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Which home for coelacanth?
(1993)
Interleukin 4 (IL-4) exerts a decisive role in the coord.ination of proteelive immune responses against parasites, particularly helminths. A disregulation of ll.r4 function is possibly involved in the genesis of allergic disease states. The search for important amino acid residues in human ll.r4 by mutational analysis of charged invariant amino acid positions identified two distinct functional sites in the 4-helix-bundle protein. Site 1 was marked by amino acid substitutions of the glutamic acid at position 9 in helix A and arginine at position 88 in helix C. Exchanges at both positions led to IL-4 variants deficient in binding to the extracellular domain of the ll.r4 receptor (IL-4ReJ. In parallel, up to 1000-fold increased concentrations of this type of variant were required to induce T -cell proliferation and B-eeil CD23 expression. Site 2 was marked by amino acid exchanges in helix D at positions 121, 124 and 125 (arginine, tyrosine and serine respectively in the wild-type).ß.A variants affected at site 2 exhibited partial agonist activity during T -cell proliferation; however, they still bound with high affinity to IL-4Rex. [The generation of an IL-4 antagonist by replacing tyrosine 124 with aspartic acid has been described before by Kruse et al. (1992) (EMBO }., 11, 3237-3244)]. These findings indicate that IL-4 functions by bind.ing IL-4Rex via site 1 which is constituted by residues on helices A and C. They further suggest that the association of a second, still undetined receptor protein with site 2 in helix D activates the receptor system and generates a transmembrane signal.
Melanoma formation in the teleost Xiphophorus is caused by a dominant genetic locus, Tu. This locus includes the Xmrk oncogene, which encodes a receptor tyrosine kinase. Tumor induction is. suppressed in wild-type fish by a tumor suppressor locus, R. Molecular genetic analyses revealed that the Tu locus emerged by nonhomologaus recombination of the Xmrk proto-oncogene with a previously uncharacterized sequence, D. This event generated an additional copy of Xmrk with a new promoter. Suppression of the new Xmrk promoter by R in parental fish and its deregulation in hybrids explain the genetics of melanoma formation in Xiphophorus.
The silver carp (Hypophthalmichthys molitrix) growth hormone (GH) genewas isolated and sequenced following amplification from genomic DNA by the polymerase chain reaction. The gene spans a region of approx. 2.5 kb nucleotides (nt) and consists of five exons. The sequence predicts a polypeptide of 210 amino acids (aa) including a putative signal peptide of 22 hydrophobic aa residues. The arrangement of exons and introns is identical to the GH genes of common carp, grass carp, and very similar to mammals and birds, but quite different from that for the GH genes of tilapia and salmonids. The silver carp GH gene shares a high homology at the nt and aa Ievels with those of grass carp (95.3% nt, 99.5% aa) and of common carp (81% nt, 95.7% aa).
Hierarchical structures among male indlviduals in a population are frequently reflected ln differences in aggressive and reproductive behavior and access to the females. In general, sodal dominance requires the Investments, which in turn then may have to be compensated for by high reproductive success. However, this hypothesls has so far only been sufficiently tested in small mating groups (one or two males with one or two females) due to the difficulties of determining paternity by conventional methods. DNA fingerprinting overcomes these problems by offering the possibility to determine genetic relationships and mating patterns within larger groups [Borke, T. (1989) Trends Ecol. Evol. 4, 139-144]. We show here that in the poecUiid fish Limia perugitu, in small matlng groups the dominant male has 8 mating success of 100%, whereas ln larger groups lts contribution to the offspring unexpectedly drops to zero.
The demonstration ofthe chromosomal mode ofsex determinationvia genetic experiments as well as the absence of heteromorphic sex chromosomes affirm poeciliid fishes as a unique group among vertebrates that are endowed with the mostprimitive form of sex chromosornes. In many different taxa the evolutionary process involved in the differentiation ofadvanced sex chromosomes is outlined through sex specifically organized repetitive sequences. In this investigation hydridization of synthetic probes specific to genomic simple repeat motifs uncovers a sex-specific hybridization pattern in certain viviparaus fishes ofthe family Poeciliidae. The hybridization pattern together with specific staining ofthe constitutive heterochromatin by C-banding reveals heterogamety in males (Poecilia reticulata) as weil as in females (P. sphenops). In P. velifera, however, C-banding alone fails to unravel the heterogametic status. The female specific W-chromosome can be detected by simple repetitive sequence probes. Therefore, the principal significance of heterochromatization as a means of generating differentiated sex chromosomes is evident.
Pericentric intrachromosomal insertion responsible for recurrence of del(11)(p13p14) in a family
(1993)
The combined use of qualitative and quantitative analysis of I I p I 3 polymorphic markers tagether with chromosomal in situ suppression hybridization (CISS) with biotin labeled probes mapping to I I p allowed us to characterize a complex rearrangement segregating in a family. We detected a pericentric intrachromosomal insertion responsible (or recurrence of del( I I )(p 13p 14) in the family: an insertion of band I I p 13-p 14 carrying the genes for predisposition to Wilms' tumor, WT I, and for aniridia, AN2, into the long arm of chromosome I I in II q 13-q 1<4. Asymptomatic balanced carriers were observed over three generations. Classical cytogenetics had failed to detect this anomaly in the balanced carriers, who were first considered to be somatic mosaics for del( II )(p 13). Two of these women gave birth to children carrying a deleted chromosome II. most likely resulting from the loss of the I I p 13 band inserted in I I q. Although in both cases the deletion encompassed exactly the same maternally inherited markers, there was a wide Variation in clinical expression. One child, with the karyotype 46,XY,del(ll)(pllpl4), presented the full-blown WAGR syndrome with anlridia, mental retardation, Wilms' tumor, and pseudohermaphroditism, but also had proteinuria and glomerular sclerosis reminiscent of Drash syndrome. In contrast, the other one, a girl with the karyotype 46,XX,del( I I )(p I 3), only had aniridia. Although a specific set of mutational sites has been observed in Drash patients, these findings suggest that the loss of one copy of the WTI gene can result in similar genital and kidney abnormalities.
Autolyzed, antigen-extracted, allogeneic (AAA) bone was prepared from human cortical bone and its morphologic, biomechanical, and osteoinductive properlies were compared with untreated (frozen) as well as lyophilized human bone. Scanning electron microscopy revealed removal of inprganic calcium phosphates and persistence of shrunken collagen fibrils on the surface of AAA bone matrix. Biomechanical testing of differently prepared bone samples showed that lyophilization increased both the modulus of elasticity (P < .00001) and the compressive strength (P < .00001 ). Depending on the depth of decalcification in the preparation of AAA bone, both measured values decreased in rehydrated AAA bone compared with untreated bone {P < .00001 ). Completely demineralized and rehydrated AAA bone was soft, flexible, and showed very little compressive strength. Differences in biomechanical behavior between samples drilled longitudinally or perpendicularly to the diaphyseal bone axis were observed. Xenogeneic human bone samples were implanted in muscle pouches of Sprague-Dawley rats for 6 weeks. AAA bone implants showed chondrogenesis and osteogenesis in 50% of the cases, while untreated or lyophilized bone implants induced no new cartilage or bone formation. As decalcification exposed xenogeneic organic matrix components, AAA bone implants provoked the highest inflammatory reaction. When AAA bone samples were implanted in immunosuppressed rats, the inflammatory reaction was suppressed and 94o/o of the implants showed endochondral bone formation. The chondroinductivity of the bone samples also was tested in vitro using neonatal rat muscle tissue to avoid interference with inflammatory cells and secreted cytokines. In this assay, 68°/o of AAA bone samples induced chondroneogenesis, while untreated as weil as lyophilized bone samples failed to induce any cartilage formation. The results clearly dernonstrafe that AAA bone has osteoinductive properties. Biomechanical stability of AAA bone implants depends on the degree of demineralization. Thus, they can be prepared in an appropriate manner for different indications in oral and maxillofacial surgery.
In Xiphophorus melanoma formation has been attributed by classical genetic findings to the overexpression of a cellular oncogene (Tu) due to elimination of the corresponding regulatory gene locus in hybrids. We have attempted to elucidate this phenomenon on the molecular biological level. Studies on the structure and expression of known proto-oncogenes revealed that several of these genes, especially the c-src gene of Xiphophorus, may act as effectors in establishing the neoplastic phenotype of the melanoma cells . However, these genes appear more to participate in secondary steps of tumorigenesis. Another gene, being termed Xmrk, which represents obviously a so far unknown proto-oncogene but with a cons iderably high similarity to the epidermal growth-factorreceptor gene, was mapped to the Tu-containing region of the chromosome. This gene shows features with respect to its structure and expression that seem to justify it to be regarded as a candidate for a gene involved in the primary processes leading to neoplastic transformation of pigment cells in Xiphophorus.
The karyotype of D. elongatus was investigated by means of C-banding, silver staining, and mithramycinand quinacrine fluorescent staining. The diploid chromosome number is 2n = 50. C-banding shows pericentromerically localized constitutive heterochromatin in every chromosome. Two of the chromosome pairs carry two telomeric nucleolus organizer regions each. No heteromorphic sex chromosomes were found.
Wilms' tumor is a childhood nephroblastoma that is postulated to arise through the inactivation of a tumor suppressor gene by a two-hit mechanism. A candidate II p 13 Wilms' tumor gene, WTI, has been cloned and shown to encode a zinc finger protein. Patients with the WAGR syndrome (Wilms' tumor, aniridia, genitourinary abnormalities, and mental retardation) have a high risk of developing Wilms' tumor and they carry constitutional deletions of one chromosome II allele encompassing the WTI gene. Analysis of the remaining WTI allele in a Wilms' tumor from a WAGR patient revealed the deletion of a single nucleotide in exon 7. This mutation likely played a key role in tumor formation, as it prevents translation of the DNA-binding zinc finger domain that is essential for the function of the WTI polypeptide as a transcriptional regulator.
Hierarchical structures among male individuals in a population are frequently reflected in differences in aggressive and reproductive behaviour and access to the females. In general social dominance requires large investments which in turn may have to be compensated for by high reproductive success. However, this hypothesis has so far only been sufficiently tested in small mating groups due to the difficulties of determining paternity by classical methods using non-molecular markers. DNA fingerprinting overcomes these problems offering the possibility to determine genetic relationships and mating patterns within larger groups. Using this approach we have recently shown (Schartl et al., 1993) that in the poeciliid fish Limia perugiae in small mating groups the dominant male has 100% mating success, while in larger groups its contribution to the offspring unexpectedly drops to zero. The reproductive failure under such social conditions is explained by the inability of the ex-male to protect all the females simultaneously against mating attempts of his numerous subordinate competitors.