Submitted to: Journal of Federation of American Societies for Experimental Biology
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/2005
Publication Date: 5/1/2005
Citation: Nichols, B.L., Avery, S., Robayo, C.C., Quezada-Calvillo, R. 2005. Soluble maltase-glucoamylase is alternatively spliced and secreted by Paneth and goblet cells in enterocyte maltase-glucoamylase Null mice [abstract]. Journal of Federation of American Societies for Experimental Biology. 19(5):A1452. Interpretive Summary:
Technical Abstract: Starch is the major energy source in the mouse diet. Knockout of intestinal membrane-bound maltase-glucoamylase (Mgam) in mice revealed presence of soluble starch digesting activity in Null jejunum and ileum that is secreted by Paneth and goblet cells. Hypotheses: 1. WT have two Mgam mRNAs, Mgamme (Membrane) and Mgamso (Soluble) 2. KO of Mgamme results in increased Mgamso mRNA. Genome sequences disclosed tandemly duplicated Mgam domains. Intestinal RNA was sequenced. Differences of Null and WT RNA expression were measured with Affymetrix 430A microarrays. WT RNA had non-allelic polymorphisms in exons 22-44 not found in Null. qRT/PCR showed that Mgamme Null ileal Mgamso mRNA increased 9 X. WT ileum RNA had both Mgam forms. RNA sequencing showed that constant domain exons 1-21 were transcribed from the 5' gene. This was followed by 3 paralogous duplications of exons 22-44; variable domains A, B, and C. The 3' RNA had constant exons 45-48. Mgamso mRNA lacked exon 2 (membrane domain) and exons 22-44 were transcribed from variable domain A. Mgamme mRNA had exon 2 and exons 22-44 were from variable domain C. A weak splice donor is in mouse intron 19 (GC replaces GT) that is conserved in rat intron 19. Microarray revealed that p14 message, a subunit of SF3b splicing factor that binds to the splice donor, was decreased 2 X in Nulls and confirmed by qRT/PCR. With a wak intron 19 splice donor and lower p14 binding, exon 22 (bp divisible by 3) from domain A becomes the Null alternate splice receptor associated with upregulated Mgamso mRNA.