Expression of Human Tyrosine Hydroxylase-Chloramphenicol Acetyltransferase (CAT) Fusion Gene in the Brains of Transgenic Mice as Examined by CAT Immunocytochemistry
We previously reported the production of transgenic (Tg) mice carrying the entire gene of human tyrosine hydroxylase (TH), and described tissue-specific, high-level expression of the transgene in catecholaminergic (CAnergic) neurons and adrenal glands.1 We subsequently found by using immunocytochemistry and in situ hybridization that human TH (hTH) was also expressed in some non-CAnergic neurons of the brain of the Tg mice, i.e., in the olfactory system (typically, the anterior olfactory nucleus and piriform cortex) and the visual system (typically, nucleus suprachiasmaticus and nucleus parabigeminalis).2 We also showed the distribution of increased numbers of TH-immunoreactive (TH-IR) cell bodies and fibers in CAnergic and non-CAnergic neurons in the Tg mouse brain by immunocytochemistry at light and electron microscopic levels, and also specific expression of hTH mRNA by the in situ hybridization technique.1–4 We further produced Tg mice, designated as TC50, TC25, and TC02, carrying 5.0-kb, 2.5-kb and 0.2-kb fragments, respectively, from the 5’-flanking region of the hTH gene fused to a reporter gene, chloramphenicol acetyltransferase (CAT). High-level CAT expression was observed in CAnergic neurons in the brain and adrenal gland of TC50 mice but also in non-CAnergic neurons, indicating that the 5.0-kb DNA fragment of the hTH gene upstream region contains activity to express CAT in CAnergic neurons but lacks some regulatory elements attenuating ectopic expression.5 In this present study, we examined the brains of TC50, TC25, and TC02 Tg mice possessing a construct containing the bacterial CAT reporter gene downstream of a 5.0-kb, 2.5-kb, or 0.2-kb DNA fragment of the hTH gene by using CAT immunohistochemistry, especially immunoelectron microscopy, and investigated the types of the cells that express CAT.
KeywordsTyrosine Hydroxylase Ventral Tegmental Area Inferior Colliculus Nucleus Raphe Dorsalis Main Olfactory Bulb
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