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Biology of Reproduction 67, 568-574 (2002)
© 2002 Society for the Study of Reproduction, Inc.

Regular Article

Variability of Placental Expression of Cyclin E Low Molecular Weight Variants1

Antonin Bukovsky2,a, Maria Cekanovaa, Michael R. Caudlea, Jay Wimalasenaa, James S. Fostera, Jeffrey A. Keenana, and Robert F. Eldera

a Laboratory for Development, Differentiation, and Cancer, Department of Obstetrics and Gynecology, The University of Tennessee Graduate School of Medicine, Knoxville, Tennessee 37920

Cyclin E, a G1 cyclin serving to activate cyclin-dependent kinase 2, is the only cyclin gene for which alternative splicing leading to structurally different proteins has been described. Different cyclin E proteins are present in tumor tissues but absent from normal (steady) tissues. Cyclin E contributes to the regulation of cell proliferation and ongoing differentiation and aging. Because trophoblast has invasive properties and differentiates into syncytium and placental aging may develop at term, we examined cyclin E protein variants in human placenta. Placental samples were collected from 27 deliveries between 33 and 41 wk and were compared with ovarian cancer (positive control). Both placental and tumor tissues showed seven cyclin E low molecular weight (LMW) bands migrating between 50 and 36 kDa. Placental expression of cyclin E showed certain variability among cases. Lowest cyclin E expression was detected in normal placentas (strong expression of Thy-1 differentiation protein in villous core and low dilatation of villous blood sinusoids). Abnormal placentas (significant depletion of Thy-1 and more or less pronounced dilatation of sinusoids) showed significant increase either of all (early stages of placental aging) or only certain cyclin E proteins (advanced aging). Our studies indicate that a similar spectrum of cyclin E protein variants is expressed in the placental and tumor tissues. Low cyclin E expression in normal placentas suggests a steady state. Overexpression of all cyclin E proteins may indicate an activation of cellular proliferation and differentiation to compensate for developing placental insufficiency. However, an enhanced expression of some cyclin E LMW proteins only might reflect an association of cyclin E isoforms with placental aging or an inefficient placental adaptation.

First decision: 25 February 2002.

1 Supported by Physician's Medical Education and Research Foundation grant 93040, Knoxville, TN, to A.B.

2 Correspondence: Antonin Bukovsky, Department of OB/GYN, UT G.S.M., 1924 Alcoa Highway, Knoxville, TN 37920. FAX: 865 544 6863; buko{at}utk.edu






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Copyright © 2002 by the Society for the Study of Reproduction.