Der(22) syndrome and velo-cardio-facial syndrome/DiGeorge syndrome share a 1.5-Mb region of overlap on chromosome 22q11.
Derivative 22 (der) syndrome is a rare disorder associated with multiple congenital anomalies, including profound mental retardation, preauricular skin tags or pits, and conotruncal heart defects. It can occur in offspring of carriers of the constitutional t(11;22)(q23;q11) translocation, owing to a 3:1 meiotic malsegregation event resulting in partial trisomy of chromosomes 11 and 22. The trisomic region on chromosome 22 overlaps the region hemizygously deleted in another congenital anomaly disorder, velo-cardio-facial syndrome/DiGeorge syndrome (VCFS/DGS). Most patients with VCFS/DGS have a similar 3-Mb deletion, whereas some have a nested distal deletion endpoint resulting in a 1.5-Mb deletion, and a few rare patients have unique deletions. To define the interval on 22q11 containing the t(11;22) breakpoint, haplotype analysis and FISH mapping were performed for five patients with der(22) syndrome. Analysis of all the patients was consistent with 3:1 meiotic malsegregation in the t(11;22) carrier parent. FISH-mapping studies showed that the t(11;22) breakpoint occurred in the same interval as the 1.5-Mb distal deletion breakpoint for VCFS. The deletion breakpoint of one VCFS patient with an unbalanced t(18;22) translocation also occurred in the same region. Hamster-human somatic hybrid cell lines from a patient with der(22) syndrome and a patient with VCFS showed that the breakpoints occurred in an interval containing low-copy repeats, distal to RANBP1 and proximal to ZNF74. The presence of low-copy repetitive sequences may confer susceptibility to chromosome rearrangements. A 1.5-Mb region of overlap on 22q11 in both syndromes suggests the presence of dosage-dependent genes in this interval. (+info)
Induction of human immunoglobulin synthesis and secretion in somatic cell hybrids of mouse myeloma and human B lymphocytes from patients with agammaglobulinemia.
Somatic cell hybrid clones were isolated from the fusion of RPC 5,4 mouse myeloma cells and B lymphocytes from three patients with agammaglobulinemia. One patient had X-linked agammaglobulinemia; the remaining two patients had common varied agammaglobulinemia. All three patients had B lymphocytes which fail to secrete immunoglobulin. The hybrid nature of the clones was established by examination of metaphase chromosome spreads. Most of the clones from all three patients expressed surface immunoglobulin of mouse and human parental origin. Clones from two of the patients had fewer cells with surface Ig than hybrids from normal persons, while clones from the third patient had large numbers of surface Ig fluorescent cells. Most of the clones from all three patients synthesized and secreted human and mouse immunoglobulin. As determined by sodium dodecyl sulfate acrylamide gel electrophoresis of radioactively labeled proteins, clones from each of the patients produced human gamma, alpha, and mu-heavy chains. These studies demonstrate the presence of functional structural genes coding for human immunoglobulin heavy chains in B lymphocytes of patients with agammaglobulinemia. Further, they represent induction in the somatic cell hybrids of a gene product not expressed in the parental B lymphocytes. (+info)
Assignment of genes for immunoglobulin kappa and heavy chains to chromosomes 6 and 12 in mouse.
Using somatic cell hybrids from fusions of lymphocytes of two different mouse stocks with the myeloma cell line X63-Ag8, we have assigned genes for the immunoglobulin heavy and kappa-type light chains to chromosomes 12 and 6, respectively. The two mouse stocks exhibit karyotypes consisting of nine pairs of metacentric chromosomes as a result of centric fusions of acrocentric chromosomes in different combinations. In the hybrid cells these metacentric chromosomes can be distinguished from the acrocentric chromosomes of myeloma origin, permitting correlation of Ig chain expression with mitotic loss of individual metacentric chromosomes. (+info)
Human cts18.1 gene: chromosomal localization and PH-domain analysis.
The human cts18.1 gene has high homology with the cytohesin gene family. By PCR analysis of a human monochromosomal somatic cell hybrid DNA panel, the cts18.1 gene was localized to chromosome 19. Diversity values of synonymous and nonsynonymous substitutions indicate that negative selection has occurred in the pleckstrin-homology (PH) domain of the cytohesin gene family. The phylogenetic tree calculated by the neighbor-joining method suggests that cts18.1 and cytohesin-2 genes are more closely related to each other than either of them is to the CLM-2 gene in the analysis of cDNA of the PH domain. (+info)
Effect of phosducin on opioid receptor function.
Phosducin (Phd) regulates the function of G proteins by its ability to tightly bind Gbetagamma subunits. Because the internalization of opioid receptors as well as the activity of adenylyl cyclase (AC) activity depends on G proteins, we tested Phd on these parameters. NG 108-15 hybrid cells stably expressing the phosphoprotein were challenged with [D-penicillamine2,D-penicillamine5]enkephalin to inhibit cAMP generation, demonstrating an increased efficacy of the opioid on AC. Studying the binding of [35S]guanosine-5'-O-(gamma-thio)-triphosphate to membranes from Phd overexpressing cells, we found that [D-penicillamine2, D-penicillamine5 ]enkephalin failed, in the presence of Phd (0.1 nM), to elevate incorporation of the nucleotide. Phd also strongly inhibited opioid-stimulated GTPase activity. NG 108-15 cells were also employed to investigate the effect of Phd on opioid receptor internalization. Control cells and cells overexpressing Phd were transiently transfected to express mu-opioid receptors fused to green fluorescence protein. In controls and in Phd overexpressing cells confocal microscopy identified fluorescence associated with the membrane. Time-lapse series microscopy of living control cells challenged with etorphine (1 microM) revealed receptor internalization within 30 min. In contrast, Phd overexpressing cells largely failed to respond to the opioid. Thus, in Phd overexpressing cells, opioids exhibit an increased efficacy despite the inhibitory action of the phosphoprotein on opioid-stimulated incorporation of [35S]guanosine-5'-O-(gamma-thio)-triphosphate. We suggest that inhibition of GTPase stabilizes the opioid-induced G protein Gi-GTP complex, which is believed to enhance AC inhibition. Finally, scavenging of Gbetagamma by Phd attenuates internalization of opioid receptors, which may contribute to the efficacy of opioids. (+info)
Non-viral neuronal gene delivery mediated by the HC fragment of tetanus toxin.
Many inherited neurological diseases and cancers could potentially benefit from efficient targeted gene delivery to neurons of the central nervous system. The nontoxic fragment C (HC) of tetanus toxin retains the specific nerve cell binding and transport properties of tetanus holotoxin. The HC fragment has previously been used to promote the uptake of attached proteins such as horseradish peroxidase, beta-galactosidase and superoxide dismutase into neuronal cells in vitro and in vivo. We report the use of purified recombinant HC fragment produced in yeast and covalently bound to polylysine [poly(K)] to enable binding of DNA. We demonstrate that when used to transfect cells, this construct results in nonviral gene delivery and marker gene expression in vitro in N18 RE 105 cells (a neuroblastoma x glioma mouse/rat hybrid cell line) and F98 (a glioma cell line). Transfection was dependent on HC and was neuronal cell type specific. HC may prove a useful targeting ligand for future neuronal gene therapy. (+info)
An integrated map of chromosome 18 CAG trinucleotide repeat loci.
Expansions of trinucleotide CAG repeats have been demonstrated in at least eight neurodegenerative disorders, and suggested to occur in several others, including bipolar disorder and schizophrenia. Chromosome 18 loci have been implicated in bipolar disorder pedigrees by linkage analysis. To address this putative link between chromosome 18 CAG trinucleotide repeats and neuropsychiatric illness, we have screened a chromosome 18 cosmid library (LL18NCO2" AD") and identified 14 novel candidate loci. Characterisation of these loci involved repeat flank sequencing, estimation of polymorphism frequency and mapping using FISH as well as radiation hybrid panels. These mapped trinucleotide loci will be useful in the investigation of chromosome 18 in neurodegenerative or psychiatric conditions, and will serve to integrate physical and radiation hybrid maps of chromosome 18. (+info)
Effects of ischemia on discontinuous action potential conduction in hybrid pairs of ventricular cells.
BACKGROUND: Acute ischemia often occurs in cardiac tissue that has prior injury, resulting in spatially inhomogeneous distributions of membrane properties and intercellular coupling. Changes in action potential conduction with ischemia, which can be associated with release of catecholamines, may be particularly important in tissue that has discontinuous conduction resulting from prior infarction, hypertrophy, or myopathy. METHODS AND RESULTS: Isolated guinea pig ventricular myocytes were electrically coupled by a coupling-clamp circuit to a comprehensive computer model of a guinea pig ventricular myocyte to assess alterations in the critical value of coupling conductance required for action potential conduction from the real cell to the model cell when the real cell was exposed to a solution that included hypoxia, acidosis, and an elevated extracellular potassium concentration to simulate acute ischemia. The "ischemic" solution increased critical coupling conductance from 6.2+/-0.1 to 7.4+/-0.2 nS and decreased the associated maximum conduction delay from 31+/-1 to 23+/-1 ms (mean+/-SEM, n=11). The ischemic solution plus 1 micromol/L norepinephrine decreased critical coupling conductance from 5.9+/-0.2 to 5.0+/-0.1 nS and increased maximum conduction delay from 31+/-2 to 54+/-4 ms (mean+/-SEM, n=8). CONCLUSIONS: The release of catecholamines with ischemia, in a setting of partially uncoupled cells, may play a major role in producing long conduction delays, which may allow reentrant pathways. (+info)