ACTH receptor (MC2R) promoter variants associated with infantile spasms modulate MC2R expression and responsiveness to ACTH.
OBJECTIVE
Adrenocorticotropin hormone (ACTH) has been the standard treatment to infantile spasms (IS). However, the mechanism of ACTH therapy is still unclear. ACTH exerts the function via melanocortin 2 receptor (MC2R). Our previous study showed a common 4-single nucleotide polymorphism (SNP) haplotype TCCT at the MC2R promoter was strongly associated with responsiveness to ACTH therapy, where these 4 SNPs [rs1893219, rs1893220, rs2186944, and a novel SNP (T>C)] were mapped at position -853, -759, -7, and -2 bp based on the transcription start site of the MC2R gene. In this study, we further elucidated functional significances of the TCCT haplotype.


METHODS
To evaluate whether the TCCT haplotype influences MC2R transcription levels, the luciferase reporter vector was used by a transient transfection. Expression of rat MC2R cDNA driven by the TCCT-carrying or TCCC-carrying promoter was detected by the real-time quantitative reverse transcription-PCR. These assays were performed on cell lines cultured in absence or presence of ACTH.


RESULTS
In the baseline, the light intensity of the luciferase reporter assay driven by the TCCT promoter was four times higher than that by the TCCC promoter. The intensity was dramatically increased in the pGL3-TCCT after ACTH stimulation, compared to that in the pGL3-TCCC. MC2R expression assay showed a 5-fold increase in the TCCT promoter in presence of ACTH, compared with that in absence of ACTH.


CONCLUSIONS
The results showed that the haplotype TCCT in MC2R promoter significantly led to increased MC2R expression and strong responses to ACTH, providing evidence of the molecular mechanism of ACTH therapy in IS.
Ding
Ying-Xue
YX
Department of Pediatrics, Chinese PLA General Hospital, Ministry of Health, Beijing, PR China.
Zou
Li-Ping
LP
He
Bing
B
Yue
Wei-Hua
WH
Liu
Zhan-Li
ZL
Zhang
Dai
D
D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D002460:Cell Line; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005786:Gene Expression Regulation / Q000187:drug effects*; D006801:Humans; D007231:Infant, Newborn; D008156:Luciferases / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide / Q000235:genetics*; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D044103:Receptor, Melanocortin, Type 2 / Q000235:genetics* / Q000378:metabolism; D013036:Spasms, Infantile / Q000235:genetics*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D018076:DNA, Complementary; D012333:RNA, Messenger; D044103:Receptor, Melanocortin, Type 2; D000324:Adrenocorticotropic Hormone; D008156:Luciferases