Emergence and evolution of neuronal genes deciphered by genome informatics

Human neuronal proteins were searched to various animal genomes along with the phylogenetic tree using higher than 50% of query cover for the homology evaluation to know the presence or absence of homologs. Using the query cover value and gene ID of searched proteins, the number of homologous genes in the genomes was identified. The results showed that numbers of genes of synaptotagmin, neuronal channel proteins and myelin sheath proteins are increased along with evolution, implicating that these genes have roles in the development of neuronal network and neurotransmission. At the emergence of mammals, MEPE is appeared but missed only in egg-laying mammals. MEPE is a brain-specific protein negatively regulating bone mineralization. The emergence of MEPE is linked with the emergence of fetal animals. HTT gene of Huntington’s disease known as poly Q disease is appeared from lamprey, an ancestor of vertebrate. The lamprey HTT protein contains only one Q but the number of Q and also P existing next to poly Q in higher animals is dramatically increased and human has the longest poly Q-poly P sequence, suggesting that increase of the length of poly Q and P may have evolutionary role in brain development. The results of gene emergence and gene number transition in this study elucidated evolutional history of neuron and brain development.

Neuronal gene

synaptotagmin

syntaxin

HTT

SNCA

MEPE

human brain

Homo sapiens

Latimeria chalumnae

Petromyzon marinus

Trichoplax adhaerens