Ultrastructure of mouse ectoplacental cone cells

Ectoplacental cone of the Muridae is an excrescence formed by proliferation of the polar trophectoderm of the bastocyst. Four types of trophoblast cells are seen in mouse ectoplacental cone on day 8 of the pregnancy: (1) trophoblast-1 at the base of the cone are polyhedral, compactly arranged and contain large nucleoli, (2) trophoblast-2 in the middle of the cone enclose several heterolysosomes, erythro-and leucophagosomes, (3) trophoblast-3, also in the middle, have several membrane-bound osmiophilic granules, (4) trophoblast-4 at the periphery of the cone are oblong and enclose many pleomorphic bodies. These morphological differences appear to be correlated with functional adaptation.     

A Highlights from MBoC Selection: A dimeric equilibrium intermediate nucleates Drp1 reassembly on mitochondrial membranes for fission

The GTPase dynamin-related protein 1 (Drp1) catalyzes mitochondrial division, but the mechanisms remain poorly understood. Much of what is attributed to Drp1’s mechanism of action in mitochondrial membrane fission parallels that of prototypical dynamin in endocytic vesicle scission. Unlike the case for dynamin, however, no lipid target for Drp1 activation at the mitochondria has been identified. In addition, the oligomerization properties of Drp1 have not been well established. We show that the mitochondria-specific lipid cardiolipin is a potent stimulator of Drp1 GTPase activity, as well as of membrane tubulation. We establish further that under physiological conditions, Drp1 coexists as two morphologically distinct polymeric species, one nucleotide bound in solution and the other membrane associated, which equilibrate via a dimeric assembly intermediate. With two mutations, C300A and C505A, that shift Drp1 polymerization equilibria in opposite directions, we demonstrate that dimers, and not multimers, potentiate the reassembly and reorganization of Drp1 for mitochondrial membrane remodeling both in vitro and in vivo.