Structure and expression of mouse aldolase genes. Brain-specific aldolase C amino acid sequence is closely related to aldolase A

Abstract

1. Brain-specific aldolase C amino acid sequence (> 75% of the coding region) was determined for the first time. Two cDNA clones, PAM1 and pAM2, were identified, from a mouse brain library, by using human aldolase B cDNA as a probe. The larger one, pAM2, identified as a cDNA for aldolase C, has been completely sequenced and covers the 5'-untranslated region of the mRNA and the codons for amino acids 1-227 of the protein. The sequence indicates that aldolase C is more akin to aldolase A than to aldolase B.2. A cDNA library from mouse muscle was also screened, allowing the identification of clones pAM3 and pAM4, which contain cDNAs for aldolase A. The sequence obtained from pAM3 covers 70% of the coding sequence (amino acids 99 -355) from the -COOH part of the protein.3. The cDNAs for the three aldolases, A, B and C, have been hybridized to RNA from various rat tissues. The results confirm the tissue specificity of the expression of the mRNA for the different isoenzymes and support the hypothesis that aldolase C expression, as aldolase A and B, is regulated at the transcriptional level or, in any case, via mRNA concentration.Three tissue-specific isoenzymes of fructose-l,6-bisphosphate aldolase have been described in mammals. The isoenzymes show specific patterns of expression in adult tissues, depending on the functions required by the different tissues [l].Aldolase A, the muscle type, is the first of the three forms to be produced in the developing embryo, and it persists as the sole form in several adult cell types such as muscle cells, blood cells and fibroblasts. Aldolase A is also expressed in kidney, brain and liver together with other isoenzymes [2].Aldolase B is expressed in the liver and small intestine, where it is directed to a specific function. In fact, it utilizes as a substrate fructose-1-phosphate, besides fructose-1,6-bisphosphate, and thus is capable of metabolizing exogenous dietary fructose [3]. In man the absence of aldolase B produces a congenital disease, the hereditary fructose intolerance [4]. Aldolase C is much less known. In mammals it is selectively expressed in the brain, where it appears to be located in astrocytes of the cerebral cortex [5]. Very low levels of immunoreactive aldolase C have also been demonstrated in erythrocytes, liver and adrenal gland [6]. Functionally it is similar to aldolase A, in that it mainly recognizes fructose-1,6-bisphosphate as substrate [l].The tissue expression of the three isoenzymes varies also according to the stage of development. Foetal liver, in fact, produces large amounts of aldolase A; this is switched off soon after birth, when aldolase B is predominantly expressed [7]. The expression of aldolase isoenzymes is modified in some pathological situations. In chemically induced rat hepato- carcinoma there is a change towards the foetal pattern, with a decrease of aldolase B production by the hepatocyte and an increase of aldolase A and/or C synthesis [8].The three isoenzymes have been extensively studied at the protein level in many organisms. The...

The structure of brain‐specific rat aldolase C mRNA and the evolution of aldolase isozyme genes

“…These studies have shed light on the structure and expression of aldolase isozyme A and B genes. Recently, partial sequences of aldolase C cDNA clones of mouse [20] and rat [21] and a nearly complete sequence of genomic clones of human aldolase C [22] have been reported. PI.…”

A new human species of aldolase A mRNA from fibroblasts

“…The identification of the characterized clone with aldolase A cDNA is based on amino acid homology with the known rabbit aldolase A translated inRNA (97%, see [12]), the partial protein sequence of human muscle aldolase A (loo%, see [30]) and the more recently published rat (97%, see [13]) and human liver (100%) aldolase A mRNA [14]. Lower amino acid homology was evident with known aldolase B mRNA sequences (69Y0, see [4,7,91) and with partial aldolase C mRNA sequences (84%, see [5]). While the present work was in progress, the sequence of a human aldolase A genomic clone, recently isolated by us (unpublished results), was found to be identical in the coding and the 3'-non-coding regions with the human fibroblast cDNA.…”

“…The AvaII -PstI fragment (210 bp) of the 5 The A vaII -PstI radiolabeled fragment, electrophoresed on a 6% denaturing polyacrylamide gel and eluted from the gel, was hybridized to total RNAs from human fibroblast, hepatoma cell line (Hep 3B), muscle and liver (30 pg) in 10 p1 of 0.1 M NaC1, 20 mM Tris, pH 7.9, 0.1 mM EDTA and sealed in glass capillaries. After 2 min at 1OO"C, the mixture was incubated at 60°C for 10 h and then diluted into an equal volume of 80 mM Tris, pH 7.9, 10 mM MgCl2, 4 mM dithiothreitol, 400 pM each dATP, dCTP, dGTP, dTTP and 5 units of AMV reverse transcriptase.…”

“…The aldolase isoenzyme system (see [l, 21 for reviews) lends itself to the study of the tissuespecific and developmental regulatory mechanisms of gene expression and can provide information on some aspects of molecular evolution. Furthermore, diseases related to alterations at the gene level, such as hereditary fructose intolerance [3], may be studied via the analysis of such alterations.Within the framework of a study of the aldolase system, we have completely sequenced a full-length cDNA for human liver aldolase B [4] and a partial cDNA for mouse brain aldolase C [5]. Other groups have elucidated the mRNA structure and expression of aldolase B in rat [6] and in humans [7 -91, and have described the aldolase B gene organization and structure in chicken [lo] and in rat [ll].…”

“…Within the framework of a study of the aldolase system, we have completely sequenced a full-length cDNA for human liver aldolase B [4] and a partial cDNA for mouse brain aldolase C [5]. Other groups have elucidated the mRNA structure and expression of aldolase B in rat [6] and in humans [7 -91, and have described the aldolase B gene organization and structure in chicken [lo] and in rat [ll].…”