title: Long human CHGA flanking chromosome 14 sequence required for optimal BAC transgenic "rescue" of disease phenotypes in the mouse Chga knockout.
abstract: Chromogranin A (CHGA) plays a catalytic role in formation of catecholamine storage vesicles and also serves as precursor to the peptide fragment catestatin, a catecholamine secretory inhibitor whose expression is diminished in the hypertensive individuals. We previously reported the hypertensive, hyperadrenergic phenotype of Chga-/- knockout (KO) mice and rescue by the human ortholog. In the present study, we compare two humanized CHGA mouse models. Into the Chga null background, by bacterial artificial chromosome transgenesis human CHGA transgene has been introduced. Both lines have the complete approximately 12 kbp CHGA gene integrated stably in the genome but have substantial differences in CHGA expression, as well as consequent sympathochromaffin biochemistry and physiology. A mouse model with longer-insert HumCHGA31 displays integration encompassing not only CHGA but also long human flanking sequences. This is in contrast to mouse model HumCHGA19 with limited flanking human sequence co-integrated. As a consequence, HumCHGA19 mice have normal though diminished pattern of spatial expression of CHGA, and 14-fold lower circulating CHGA, with failure to rescue KO phenotypes to normalcy. In the longer-insert HumCHGA31 mice, catecholamine secretion, exaggerated responses to environmental stress, and hypertension were all alleviated. Promoter regions of the transgenes in both HumCHGA19 and HumCHGA31 display minimal CpG methylation, weighing against differential "position effects" of integration, and thus suggesting that lack of cis elements required for optimal CHGA expression occurs in HumCHGA19 mice. Such "humanized" CHGA mouse models may be useful in probing the physiological consequences of variation in CHGA expression found in humans, with consequences for susceptibility to hypertension and cardiovascular disease.
authors.affiliation: Department of Medicine, University of California at San Diego, San Diego, CA 92093-0838, USA. svaingankar@ucsd.edu
authors.forename: Sucheta M
authors.initials: SM
authors.lastname: Vaingankar
authors.forename: Ying
authors.initials: Y
authors.lastname: Li
authors.forename: Angelo
authors.initials: A
authors.lastname: Corti
authors.forename: Nilima
authors.initials: N
authors.lastname: Biswas
authors.forename: Jiaur
authors.initials: J
authors.lastname: Gayen
authors.forename: Daniel T
authors.initials: DT
authors.lastname: O'Connor
authors.forename: Sushil K
authors.initials: SK
authors.lastname: Mahata
mesh_terms: D000311:Adrenal Glands / Q000473:pathology; D000818:Animals; D001483:Base Sequence; D001794:Blood Pressure; D002395:Catecholamines / Q000378:metabolism; D053379:Chromogranin A / Q000172:deficiency / Q000235:genetics* / Q000378:metabolism; D022202:Chromosomes, Artificial, Bacterial / Q000235:genetics*; D002883:Chromosomes, Human, Pair 14 / Q000235:genetics*; D018628:Gene Dosage; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D016254:Mutagenesis, Insertional / Q000235:genetics; D010641:Phenotype; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012149:Restraint, Physical; D013312:Stress, Physiological; D019076:Transgenes / Q000235:genetics
chemical_list: C506150:CHGA protein, human; D002395:Catecholamines; D053379:Chromogranin A; D012333:RNA, Messenger; C506155:chromogranin A, mouse