A novel microtubule-associated protein-2 expressed in oligodendrocytes in multiple sclerosis lesions

Elucidation of the mechanisms involved in the regeneration of oligodendrocytes and remyelination is a central issue in multiple sclerosis (MS) research. We recently identified a novel alternatively spliced, developmentally regulated oligodendrocyte-specific protein designated microtubule-associated protein-2+13 [microtubule-associated protein-2 expressing exon 13 (MAP-2+13)]. MAP-2+13 is expressed in human fetal oligodendrocytes during process extension and myelination but is minimally expressed in normal mature CNS. To test the hypothesis that MAP-2+13 is reexpressed in regenerating oligodendrocytes in MS lesions, we examined the brains of MS patients for the expression of this protein. By immunocytochemistry using a series of monoclonal antibodies specific for MAP-2+13, we determined that MAP-2+13 expression was up-regulated in all 31 lesions from 10 different MS brains. MAP-2+13 was expressed in regenerating oligodendrocytes associated with demyelinated lesions, with the highest counts found in regions of extensive remyelination. By electron microscopy, MAP-2+13 was localized to oligodendrocytes engaged in remyelination, evident by their process extension and association with thinly myelinated (remyelinated) and demyelinated axons. These results suggest a hitherto unsuspected role for this microtubule-associated protein in oligodendrocyte function during development and myelin repair.     

Conserved and clustered RNA recognition sequences are a critical feature of signals directing RNA localization in Xenopus oocytes

Although it is widely regarded that the targeting of RNA molecules to subcellular destinations depends upon the recognition of cis-elements found within their 3' untranslated regions (UTR), relatively little is known about the specific features of these cis-sequences that underlie their function. Interaction between specific repeated motifs within the 3' UTR and RNA-binding proteins has been proposed as a critical step in the localization of Vg1 RNA to the vegetal pole of Xenopus oocytes. To understand the relative contributions of repeated localization element (LE) sequences, we used comparative functional analysis of Vg1 LEs from two frog species, Xenopus laevis and Xenopus borealis. We show that clusters of repeated VM1 and E2 motifs are required for efficient localization. However, groups of either site alone are not sufficient for localization. In addition, we present evidence that the X. borealis Vg1 LE is recognized by the same set of RNA-binding proteins as the X. laevis Vg1 LE and is capable of productive interactions with the X. laevis transport machinery as it is sufficient to direct vegetal localization in X. laevis oocytes. These results suggest that clustered sets of cis-acting sites within the LE direct vegetal transport through specific interactions with the localization machinery.     

The phylogeny and a new classification of the gingers (Zingiberaceae): evidence from molecular data

The pantropical Zingiberaceae is the largest family in the order Zingiberales with 53 genera and over 1200 species. Classifications of the family first proposed in 1889 and refined by others since that time recognize four tribes (Globbeae, Hedychieae, Alpinieae, and Zingibereae) based on morphological features, such as number of locules and placentation in the ovary, development of staminodia, modifications of the fertile anther, and rhizome-shoot-leaf orientation. New phylogenetic analyses based on DNA sequences of the nuclear internal transcribed spacer (ITS) and plastid matK regions suggest that at least some of these morphological traits are homoplasious and three of the tribes are paraphyletic. The African genus Siphonochilus and Bornean genus Tamijia are basal clades. The former Alpinieae and Hedychieae for the most part are monophyletic taxa with the Globbeae and Zingibereae included within the latter. The results of these phylogenetic investigations are used to propose a new classification of the Zingiberaceae that recognizes four subfamilies and four tribes: Siphonochiloideae (Siphonochileae), Tamijioideae (Tamijieae), Alpinioideae (Alpinieae, Riedelieae), and Zingiberoideae (Zingibereae, Globbeae). Morphological features congruent with this classification and the taxonomic status of various monotypic genera are discussed.     

Poly(alpha-alkyl gamma-glutamate)s of microbial origin. 2. On the microstructure and crystal structure of poly(alpha-ethyl gamma-glutamate)s

The stereochemical microstructure and crystalline structure of nearly racemic poly(alpha-ethyl gamma,DL-glutamate) obtained by esterification of biosynthetic poly(gamma-glutamic acid) were examined by NMR, DSC, and powder X-ray diffraction. The two enantiomerically pure poly(alpha-ethyl gamma-glutamate)s, as well as the racemic stereocopolymers with random and alternating microstructure, were prepared by chemical synthesis and studied in parallel to help in the interpretation of the data. The (13)C NMR analysis revealed that biosynthetic poly(alpha-ethyl gamma,DL-glutamate) consists of a block stereocopolymer accompanied by minor amounts of a mixture of the two optically pure homopolymers. The polymer is crystalline, with a degree of crystallinity and crystal structure essentially similar to those displayed by the optically pure polymers but clearly different from the alternating copolymer. Conversely, the racemic stereocopolymer with a random microstructure prepared by chemical synthesis is amorphous. The crystal structure of the racemic mixture of the D- and L-homopolymers seems to be very close to that of the biosynthetic stereocopolymer, although some indications suggesting the existence of a stereocomplex were found.     

Founder mutation R245H of Sanfilippo syndrome type A in the Cayman Islands

Sanfilippo A syndrome is an autosomal recessive lysosomal storage disease. This disease was reported in the Cayman Islands population with carrier frequency of 1/7 to 1/10 in the West Bay district of Grand Cayman. The carrier testing of Sanfilippo A disease for families at risk was carried out using the thermal characteristics of sulfamidase activity. In the present study, a search for mutations in the sulfamidase gene in an index family was performed. In addition, 77 individuals, relatives of children with Sanfilippo A syndrome, were also studied by single-strand conformation polymorphism (SSCP), restriction fragment-length polymorphism (RFLP) analyses, and sequencing. A single mutation, G746A (R245H), was found in the family, with the patient being homozygous and both parents and 1 of the 3 siblings being carriers. Among the 77 family members of the patient with Sanfilippo syndrome, the same mutation was found among carriers of the disease. The finding of a single mutation supports the idea of a founder effect, which facilitates accurate carrier identification of Sanfilippo A syndrome in the population of Cayman Islands.     

An unusual orientation for Tyr75 in the active site of the aspartic proteinase from Saccharomyces cerevisiae

The structures of the native Saccharomyces cerevisiae proteinase A have been solved by molecular replacement in the monoclinic and trigonal crystal forms and refined at 2.6-2.7A resolution. These structures agree overall with those of other uninhibited aspartic proteinases. However, an unusual orientation for the side chain of Tyr75, a conserved residue on the flexible "flap" that covers the active site and is important for the activity of these enzymes, was found in the trigonal crystals. A similar conformation of Tyr75 occupying the S1 substrate-binding pocket was previously reported only for chymosin (where it was interpreted as representing a "self-inhibited" state of the enzyme), but for no other aspartic proteinases. Since this orientation of Tyr75 has now been seen in the structures of two members of the family of aspartic proteinases, it might indicate that the placement of that residue in the S1 substrate-binding pocket might have some functional significance, analogous to what was seen for self-inhibited structures of serine proteinases.