Expression of the duck alpha-enolase/tau-crystallin gene in transgenic mice

Multifunctional roles of γ-enolase in the central nervous system: more than a neuronal marker

Enolase, a multifunctional protein with diverse isoforms, has generally been recognized for its primary roles in glycolysis and gluconeogenesis. The shift in isoform expression from α-enolase to neuron-specific γ-enolase extends beyond its enzymatic role. Enolase is essential for neuronal survival, differentiation, and the maturation of neurons and glial cells in the central nervous system. Neuron-specific γ-enolase is a critical biomarker for neurodegenerative pathologies and neurological conditions, not only indicating disease but also participating in nerve cell formation and neuroprotection and exhibiting neurotrophic-like properties. These properties are precisely regulated by cysteine peptidase cathepsin X and scaffold protein γ1-syntrophin. Our findings suggest that γ-enolase, specifically its C-terminal part, may offer neuroprotective benefits against neurotoxicity seen in Alzheimer's and Parkinson's disease. Furthermore, although the therapeutic potential of γ-enolase seems promising, the effectiveness of enolase inhibitors is under debate. This paper reviews the research on the roles of γ-enolase in the central nervous system, especially in pathophysiological events and the regulation of neurodegenerative diseases.

Candida albicans ENO1 null mutants exhibit altered drug susceptibility, hyphal formation, and virulence

We previously showed that the expression of ENO1 (enolase) in the fungal pathogen Candida albicans is critical for cell growth. In this study, we investigate the contribution of the ENO1 gene to virulence. We conducted our functional study of ENO1 in C. albicans by constructing an eno1/eno1 null mutant strain in which both ENO1 alleles in the genome were knockouted with the SAT1 flipper cassette that contains the nourseothricin-resistance marker. Although the null mutant failed to grow on synthetic media containing glucose, it was capable of growth on media containing yeast extract, peptone, and non-fermentable carbon sources. The null mutant was more susceptible to certain antifungal drugs. It also exhibited defective hyphal formation, and was avirulent in BALB/c mice.

Gene co-option in physiological and morphological evolution

Co-option occurs when natural selection finds new uses for existing traits, including genes, organs, and other body structures. Genes can be co-opted to generate developmental and physiological novelties by changing their patterns of regulation, by changing the functions of the proteins they encode, or both. This often involves gene duplication followed by specialization of the resulting paralogous genes into particular functions. A major role for gene co-option in the evolution of development has long been assumed, and many recent comparative developmental and genomic studies have lent support to this idea. Although there is relatively less known about the molecular basis of co-option events involving developmental pathways, much can be drawn from well-studied examples of the co-option of structural proteins. Here, we summarize several case studies of both structural gene and developmental genetic circuit co-option and discuss how co-option may underlie major episodes of adaptive change in multicellular organisms. We also examine the phenomenon of intraspecific variability in gene expression patterns, which we propose to be one form of material for the co-option process. We integrate this information with recent models of gene family evolution to provide a framework for understanding the origin of co-optive evolution and the mechanisms by which natural selection promotes evolutionary novelty by inventing new uses for the genetic toolkit.

Purification and properties of gammagamma-enolase from pig brain

Isoelectric focusing revealed three enolase isoforms in pig brain, which were designated as alphaalpha-(pI = 6.5), alphagamma- (pI = 5.6), and gammagamma-enolase (pI = 5.2). The pI of purified gammagamma-enolase was also 5.2. The gammagamma-enolase isoform of enolase was purified from pig brain by a purification protocol involving heating to 55 degrees C for 3 min, acetone precipitation, ammonium sulfate precipitation (40%-80%), DEAE Sephadex ion-exchange chromatography (pH 6.2), and Sephadex G200 gel filtration. The final specific activity was 82 units/mg protein. As with other vertebrate enolases, gammagamma-enolase from pig proved to be a dimer with a native mass of 85 kDa and a subunit mass of 45 kDa. The pH optimum for the reaction in the glycolytic direction is 7.2. The Km values for 2-PGA, PEP, and Mg2+ were determined to be 0.05, 0.25, and 0.50 mM, respectively, similar to Km values of other vertebrate enolases. The amino acid composition of pig gammagamma-enolase, as determined by amino acid analysis, shows strong similarity to the compositions of gammagamma-enolases from rat, human, and mouse, as determined from their amino acid sequences. Despite the differences seen with some residues, and considering the ways that the compositions were obtained, it is assumed that pig gammagamma-enolase is more similar than the composition data would indicate. Moreover, it is likely that the sequences of pig gammagamma-enolase and the other gammagamma-enolases are almost identical. Li+ proved to be a noncompetitive inhibitor with either 2-PGA or Mg2+ as the variable substrate. This enolase crystallized in the monoclinic space group P2, or P2(1). An Rsymm <5% was obtained for data between 50 and 3.65 A, but was a disappointing 30% for data between 3.65 and 3.10 A, indicating crystal disorder.

A retinaldehyde dehydrogenase as a structural protein in a mammalian eye lens. Gene recruitment of eta-crystallin

eta-Crystallin is a taxon-specific crystallin, a major component of the eye lens in elephant shrews (Macroscelidea). Sequence analysis of eta-crystallin from two genera of elephant shrews and expression of recombinant eta-crystallin show that the protein is a cytoplasmic (class 1) aldehyde dehydrogenase (ALDH1, EC 1.2.1.3) with activity for the oxidation of retinaldehyde to retinoic acid. Unlike many other mammals, elephant shrews have two ALDH1 genes. One encodes ALDH1/eta-crystallin which, in addition to its very high expression in lens, is also the predominant form of ALDH1 expressed in other parts of the eye. The second gene encodes a "non-lens" ALDH1 (ALDH1-nl) which is the predominant form expressed in liver. This pattern of tissue preference contrasts with other mammals which make use of the same major ALDH1 transcript in both ocular and non-ocular tissues. Thus the gene recruitment of ALDH1/eta-crystallin as a structural protein in elephant shrew lenses is associated with its collateral recruitment as the major form of ALDH1 expressed in other parts of the eye.

Transgenic models for eye malformations

Several lines of transgenic mice developing eye malformations have been described in the literature and appear to be of increasing interest for the study of eye teratology in humans, since gene expression and regulation can be studied in the developing animal. Transgenic applications are briefly described here and an overview of existing transgenic mouse models carrying different eye abnormalities is given according to the major diagnosis (e.g., cataract, microphthalmia, anterior segment dysgenesis, retinal dysplasia). Interestingly, many transgenic models exhibit pathological findings similar to those observed in human pediatric ophthalmology. Unfortunately, detailed embryological studies in transgenic mice bearing congenital eye malformations are not available for all lines. Thus, the importance of creating further transgenic models to study the function of morphogenes and growth factors in eye development is also discussed.

Lens crystallins: gene recruitment and evolutionary dynamism

In a novel evolutionary process, enzymes and stress proteins have undergone direct gene recruitment as eye lens crystallins in a number of independent events. This may have allowed a dynamic response to changing visual environment during evolution. In spite of their diversity, many crystallins may share an origin in essential developmental processes such as cell elongation.