Glutamate receptor
Glutamate receptors are synaptic and non synaptic receptors located primarily on the membranes of neuronal and glial cells. Glutamate (the conjugate base of glutamic acid) is abundant in the human body, but particularly in the nervous system and especially prominent in the human brain where it is the body's most prominent neurotransmitter, the brain's main excitatory neurotransmitter, and also the precursor for GABA, the brain's main inhibitory neurotransmitter. Glutamate receptors are responsible for the glutamate-mediated postsynaptic excitation of neural cells, and are important for neural communication, memory formation, learning, and regulation.
DUF1220
The copy number of DUF1220 domains increases generally as a function of a species's evolutionary proximity to humans. The increase in the number of copies that are present in connection with DUF1220 also seem to have a direct correlation with several phenotypes of the brain including the increase in brain size as seen through evolution. DUF1220 copy number is the highest in humans (~289, with some person-to-person variations) and shows the largest HLS increase in copy number (an additional 160 copies) of any protein coding region in the human genome. DUF1220 copy number is reduced in African great apes (estimated 125 copies in chimpanzees), further reduced in orangutan (92) and Old World monkeys (35), single- or low-copy in non-primate mammals and absent in non-mammals. DUF1220 domains are approximately 65 amino acids in length and are encoded by a two-exon doublet. In the human genome, DUF1220 sequences are located primarily on chromosome 1 in region 1q21.1-q21.2, with several copies also found at 1p36, 1p13.3, and 1p12. Sequences encoding DUF1220 domains show rhythmicity, resonance and signs of positive selection, especially in primates, and are expressed in several human tissues including brain, where their expression is restricted to neurons.