The discrepancy between mRNA levels and protein levels of the HTR1A, which showed high densities of binding sites in both, HF and the NCL compared to other monoaminergic receptors, can be explained by the fact that the ligands access the protein levels binding both, pre- and postsynaptic sites, while 5HTR1A mRNA cannot be detected in axon terminals (Vilaro et al., 2020). The gene discussed is HTR1A; the disease is hydrops fetalis.