What causes Angelman Syndrome?!

Many of the characteristic features of Angelman syndrome result from the loss of function of a gene called UBE3A. People normally inherit one copy of the UBE3A gene from each parent. Both copies of this gene are turned on (active) in many of the body's tissues. In certain areas of the brain, however, only the copy inherited from a person's mother (the maternal copy) is active.
Ubiquitin is a small regulatory protein
Protein
Proteins are organic compounds made of amino acids arranged in a linear chain and folded into a globular form. The amino acids in a polymer are joined together by the peptide bonds between the carboxyl and amino groups of adjacent amino acid residues...

that has been found in almost all cells (ubiquitously) with nuclei (eukaryotes). It directs proteins to recycling and other functions.
Most cases of Angelman syndrome are not inherited, particularly those caused by a deletion in the maternal chromosome 15 or by paternal uniparental disomy. These genetic changes occur as random events during the formation of reproductive cells (eggs and sperm) or in early embryonic development. Affected people typically have no history of the disorder in their family.

Rarely, a genetic change responsible for Angelman syndrome can be inherited. For example, it is possible for a mutation in the UBE3A gene or in the nearby region of DNA that controls gene activation to be passed from one generation to the next.
The ubiquitination system functions in a wide variety of cellular processes, including:

* Antigen processing
Antigen processing
Antigen processing is a biological process that prepares antigens for presentation to special cells of the immune system called T lymphocytes. This process involves two distinct pathways for processing of antigens from an organism's own proteins or intracellular pathogens , or from phagocytosed...

* Apoptosis
Apoptosis
Apoptosis is the process of programmed cell death that may occur in multicellular organisms. Biochemical events lead to characteristic cell changes and death. These changes include blebbing, loss of cell membrane asymmetry and attachment, cell shrinkage, nuclear fragmentation, chromatin...

* Biogenesis
Biogenesis
Biogenesis is the process of lifeforms producing other lifeforms, e.g. a spider lays eggs, which develop into spiders. It may also refer to biochemical processes of production in living organisms.-Generatio spontanea:...

of organelles
* Cell cycle and division
* DNA transcription
Transcription (genetics)
Transcription is the process of creating an equivalent RNA copy of a sequence of DNA. Both RNA and DNA are nucleic acids, which use base pairs of nucleotides as a complementary language that can be converted back and forth from DNA to RNA in the presence of the correct enzymes...

and repair
* Differentiation and development
* Immune response and inflammation
* Neural and muscular degeneration
* Morphogenesis of neural networks
* Modulation of cell surface receptors, ion channels and the secretory pathway
* Response to stress and extracellular modulators
* Ribosome biogenesis
* Viral infection

http://www.absoluteastronomy.com/topics/…
http://ghr.nlm.nih.gov/condition/angelma…