Low expression of Neu2 sialidase in the thymus of SM/J mice-existence of neuraminidase positive cells "Neu-medullocyte" in the murine thymus.
We have already reported that the homogenate of the A/J mouse thymus shows a high sialidase activity at the neutral pH region and that in both soluble and membrane fractions optimal pH was 6.5-7 (Kijimoto-Ochiai et al., Glycoconj. J., 20:375-384, 2004). In the present study, we investigated the level of sialidase activities in the thymus of the SM/J mouse, a mouse strain that we know to have a Neu1(a) allele that reveals a low level of sialidase activity in the liver. We found that while in the A/J thymus the soluble sialidase activity at pH 6.5 was high, the SM/J thymus lacked all such activity. A QTL analysis of SMXA recombinant inbred strains showed that soluble sialidase activity correlated well with the D1Mit8/9 marker on chromosome 1. The murine whole DNA-sequence data and the results of our FISH analysis (Kotani et al., Biochem. Biophys. Res. Comm., 286:250-258, 2001) showed that this location is consistent with the position of Neu2 gene. We confirmed that it is hard to detect the Neu2 enzyme of the SM/J mouse thymus by an anti-Neu2 antibody using a Western blot analysis. We also found that while the mRNA expression of Neu2 was quite normal in the SM/J mouse liver, it was very low in the SM/J mouse thymus. We therefore conclude that the lack of soluble sialidase activity in the SM/J mouse thymus is due to the thymus-specific low expression level of the Neu2 gene. We have previously shown that the sialidase positive cell which contains the Mac-1 and immunoglobulin, and which is located sparsely in the corticomedullar region or medullary region of the A/J mouse thymus (Kijimoto-Ochiai et al., Glycoconj. J., 20:375-384, 2004). We showed now in this paper that the detection of this cell in the SM/J mouse thymus at pH 7.0 was difficult. We propose, therefore, to name the cell "Neu-medullocyte".
Institute of Immunology/Genetic Medicine, Hokkaido University, N15, W7, Sapporo, 060-0815, Japan. sko@cris.hokudai.ac.jp
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S
Kijimoto-Ochiai
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T
Koda
T
T
Suwama
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H
Matsukawa
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M
Fujii
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Tomobe
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M
Nishimura
D000818:Animals; D001483:Base Sequence; D002469:Cell Separation; D017931:DNA Primers / Q000235:genetics; D005434:Flow Cytometry; D015870:Gene Expression; D017404:In Situ Hybridization, Fluorescence; D008099:Liver / Q000201:enzymology; D051379:Mice; D008815:Mice, Inbred Strains; D009439:Neuraminidase / Q000235:genetics / Q000378:metabolism*; D040641:Quantitative Trait Loci; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011995:Recombination, Genetic; D012995:Solubility; D013950:Thymus Gland / Q000166:cytology* / Q000201:enzymology*; D014018:Tissue Distribution
D017931:DNA Primers; D012333:RNA, Messenger; C513678:Neu2 protein, mouse; D009439:Neuraminidase