Cytochalasin induces abnormal anaphase in crane-fly spermatocytes and causes altered distribution of actin and centromeric antigens

Inhibition of cytokinesis by cytochalasins without an effect on karyokinesis has been demonstrated in several types of cells. We report here that treating crane-fly spermatocytes with cytochalasins at concentrations (10 M CE, 100 M CD, and 200 CB) in excess of that needed to inhibit cell division induces one or more half-bivalents to lag at anaphase during the first meiotic division. The behavior of the laggards is similar to that of maloriented half-bivalents. Following treatment at these concentrations, probing with rhodamine-phalloidin or bodipy-phallacidin reveals loss of filamentous actin from the poles and its appearance in the spindle, predominantly in regions where centromeres and kinetochores are normally found. When either N350 anti-actin monoclonal antibody or rhodamine DNase I was used to probe for actin in cytochalasin-treated cells, a similar redistribution of actin was observed. CD and CE treatments alter the pattern of fluorescence at centromere/kinetochore regions after staining with scleroderma CREST serum: CREST-positive structures become broader, with spikes extending from them toward the pole; in addition, some strands of CREST fluorescence appear that are apparently extraneous, and not associated with chromosomes. Probes for actin yield staining patterns in centromere/kinetochore regions that match closely the cytochalasin-altered pattern of CREST staining. Our finding of actin in the vicinity of kinetochores under conditions that result in abnormal chromosome behavior raises numerous questions about the possible role(s) of actin in meiosis, particularly in chromosome orientation.Abbreviations CREST calcinosis, Raynaud's phenomenon, esophageal dysmotility, sclerodactyly, telangiectasiaby W.C. Earnshaw