance Ca2+-activated K+ channels (IKCa), in part through their ability to regulate cell volume. We used cytotrophoblasts in primary culture to test the hypotheses that IKCa participate in the formation of multinucleated syncytiotrophoblast and in syncytiotrophoblast volume homeostasis. Cytotrophoblasts were isolated from normal term placentas and cultured for 66 h. This preparation recreates syncytiotrophoblast formation in vivo, as mononucleate cells (15 h) fuse into multinucleate syncytia (66 h) concomitant with elevated secretion of human chorionic gonadotropin (hCG). Cells were treated with the IKCa inhibitor TRAM-34 (10 µM) or activator DCEBIO (100 µM). Culture medium was collected to measure hCG secretion and cells fixed for immunofluorescence with anti-IKCa and anti-desmoplakin antibodies to assess IKCa expression and multinucleation respectively. K+ channel activity was assessed by measuring 86Rb efflux at 66 h. IKCa immunostaining was evident in nucleus, cytoplasm and surface of mono- and multinucleate cells. DCEBIO increased 86Rb efflux 8.3-fold above control and this was inhibited by TRAM-34 (85%; p<0.0001). Cytotrophoblast multinucleation increased 12-fold (p<0.05) and hCG secretion 20-fold (p<0.05), between 15 and 66 h. Compared to controls, DCEBIO reduced multinucleation by 42% (p<0.05) and hCG secretion by 80% (p<0.05). TRAM-34 alone did not affect cytotrophoblast multinucleation or hCG secretion. Hyposmotic solution increased 86Rb efflux 3.8-fold (p<0.0001). This effect was dependent on extracellular Ca2+, inhibited by TRAM-34 and 100 nM charybdotoxin (85% (p<0.0001) and 43% respectively) but unaffected by 100 nM apamin. In conclusion, IKCa are expressed in cytotrophoblasts and their activation inhibits the formation of multinucleated cells in vitro. IKCa are stimulated by syncytiotrophoblast swelling implicating a role in syncytiotrophoblast volume homeostasis. Inappropriate activation of IKCa in pathophysiological conditions could compromise syncytiotrophoblast turnover and volume homeostasis in pregnancy disease