A developmental biological study of aldolase gene expression in Xenopus laevis

Koichiro SHIOKAWA^1,#, Eri KAJITA^1,##, Hiroshi HARA^*,2, Hitomi YATSUKI³, Katsuji HORI^3,###

¹Laboratory of Molecular Embryology, Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Hongo 7-3-1, Bunkyo ku, Tokyo 113-0033, Japan
²Medical Research Laboratories, Taisho Pharmaceutical Campany Ltd., Yoshino-cho 1-403, Ohmiya-shi Saitama, 330-0031, Japan
³Department of Biochemistry, Saga Medical School, 5-1-1 Nabeshima, Saga 849-0937, Japan

We cloned cDNAs for Xenopus aldolases A, B and C. These three aldolase genes are localized on different chromosomes as a single copy gene. In the adult, the aldolase A gene is expressed extensively in muscle tissues, whereas the aldolase B gene is expressed strongly in kidney, liver, stomach and intestine, while the aldolase C gene is expressed in brain, heart and ovary. In oocytes aldolase A and C mRNAs, but not aldolase B mRNA, are extensively transcribed. Thus, aldolase A and C mRNAs, but not B mRNA, occur abundantly in eggs as maternal mRNAs, and strong expression of aldolase B mRNA is seen only after the late neurula stage. We conclude that aldolase A and C mRNAs are major aldolase mRNAs in early stages of Xenopus embryogenesis which proceeds utilizing yolk as the only energy source. aldolase B mRNA, on the other hand, is expressed only later in development in tissues which are required for dietary fructose metabolism. We also isolated the Xenopus aldolase C genomic gene (ca. 12 kb) and found that its promoter (ca. 2 kb) contains regions necessary for tissue-specific expression and also a GC rich region which is essential for basal transcriptional activity.

Key words: aldolase A, B and C mRNAs, embryo-type aldolase mRNA composition, tissue specific expression pattern.