Biol Cell. 2007 May;99(5):273-87 doi:10.1042/BC20060124

Spada F, Koch J, Sadoni N, Mitchell N, Ganot P, De Boni U, Zink D, Thompson EM.

Conserved patterns of nuclear compartmentalization are not observed in the chordate Oikopleura.

“[In endocycling cells,] simultaneous staining of DNA, RNA and membranes showed [...] deep invaginations of the nuclear envelope.” “O. dioica endocycling nuclei showed no polytenization or in loco gene amplification.” “An oikosin 6 probe [indicated] a family of related genes at multiple loci. Oikosin 4 and 6 were physically linked in a number of BAC clones.” “[Antibodies against splicing factors] failed to detect speckles in O. dioica endocycling nuclei and no interchromatin cluster granules were observed in the TEM images, suggesting these nuclei lack prominent splicing-factor domains.”