MEG3 is a maternally expressed, imprinted long non-coding RNA gene
A gene is a molecular unit of heredity of a living organism. It is a name given to some stretches of DNA and RNA that code for a type of protein or for an RNA chain that has a function in the organism. Living beings depend on genes, as they specify all proteins and functional RNA chains...

. At least 12 different isoforms of MEG3 are generated by alternative splicing
Alternative splicing
Alternative splicing is a process by which the exons of the RNA produced by transcription of a gene are reconnected in multiple ways during RNA splicing...

. Expression of MEG3 is lost in cancer cells. It acts as a growth suppressor in tumour cells, and activates p53
p53 , is a tumor suppressor protein that in humans is encoded by the TP53 gene. p53 is crucial in multicellular organisms, where it regulates the cell cycle and, thus, functions as a tumor suppressor that is involved in preventing cancer...

. A pituitary transcript variant has been associated with inhibited cell proliferation. Studies in mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...

 and sheep suggest that an upstream intergenic differentially methylated region regulates imprinting of the region. The expression profile in mouse of the co-regulated Meg3 and Dlk1
Protein delta homolog 1 is a protein that in humans is encoded by the DLK1 gene.It is expressed as a transmembrane protein, but a soluble form cleaved off by ADAM17 is active in inhibiting adipogenesis, the differentiation of pre-adipocytes into adipocytes.It is a member of the EGF-like family of...

 genes suggests a causative role in the pathologies found in uniparental disomy
Uniparental disomy
Uniparental disomy occurs when a person receives two copies of a chromosome, or part of a chromosome, from one parent and no copies from the other parent.. UPD could involve isodisomy or heterodisomy ....

 animals, characterized by defects in skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...

 maturation, bone
Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

 formation, placenta
The placenta is an organ that connects the developing fetus to the uterine wall to allow nutrient uptake, waste elimination, and gas exchange via the mother's blood supply. "True" placentas are a defining characteristic of eutherian or "placental" mammals, but are also found in some snakes and...

 size and organization and prenatal lethality. The sheep homolog
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...

 is associated with the callipyge mutation
Glossary of sheep husbandry
The raising of domestic sheep has occurred in nearly every inhabited part of the globe, and the variations in cultures and languages which have kept sheep has produced a vast lexicon of unique terminology used to describe sheep husbandry...

 which in heterozygous individuals affects a muscle-specific long-range control element located in the DLK1-GTL2 intergenic region and results in the callipyge muscular hypertrophy
Hypertrophy is the increase in the volume of an organ or tissue due to the enlargement of its component cells. It should be distinguished from hyperplasia, in which the cells remain approximately the same size but increase in number...

. The non-Mendelian inheritance pattern, known as polar overdominance
Polar overdominance
Polar overdominance is a unique form of inheritance whereby a mutant Callipyge allele must be inherited from the father to cause muscle hypertrophy .-See also:*Imprinting...

, likely results from the combination of the cis-effect on the expression levels of genes in the DLK1-GTL2 imprinted domain, and trans
In the field of molecular biology, trans-acting , in general, means "acting from a different molecule"...

interaction between the products of reciprocally imprinted genes.

Further reading

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