Identification of two novel HTR4b splice variants by 3′RACE. (A) Three different isoforms were identified by 3′RACE. (A′) Schematic illustration of the 3′UTRs of full length HTR4b and the novel isoforms HTR4b_2 and HTR4b_3. miRNA binding sites are indicated by ‘I-III’ (in blue). Arrows reflect positions of 3′RACE primers. (B) Expression pattern of the three HTR4b isoforms in different human GI tissues. ARF1 served as cDNA integrity and loading control. Respective PCR images were cropped for figure implementation. (C) Relative luciferase activity of HTR4b_2 and HTR4b 3′UTR reporter gene constructs (n = 3) and (D) Relative 5-HT4b and b2 receptor levels quantified by In Cell Western experiments (n = 3) in HEK293T. Values are means ± SEM., **p < 0.01, ***p < 0.001. Unpaired t-test.