Molecular pathological study on the expression of Metallothionein gene in the brain of aged dog.

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We have isolated and determined the complete nucleotide sequence of canine metallothionein-I (MT-I) and MT-III cDNA.The predicted amino acid sequence of the canine MT-III showed a high homology (93%, 87% identity) to that of human and mouse MT-III.The canine MT-III had two insertions relative to known mammalian MT-I and MT-II : a threonine after the fourth amino acid and a block of six amino acids near the carboxyl terminus. Following sysnthesis of a polypeptide specific for canine MT-III (Cys-Lys-Gly-Gly-Glu-Gly-Thr-Glu-Ala-Glu-Alu-Glu-Lys), we have generated a polyclonal antibody canine MT-III.Expression of the canine MT-III mRNA was found exclusively in the central nervous system, where neurons in the olfactory bulb, hippocampus, thalamus and cerebral cortex showed predominant signals. The findings were also supported by the MT-III immunohistochemistry. In situ hybridization demonstrated age-related increases of MT-I expression, whereas MT-III was shown to be expressed through the brain at birth. There was no relationship between the MTs expression and amyloid deposition.