[The first child from an ultrarapidly frozen embryo in Finland]. / Ensimmäinen lapsi Suomessa ultranopeasti jäädytetystä alkiosta.

Transfers of frozen embryos are an important part of infertility treatments. In Finland, surplus embryos have been frozen over the years with the so-called slow method, which employs a programmable freezing device. In 1985 the first freezing trials with egg cells and embryos were initiated worldwide with the so-called vitrification method, in which the cells are actually not frozen but instead become glassified. This method, which has been found to be effective and gentle to the cells, is gradually gaining ground also in Finland. After thawing and transfer, a pregnancy and a healthy child developed from a blastocyst vitrified at our clinic.

Characterization of the Rab8-specific membrane traffic route linked to protrusion formation.

Rab8 has a drastic effect on cell shape, but the membrane trafficking route it regulates is poorly defined. Here, we show that endogenous and ectopically expressed Rab8 is associated with macropinosomes generated at ruffling membrane domains. These macropinosomes fuse or transform into tubules that move toward the cell center, from where they are recycled back to the leading edge. The biogenesis of these tubules is dependent on actin and microtubular dynamics. Expression of dominant-negative Rab8 mutants or depletion of Rab8 by RNA interference inhibit protrusion formation, but promote cell-cell adhesion and actin stress fiber formation, whereas expression of the constitutively active Rab8-Q67L has the opposite effect. Rab8 localization overlaps with both Rab11 and Arf6, and is functionally linked to Arf6. We also demonstrate that Rab8 activity is needed for the transport of transferrin and the transferrin receptor to the pericentriolar region and to cell protrusions, and that Rab8 controls the traffic of cholera toxin B to the Golgi compartment. Finally, Rab8 colocalizes and binds specifically to a synaptotagmin-like protein (Slp1/JFC1), which is involved in controlling Rab8 membrane dynamics. We propose that Rab8 regulates a membrane-recycling pathway that mediates protrusion formation.