Unusual Biomolecular Condensates Containing Nucleoporins or Lamin in the Germinal Vesicle of the Common Frog

The nucleus (germinal vesicle, GV) of late vitellogenic oocytes of the European common frog, Rana temporaria , was found to contain biomolecular condensates (BioMCs) that accumulate nucleoporins Nup93, Nup 35, or a protein recognized by antibodies against lamin B. Apart, the studied nucleoporins are diffusely distributed throughout the GV and seem not present in peculiar structures, annuli , previously thought to represent nucleoplasmic autonomous pore complexes. Intranuclear membrane compartments (e.g., modified nuclear annulata lamellae ), previously considered to represent derivatives of the nuclear envelope, did not show the presence of the studied nucleoporins and lamin. The molecular composition and functions of the extrachromosomal nuclear structures characteristic of R. temporaria oocytes, including the new type of BioMCs described here, remain unknown, highlighting the complexity of the internal organization of the GV.