Pore-linked filaments in anura spermatocyte nuclei

Abstract

Pore-linked fi laments were visualized in spreads of anuran spermatocyte nuclei using transmission electron microscope. We used Odontophrynus diplo and tetraploid species having the tetraploid frogs reduced metabolic activities. The fi laments with 20-40 nm width are connected to a ring component of the nuclear pore complex with 90-120 nm and extend up to 1µm (or more) into the nucleus. The fi laments are curved and connect single or neighboring pores. The intranuclear fi laments are associated with chromatin fi bers and related to RNP particles of 20-25 nm and spheroidal structures of 0.5µm, with variations. The aggregates of several neighboring pores with the fi laments are more commonly observed in 4n nuclei. We concluded that the intranuclear fi laments may correspond to the fi brillar network described in Xenopus oocyte nucleus being probably related to RNA transport. The molecular basis of this RNA remains elusive. Nevertheless, the morphological aspects of the spheroidal structures indicate they could correspond to nucleolar chromatin or to nucleolus-derived structures. We also speculate whether the complex aggregates of neighboring pores with intranuclear fi laments may correspond to pore clustering previously described in these tetraploid animals using freeze-etching experiments.

Review Polyploidy and epigenetic events in the evolution of Anura

“…Along the same line of investigation, further electron microscopic description of complex aggregates of neighboring NPCs in the 4n species indicated a phenotype of low metabolic activity (Beçak and Fukuda-Pizzocaro, 2007).…”

Research Article Evolution, Epigenetic inheritance, Development – a diplo/tetraploid model for Anura evolution

“…Further studies on hemoglobin traits between allopatric populations of O. americanus 4n showed differences related to the process of diversification (Cianciarullo et al, 2019) Electron microscope studies showed that there are lower number of nuclear pore complexes (NPC) in the 4n with changes in the transport of products to the cytoplasm (Maul et al, 1980). Also, description by electron microscopy of complex aggregates of neighboring NPC in the 4n species may be related to a lower metabolic activity (Beçak and Fukuda-Pizzocaro, 2007).…”