The large 45S rDNA chromosome sites have often been analyzed in fish. In contrast, little is known about the 5S genes in this animal group. In the genus Leporinus, the NOR chromosomal location has been shown to be very diverse. In the present work, chromosome mapping of 5S rDNA in three anostomids, Leporinus elongatus, L. obtusidens and L. friderici, is investigated using fluorescence in-situ hybridization (FISH) with PCR-obtained 5S probes and primed in-situ labeling (PRINS). Major 5S rDNA chromosomal sites were found to be subterminally located in a small metacentric pair, while minor ones were detected near the centromeric region of a medium-sized submetacentric pair in all studied species. The 5S rDNA genes were not associated with the NORs or sex chromosomes. A highly conserved chromosomal location of these genes appears to characterize the karyotype evolution of this fish group.

/pdf/chromosomal-localization-of-5s-rdna-genes-in-leporinus-fish-2lokd439ij.pdf

Chromosomal localization of 5S rDNA genes in Leporinus fish (Anostomidae, Characiformes).

The major histocompatibility complex (MHC) is a genetic region that has been extensively studied by immunologists, molecular biologists, and evolutionary biologists. Nevertheless, our knowledge of how the MHC acquired its present-day organization is quite limited. The recent discovery that the mammalian genome contains regions paralogous to the MHC has led us to the proposal that the MHC region of jawed vertebrates arose as a result of ancient chromosomal duplications. Here, I review the current status of this proposal.

The chromosomal duplication model of the major histocompatibility complex

Comparative gene mapping and chromosome painting permit the tentative reconstruction of ancestral karyotypes. The modern human karyotype is proposed to differ from that of the most recent common ancestor of catarrhine primates by two major rearrangements. The first was the fission of an ancestral chromosome to produce the homologues of human chromosomes 14 and 15. This fission occurred before the divergence of gibbons from humans and other apes. The second was the fusion of two ancestral chromosomes to form human chromosome 2. This fusion occurred after the divergence of humans and chimpanzees. Moving further back in time, homologues of human chromosomes 3 and 21 were formed by the fission of an ancestral linkage group that combined loci of both human chromosomes, whereas homologues of human chromosomes 12 and 22 were formed by a reciprocal translocation between two ancestral chromosomes. Both events occurred at some time after our most recent common ancestor with lemurs. Less direct evidence suggests that the short and long arms of human chromosomes 8, 16 and 19 were unlinked in this ancestor. Finally, the most recent common ancestor of primates and artiodactyls is proposed to have possessed a chromosome that combined loci from human chromosomes 4 and 8p, a chromosome that combined loci from human chromosomes 16q and 19q, and a chromosome that combined loci from human chromosomes 2p and 20.

A brief history of human autosomes.

The first compilation of the pig gene map was published in 1984 by Echard and contained only 36 genes organized into 14 linkage and syntenic groups. Among these 14 groups, only 4 were assigned to a chromosome, but no regional localization was determined. Since that time, two main techniques, in situ hybridization and somatic cell genetics, were developed to increase the amount of data on the cytogenetic map, and in the last version published in 1995 (Yerle et al. 1995) 154 loci are listed and located on a specific chromosome. The third International Pig Gene Mapping Workshop (PGM3) was held in 1996 during the 25th ISAG conference (Tours, France). During this meeting, we presented an updated version of the cytogenetic map, gathering 436 markers, and this map is summarized here. The cytogenetic map contains informations on the localization of genes (coding sequences) corresponding to the conserved part of the genome and of anonymous DNA markers. The knowledge of conserved regions among species (here, human and pig), not only increases the understanding of genome evolution, but also provides a framework for accelerating the localization of further genes in domestic species. Several approaches have been developed since the beginning of 1995 to increase the information available at this level. One of these strategies, named Zoo-FISH, consists of using each chromosome of one species as a probe and hybridizes it on the metaphases of the other species, under conditions in which hybridization of repeated sequences is suppressed. Using this technique, Scherthan and coworkers have demonstrated that human probes could be used to paint the X Chromosome (Chr) of several distantly related mammals, including whales and rodents (Scherthan et al. 1994). This strategy has proven to be a powerful approach for genome comparison and has been successfully applied to the comparison of human and porcine chromosomes. Heterologous hybridization was first carried out with human painting probes on pig metaphases. These monodirectional experiments were restricted to the identification of homologies but without localization (Rettenberger et al. 1995c; Frrnicke et al. 1996). Goureau and coworkers have developed a bidirectional approach that allowed them to define the correspondences between human and porcine chromosomes, segments to segments (Goureau et al. 1996). Another strategy was developed recently to increase the data available at the comparative mapping level (Lyons et al. 1996). In 1993, O'Brien and coworkers listed a set of coding genes spaced across the human genome that could be used as \"anchor loci.\" For each of them, they defined a specific set of primers suitable for PCR analysis. These \"comparative anchor tagged sequences\" (CATs) promise to facilitate the construction of the comparison of maps. Since the publication of the PiGMaP consortium cytogenetic map (Yerle et al. 1995), the most significant fact is that a large effort has been undertaken to increase the links between the genetic and cytogenetic maps of the pig by mapping polymorphic markers on the cytogenetic map. A great number of genetic data

The cytogenetic map of the domestic pig (Sus scrofa domestica)

The dog offers an increasingly important model for several human diseases, including cancer. Accordingly, the results of canine gene mapping studies will be of considerable significance. Herein, we have addressed the mapping of the canine gene ERBB2 (alias HER2, NEU). ERBB2 is a protooncogene encoding a tyrosine kinase receptor protein, the overexpression of which correlates with a more rapid progression and a worse prognosis in breast cancer. In addition, it apparently plays a role in the development of other tumors as well. By fluorescence in situ hybridization (FISH), we have mapped the canine ERBB2 to 1q13.1. Cytogenetic studies of canine tumors revealed that this region is very often affected by clonal chromosome aberrations in tumors of the dog.

The canine ERBB2 gene maps to a chromosome region frequently affected by aberrations in tumors of the dog (Canis familiaris).

5S rRNA is one of the two small RNA molecules localized in the large ribosomal subunit and thereby is involved in protein synthesis. 5S rRNAs from many different organisms have been sequenced, and more than 700 5S rRNA transcripts and 5S rRNA gene sequences have been compiled (Specht et al. 1991). The 5S rRNA genes have been studied in a large number of organisms (reviewed in Korn 1982; Geiduscheck and Tocchini-Valentini 1988; Willis 1993). Compared with the lower eukaryotes, thorough knowledge of the 5S rRNA genes in mammals is scarce. The

Porcine 5S rRNA genes map to 14q23 revealing syntenic relation to human HSPA6- and 7

5S rRNA genes in Macaca fascicularis map to Chromosome lp in three loci

By in situ hybridization we show that the 5s rRNA genes in the mink map to chromosome 2q in three loci. The 2q1.1 locus containing 34 %) of the 5s rDNA, maps close to the centromere, and the remaining two loci of the 5s rDNA map to 2q1.3 (52 %) and to 2q2.3. (14%). These data were obtained with a tritiated transcript of the 5s rRNA gene containing 121 bp. In a comparative FISH study performed with a biotinylated transcript of the 5s rRNA gene the procedure failed to detect the 2q2.3 site. A closely corresponding difference between the two procedures experienced previously in man and in the crab-eating macaque is discussed. The present results suggest a homology between 2q in the mink and part of 1q in man harbouring the 5s rRNA genes in 1q42.13 and 1q31, respectively.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1601-5223.1998.00017.x

Mink 5S rRNA genes map to 2q in three loci suggesting conservation of synteny with human 1q.

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Porcine 5S rRNA genes map to 14q23 revealing syntenic relation to human HSPA6- and 7

5S rRNA genes in Macaca fascicularis map to Chromosome lp in three loci

Mink 5S rRNA genes map to 2q in three loci suggesting conservation of synteny with human 1q.