In two swordtail species of the genus Xiphophorus, the onset of puberty has been shown to be modulated at the P locus by sequence polymorphism and gene copy-number variation affecting the type 4 melanocortin hormone receptor Mc4r. The system works through the interaction of two allelic types, one encoding wild type and the other dominant-negative receptors. We have analyzed the structure and evolution of the P locus in the platyfish Xiphophorus maculatus, where as many as nine alleles of P determining the onset of sexual maturity in males and females, fecundity in females, and adult size in males are located on both the X and Y chromosomes in a region linked to the master sex-determining locus. In this species, mc4r has been amplified to up to 10 copies on both the X and Y chromosomes through recent large serial duplications. Subsequently, mc4r paralogues have diverged considerably into many different subtypes. Certain copies have acquired new untranslated regions through genomic rearrangements, and transposable element insertions and other mutations have accumulated in promoter regions, possibly explaining observed deviations from the classical mc4r transcriptional pattern. In the mc4r-coding sequence, in-frame insertions and deletions as well as nonsense and missense mutations have generated a high diversity of Mc4r-predicted proteins. Most of these variants are expressed in embryos, adults, and/or tumors. Functional receptor characterization demonstrated major divergence in pharmacological behavior for Mc4r receptors encoded by different copies of platyfish mc4r, with differences in constitutive activity as well as binding and stimulation by hormones. The high degree of allelic and copy-number variation observed between individuals can explain the high level of polymorphism for sexual maturation, fecundity, and body size in the platyfish: multiple combinations of Mc4r variants with different biochemical properties might interact to modulate the melanocortin signaling that regulates the hypothalamus-pituitary-gonadal axis.

Precancerous epithelial lesions are sites of uncontrolled cellular proliferation, generated by irreversible genetic changes. Not all of these lesions progress to invasive cancer, some may even regress, but early detection of abnormal cells can be crucial for survival of the patient. Diagnosis is mainly performed by using morphological parameters. Proliferation markers can facilitate the analysis, if they show a consistent expression, and distinguish between healthy and malignant cells. The fully human monoclonal IgM antibody PAM-1 was isolated from a patient with stomach carcinoma and binds to a new variant of cysteine-rich fibroblast growth factor receptor 1 (CFR-1). This CFR-1/PAM-1 receptor is expressed on nearly all of the epithelial cancers of every type and origin, but not on healthy tissue. It is also present on precursor lesions found in: Helicobacter pylori-induced gastritis, intestinal metaplasia and dysplasia of the stomach, ulcerative colitis-related dysplasia and adenomas of the colon, Barrett's metaplasia and dysplasia of the esophagus, squamous cell metaplasia and dysplasia of the lung, and cervical intraepithelial neoplasia. The unique, growth-dependent expression of this new CFR-1 isoform makes the PAM-1 antibody an ideal diagnostic tool for the detection of precancerous and cancerous lesions.

Innate immune mechanisms are crucial for first defense and initiation of secondary responses to “nonself” structures. This has been shown for bacterial antigens, but the recognition and defence-activity against malignant cells is still obscure. By using human hybridoma-technology we have isolated hundreds of human monoclonal antibodies from different patients with different tumours. All of these antibodies are of IgM type, none of them was an affinity-maturated IgG or IgA type. We have sequenced several of these antibodies and have characterised binding pattern and determined origin and genetics. It was found that all IgM antibodies are not or only less mutated (germ-line coded), and bind to carbohydrates on modified tumourspecific receptors (DAF, CFR-1). The degree of crossreactivity to other tumours correlates with the grade of mutations in coding regions. By using an anti-idiotypic antibody, we could show, that the IgM-producing cells are CD5 positive. The striking similarities between the humoral response to bacteria and tumor cells, presented here, makes it likely that the same or similar recognition and defense mechanisms are used. Origin, reactivity pattern and genetics of these real tumor-specific antibodies are close to that what we know from the defense to bacterial structures and it is likely that innate imunity is not only resposible for recognition and elimination of bacterial structure but also for removal of malignant cells. [16.45–17.05] A human monoclonal antibody (HMMC-1) that selectively recognizes müllerian duct-related carcinomas Atsushi Suzuki , Shiro Nozawa, Daisuke Aoki , Katsumi Tsukazaki , Nobuyuki Susumu , Motoko Sakayori , Nao Suzuki , Makio Mukai, Kyoko Kojima-Aikawa, Michiko N. Fukuda and Isao Ishida Department of Obstetrics and Gynecology, School of Medicine, Keio University, Tokyo, Japan Division of Diagnostic Pathology, School of Medicine, Keio University, Tokyo, Japan Department of Chemistry, Faculty of Science, Ochanomizu University, Tokyo, Japan Glycobiology Department, The Burnham Institute, La Jolla, CA, USA Pharmaceutical Research Laboratory, Kirin Brewery Co., Ltd., Gunma, Japan

A high level of genetic variability affects pigmentation, melanoma formation, sex determination and sexual maturity in the fish Xiphophorus. Gene loci encoding these traits have been mapped to a subtelomeric region of the sex chromosomes that very frequently undergoes DNA rearrangements including duplications, amplifications, deletions and transpositions. This conspicuous genomic fluidity might generate new sex-linked gene regulations and functions, and be involved in the initiation of gonosome differentiation around the major sex-determining locus in Xiphophorus.

Melanoma formation in certain interspecific hybrids of the genus Xiphophorus (Teleostei: Poeciliidae) is associated with the overexpression of the Xmrk receptor tyrosine kinase oncogene. The Xmrk oncogene arose by duplication of the pre-existing Xmrk protooncogene in a highly unstable subtelomeric region of the X and Y sex chromosomes undergoing frequent rearrangements including duplications, deletions, amplifications, and transpositions. Some of these rearrangements are likely to be responsible for the overexpression of the Xmrk oncogene in melanoma. The oncogene itself is very unstable in Xiphophorus and is frequently removed by deletion or disrupted by transposable elements. The Xmrk oncogene region displays a high concentration of retroelements not observed in the corresponding Xmrk protooncogene region. Particularly, a retrovirus long terminal repeat-like sequence was amplified in the proximity of the Xmrk oncogene. Additional genes, some of them also duplicated copies, were detected in this region and might be involved in modulating the melanoma's phenotype.