Xfin: an embryonic gene encoding a multifingered protein in Xenopus.

The Xenopus laevis genome was screened for putative DNA-binding gene products by using the 'finger' region of the Drosophila gene Krüppel as a probe. The one gene detected, named Xfin, codes for a protein with 37 finger domains that comprise nearly 90% of the protein. In the light of studies by Rhodes and Klug (Cell, 46, 123-132, 1986), these data suggest that the Xfin protein has the capacity to bind an unusually large stretch (185 bases) of DNA. The Xfin gene is expressed as a maternal and zygotic mRNA that undergoes extensive polyadenylation changes during early development. The Xfin mRNA expression pattern and the potential DNA binding activity of the protein point to the possibility that the Xfin gene may have a role in controlling gene activity during early embryonic development.     

Endosymbiotic origin and codon bias of the nuclear gene for chloroplast glyceraldehyde-3-phosphate dehydrogenase from maize

Summary The nuclei of plant cells harbor genes for two types of glyceraldehyde-3-phosphate dehydrogenases (GAPDH) displaying a sequence divergence corresponding to the prokaryote/eukaryote separation. This strongly supports the endosymbiotic theory of chloroplast evolution and in particular the gene transfer hypothesis suggesting that the gene for the chloroplast enzyme, initially located in the genome of the endosymbiotic chloroplast progenitor, was transferred during the course of evolution into the nuclear genome of the endosymbiotic host. Codon usage in the gene for chloroplast GAPDH of maize is radically different from that employed by present-day chloroplasts and from that of the cytosolic (glycolytic) enzyme from the same cell. This reveals the presence of subcellular selective pressures which appear to be involved in the optimization of gene expression in the economically important graminaceous monocots.     

Mapping of the gene for anti-müllerian hormone to the short arm of human chromosome 19

The gene coding for human anti-Müllerian hormone (AMH) was localized to subbands p13.2----p13.3 on chromosome 19, using in situ hybridization and Southern blot analysis of a panel of man-mouse and man-hamster somatic cell hybrids.     

Atrazine and diuron resistant plants from photoautotrophic protoplast-derived cultures of Nicotiana plumbaginifolia

Atrazine and diuron resistant clones were isolated from diploid photoautotrophic protoplastderived colonies of Nicotiana plumbaginifolia. Protoplasts were mutagenised with 0.1 mM N-ethyl-N-nitrosourea and colonies were screened for resistance after plating. Selection of calli was carried out on their ability to grow and green on a selective medium containing either atrazine or diuron. Plants were regenerated from most tolerant calli. Herbicide spray showed that plants of 6 and 4 clones were resistant to atrazine and diuron, respectively.Abbreviations Atrazine 2-chloro-4-ethylamino-6-isopropyl-amino-s-triazine - diuron 3-(3,4-dichlorophenyl)-1,1-dimethylurea - NEU N-ethyl-N-nitrosourea - PSII photosystem II     

Temperature-dependent osmotic permeability in glycoproteion containing liposomes

The osmotic water outflow of large multilamellar liposomes containing ₁-acid glycoprotein was measured at a temperature near the lipid's phase transition temperature. The liposomes were formed from a mixture of DPPC, cholesterol and glycoprotein in molar ratios 100:20:1, by continuous sucrose density gradient centrifugation. These liposomes captured 35% of the radiolabeled glycoprotein. The temperature-dependent experiments showed that near phase transition temperature the initial rate of water outflow increased drastically in comparison with glycoprotein free liposomes incubated in buffer containing glycoprotein. We suggested that eventual a channel mechanism may be involved due to spontaneous incorporation of glycoprotein into the bilayer.     

Chromium in plants

Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance. For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared to 0.5–1.5 μg/g).     

Structure and mapping of the fosB gene. FosB downregulates the activity of the fosB promoter.

We have determined the genomic structure of the fosB gene and shown that it consists of 4 exons and 3 introns at positions also found in the c-fos gene. By deletion analysis we have characterized a region upstream of the TATA box which is the promoter region of the gene. Several consensus sequences have been identified, including an SRE and AP-1 binding site whose relative positions are identical to those in the 5' upstream region of the c-fos gene. We have also shown that FosB and c-Fos can downregulate the activity of the fosB promoter to a similar extent. The fosB gene is located in the [A1-B1] region of mouse chromosome 7.     

The intron 7 donor splice site transition: a second Tay-Sachs disease mutation in French Canada

Mutations at the hexosaminidase A (HEXA) gene which cause Tay-Sachs disease (TSD) have elevated frequency in the Ashkenazi Jewish and French-Canadian populations. We report a novel TSD allele in the French-Canadian population associated with the infantile form of the disease. The mutation, a GA transition at the +1 position of intron 7, abolishes the donor splice site. Cultured human fibroblasts from a compound heterozygote for this transition (and for a deletion mutation) produce no detectable HEXA mRNA. The intron 7+1 mutation occurs in the base adjacent to the site of the adult-onset TSD mutation (G805A). In both mutations a restriction site for the endonuclease EcoRII is abolished. Unambiguous diagnosis, therefore, requires allele-specific oligonucleotide hybridization to distinguish between these two mutant alleles. The intron 7+1 mutation has been detected in three unrelated families. Obligate heterozygotes for the intron 7+1 mutation were born in the Saguenay-Lac-St-Jean region of Quebec. The most recent ancestors common to obligate carriers of this mutation were from the Charlevoix region of the province of Quebec. This mutation thus has a different geographic centre of diffusion and is probably less common than the exon 1 deletion TSD mutation in French Canadians. Neither mutation has been detected in France, the ancestral homeland of French Canada.     

A minority of 46,XX true hermaphrodites are positive for the Y-DNA sequence including SRY

Summary A total of 30 cases of 46,XX true hermaphroditism was analysed for Y-DNA sequences including the recently cloned gene for male testis-determination SRY. In 3 cases, a portion of the Y chromosome including SRY was present and, in 2 cases, was localised, to Xp22 by in situ hybridisation. Since previous studies have shown that the majority of XX males are generated by an X-Y chromosomal interchange, the Xp22 position of the Yp material suggests that certain cases of hermaphroditism can arise by the same meiotic event. The phenotype in the 3 SRY-positive cases may be caused by X-inactivation resulting in somatic mosaicism of testis-determining factor expression giving rise to both testicular and ovarian tissues. Autosomal or X-linked mutation(s) elsewhere in the sex-determining pathway may explain the phenotype observed in the remaining 27 SRY-negative cases.