title: Differential activity by polymorphic variants of a remote enhancer that supports galanin expression in the hypothalamus and amygdala: implications for obesity, depression and alcoholism.
abstract: The expression of the galanin gene (GAL) in the paraventricular nucleus (PVN) and in the amygdala of higher vertebrates suggests the requirement for highly conserved, but unidentified, regulatory sequences that are critical to allow the galanin gene to control alcohol and fat intake and modulate mood. We used comparative genomics to identify a highly conserved sequence that lay 42 kb 5' of the human GAL transcriptional start site that we called GAL5.1. GAL5.1 activated promoter activity in neurones of the PVN, arcuate nucleus and amygdala that also expressed the galanin peptide. Analysis in neuroblastoma cells demonstrated that GAL5.1 acted as an enhancer of promoter activity after PKC activation. GAL5.1 contained two polymorphisms; rs2513280(C/G) and rs2513281(A/G), that occurred in two allelic combinations (GG or CA) where the dominant GG alelle occurred in 70-83 % of the human population. Intriguingly, both SNPs were found to be in LD (R(2) of 0.687) with another SNP (rs2156464) previously associated with major depressive disorder (MDD). Recreation of these alleles in reporter constructs and subsequent magnetofection into primary rat hypothalamic neurones showed that the CA allele was 40 % less active than the GG allele. This is consistent with the hypothesis that the weaker allele may affect food and alcohol preference. The linkage of the SNPs analysed in this study with a SNP previously associated with MDD together with the functioning of GAL5.1 as a PVN and amygdala specific enhancer represent a significant advance in our ability to understand alcoholism, obesity and major depressive disorder.
authors.affiliation: School of Medical Sciences, Institute of Medical Sciences, Foresterhill, University of Aberdeen, Aberdeen, Scotland, UK.
authors.forename: Scott
authors.initials: S
authors.lastname: Davidson
authors.forename: Marissa
authors.initials: M
authors.lastname: Lear
authors.forename: Lynne
authors.initials: L
authors.lastname: Shanley
authors.forename: Benjamin
authors.initials: B
authors.lastname: Hing
authors.forename: Amanda
authors.initials: A
authors.lastname: Baizan-Edge
authors.forename: Annika
authors.initials: A
authors.lastname: Herwig
authors.forename: John P
authors.initials: JP
authors.lastname: Quinn
authors.forename: Gerome
authors.initials: G
authors.lastname: Breen
authors.forename: Peter
authors.initials: P
authors.lastname: McGuffin
authors.forename: Andrew
authors.initials: A
authors.lastname: Starkey
authors.forename: Perry
authors.initials: P
authors.lastname: Barrett
authors.forename: Alasdair
authors.initials: A
authors.lastname: MacKenzie
mesh_terms: D000437:Alcoholism / Q000235:genetics*; D000679:Amygdala / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D003863:Depression / Q000235:genetics*; D004742:Enhancer Elements, Genetic / Q000502:physiology; D019004:Galanin / Q000096:biosynthesis / Q000235:genetics*; D005786:Gene Expression Regulation; D014644:Genetic Variation / Q000235:genetics; D006801:Humans; D007031:Hypothalamus / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D009447:Neuroblastoma / Q000235:genetics; D009765:Obesity / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide / Q000502:physiology; D051381:Rats
chemical_list: D019004:Galanin