title: Genetic mapping of putative Chrna7 and Luzp2 neuronal transcriptional enhancers due to impact of a transgene-insertion and 6.8 Mb deletion in a mouse model of Prader-Willi and Angelman syndromes.
abstract: BACKGROUND
  Prader-Willi and Angelman syndrome (PWS and AS) patients typically have an approximately 5 Mb deletion of human chromosome 15q11-q13, of opposite parental origin. A mouse model of PWS and AS has a transgenic insertion-deletion (TgPWS/TgAS) of chromosome 7B/C subsequent to paternal or maternal inheritance, respectively. In this study, we define the deletion endpoints and examine the impact on expression of flanking genes.
  
  
  RESULTS
  Using molecular and cytological methods we demonstrate that 13 imprinted and 11 non-imprinted genes are included in the TgPWS/TgAS deletion. Normal expression levels were found in TgPWS brain for genes extending 9.1- or 5.6-Mb centromeric or telomeric of the deletion, respectively. Our molecular cytological studies map the proximal deletion breakpoint between the Luzp2 and Siglec-H loci, and we show that overall mRNA levels of Luzp2 in TgPWS and TgAS brain are significantly reduced by 17%. Intriguingly, 5' Chrna7 shows 1.7-fold decreased levels in TgPWS and TgAS brain whereas there is a > or =15-fold increase in expression in neonatal liver and spleen of these mouse models. By isolating a Chrna7-Tg fusion transcript from TgAS mice, we mapped the telomeric deletion breakpoint in Chrna7 intron 4.
  
  
  CONCLUSIONS
  Based on the extent of the deletion, TgPWS/TgAS mice are models for PWS/AS class I deletions. Other than for the first gene promoters immediately outside the deletion, since genes extending 5.6-9.1 Mb away from each end of the deletion show normal expression levels in TgPWS brain, this indicates that the transgene array does not induce silencing and there are no additional linked rearrangements. Using gene expression, non-coding conserved sequence (NCCS) and synteny data, we have genetically mapped a putative Luzp2 neuronal enhancer responsible for approximately 33% of allelic transcriptional activity. The Chrna7 results are explained by hypothesizing loss of an essential neuronal transcriptional enhancer required for approximately 80% of allelic Chrna7 promoter activity, while the Chrna7 promoter is upregulated in B lymphocytes by the transgene immunoglobulin enhancer. The mapping of a putative Chrna7 neuronal enhancer inside the deletion has significant implications for understanding the transcriptional regulation of this schizophrenia-susceptibility candidate gene.
authors.affiliation: Center for Neurobiology and Behavior, Department of Psychiatry, University of Pennsylvania, Philadelphia, PA 19104, USA. Mihaela.Stefan@chp.edu
authors.forename: Mihaela
authors.initials: M
authors.lastname: Stefan
authors.forename: Kathryn C
authors.initials: KC
authors.lastname: Claiborn
authors.forename: Edyta
authors.initials: E
authors.lastname: Stasiek
authors.forename: Jing-Hua
authors.initials: JH
authors.lastname: Chai
authors.forename: Tohru
authors.initials: T
authors.lastname: Ohta
authors.forename: Richard
authors.initials: R
authors.lastname: Longnecker
authors.forename: John M
authors.initials: JM
authors.lastname: Greally
authors.forename: Robert D
authors.initials: RD
authors.lastname: Nicholls
mesh_terms: D000483:Alleles; D017204:Angelman Syndrome / Q000235:genetics*; D000818:Animals; D001921:Brain / Q000378:metabolism; D002503:Centromere / Q000648:ultrastructure; D002874:Chromosome Mapping / Q000379:methods*; D004268:DNA-Binding Proteins / Q000235:genetics*; D004195:Disease Models, Animal; D004742:Enhancer Elements, Genetic; D017353:Gene Deletion; D005786:Gene Expression Regulation; D020868:Gene Silencing; D018392:Genomic Imprinting; D007136:Immunoglobulins / Q000378:metabolism; D017404:In Situ Hybridization, Fluorescence; D007438:Introns; D051379:Mice; D008957:Models, Genetic; D009474:Neurons / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D020161:Physical Chromosome Mapping; D011218:Prader-Willi Syndrome / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011978:Receptors, Nicotinic / Q000235:genetics*; D012559:Schizophrenia / Q000235:genetics; D016615:Telomere / Q000648:ultrastructure; D014018:Tissue Distribution; D014158:Transcription, Genetic; D019076:Transgenes; D015854:Up-Regulation; D064569:alpha7 Nicotinic Acetylcholine Receptor
chemical_list: C579167:Chrna7 protein, human; C579166:Chrna7 protein, mouse; D004268:DNA-Binding Proteins; D007136:Immunoglobulins; C476395:Luzp2 protein, mouse; D011978:Receptors, Nicotinic; D064569:alpha7 Nicotinic Acetylcholine Receptor