Alternative splicing in the coding region of human aromatic L-amino acid decarboxylase mRNA

Total RNA from human neuroblastoma cells (SK-N-SH) was reverse transcribed and amplified using primers specific for aromatic L-amino acid decarboxylase (AADC). Two polymerase chain reaction (PCR) products were observed following agarose electrophoresis. Cycle sequencing of the PCR products revealed the larger fragment (414 bp) to be identical to the published human cDNA sequence (Type I). Sequencing of the smaller band (300 bp) demonstrated a form missing exon three (Type II). Both types of the mRNA were colocalized in human brain regions (gray matter and white matter) and other human tissues (liver, kidney, adipose, heart, adrenal gland and keratinocytes). The relative concentrations varied in each tissue studied but specific neuronal or non-neuronal patterns were not apparent. The study demonstrates alternative splicing within the coding region of the human AADC mRNA and the results suggest the possibility that two proteins are derived from the AADC gene in human tissues.