Biochemical approaches of Epigenetics

Chromatin is composed of DNA, histones, and other tightly associated proteins. Modifications of the DNA and of histones directly or indirectly control the regulation of DNA-related processes like transcription. Globally, the chromatin in a nucleus can be functionally divided into active and accessible euchromatin and inactive and condensed heterochromatin. Heterochromatin exists in two forms: facultative and constitutive heterochromatin. Facultative heterochromatin is a flexible form of heterochromatin and can be found in various chromosomal regions, when gene-coding regions need to be repressed. Its size varies from gene clusters to an entire chromosome (the inactive X in female cells). Facultative heterochromatin is frequently marked by specific histone modifications such as H2AK119Ub and H3K27me3, mediated by the polycombrepressor complexes (PRC) 1 and 2, respectively. Constitutive heterochromatin forms at specific regions of the genome, which are characterized by arrays of tandem DNA repeats: at the centromeres (minor satellite repeats), telomeres (telomeric repeats), and pericentric regions (major satellite repeats).

Maintenance of the heterochromatic nature of pericentric DNA is important for proper cell functions; failure impairs cell viability, induces chromosomal instabilities, and increases the risk of tumorigenesis. Therefore, pericentric heterochromatin has for a long time been considered as an inert, highly condensed, and inaccessible domain.

In the nuclei of most mammalian cells, pericentric heterochromatin is characterized by DNA methylation, histonemodifications such as H3K9me3 and H4K20me3, and specific binding proteins like heterochromatin-binding protein 1 isoforms (HP1 isoforms). Maintenance of this specialized chromatin structure is of great importance for genome integrity and for the controlled repression of the repetitive elements within the pericentric DNA sequence. Here we have studied histone modifications at pericentric heterochromatin during primordial germ cell (PGC) development using different fixation conditions and fluorescent immunohistochemical and immunocytochemical protocols.

Submit your talk on session  Biochemical approaches of Epigenetics taking place at Vienna: https://epigenetics.expertconferences.org/abstract-submission.php