Transient expression of tyrosine hydroxylase promoter/reporter gene constructs in the olfactory epithelium of transgenic mice.
Maturation and survival of olfactory receptor neurons (ORNs) are hypothesized to depend on trophic support from the olfactory bulb during both development and regeneration of the olfactory epithelium (OE). The current study characterized transgene expression in two independently derived transgenic mouse lines in which 9 kb of tyrosine hydroxylase (TH) promoter was utilized to drive either enhanced green fluorescent protein (TH/eGFP) or LacZ (TH/beta-gal) reporters. Transgene expression, found primarily on dorsal aspects of the OE, the dorsal septum and endoturbinate II, resembled the Zone one distribution of olfactory receptor genes. Labeled cells were ovoid to fusiform with dendrites that projected to the epithelial surface but only rarely exhibited discernable cilia. Axons were short and did not extend beyond the basal lamina. As only a subpopulation of the cells contained olfactory marker protein, indicative of ORN maturation, the transgene expressing cells were likely immature neuronal precursors. Demonstration of transgene expression without either TH mRNA or protein was consistent with low basal level transcriptional activity of endogenous TH that may reflect differences between TH and reporter protein stability. Molecules identifying specific olfactory-derived cell populations, PDE2 and LHRH, also did not co-localize with either reporter. A higher than predicted proportion of apoptotic neonatal transgene-expressing cells accounted for their apparent paucity in adult mice. These studies support the concept that transgene expressing cells exhibiting morphological and biochemical characteristics of presumptive ORNs are unable to mature and undergo apoptotic cell death possibly because they lack trophic support.
Sasaki
Hayato
H
Weill Medical College, Cornell University, The Burke Medical Research Institute, White Plains, New York 10605, USA.
Berlin
Roseann
R
Baker
Harriet
H
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000235:genetics; D002395:Catecholamines / Q000096:biosynthesis; D002454:Cell Differentiation / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D005260:Female; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D017930:Genes, Reporter / Q000235:genetics*; D049452:Green Fluorescent Proteins / Q000235:genetics; D007763:Lac Operon / Q000235:genetics; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D008822:Mice, Transgenic; D009414:Nerve Growth Factors / Q000235:genetics* / Q000378:metabolism; D009831:Olfactory Mucosa / Q000254:growth & development* / Q000378:metabolism; D018034:Olfactory Receptor Neurons / Q000254:growth & development* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012333:RNA, Messenger / Q000378:metabolism; D019076:Transgenes / Q000235:genetics; D014446:Tyrosine 3-Monooxygenase / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism
D002395:Catecholamines; D009414:Nerve Growth Factors; D012333:RNA, Messenger; D049452:Green Fluorescent Proteins; D014446:Tyrosine 3-Monooxygenase