Question

What is the effect of genomic imprinting on cancer and what is the possible connection of the recent rise in imprinting disorders with assisted reproductive technologies.

Answer 1

ANSWERS :-

1) Effects of genomic imprinting on cancer:

* Genomic imprinting is an inheritance process independent of the classical Mendelian inheritance.

* genomic imprinting is an epigenetic modification of a specific parental allele of gene, or the chromosome on which it resides, in the gamete or zygote leading to differential expression of the two alleles of the gene in somatic cells of the offspring.

* Although we inherit two copies of all genes, except those that reside on the sex chromosomes, there is a subset of these genes in which only the paternal or maternal copy is functional. This phenomenon of monoallelic, parent-of-origin expression of genes is termed genomic imprinting. Imprinted genes are normally involved in embryonic growth and behavioural development, but occasionally they also function inappropriately as oncogenes and tumor suppressor genes.

* Variety of genetic changes influence the development and progression of cancer. These changes may result from inherited or spontaneous mutations. Observations identified that Cancer genomes undergo changes in their methylation state and control of parental allele - specific methylation and expression of imprinted loci is lost in several cancers.

*Hydatidiform mole and complete ovarian teratomas, the gene of each of which is derived from a single parental origin, show that an imbalance of maternal and paternal genome equivalents leads to neoplastic growth.

2) possible connection of the racent rise in imprinting dissorders with assisted reproductive technologies :-

* Imprinting disorders are a group of congenital diseases characterized by overlapping clinical features affecting growth, development and metabolism, and common molecular disturbances, affecting genomically imprinted chromosomal regions and genes.

* Children bone by assisted reproductive technologies are at an increased risk of having imprinting disorders.

*Assisted reproductive technology may affect methylation status of imprinted regions in DNA, leading to imprinting disorders.

* Disruption in imprinting associated with significant pathologies like Angelman syndrome, Beckwith -wiedemann syndrome and Prader-willi syndrome.

* Manipulation of oocytes and embryos in ART coincides with the timings of epigenetic reprogramming imprinting.