• HTR3A belongs to the ligand-gated ion channel receptor superfamily. It encodes subunit A of the type 3 receptor for 5-hydroxytryptamine (serotonin), a biogenic hormone that functions as a neurotransmitter, a hormone, and a mitogen. HTR3A causes fast, depolarizing responses in neurons after activation. Alternatively spliced transcript variants encoding different isoforms have been identified.
• HTR3A gene encodes subunit A of the type 3 receptor for 5-hydroxytryptamine (serotonin), a biogenic hormone that functions as a neurotransmitter, a hormone, and a mitogen. This receptor causes fast, depolarizing responses in neurons after activation. It appears that the heteromeric combination of A and B subunits is necessary to provide the full functional features of this receptor, since either subunit alone results in receptors with very low conductance and response amplitude. Alternatively spliced transcript variants encoding different isoforms have been identified.

Gene targeting strategy for B-hHTR3A mice. The exons 1-9 of mouse Htr3a gene that encode signal peptide, extracellular domain, transmembrane domain and cytoplasmic region are replaced by human counterparts in B-hHTR3A mice. The promoter, 5`UTR and 3`UTR region of the mouse gene are replaced by the promoter, 5`UTR and 3`UTR region of the human gene. The human HTR3A expression is driven by human HTR3A promoter, while mouse Htr3a gene transcription and translation will be disrupted.

Strain specific analysis of HTR3A mRNA expression in wild-type C57BL/6 mice and B-hHTR3A mice by RT-PCR. brain RNA were isolated from wild-type C57BL/6 mice (+/+) and homozygous B-hHTR3A mice (H/H), then cDNA libraries were synthesized by reverse transcription, followed by PCR with mouse or human HTR3A primers. Mouse Htr3a mRNA were detectable only in wild-type C57BL/6 mice. Human HTR3A mRNA was detectable only in homozygous B-hHTR3A mice but not in wild-type mice. 

Western blot analysis of HTR3A protein expression in homozygous B-hHTR3A mice. Various tissue lysates were collected from wild-type C57BL/6 mice (+/+)  and homozygous B-hHTR3A mice (H/H), and then analyzed by western blot with anti-HTR3A antibody(Abcam, ab13897). 40 μg total proteins were loaded for western blotting analysis. hHTR3A was detected in brain, stomach, small intestine and colon.