No abstract

CTCF is a multifunctional nuclear factor involved in many cellular processes like gene regulation, chromatin insulation and genomic organization. Recently, CTCF has been shown to be involved in the transcriptional regulation of ribosomal genes and nucleolar organization in Drosophila cells and different murine cell types, including embryonic stem cells. Moreover, it has been suggested that CTCF could be associated to the nucleolus of human erythroleukemic K562 cells. In the present work, we took advantage of efficient small hairpin RNA interference against human CTCF to analyze nucleolar organization in HeLa cells. We have found that key components of the nucleolar architecture are altered. As a consequence of such alterations, an upregulation of ribosomal gene transcription was observed. We propose that CTCF contributes to the structural organization of the nucleolus and, through epigenetic mechanisms, to the regulation of the ribosomal gene expression.

An ultrastructural study was made of basidiospores from nine species of Dacrymycetales: Calocera macrospora, C. viscosa, Dacrymyces dictyosporus, D. chrysospermus, Dacryopinax elegans, Da. spathularia, Da. lowyi, Guepiniopsis alpina, and G. buccina. Spore walls and septa analyzed with transmission electron microscopy revealed the absence or presence of discrete lateral wall layers as well as septal pores that appear diagnostic at the species level.

Follicles are ovarian structures that contain a single germ cell. During the mammalian reproductive lifetime, ovarian follicles mature through the process of follicular development, with the aim of selecting oocytes for ovulation. As part of this process, several follicles are eliminated by means of follicular atresia, a mechanism that mainly involves apoptosis. Nevertheless, it has been shown that there are other routes of programmed cell death in the ovary including autophagy, paraptosis, and necroptosis. Surprisingly, the endoplasmic reticulum is involved in these different programmed cell death pathways. Moreover, there are several evidences for the pathways triggered by intra-and extracellular signals in endoplasmic reticulum-induced cell death. Thus, it is important to analyze the participation of endoplasmic reticulum in follicular atresia.