The visualization of dopamine neurons

Summary:
The phenomenon of genomic imprinting, in which genes are expressed only from paternal or maternal alleles, is critical in normal mammalian development. Dopa decarboxylase is an enzyme that catalyzes the conversion of L-dopa to dopamine, which is encoded by the Ddc gene. The pattern of Ddc expression in the brain remains unclear. To examine the expression of Ddc, we generated red fluorescent protein knock-in reporter (Ddc-hKO1) mice. The detailed analysis of the brains of heterozygous mice carrying the Ddc-hKO1 gene on either the paternal or maternal chromosome revealed that Ddc is preferentially expressed from the maternal chromosome in the major dopamine neurons in the midbrain, from both chromosomes in neurons located in the midbrain to the brainstem, and from the paternal chromosome in the hypothalamus. In neurons located from the midbrain to the brainstem, expression is preferentially derived from both chromosomes. Each Ddc-expressing neuron has a unique function in its domain, such as feeding, motivation, and learning. It is believed that paternally and maternally derived chromosomes function differently in these neurons, which could help with aging and disease research.