The bridge-partitioning complex is absent in a distinct type of defective germ cell division in the gonads of the golden hamster.

Abstract

Intercellular bridges (IBs) connecting the cytoplasms of a defined type of defective germ cell division ("arrested mitoses") in male and female gonads of the immature golden hamster were studied by electron microscopy. In both sexes, such cells appear at the time when germ cells switch from mitotic proliferation to the onset of meiotic prophase, i.e., during a short perinatal period in the female and during pubertal maturation in the male golden hamster. These cells are arrested and finally degenerate. IBs of these cells completely lack the bridge-partitioning complex (BPC), a structure composed of a stack of transverse endomembrane cisternae which normally fills the IBs during subsequent divisions of bridge-connected germ cells. This unique exception from the usual course of clonal proliferation of mammalian germ cells has several implications: (1) The supposed barrier function of the BPC is missing in the defective germ cell divisions; (2) the failure to form the BPC might be related to a disturbed microtubule apparatus in the cells; (3) the absence of the BPC possibly reflects the influence of conflicting environmental signals, inducing both mitotic and early meiotic mechanisms in the cells at this crucial point of gametogenesis.