The balance between heterochromatin and
euchromatin is very dynamic.
Amiel et al., "Loss-of-function mutations in
Euchromatin histone methyl transferase 1 (EHMT1) cause the 9q34 subtelomeric deletion syndrome," American Journal of Human Genetics, vol.
The nuclei possess fine granulated
euchromatin and heterochromatin with the latter adjacent to the nuclear envelope (Fig.
Heterochromatin is a characteristic component of the eukaryotic nucleus which, as opposed to
euchromatin, is highly compacted, non-coding and contains highly repetitive DNA sequences (Swanson et al., 1981; Brutlag, 1980).
(2005) noted that normal Bs consist of a diminutive short arm, a centromere, a proximal heterochromatin block, a stretch of
euchromatin, followed by four blocks of heterochromatin and the distal-most
euchromatin.
For mosaic tetrasomy 18p, the variability and severity of clinical phenotype might be influenced by
euchromatin content, the degree of mosaicism, etc.
Furthermore, More, Raza, and Vince (2012) found that the diluent diacetyl had the potential to replace thymine with guanine in
euchromatin regions, resulting in the disruption of hydrogen and disulfide bonds in the tertiary structure of enzymes important for mitosis.
Traditionally,
euchromatin is considered an area of the genome that is transcriptionally active, while heterochromatin is transcriptionally silent.
Histone methyltransferases g9a and glp form heteromeric complexes and are both crucial for methylation of
euchromatin at h3-k9.
[75] reported the global reduction of heterochromatin marker H3K9Me2, increase of
euchromatin marker H3K4Me3, and increase of the transcriptional marker H3K36Me3 during the EMT progress, which are mostly dependent upon lysine-specific deaminase-1 (Lsd1).
Cell nucleus was elliptic in the center with a single nucleolus and had normal
euchromatin and scattered heterochromatin.