Alexander Froschauer

Technische Universität Dresden | TUD · Institute for Zoology

In anti-doping science, the knowledge of drug metabolism is a prerequisite to identify analytical targets for the detection of misused prohibited substances. As the most obvious way to study xenobiotic metabolism, the administration to human volunteers, faces ethical concerns, there is a need for model systems. In the present study, we investigated...

In vitro assessment of genotoxicity as an early warning tool for carcinogenicity mainly relies on recording cytogenetic damages (micronuclei, nucleoplasmic bridges) in tumour-derived mammalian cell lines like V79 or CHO. The forecasting power of the corresponding standardised test is based on epidemiological evidence between micronuclei frequencies...

As the male reproductive organ, the main task of the testis is the production of fertile, haploid spermatozoa. This process, named spermatogenesis, starts with spermatogonial stem cells, which undergo a species-specific number of mitotic divisions until starting meiosis and further morphological maturation. The pituitary gonadotropins, luteinizing...

Techniques for conditional gene or protein expression are important tools in developmental biology and in the analysis of physiology and disease. On the protein level, the tunable and reversible expression of proteins can be achieved by the fusion of the protein of interest to a destabilizing domain (DD). In the absence of its specific ligand (Shie...

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...

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Maintenance of pluripotency in stem cells is tightly regulated among vertebrates. One of the key genes in this process is oct4, also referred to as pou5f1 in mammals and pou2 in teleosts. Pou5f1 evolved by duplication of pou2 early in the tetrapod lineage, but only monotremes and marsupials retained both genes. Either pou2 or pou5f1 was lost from t...

In model teleost fishes like the medaka and the zebrafish many genes which have been identified in genome sequencing projects await their functional characterization. Techniques for the effective generation of transgenic animals are a prerequisite for this challenging task, and, due to their transparency, fish offer the possibility to combine the u...

A consensus sequence, encoding a putative DNA polymerase type B derived from a Polinton transposon, was assembled from the sex determination region of Xiphophorus maculatus. This predicted protein, which is 1,158 aa in length, contains a DNA_pol_B_2 domain and a DTDS motif. The DNA polymerase type B gene has about 10 copies in the haploid X. macula...

In contrast to mammals and birds, fish display an amazing diversity of genetic sex determination systems, with frequent changes during evolution possibly associated with the emergence of new sex chromosomes and sex-determining genes. To better understand the molecular and evolutionary mechanisms driving this diversity, several fish models are studi...

In order to better understand the molecular and evolutionary mechanisms driving sex determination in fish, bacterial artificial chromosome (BAC) contigs covering the sex determination region of the X and Y sex chromosomes of the platyfish Xiphophorus maculatus have been constructed. Initial analysis of these contigs led to the identification of ele...

A consensus sequence, encoding a putative DNA polymerase type B, was assembled from the sex determination region of Xiphophorus maculatus . This predicted protein, which is 1158aa in length, contains a DNA_pol_B_2 domain and a DTDS motif. The DNA polymerase type B gene has about 10 copies in the haploid X. maculatus, genome with one Y-specific copy...

In mammals, the anti-Müllerian hormone (Amh) is responsible for the regression of the Müllerian ducts; therefore, Amh is an important factor of male sex differentiation. The amh gene has been cloned in various vertebrates, as well as in several teleost species. To date, all described species show a sexually dimorphic expression of amh during sex di...

Genome sequences from the pufferfishes Takifugu rubripes (Fugu) and Tetraodon nigroviridis, the zebrafish Danio rerio and the medaka Oryzias latipes together with genomic data from various other fish species have opened an important era of comparative genomics shedding a new light on the structure and evolution of vertebrate genomes. For instance,...

Due to the presence of genetically well-defined sex chromosomes, with a relatively restricted sex-determination region containing markers identified at the molecular level, the platyfish Xiphophorus maculatus is one of the best models for the positional cloning of a master sex-determining gene in fish. Both male and female heterogametes and three d...

The sex-determining region of the sex chromosomes of the platyfish Xiphophorus maculatus contains several copies of a recently described class of DNA transposons called Helitrons, which probably transpose through a mechanism involving rolling circle replication. The unique open reading frame of platyfish elements encodes a 2816 amino-acid protein w...

A family of functional neogenes called Mart, related to the gag gene of Sushi-like long terminal repeat retrotransposons from fish and amphibians, is present in the genome of human (11 genes) and other primates, as well as in mouse (11 genes), rat, dog (12 genes), cat, and cow. Mart genes have lost their capacity of retrotransposition through non-f...

Fische der Gattung Xiphophorus stellen eines der am besten untersuchten Modellsysteme zur Untersuchung genetischer Geschlechtsbestimmung innerhalb dieser Klasse von mehr als 24.000 Arten dar. X. maculatus kann männliche (XX/ XY) oder weibliche (WY/ YY) Heterogametie aufweisen. Zusätzlich sind atypische Geschlechtsbestimmungssysteme beschrieben word...

In contrast to the situation observed in mammals and birds, a switching between different sex determination systems frequently occurred during the evolution of the teleost fish lineage. This might be due to a frequent turnover of sex-determining signals at the top of the sex determination cascade (master sex-determining genes in the case of genetic...

The Xmrk oncogene involved in melanoma formation in the fish Xiphophorus was formed relatively recently by duplication of the epidermal growth factor co-orthologue egfrb. In the platyfish X. maculatus, Xmrk is located close to the major sex-determining locus in a subtelomeric region of the X and Y sex chromosomes that frequently undergoes duplicati...

The fish retrotransposable element Zebulon encodes a reverse transcriptase and a carboxy-terminal restriction enzyme-like endonuclease, and is related phylogenetically to site-specific non-LTR retrotransposons from nematodes. Zebulon was detected in the pufferfishes Tetraodon nigroviridis and Takifugu rubripes, as well as in the zebrafish Danio rer...

On or before Jul 29, 2011 this sequence version replaced gi:34762034, gi:34762035, gi:34762033.

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 transpos...

The DMRT genes constitute a family of genes, which possess a common motif called the DM domain. DMRT1 is considered to be involved in sex determination and/or sex differentiation, but not much information exists about the function of the other gene family members. We cloned DMRT genes of two important model fish species, the medaka, Oryzias latipes...

Despite the major importance of sex determination in aquaculture, no master sex-determining gene has been identified so far in teleost fish. In the platyfish Xiphophorus maculatus, this master gene is flanked by two receptor tyrosine kinase genes, the Xmrk oncogene responsible for melanoma formation in some Xiphophorus interspecific hybrids, and it...

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 fr...

All autonomous non-long terminal repeat (non-LTR) retrotransposons reported to date in vertebrates encode an apurinic/apyrimidinic endonuclease-like enzyme necessary for target sequence cleavage and subsequent target-primed reverse transcription. We describe here vertebrate non-LTR retrotransposons encoding another type of endonuclease more related...

Jule is the second complete long-terminal-repeat (LTR) Ty3/Gypsy retrotransposon identified to date in vertebrates. Jule, first isolated from the poeciliid fish Xiphophorus maculatus, is 4.8 kb in length, is flanked by two 202-bp LTRs, and encodes Gag (structural core protein) and Pol (protease, reverse transcriptase, RNase H, and integrase, in tha...

The platyfish (Xiphophorus maculatus), in which sex chromosomes are evident from stable and predictable inheritance of sex, is one of the best-studied lower vertebrates with respect to sex determination. In order to identify the structural equivalent for this in the karyotype, which does not contain heteromorphic pairs of chromosomes, two sex-linke...

On Sep 22, 2003 this sequence version replaced gi:11138679.

On Mar 1, 2005 this sequence version replaced gi:11138680.

Aquatic pollution by release of synthetic chemicals has become of major concern in our society. Within the last 100 years, approximately 4 million new substances have been developed, the effects of which on organisms are at least partly still. Since genotoxins ränge among the most serious threats to biota and play an important role in carcinogenesi...

On Sep 22, 2003 this sequence version replaced gi:9081817.