Abstract

The 22q11.2 deletion syndrome (22q11DS) encompasses DiGeorge syndrome, velo-cardio-facial syndrome and conotruncal anomaly face syndrome and is due to a microdeletion of chromosome 22q11.2. This is the most frequent known interstitial deletion found in humans with an incidence of 1 in 4,000 live births. A large number of clinical findings have been reported in affected patients, including cardiac defects, characteristic facial features, thymichypoplasia, cleft palate, hypoparathyroidism, learning difficulties and psychiatric disorders. A comprehensive evaluation and follow-up program is necessary for patients with 22q11DS. A striking aspect of the 22q11DS phenotype is its variability, the basis of which remains unclear, and no phenotype-genotype correlation has been made. The structures primarily affected in patients with 22q11DS are derivatives of the embryonicpharyngeal arches and pouches suggesting that haplo-insufficiency of the gene(s) on the deleted region, spanning 2-3 Mb, is important in pharyngeal arch/pouch development. Extensive gene searches have been successful in identifying more than 30 genes in the deleted segment. Although standard positional cloning has failed to demonstrate a role for any of these genes in the syndrome, the use of experimental animal models and advanced genome manipulation technologies in mice have been providing an insight into the developmental role of some of these genes, including TBX1, HIRA, UFD1L and CRKL. A multifaceted approach to dissect the clinical and genetic aspects of 22q11DS would develop a deeper understanding of the embryological basis of this complex syndrome and the associated malformations, including congenital heart diseases. (Presented at the 1235th Meeting, October 30, 2001.)

The Tissue Engineering Research Center (TERC) is an interdisciplinary institution for R&D of regenerative device based on human adult stem cells. Development of a high throughput screening system of genetic networks that employ the self-renewal and differentiation of human adult stem cells is one of the major subjects of TERC toward reorganization of complex functions of human organs. We have developed a transfection array system that places DNA and cells onto a glass slide in a sequence- dependent spatial distribution allowing transfection and screening to take place on the same slide. Variable transfection reagents and conditions were investigated to increase the efficiency of transfection and reduce cross-contamination between different spots on the slide. A highly dense transfection array allowed the genetic selection of a red fluorescent protein expression vector from 800 different plasmid samples on a 7.5 cm × 2.5 cm glass plate. By using a transfection array system optimized for HeLa cell line, anti-proliferative 20-residue peptides were screened based on the phenotypic changes in the HeLa cells. A designed syntheticpeptide was selected from the library and showed growth-inhibition activity in HeLa cells. Our results demonstrated that the transfection array system miniaturizes and speeds up functional screening of genes. The transfection array system would be applied to a high throughput system for screening of geneticnetw orks in mammalian cells. (Presented at the 1237th Meeting, November 22, 2001.)

<Background and objectives> In liver transplantation (OLT), rejection and hypothermic ischaemia-reperfusion (I/R) injury are the primary causes of graft dysfunction. Both rejection of and hypothermic I/R injury to the newly implanted liver are associated with alterations to the microcirculation of the organ. In the current study we investigated the early (1-2 hr) and intermediate effects (up to 7 days) on the hepatic microcirculation of (i) OLT with and without rearterialsation and (ii) acute rejection. In addition, we investigated the ability of endothelin receptor blackade to reduce hypothermic I/R injury during reperfusion. <Methods> All experiments were performed with the approval of the University of Otago Animal Ethics Committee. OLT, using either Lewis-to-Lewis (syngeneic) or DA-to-Lewis (allogeneic) donor-recipient combinations, was performed under ether anaesthesia. The hepatic microcirculation was investigated by intravital fluorescence microscopy (IVFM). At the end of all experiments, the animals were were killed by an overdoes of anaesthetic. <Results> Seven days following OLT with graft rearterialization (AOLT) (Lewis-to-Lewis), the hepatic microcirculation was essentially normal. OLT without graft rearterialisation (NOLT) led to reduced sinusoidal perfusion and to significant leukocyte adhesion thus indicating the importance of arterial blood flow to the transplanted liver. Hypothermicstorage of the liver prior to AOLT, led to a time-dependent increase in injury to the hepatic microcirculation (reduced sinusoidal perfusion, increased leukocyte adhesion, elevated plasma AST and ALT levels) during early graft reperfusion which was amelioriated by an endothelin ET_A receptor antagonist but not by an ET_B receptor antagonist. After 17 hr cold storage in UW solution, significant apoptosis was in evidence which was accompanied by a disruption of the hepatic microcirculation in the newly implanted AOLT graft. Treatment with an ET_A receptor antagonist again reduced liver injury which indicated that endothelin-1 may be involved in the I/R injury encountered during OLT. The pattern of changes to the hepatic microcirculation observed during rejection (DA-to-Lewis) was characterised by early apoptosis (from 2 days), perfusion failure (from 4 days), leukocyte adhesion (from 4 days) leading to complete disruption of the hepatic microcirculation by 7 days post-OLT. Signs of periportal vascular injury (from 2 days) were also in evidence. <Conclusions> From our results we conclude that changes to the hepatic microcirculation occur in both I/R-induced injury and in acute rejection. <Study supported by grants from the Stanley Thomas Johnson Foundation, New Zealand Lottery Grants Board, the Otago Medical Research Foundation.> (Presented at the 1241st Meeting, December 18, 2001.)

Intercellular junctions provide structural support and spatial cues that establish and maintain tissue organization. Adherens junctions and desmosomes are the two major classes of adhesive intercellular junctions that are assembled by keratinocytes. In both types of junctions, calcium dependent adhesion molecules termed cadherins are the major transmembrane proteins involved in intercellular adhesion. In adherens junctions, the classical cadherins such as E-cadherin are coupled to the actin cytoskeleton. In contrast, the desmosomal cadherins are linked to the intermediate filament network. Armadillo proteins are a family of cytoplasmic molecules that link the cadherins to the appropriate cytoskeletal networks. In the adherens junctions, the major armadillo family protein is beta-catenin, which couples E-cadherin to a series of actin associated proteins such as alpha-catenin and alpha-actinin. An analogous arrangement is present in desmosomes, where the armadillo family protein plakoglobin couples the desmosomal cadherins to the intermediate filament binding protein desmoplakin. Recent work has identified a new subclass of armadillo family proteins termed the p120/plakophilin family. The precise function of these molecules is not yet known, but they appear to be important in clustering cadherins during junction assembly. A number of important discoveries have been made over the last 10 years demonstrating that numerous skin diseases result from either autoimmune targeting of desmosomal cadherins or from defects in genes encoding desmosomal proteins. Current research is focused on understanding the detailed mechanisms of intercellular junction assembly as well as the mechanisms by which junction assembly is compromised during cutaneous disease states. (Presented at the 1244th Meeting, January 22, 2002.)

[Home][Latest Issue][Past Issues][Search for Articles][Releted Links][About the Journal]
[Editors][Instructions to Authors][Subscription Information][Feed Back]