Table 1.

(A) Expression pattern of GPR39 in published studies. GPR39 shows variable expression in published literature dependent on splice variant, species, and detection method. (B) In-vitro GPR39 expression and signaling cascades.GPR39 over-expression (OE) in in-vitro systems generate G-protein signaling cascades.

(A)
Organism	Detection Method	Probe Source	GPR39 Variant Detected	Expression Pattern	Publication Source
Human	Northern blot for RNA, probe using 32P- Labeled DNA fragment with complete open reading frame	Fetal human brain cDNA library, GPR39 isolated by rapid PCR in search for relatives of Growth Hormone Secretagogue Receptor and Neurotensin Receptor Type 1.	1a, 1b	Amygdala, caudate nucleus, corpus callosum, hippocampus, substantia nigra, thalamus, cerebellum, cerebral cortex, medulla, spinal cord, occipital pole, frontal lobe, temporal lobe	[8]
Mouse	In situ hybridization, mRNA	Mouse	1a, 1b. Probe does not overlap with LYPD1/ MGC29643 antisense gene	Amygdala, hippocampus (dentate gyrus, CA1, CA3), auditory cortex, layer 2 piriform cortex, ventral pallidum, inferior olive, NOT in hypothalamus	[10]
Rat	Quantitative RT-PCR (QPCR), in situ hybridization	Rat	1a	Very low expression in CNS; high expression in peripheral metabolic organs	[12]
Rat	Quantitative RT-PCR (QPCR)	Rat	1b	Widely expressed but low expression in cerebellum, cortex, pons, hippocampus, hypothalamus, striatum, amygdala, septum. 1b overlaps with antisense gene LYPD1, which is expressed strongly in all brain regions.	[12]
Mouse	Quantitative RT-PCR (QPCR),	Mouse	1a	Low levels in whole brain, septum, hypothalamus, hippocampus	[24]
Mouse	GPR39 promoter expressing LacZ instead of GPR39, no functional GPR39	Mouse	1a, 1b	Septum, hippocampus (dentate gyrus), amygdala (discrete cells), NO hypothalamic expression. Strong expression in small intestine nerve plexus.	[24]
Rat	Quantitative RT-PCR (QPCR)	Rat	1a, 1b	Pituitary, hypothalamus, cerebellum, cerebrum	[11]
Mouse	RT-PCR in GPR39 KO mice and WT littermates	Mouse	1a, 1b	Low brain expression	[25]
Rat	Quantitative RT-PCR (QPCR)	Rat	1a, 1b	NOT in pituitary or hypothalamus	[26]
Human	Protein— immunohistochemistry, antibody to GPR39 third extracellular domain	Anti-human antibody	1a	Staining in microglia and peri- capillary cells (pericytes), higher density of GPR39 expressing microglia in mild cognitive impairment brains	[7]
(B)
In vitro System	Intervention	GPR39 Variant	Result		Publication Source
CHO cells (hamster ovary), HEK293T cells (human kidney)	GPR39 cDNA expression	1a, 1b	Increased obestatin stimulation with cAMP production; GPR39 constitutively activates serum response element (SRE)		[11]
COS-7 cells (monkey kidney)	GPR39 expression from human stomach cDNA library	1a, 1b	Zn2+ stimulated Gs pathway and cAMP increase; high constitutive activity		[26]
HEK293T cells (human kidney)	GPR39 overexpression from human cDNA	1a, 1b	GPR39 constitutively active through SRE- mediated transcriptional activity		[25]
CHO-K1 cells (hamster ovary)	Human and mouse GPR39 cDNA (1a) from genomic DNA, rat GPR39 obtained by RT-PCR from cDNA of rat liver.	1a, 1b	Zn2+ identified as GPR39 agonist in fetal bovine serum peptide extraction, showed Zn mobilizes calcium through Gαq-PLC pathway for human, mouse, and rat GPR39.		[27]