Cartographic study: Breakpoints in 1574 families carrying human reciprocal translocations

Reciprocal translocations (rcp) are among the most common constitutional chromosomal aberrations in man. Using a European database of 1574 families carrying autosomal rcp, a cartographic study was done on the breakpoints involved. The breakpoints are non-randomly distributed along the different chromosomes, indicating “hot spots”. Breakpoints of rcp that result in descendants that are unbalanced chromosomally at birth are more frequent in a distal position on chromosomal arms, and 65% of them are localised in R-bands. Among the R-bands, bands rich in GC islands and poor in Alu repetitive sequences are more frequently the site of breakpoints, as well as bands that include a fragile site. This result suggests that the variation in degree of methylation in GC islands could be involved in chromosomal breakage and hence in chromosomal rearrangements. Received: 10 April 1995 / Revised: 1 July 1995     

Human reciprocal translocations: is the unbalanced mode at birth predictable?

Two methods of prediction for the risk of unbalance at birth were tested on a large data base of reciprocal translocation (1376 families): the pachyten diagram predictive method (PDPmethod) and the discriminant method (Dmethod). These method succeeded in correctly predicting the segregation mode in 66% of the data for the PDPmethod and in 80% of the data for the Dmethod. The quality of chromosome material (in particular R bands) must be taken into account for more accurate prediction. Some difficulties still exist in predicting the 31 tertiary segregation mode, which can frequently be incorrectly classified as the adjacent 1 mode.     

Soluble fractalkine prevents monocyte chemoattractant protein-1-induced monocyte migration via inhibition of stress-activated protein kinase 2/p38 and matrix metalloproteinase activities

In this study, we address the question of the cross-talk between two chemokines that are cosecreted during inflammation, namely monocyte chemoattractant protein-1 (MCP-1) and soluble fractalkine (s-FKN), toward monocyte migration. We found that s-FKN fails to induce MonoMac6 cell migration per se. Interestingly, this chemokine antagonizes transendothelial migration and chemotaxis of MonoMac6 cells and freshly isolated human monocytes induced by MCP-1, indicating a direct effect of s-FKN on monocytic cells. In this study, we found that stress-activated protein kinase (SAPK)1/c-Jun N-terminal kinase 1 and SAPK2/p38 are involved in the control of MCP-1-induced MonoMac6 cell migration. We demonstrated that s-FKN abrogates the MCP-1-induced SAPK2/p38 activation as well as the upstream Pyk2 activity. Furthermore, we observed that s-FKN also inhibits the activity of a major matrix metalloproteinase (MMP), namely MMP-2. Taken collectively, our results indicate that the s-FKN antagonizes the chemoattractant effect of MCP-1 on monocytes, likely by inhibiting crucial signaling pathways, like SAPK2/p38 and MMP-2 activities.     

Probing the substrate specificity of four different sialyltransferases using synthetic beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->O) (CH(2))7CH3 analogues general activating effect of replacing N-acetylglucosamine by N-propionylglucosamine

The acceptor specificities of ST3Gal III, ST3Gal IV, ST6Gal I and ST6Gal II were investigated using a panel of beta-D-Galp-(1-->4)-beta-D-GlcpNAc-(1-->2)-alpha-D-Manp-(1-->O)(CH(2))(7)CH(3) analogues. Modifications introduced at either C2, C3, C4, C5, or C6 of terminal D-Gal, as well as N-propionylation instead of N-acetylation of subterminal D-GlcN were tested for their influence on the alpha-2,3- and alpha-2,6-sialyltransferase acceptor activities. Both ST3Gal enzymes displayed the same narrow acceptor specificity, and only accept reduction of the Gal C2 hydroxyl function. The ST6Gal enzymes, however, do not have the same acceptor specificity. ST6Gal II seems less tolerant towards modifications at Gal C3 and C4 than ST6Gal I, and prefers beta-D-GalpNAc-(1-->4)-beta-D-GlcpNAc (LacdiNAc) as an acceptor substrate, as shown by replacing the Gal C2 hydroxyl group with an N-acetyl function. Finally, a particularly striking feature of all tested sialyltransferases is the activating effect of replacing the N-acetyl function of subterminal GlcNAc by an N-propionyl function.     

Slug Controls Stem/Progenitor Cell Growth Dynamics during Mammary Gland Morphogenesis

Background

Morphogenesis results from the coordination of distinct cell signaling pathways controlling migration, differentiation, apoptosis, and proliferation, along stem/progenitor cell dynamics. To decipher this puzzle, we focused on epithelial-mesenchymal transition (EMT) “master genes”. EMT has emerged as a unifying concept, involving cell-cell adhesion, migration and apoptotic pathways. EMT also appears to mingle with stemness. However, very little is known on the physiological role and relevance of EMT master-genes. We addressed this question during mammary morphogenesis. Recently, a link between Slug/Snai2 and stemness has been described in mammary epithelial cells, but EMT master genes actual localization, role and targets during mammary gland morphogenesis are not known and we focused on this basic question.

Methodology/Principal Findings

Using a Slug–lacZ transgenic model and immunolocalization, we located Slug in a distinct subpopulation covering about 10–20% basal cap and duct cells, mostly cycling cells, coexpressed with basal markers P-cadherin, CK5 and CD49f. During puberty, Slug-deficient mammary epithelium exhibited a delayed development after transplantation, contained less cycling cells, and overexpressed CK8/18, ER, GATA3 and BMI1 genes, linked to luminal lineage. Other EMT master genes were overexpressed, suggesting compensation mechanisms. Gain/loss-of-function in vitro experiments confirmed Slug control of mammary epithelial cell luminal differentiation and proliferation. In addition, they showed that Slug enhances specifically clonal mammosphere emergence and growth, cell motility, and represses apoptosis. Strikingly, Slug-deprived mammary epithelial cells lost their potential to generate secondary clonal mammospheres.

Conclusions/Significance

We conclude that Slug pathway controls the growth dynamics of a subpopulation of cycling progenitor basal cells during mammary morphogenesis. Overall, our data better define a key mechanism coordinating cell lineage dynamics and morphogenesis, and provide physiological relevance to broadening EMT pathways.     

Identification and functional expression of a second human beta-galactoside alpha2,6-sialyltransferase, ST6Gal II.

BLAST analysis of the human and mouse genome sequence databases using the sequence of the human CMP-sialic acid:beta-galactoside alpha-2,6-sialyltransferase cDNA (hST6Gal I, EC2.4.99.1) as a probe allowed us to identify a putative sialyltransferase gene on chromosome 2. The sequence of the corresponding cDNA was also found as an expressed sequence tag of human brain. This gene contained a 1590 bp open reading frame divided in five exons and the deduced amino-acid sequence didn't correspond to any sialyltransferase already known in other species. Multiple sequence alignment and subsequent phylogenic analysis showed that this new enzyme belonged to the ST6Gal subfamily and shared 48% identity with hST6Gal-I. Consequently, we named this new sialyltransferase ST6Gal II. A construction in pFlag vector transfected in COS-7 cells gave raise to a soluble active form of ST6Gal II. Enzymatic assays indicate that the best acceptor substrate of ST6Gal II was the free disaccharide Galbeta1-4GlcNAc structure whereas ST6Gal I preferred Galbeta1-4GlcNAc-R disaccharide sequence linked to a protein. The alpha2,6-linkage was confirmed by the increase of Sambucus nigra agglutinin-lectin binding to the cell surface of CHO transfected with the cDNA encoding ST6Gal II and by specific sialidases treatment. In addition, the ST6Gal II gene showed a very tissue specific pattern of expression because it was found essentially in brain whereas ST6Gal I gene is ubiquitously expressed.