Wool fibre crimp is determined by mitotic asymmetry and position of final keratinisation and not ortho- and para-cortical cell segmentation

Crimp, a distinguishing feature of sheep fibres, significantly affects wool value, processing and final fabric attributes. Several explanations for fibre bending have been proposed. Most concentrate on relative differences in the physicochemical properties of the cortical cells, which comprise the bulk of the fibre. However, the associations between cortical properties and fibre crimp are not consistent and may not reflect the underlying causation of fibre curvature (FC). We have formulated a mechanistic model in which fibre shape is dictated primarily by the degree of asymmetry in cell supply from the follicle bulb, and the point at which keratinisation is completed within the follicle. If this hypothesis is correct, one would anticipate that most variations in fibre crimp would be accounted for by quantitative differences in both the degree of mitotic asymmetry in follicle bulbs and the distance from the bulb to the point at which keratinisation is completed. To test this hypothesis, we took skin biopsies from Merino sheep from sites producing wool differing widely in fibre crimp frequency and FC. Mitotic asymmetry in follicle bulbs was measured using a DNA-labelling technique and the site of final keratinisation was defined by picric acid staining of the fibre. The proportion of para- to ortho-cortical cell area was determined in the cross-sections of fibres within biopsy samples. Mitotic asymmetry in the follicle bulb accounted for 0.64 (P < 0.0001) of the total variance in objectively measured FC, while the point of final keratinisation of the fibre accounted for an additional 0.05 (P < 0.05) of the variance. There was no association between ortho- to para-cortical cell ratio and FC. FC was positively associated with a subjective follicle curvature score (P < 0.01). We conclude that fibre crimp is caused predominantly by asymmetric cell division in follicles that are highly curved. Differential pressures exerted by the subsequent asymmetric cell supply and cell hardening in the lower follicle cause fibre bending. The extent of bending is then modulated by the point at which keratinisation is completed; later hardening means the fibre remains pliable for longer, thereby reducing the pressure differential and reducing fibre bending. This means that even highly asymmetric follicles may produce a straight fibre if keratinisation is sufficiently delayed, as is the case in deficiencies of zinc and copper, or when keratinisation is perturbed by transgenesis. The model presented here can account for the many variations in fibre shape found in mammals.     

GALNT11 as a new molecular marker in chronic lymphocytic leukemia

Aberrant mucin O-glycosylation often occurs in different cancers and is characterized by immature expression of simple mucin-type carbohydrates. At present, there are some controversial reports about the Tn antigen (GalNAcα-O-Ser/Thr) expression and there is a great lack of information about the [UDP-N-acetyl-α-d-galactosamine:polypeptide N-acetylgalactosaminyltransferase (GalNAc-Ts)] expression in chronic lymphocytic leukemia (CLL). To gain insight in these issues we evaluated the Tn antigen expression in CLL patient samples using two Tn binding proteins with different fine specificity. We also studied the expression from 14 GalNAc-Ts genes in CLL patients by RT-PCR. Our results have provided additional information about the expression level of the Tn antigen, suggesting that a low density of Tn residues is expressed in CLL cells. We also found that GALNT11 was expressed in CLL cells and normal T cell whereas little or no expression was found in normal B cells. Based on these results, GALNT11 expression was assessed by qPCR in a cohort of 50 CLL patients. We found significant over-expression of GALNT11 in 96% of B–CLL cells when compared to normal B cells. Moreover, we confirmed the expression of this enzyme at the protein level. Finally we found that GALNT11 expression was significantly associated with the mutational status of the immunoglobulin heavy chain variable region (IGHV), [?²(1) = 18.26; P < 0.0001], lipoprotein lipase expression [?²(1) = 13.72; P = 0.0002] and disease prognosis [?²(1) = 15.49; P < 0.0001]. Our evidence suggests that CLL patient samples harbor aberrant O-glycosylation highlighted by Tn antigen expression and that the over-expression of GALNT11 constitutes a new molecular marker for CLL.     

Isocitrate dehydrogenase 1 R132C mutation occurs exclusively in microsatellite stable colorectal cancers with the CpG island methylator phenotype

The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features.     

When galaxiid and salmonid fishes meet–a family reunion in New Zealand

New Zealand's small freshwater fish fauna has been augmented by introductions of exotic species, primarily salmonids. Brown and rainbow trout have been successful and the chinook salmon has established anadromous populations. Although few explicit data are available, it appears that addition of large salmonids has had harmful impacts on some indigenous species, particularly several galaxiids; these appear to result from predation and competitive exclusion. Interactions may be chronic or catastrophic. It is difficult to determine causes of chronic interactions, many instances of which are likely to be occurring and escaping notice. Further, it is difficult to separate the effects of human-induced habitat deterioration from inter-specific interactions. Catastrophic interactions are much easier to observe but even here determining the nature of interactions and ascribing causes is fraught with difficulties.     

Electron microscopy of thin-sectioned three-dimensional crystals of SecA protein from Escherichia coli: structure in projection at 40 A resolution.

SecA is a single-chain, membrane-associated polypeptide (102 kDa) which functions as an essential component of the protein export machinery of Escherichia coli. SecA has been crystallized from ammonium sulfate as small, three-dimensional bipyramidal crystals (0.1 x 0.1 x 0.05 mm). These crystals did not demonstrate detectable diffraction of X-rays from rotating anode sources. For study by electron microscopy, individual crystals were cross-linked in glutaraldehyde and OsO4 solutions, dehydrated, embedded in epoxy resin, and sectioned normal to crystallographic axial directions inferred from the external morphology of the crystals. Fourier transformation of processed images of untilted thin sections stained with uranyl acetate and lead citrate show reflections extending to 31 A resolution. Diffraction data and reconstructed images of the projected density of the unit cell contents indicate that the bipyramidal SecA crystals belong to orthorhombic space group C222(1) with unit cell dimensions a = 414 A, b = 381 A, and c = 243 A. Filtered images and density maps of mutually orthogonal projections of the unit cell contents are consistent with a three-dimensional model in which the asymmetric unit contains eight SecA monomers. The large unit cell dimensions and packing of protein monomers suggest that SecA is crystallizing as an oligomer of either dimers or tetramers.     

The small-subunit ribosomal RNA gene sequences from the hypotrichous ciliates Oxytricha nova and Stylonychia pustulata

We have determined the complete nucleotide sequence of the small- subunit ribosomal RNA genes for the ciliate protozoans Stylonychia pustulata and Oxytricha nova. The sequences are homologous and sufficiently similar that these organisms must be closely related. In a phylogeny inferred from comparisons of several eukaryotic small-subunit ribosomal RNAs, the divergence of the ciliates from the eukaryotic line of descent is seen to coincide with the radiation of the plants, the animals, and the fungi. This radiation is preceded by the divergence of the slime mold, Dictyostelium discoideum.      

Alignment of the genetic and physical maps in the dpy-5 bli-4 (I) region of C. elegans by the serial cosmid rescue of lethal mutations

Lethal mutations in the 0.5 map unit region between dpy-5 and bli-4 on chromosome I in Caenorhabditis elegans were serially rescued using cosmid-containing transgenic strains. All the lethal mutations analyzed came from a set of 495 EMS-induced, sDp2-rescued lethals described previously. Germline transformation with cosmid DNA was used to create 25 transgenic strains bearing heritable extrachromosomal arrays. These arrays were used as small duplications for the fine-scale mapping of essential genes, via the rescue of lethal mutations. Lethal mutations in 13 essential genes have been phenotypically rescued, allowing the alignment of the genetic and physical maps in this region. Extrachromosomal arrays were found to be transmitted 2- to 7-fold less frequently in oocytes than in hermaphrodite sperm for 12 of the 16 arrays that were examined. Three of these strains showed a subsequent 4- to 13-fold increase in array stability in oocytes. This phenomenon may be influenced by cosmid sequences. Early mitotic loss of the arrays was observed in all 17 transgenic strains examined, suggesting that loss of the array can occur at any time during development when cell divisions are occurring. As a result of this work, 13 of the essential loci positioned between dpy-5 and bli-4 are anchored to the physical map, thereby providing links between the physical and genetic maps on average every 85 kb. Received: 8 May 1996 / Accepted: 27 January 1997