during embryonic development for the maturation and development of cardiac myocytes. However, during early childhood and throughout adulthood, ANP expression is suppressed or kept to a minimum in the ventricle. Thus, an abnormal induction of the ANP gene can lead to ventricular hypertrophy and severe cardiac consequences. In order to maintain the repression of the gene, NRSF (neuron-restrictive silencer factor) or REST binds to the NRSE region in the 3’untranslated region of the ANP gene. Furthermore, the NRSF-NRSE complex recruits a transcriptional corepressor known as mSin3. This leads to the activity of histone deacetylase in the region and the repression of the gene. Therefore, studies have revealed the correlation between REST/NRSF and RE1/NRSE in regulating the ANP gene expression in ventricular myocytes. A mutation in either the NRSF or NRSE can lead to an undesirable development of ventricular myocytes, due to lack of repression, which can then cause ventricular hypertrophy. Left ventricular hypertrophy, for example, increases an individual's chance of sudden death due to a ventricular arrhythmia resulting from the increased ventricular mass. In addition to the influence on the ANP gene, the NRSE sequence regulates other cardiac embryonic genes, such as brain natriuretic peptide BNP, skeletal α-actin, and Na, K – ATPase α3 subunit. Hence, the regulatory activity of both NRSE and NRSF in mammals prevents not only neural dysfunctions but also physiological and phenotypical abnormalities in other non-neuronal regions of the body. Mutations in polycomb-group response elements (PREs) The Polycomb-group (PcG) regulatory complexes are known for their influence in the epigenetic regulation of stem cells, especifically in hematopoietic stem cells. The Polycomb Repressive Complex 1 (PRC 1) is directly involved in the process of hematopoiesis, and functions together with, for example, the PcG gene “Bmi1”. Studies in mice indicate that organisms with mutated “Bmi1” demonstrate deficient mitochondrial functioning, and also hindered the ability of hematopoietic cells to self-renew. Likewise, mutations in PRC2 genes were related to hematological conditions such as acute lymphoblastic leukemia (ALL), which is a form of leukemia. Hence, Polycomb-group genes and proteins are involved in the proper maintenance of hematopoiesis in the body. References External links Gene expression