Title

Tissue distribution and alternative splicing of Art2a and b transcripts in C57BL/6 mice

Date of Completion

January 1999

Keywords

Biology, Molecular|Biology, Genetics|Health Sciences, Immunology

Degree

Ph.D.

Abstract

The molecule ART2 in the rat is an ADP-ribosyl transferase (ADP-RT) and NAD glycohydrolase that is GPI anchored to the membrane of T cells, including intraepithelial lymphocytes, and natural killer cells. ART2+ T cells in circulation are putatively protective against insulin dependent diabetes mellitus in the BB/Wor rat model of the disease. The regulation of ART2 expression at multiple molecular and cellular levels and its possible involvement in cellular proliferation and cytotoxicity against targets indicate that it is a molecule of importance to normal cell physiology. We were interested in the characterization of this molecule in mice initially by examining its spatial distribution and regulation. Because of a lack of antibodies to detect the murine Art2s, we have relied on RT-PCR. ^ Unlike the rat, which has one ART2 gene, the mouse has 2 tandemly located genes, Art2a and Art2b. We find that Art2a is the predominant Art2 in the spleens of most mice, except C57BL/6 mice (B6), which have a stop codon in Art2a, rendering the ADP-RT inactive. We have shown that this locus choice is regulated in cis to the Art2 loci. Art2b predominates in most B6 organs that are Art2+ and is found in T cells. The only exception is the small and large intestine where Art2a is found at a ratio equivalent to Art2b in the former and Art2a is the only Art2 in the latter. Art2a is located in a nonlymphoid population of cells in the intestinal epithelial layer and, interestingly, is found in multiple forms wherever it is located. We have cloned and sequenced at least 4 species of alternatively spliced Art2a from the colon including full length Art2a and 3 Art2a RNAs that utilize a cryptic 5 splice site that eliminates the stop codon. ^ These data suggest that Art2's ADP-RT activity is important to T cells because they utilize the active Art2, even if it is not the usual gene used. The processing of Art2a in the C57BL/6J colon implies that Art2b cannot substitute for an inactive ADP-RT in this organ and that Art2a may have other function apart from those described. ^