The mouse Mid1 gene: implications for the pathogenesis of Opitz syndrome and the evolution of the mammalian pseudoautosomal region

We have recently reported isolation of the gene responsible for X- linked Opitz G/BBB syndrome, a defect of midline development. MID1 is located on the distal short arm of the human X chromosome (Xp22. 3) and encodes a novel member of the B box family of zinc finger proteins. We have now cloned the murine homolog of MID1 and performed preliminary expression studies during development. Mid1 expression in undifferentiated cells in the central nervous, gastrointestinal and urogenital systems suggests that abnormal cell proliferation may underlie the defect in midline development characteristic of Opitz syndrome. We have also found that Mid1 is located within the mouse pseudoautosomal region (PAR) in Mus musculus , while it seems to be X- specific in Mus spretus. Therefore, Mid1 is likely to be a recent acquisition of the M. musculus PAR. Genetic and FISH analyses also demonstrated a high frequency of unequal crossovers in the murine PAR, creating spontaneous deletion/duplication events involving Mid1. These data provide evidence for the first time that genetic instability of the PAR may affect functionally important genes. In addition, we show that MID1 is the first example of a gene subject to X-inactivation in man while escaping it in mouse. These data contribute to a better understanding of the molecular content and evolution of the rodent PAR.      

Expression of blood group antigens including HLA markers in human adult liver

The localisation of the principal blood group antigens has been studied in human liver. These blood group antigens included the erythrocyte antigens and the antigen of the major histocompatibility complex. This study was performed by the indirect immunofluorescence technique using polyclonal antibodies of human or animal origin and monoclonal antibodies from hybridomas. This study has shown that the normal hepatocyte is lacking in blood group antigens. On the contrary, the biliary cell was rich in antigenic markers: the main antigens expressed were Lewis, Pr, HLA-A and B antigens. In Kupffer cells, only i and HLA-DR antigens were clearly expressed. The endothelial cells of blood vessels mainly show A, B, H, HLA-A and B antigens; HLA-DR and Pr are slightly expressed. HLA-DR antigens were more strongly expressed on veins than on arteries. Dendritic cells have been identified in the portal space of human liver. They bore i and HLA-DR antigens.     

Ewing’s肉瘤细胞X-射线照射后TNF-α和TGF-β mRNA表达的研究

 目的　研究Ewing’s肉瘤细胞系 (RM 82 )X 射线外照射后肿瘤坏死因子 (TNF α)和转化生长因子 (TGF β)mRNA表达水平的变化 ,探讨X 射线诱导内源性TNF α和TGF β产生的可能性及意义。 方法　应用实时荧光RT PCR ,检测接受不同剂量X 线照射 (2Gy ,5Gy ,10Gy ,2 0Gy ,30Gy ,4 0Gy)和受照后不同时间 (1h ,3h ,6h ,12h ,2 4h ,4 8h ,72h)。TNF α和TGF βmRNA表达水平的变化。 结果　RM 82细胞TNF αmRNA表达水平较外照射前显著升高。一方面受照后TNF αmRNA表达逐渐升高 ,照射剂量达 4 0Gy时TNF αmRNA表达水平达高峰 ,为正常对照组的 10 8倍 ;另一方面 ,照射后 3h后TNF αmRNA表达逐渐升高 ,6h达高峰 ,为正常对照组的 18倍。相反 ,TGF βmRNA表达水平X 射线照射前后无显著变化。结论　Ewing’s肉瘤细胞系 (RM 82 )接受X 线照射后TNF αmRNA表达明显升高 ,且呈现时间、剂量依赖性。放射治疗可诱导Ewing’s肉瘤细胞系 (RM 82...     

Erythromycin treatment for gastrointestinal dysmotility in preterm infants

To report our clinical experience on the use of oral erythromycin for the treatment of severe gastrointestinal dysmotility in preterm infants.

Methodology:

A case series study of seven preterm infants (six were very low birthweight) with severe intestinal dysmotility in a tertiary neonatal centre.

Results:

All responded favourably without adverse effects and tolerated full enteral feeding within 1–2 weeks of the commencement of the drug.

Conclusions:

As prolonged total parenteral nutrition carries significant risk of complications, this therapy could be considered in selected preterm infants who fail to establish enteral feeding after an extended period, and in whom an anatomically obstructive lesion of the gastrointestinal tract has been excluded. Meanwhile, we would caution against the widespread implementation of this therapeutic approach until formal evaluation by randomized controlled trials have established the exact role of erythromycin, or its analogues, in the treatment of intestinal dysmotility in preterm infants.     

The cyanobacterial taxis protein HmpF regulates type IV pilus activity in response to light

Motility is ubiquitous in prokaryotic organisms including the photosynthetic cyanobacteria where surface motility powered by type 4 pili (T4P) is common and facilitates phototaxis to seek out favorable light environments. In cyanobacteria, chemotaxis-like systems are known to regulate motility and phototaxis. The characterized phototaxis systems rely on methyl-accepting chemotaxis proteins containing bilin-binding GAF domains capable of directly sensing light, and the mechanism by which they regulate the T4P is largely undefined. In this study we demonstrate that cyanobacteria possess a second, GAF-independent, means of sensing light to regulate motility and provide insight into how a chemotaxis-like system regulates the T4P motors. A combination of genetic, cytological, and protein–protein interaction analyses, along with experiments using the proton ionophore carbonyl cyanide m-chlorophenyl hydrazine, indicate that the Hmp chemotaxis-like system of the model filamentous cyanobacterium Nostoc punctiforme is capable of sensing light indirectly, possibly via alterations in proton motive force, and modulates direct interaction between the cyanobacterial taxis protein HmpF, and Hfq, PilT1, and PilT2 to regulate the T4P motors. Given that the Hmp system is widely conserved in cyanobacteria, and the finding from this study that orthologs of HmpF and T4P proteins from the distantly related model unicellular cyanobacterium Synechocystis sp. strain PCC6803 interact in a similar manner to their N. punctiforme counterparts, it is likely that this represents a ubiquitous means of regulating motility in response to light in cyanobacteria.

Motility is ubiquitous in prokaryotic organisms, including both swimming motility in aqueous environments and twitching or gliding motility on solid surfaces, and enables these organisms to optimize their position in response to various environmental factors. Among the photosynthetic cyanobacteria, surface motility is widespread and facilitates phototaxis to seek out favorable light environments (1, 2), and, for multicellular filamentous cyanobacteria, plays a key role in dispersal as well as the establishment of nitrogen-fixing symbioses with eukaryotes (3) and the formation of supracellular structures (3–5).Current understanding of cyanobacterial surface motility at the molecular level has been informed primarily by studies of two model organisms, the unicellular strain Synechocystis sp. strain PCC6803 (herein Synechocystis) and the filamentous strain Nostoc punctiforme ATCC29133/{"type":"entrez-protein","attrs":{"text":"PCC73102","term_id":"1245706357"}}PCC73102, where motility is exhibited only by differentiated filaments termed “hormogonia.” Motility in both organisms is powered by a type IV pilus (T4P) system where the ATPases PilB and PilT drive the extension and subsequent retraction, respectively, of pili which adhere to the substrate and pull the cells forward (for review, see ref. 6). In Synechocystis, the T4P motors are distributed throughout the entire cell, allowing a 360 ° range of motion (7), whereas in N. punctiforme they are confined to rings at the cell poles (8), resulting in movement only along the long axis of the filament. Comparative genomics implies that this mechanism of motility is widely conserved among cyanobacteria (9).Both Synechocystis and N. punctiforme employ chemotaxis-like systems to regulate motility. One of these systems, the Hmp chemotaxis-like system of N. punctiforme (3, 10), and its orthologous counterpart, the Pil chemotaxis-like system of Synechocystis (11), includes homologs to the canonical Escherichia coli chemotaxis complex (for review, see ref. 12), including the histidine kinase CheA, the adaptor protein CheW, the response regulator CheY, and the methyl-accepting chemotaxis protein MCP. These systems are essential for motility in their respective organisms and appear to regulate the T4P motors, although there are distinct differences in the phenotypes for inactivation of the components from each. In Synechocystis, null mutations either enhance or reduce the level of surface piliation (11), whereas in N. punctiforme they disrupt the coordinated polarity, but not the overall level of piliation, and affect various other aspects of hormogonium development (3, 10). In N. punctiforme, the subcellular localization of this system has been determined and has been found arrayed in static, bipolar rings similar to the T4P motors (3). However, the signals that are perceived by the MCPs and the precise mechanism by which these systems modulate T4P activity is currently undefined.Recently, an additional component of the Hmp system, HmpF, was characterized (9). HmpF is a predicted coiled-coil protein and is ubiquitous to, but confined within, the cyanobacterial lineage (9). It is essential for accumulation of surface pili and exhibits dynamic, unipolar localization to the leading poles of most cells in hormogonium filaments (9). Based on these findings, a model has been proposed where the localization of HmpF is regulated by the other components of the Hmp system, and in turn, the unipolar accumulation of HmpF leads to the activation of the T4P motors on one side of the cell to facilitate directional movement.A second chemotaxis-like system in each organism, the Ptx system of N. punctiforme (13) and the Pix system of Synechocystis (14, 15), is essential for positive phototaxis. These systems contain MCPs with cyanobacteriochrome sensory domains capable of perceiving light (for review, see ref. 16). Disruption of the Pix system results in negative phototaxis under light conditions that normally produce a positive phototactic response (14). Several other proteins containing cyanobacteriochromes, and one containing a BLUF domain, also modulate phototaxis in Synechocystis (for review, see ref. 6). In N. punctiforme, disruption of the Ptx system abolishes the phototactic response completely, resulting in uniform movement in all directions regardless of the light conditions (13), and there are currently no other proteins reported to modulate phototaxis. More recently, a motile, wild isolate of the model unicellular cyanobacterium Synechococcus elongatus sp. PCC7942 was shown to possess a chemotaxis-like system that modulates phototaxis in a manner similar to that of the N. punctiforme Ptx system (17). How these systems influence T4P activity to facilitate phototaxis is also currently unknown.There is also a substantial body of literature on motility and phototaxis in cyanobacteria, primarily based on observational studies of various filamentous strains, that predates the development of genetically tractable model organisms (for review, see ref. 18). These reports suggested that the photosystems may serve a sensory role in modulating phototaxis and that proton motive force (PMF) powers motility (19, 20), a finding that is inconsistent with the theory that cyanobacteria possess a common T4P-based gliding motor driven by ATP hydrolysis. In this study, we help reconcile this historical data with more recent molecular studies by providing evidence that the Hmp chemotaxis-like system senses light, possibly indirectly through alterations in PMF, and in turn modulates the interaction of HmpF with the T4P base to activate the motors.     

Human burst-forming units-erythroid need direct interaction with stem cell factor for further development

To understand the factors that regulate the early growth and development of immature erythroid progenitor cells, the burst-forming units-erythroid (BFU-E), it is necessary to have both highly purified target cells and a medium free of serum. When highly purified human blood BFU-E were cultured in a serum-free medium adequate for the growth of later erythroid progenitors, BFU-E would not grow even with the addition of recombinant human interleukin-3 (rIL-3), known to be essential for these cells. However, the addition of recombinant human stem cell factor (rSCF), which supports germ cell and pluripotential stem cell growth, stimulated BFU-E to grow equally well in serum-free as in serum-containing medium. Limiting dilution studies showed that rSCF acts directly on the BFU-E that do not require accessory cells for growth. Furthermore, rSCF was necessary for BFU-E development during the initial 7 days of culture, until these cells reached the stage of the late progenitors, the colony-forming units-erythroid (CFU-E). These studies indicate that early erythropoiesis is dependent on the direct action of SCF that not only affects early stem cells but is continually necessary for the further development of committed erythroid progenitor cells until the CFU-E stage of maturation.