DiGeorge anomaly in an infant with deletion of chromosome 22 and dup(9p) due to adjacent type II disjunction.

A term white girl presented with low birth weight, minor anomalies, and congenital heart defects. The infant had microcephaly, upslanting palpebral fissures, prominent nasal bridge, short philtrum, thin upper lip vermilion, down-turned corners of the mouth, receding mandible, and short broad neck. The hands showed proximal placement of the thumbs, bilateral clinodactyly of the index finger, and bilateral transverse crease. Both hands were clenched, with the index finger overlapping the third finger and the fifth finger overlapping the fourth. There was also talipes calcaneo-valgus, bilateral dorsiflexion of the metatarsophalangeal joints, flexion of the interphalangeal joints, and hypoplasia of all nails. The patient's karyotype was 46,XX,-22, + der(9)t(9;22)(q21.13;q12.1)mat; the mother had the balanced translocation 46,XX,t(9;22)(9pter----9q21.13::22q12.1----22qter++ +;22pter---- 22q12.1::9q21.3----9qter). The infant died at age 10 days, and the autopsy showed absent thyroid isthmus and rudimentary thymus, with one small ectopic parathyroid attached to it. The lungs were hypoplastic, with abnormal lobation. The cardiac anomalies included truncus arteriosus, truncal valve stenosis, single carotid trunk, subclavian arteries arising from the distal part of the aortic arch, atrial and ventricular septal defects, right ventricular hypertrophy, and a hypoplastic left pulmonary artery. Also, multiple small accessory spleens were present in addition to a normal-sized spleen. This case combines features associated with DiGeorge anomaly and dup(9p). The chromosome abnormality in this patient appears to have arisen in a maternal germ cell due to adjacent type II disjunction.

Similar and synergistic inhibition of gap-junctional communication by ras transformation and tumor promoter treatment of mouse primary keratinocytes.

Modulation of gap junctional communication (GJIC) is likely to play an important role in tumorigenesis, as suggested by the action of tumor promoters and certain oncogene products. In this report we examine the effects of ras transformation and TPA (12-O-tetradecanoylphorbol-13-acetate) treatment on GJIC of murine primary keratinocytes. Introduction of the ras oncogene into primary keratinocyte cultures by Harvey Sarcoma virus (HaSV) infection is sufficient to cause a 70-80% reduction in their GJIC as measured by Scrape-Loading/Dye Transfer technique. Furthermore, while a 100% increase in GJIC is observed when normal keratinocyte cultures are induced to differentiate by addition of calcium, no such increase can be detected with their ras transformed counterparts. As with ras, TPA treatment of normal keratinocytes results in a 70-80% reduction of GJIC both under low and high calcium conditions. TPA treatment of keratinocytes already transformed by ras completely abolishes GJIC of these cells, regardless of calcium concentrations. The similar and synergistic effects of ras and TPA on GJIC of primary keratinocytes suggest that inhibition of this function represents an important early step in transformation of these cells.

Potential role of the human Ha-ras oncogene in the inhibition of gap junctional intercellular communication.

The modulation of gap junctional intercellular communication (GJIC) plays an important role during tumor promotion. Several tumor-promoting agents are known to inhibit this form of cellular coupling. In addition, tumor cells and cells expressing certain oncogenic products have been shown to exhibit inhibited or reduced GJIC. The Ha-ras oncogene is expressed in a wide variety of human tumors from different tissues. Its p21 product is a membrane-bound polypeptide, the function of which is not fully characterized. We tested the effects of the expression of the human c-Ha-ras-1 oncogene, derived from the EJ/T4 bladder carcinoma cell line, on the ability of the Chinese hamster V79 cells to conduct gap junctional communication. The junctional competence was studied by two different methods, the scrape-loading/dye transfer technique and the metabolic cooperation assay. The results indicate a strong correlation between the expression of p21 ras protein and the inhibition of gap junctional function. Assuming that reversible inhibition of intercellular communication plays a role during tumor promotion and stable inhibition during the tumor progression phase of carcinogenesis, our data suggest that, while chemical tumor promoters and the ras oncogenes might work by different biochemical mechanisms, they both affect a critical cellular function; namely, GJIC.

Anchored cell analysis/sorting coupled with the scrape-loading/dye-transfer technique to quantify inhibition of gap-junctional intercellular communication in WB-F344 cells by 2,2',4,4',5,5'-hexabromobiphenyl.

Inhibition of intercellular communication has been hypothesized to play a role in tumor promotion. The compound 2,2',4,4',5,5'-hexabromobiphenyl (245-HBB) is a tumor promoter in vivo and blocks intercellular communication in vitro. The scrape-loading/dye-transfer (SL/DT) assay was used to assess this in vitro effect at varying concentrations of 245-HBB. The SL/DT technique is based on the intracellular loading of a fluorescent dye, lucifer yellow (LY), and monitoring its transfer into adjacent cells via patent gap junctions. Confluent WB-F344 (rat epithelial) cells were exposed to various noncytolethal concentrations of 245-HBB. Transfer of LY was then quantified with anchored cell analysis/sorting (ACAS 470, Meridian Instruments, Okemos, Mich.). The results indicate an inverse correlation between the degree of fluorescence in secondary LY-recipient cells and the treatment concentration. The coupling of these two new methods of cellular biology provided rapid quantitative analysis of dye transfer in measuring the concentration/response of modulation of gap-junctional permeability in cultured cells.

Dieldrin inhibition of gap junctional intercellular communication in rat glial cells as measured by the fluorescence photobleaching and scrape loading/dye transfer assays.

Application of the fluorescence-recovery after photobleaching (FRAP analysis) technique and scrape loading/dye transfer assay was made to measure the presence of gap junctional communication in primary rat glial cells in vitro in the presence and absence of the neurotoxicant and tumor promoter dieldrin, a chlorinated insecticide. Results demonstrate that primary rat glial cells are able to exhibit gap junctional intercellular communication and that dieldrin at noncytotoxic concentrations can modulate gap junctional communication as early as 10 min after exposure to the chemical and that the effect is reversible after 4 hr recovery from the dieldrin exposure. Both the FRAP analysis and the scrape loading/dye transfer assay have validated the observation that dieldrin inhibits gap junctional communication in other cell types using different techniques to measure gap junction function. These results were interpreted as an indication that inhibition of gap junctional communication might contribute to the cellular mechanism of dieldrin's neurotoxicity.

Flow cytometry and scrape-loading/dye transfer as a rapid quantitative measure of intercellular communication in vitro.

We describe two flow cytometric assays performed on populations of cells which have been stained with various fluorescent tracer molecules by the scrape-loading technique. One assay uses a simple one-color analysis on a flow cytometer by quantitating the fluorescence intensity of scrape-loaded lucifer yellow CH (LY) in individual cells. The other assay utilizes a two-color analysis on a cell sorter whereby cells which are initially loaded (donors) are identified by their uptake of both rhodamine isothiocyanate-dextran and LY, whereas the recipients of dye transfer are identified as having LY only. Agents which have been shown to inhibit intercellular communication in other assays exhibit similar blocking activity in LY transfer and this is readily quantitated by flow cytometry. The two-color analysis has the added advantage of being able to identify both donors and recipients in a highly quantitative manner.

Contact insensitivity of a subpopulation of normal human fetal kidney epithelial cells and of human carcinoma cell lines.

Early passage normal human fetal kidney epithelial cells were inoculated on top of a confluent monolayer of X-ray lethally irradiated human fibroblasts to determine the colony-forming ability of these epithelial cells. The results indicate that the great majority of the epithelial cells did not have the clonogenic ability on the fibroblast cell mat, although they were capable of colony formation on plastic surface without the cell mat. A small subpopulation of these epithelial cells, however, was able to proliferate on the cell mat. These contact-insensitive fetal epithelial cells were found to be deficient in gap junction-mediated intercellular communication, to contain keratin and gamma-glutamyl transpeptidase but not fibronectin. These contact-insensitive cells appear to have greater proliferative potential than the parental cell population and to exist transiently in early passage but not in late passage culture. The ability of proliferation on cell mat was found to be shared by 22 different human carcinoma cell lines that were tested. This unique clonogenic ability of normal contact-insensitive and human carcinoma cells on the cell mat could provide a selection method for presumptive normal stem and tumor cells and for an assay for screening potential antitumor drugs and assessing the efficacy of chemotherapeutic drugs against a given tumor.

Scrape-loading and dye transfer. A rapid and simple technique to study gap junctional intercellular communication.

Gap junction-mediated intercellular communication has been recognized in cells from different tissues of various organisms and has been implicated in a variety of cellular functions and dysfunctions. Here we describe a new, direct and rapid technique with which to study this cellular phenomenon. It employs scrape-loading to introduce a low molecular weight (MW) fluorescent dye, Lucifer yellow CH (MW 457.2) into cells in culture and allows the monitoring of its transfer into contiguous cells. In communication-competent cells the dye transmission occurred within minutes after loading. The involvement of membrane junctions in Lucifer yellow transfer was verified by the concurrent loading of a high MW marker dye conjugate, rhodamine dextran (MW 10,000). Once introduced intracellularly the rhodamine dextran is unable to cross the relatively narrow membrane junctions. Chemicals of variable potency known to block junctional communication were tested in Chinese hamster V79 cells and other mammalian cells. The results showed effective blockage of the dye transfer at non-cytotoxic doses. This new technique can be applied to a wide variety of mammalian (including human) cells. In addition, it has the potential to be utilized as a rapid screening assay to detect chemicals that can modulate intercellular communication and to study their mechanism of action.