Supplementary Material for: Quantitative mRNA Analysis of Serotonin 5-HT<sub>4</sub> and Adrenergic β<sub>2</sub> Receptors in the Mouse Embryonic Telencephalon

2010-08-31T00:00:00Z (GMT) by Hernandez M.C. Janušonis S.
The adrenergic β<sub>2</sub> receptor (β<sub>2</sub>-AR) gene is embedded (nested) within the serotonin 5-HT<sub>4</sub> receptor (5-HT<sub>4</sub>-R) gene and these two receptors can interact at the transcriptional and post-transcriptional levels. The mouse 5-HT<sub>4</sub>-R gene contains a number of exons and codes at least four mRNA splice variants (5-HT<sub>4(a)</sub>-R, 5-HT<sub>4(b)</sub>-R, 5-HT<sub>4(e)</sub>-R, 5-HT<sub>4(f)</sub>-R), whereas the β<sub>2</sub>-AR gene is intronless. Since 5-HT<sub>4</sub>-Rs and β<sub>2</sub>-ARs can form homodimers and heterodimers and they increase intracellular cAMP levels, these receptors may be important for integrating serotonergic and noradrenergic signals at the single-neuron level. Both 5-HT<sub>4</sub>-R and β<sub>2</sub>-AR have been implicated in autism spectrum disorders, depression, and Alzheimer’s disease. In the fetal brain, these receptors may mediate the effects of stress on neurodevelopmental processes. We used quantitative reverse-transcription PCR (qRT-PCR) to investigate the developmental expression of 5-HT<sub>4</sub>-R and β<sub>2</sub>-AR in the mouse telencephalon at embryonic days (E) 13–18. At E13–E14, the mRNA levels of all 5-HT<sub>4</sub>-R splice variants were very low, but by E17–E18 they increased 7-fold (5- HT<sub>4(a)</sub>-R), 5-fold (5-HT<sub>4(b)</sub>-R), 9-fold (5-HT<sub>4(e)</sub>-R), and 11-fold (5-HT<sub>4(f)</sub>-R). The expression of 5-HT<sub>4(a)</sub>-R and 5-HT<sub>4(b)</sub>-R was rapidly upregulated between E14 and E15, at the time when the thalamocortical projections arrive in the telencephalon. This pattern was not observed in the expression of 5-HT<sub>4(e)</sub>-R and 5-HT<sub>4(f)</sub>-R, the mRNA levels of which showed a steady, gradual increase from E13 to E18. The β<sub>2</sub>-AR mRNA levels were relatively high throughout the studied period of development and increased only by 70% from E13–E14 to E17–E18. These findings suggest that 5-HT<sub>4</sub>-R splice variants and β<sub>2</sub>-ARs are differentially regulated in the embryonic telencephalon and that their relative amounts may carry developmentally important information.