Gene conversions in the horse alpha-globin gene complex

The sequences of the linked alpha 2- and alpha 1-globin genes of the equine BI and BII haplotypes are greater than 99% identical within a 1.2-kb region extending from approximately 75 bp upstream of the putative cap site to a point approximately 150 bp 3' to the poly A addition signal. Differences between the alpha 2 and alpha 1 genes that are common to both haplotypes indicate that a major gene conversion occurred approximately 12 Myr ago and that this has been followed by shorter, more localized, conversions. Interhaplotype (allelic) comparisons at the alpha loci suggest that the BI and BII haplotypes have probably existed independently greater than or equal to 0.5 Myr and that the alpha 1 genes may have undergone a recent interchromosomal gene conversion.      

Genetic Control of Quantitative Variation in Self-Incompatibility Proteins Detected by Immunodiffusion

Single radial immunodiffusion was used to study the self-incompatibility (S) proteins present in stigmas of two inbred lines of Brassica oleracea: a self-incompatible line and a self-compatible mutant derived from it. The genetic basis of observed quantitative differences in S proteins between the two inbreds was shown to be determined by a single gene with dosage effects. Self-pollination of individual plants with high, intermediate and low levels of S protein in the stigmas, respectively, resulted in low, intermediate and high seed set.     

Brain, eye, and face defects as a result of ectopic localization of Sonic hedgehog protein in the developing rostral neural tube.

BACKGROUND: Normal development of the face, eyes, and brain requires the coordinated expression of many genes. One gene that has been implicated in the development of each of these structures encodes the secreted protein, Sonic hedgehog (Shh). During central nervous system development, Shh is required for ventral specification along the entire neural axis. To further explore the role of Shh in chick brain and craniofacial development, we overexpressed Shh in the developing rostral neural tube METHODS: In order to determine if Shh is sufficient to ventralize the forebrain, we localized ectopically recombinant Shh protein to the rostral neural tube of chick embryos. The resulting embryos were evaluated morphologically and by assaying gene expression. RESULTS: Disruption in normal gene expression patterns was observed with a reduction or loss in expression of genes normally expressed in the dorsal forebrain (wnt-3a, wnt-4, and Pax-6) and expansion of ventrally expressed genes dorsally (HNF-3beta, Ptc). In addition to the genetic alterations observed in the neural tube, a craniofacial phenotype characterized by a reduction in many cranial neural crest-derived structures was observed. The eyes of Shh-treated embryos were also malformed. They were small with expansion of the retinal pigmented epithelium, enlarged optic stalks, and a reduction of neural retina. DISCUSSION: The ectopic localization of recombinant Shh protein in the rostral neural tube resulted in severe craniofacial anomalies and alterations of gene expression predicted by other studies. The system employed appears to be a model for studying the embryogenesis of malformations that involve the brain, eyes, and face.     

Production and characterization of the Brassica oleracea self-incompatibility locus glycoprotein and receptor kinase in a baculovirus infected insect cell culture system

Self-incompatibility is a phenomenon that involves recognition of self versus non-self pollen, leading to the rejection of self-related pollen and preventing self-fertilization. In this study, we used a baculovirus-infected insect cell culture system to express two Brassica oleracea stigma-specific proteins required for self-incompatibility: the S-locus glycoprotein, a soluble cell wall-localized glycosylated protein, and the S-locus receptor kinase, a receptor-like integral plasma membrane glycoprotein with serine/threonine kinase activity. Insect cells expressing the S-locus receptor kinase were used in conjunction with immunofluorescence and a whole cell enzyme-linked immunosorbant assay to demonstrate that the receptor is targeted to the cell surface and is oriented with its N-terminal S domain towards the outside of the cell. Received: 20 January 1999 / Revision accepted: 13 April 1999     

Metabolic Effects of Blocking Lactate Transport in Brain Cortical Tissue Slices Using an Inhibitor Specific to MCT1 and MCT2

A novel inhibitor of lactate transport, AR-C122982, was used to study the effect of inhibiting the monocarboxylate transporters MCT1 and MCT2 on cortical brain slice metabolism. We studied metabolism of l-[3-¹³C]lactate, and d-[1-¹³C]glucose under a range of conditions. Experiments using l-[3-¹³C]lactate showed that the inhibitor AR-C122982 altered exchange of lactate. Under depolarizing conditions, net flux of label from d-[1-¹³C]glucose was barely altered by 10 or 100 nM AR-C122982. In the presence of AMPA or glutamate there were increases in net flux of label and metabolic pool sizes. These data suggest lactate may supply compartments in the brain not usually directly accessed by glucose. In general, it would appear that movement of lactate between cell types is not essential for metabolic activity, with the heavy metabolic workloads imposed being unaffected by inhibition of MCT1 and MCT2. Further experiments investigating the mechanism of operation of AR-C122982 are necessary to corroborate this finding.     

Arabidopsis Species Hybrids-Emerging Model Systems for the Analysis of Species Differences

   apd: 9 March 2001