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DMRT genes encode a large family of transcription factors which share an unusual cysteine-rich DNA-binding motif, the DM domain. DM family members have been studied in the context of sexual development; in particular, the DMRT1 gene appeared to be the one most directly involved in sex determination, but its activity is largely unexplored and possible downstream targets of this factor have yet to be identified. DMRT1 of the lacertid lizard Podarcis sicula (PsDMRT1) was isolated as a model to study differential gene expression during the seasonal reproductive cycle of an ectothermal species. The adult testis of P. sicula exhibits full activity in spring, complete regression in summer and a slow autumnal recrudescence without spermiation. We cloned a 591-bp partial ORF of the PsDMRT1 fragment, whose putative amino acid sequence contains the conserved DM domain. Northern blot analysis of mRNA from different tissues of P. sicula individuals captured in spring demonstrated DMRT1 transcripts only in testis. Semi-quantitative RT-PCR and in situ hybridization experiments showed peak PsDMRT1 expression in spring, lower expression in autumn and no expression during the period of gonad regression. A possible correlation between androgen level variations and PsDMRT1 transcripts is hypothesized and discussed. Finally, data showed that PsDMRT1 is expressed only in spermatogenic cells, before the second meiotic division, suggesting that its role is confined to the proliferation and maintenance of spermatogonia and spermatocytes.

We hybridized human chromosome-specific DNA probes to metaphases of the New World monkey Ateles geoffroyi to map the chromosomal homology between these two species. In the haploid Ateles geoffroyi karyotype the total number of signals was 51 for the 22 human autosomal probes used. Compared with Old World monkeys, the number of translocations found in the black-handed spider monkey karyotype was quite striking. The majority of these translocations are apparently Robertsonian and no reciprocal translocations were revealed. Nine autosomal human chromosome probes (11, 13, 14, 17, 18, 19, 20, 21, 22) provided only two signals each per metaphase, but six of these were translocated to subregions of different spider monkey chromosomes. The other 13 autosomal human chromosome paints (1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 16) provided fragmented signals. Three human probes (5, 8, 10) provided signals located on two pairs of spider monkey chromosomes. Four human paints (2, 3, 4, 12) provided hybridization signals on three pairs of chromosomes. Probes 6, 7, 15 provided six signals each on two pairs of chromosomes; probe 16 gave eight signals on two pairs of spider monkey chromosomes and probe 1 gave 12 signals on four pairs of chromosomes. The synteny between segments to human 18/8 appears to be an apomorphic ancestral condition for all New World monkeys. A synteny between regions homologous to human 16/10, 5/7 and 2/16 HSA is probably an apomorphic ancestral condition for all Cebidae. The syntenic association 3/15 and 4/1 is an apomorphic condition for the Atelinae.

Polypterids are a group of Osteichthyan fish whose evolutionary relationships with closer basal ray-finned and lobe-finned fish have been disputed since their discovery. Very little is known about the evolutive karyology in the whole Polypteriformes group. In order to fill this gap, a cytogenetic analysis of Erpetoichthys calabaricus species was performed, using both classical and molecular techniques. Karyotype structure (2n = 36; FN = 72), chromosome location of telomeric sequences (TTAGGG) n and ribosomal 5S and 18S rRNA genes were examined in twenty specimens of E. calabaricus by using Ag-NOR, classical C-banding, sequential CMA3/4′,6-diaminidino-2-phenylindole (DAPI) staining and fluorescent in situ hybridization (FISH). CMA3 marked all centromerical and some (n°1 and n°15) telomeric regions. Staining with Ag-NOR and CMA3 showed the presence of two NORs on the p arm of the chromosome pair n°1. Hybridization with telomeric probes (TTAGGG) n showed signals at the end of all chromosomes. 5S rDNA was cloned and sequenced. After the alignment, the 5S rRNA sequences revealed an organization made up of two different classes of tandem arrays (type I and type II). FISH with 5S rDNA marked the telomeric regions of the small chromosome pair n°15, while FISH with 18S rDNA marked the telomeric region of the pair n°1. The results obtained were compared with cariological data on closer species now available in literature.

Polypteridae is a family of archaic freshwater African fish that constitute an interesting subject for the study of the karyological evolution in vertebrates, on account of their primitive morphological characters and peculiar relationships with lower Osteichthyans. In this paper, a cytogenetic analysis on twenty specimens of both sexes of Polypterus ornatipinnis the ornate "bichir", coming from the Congo River basin, was performed by using both classical and molecular techniques. The karyotypic formula (2n=36; FN=72) was composed of 26 M+10 SM. The Alu I banding, performed to characterize heterochromatin in this species, was mainly centromeric. Both the chromosome location of the ribosomal 5S and 18S rRNA genes were examined by using Ag-NOR, classical C-banding, CMA3 staining and FISH. CMA3 marked all centromerical regions and showed the presence of two GC rich regions on the p arm of the chromosome pair n°1 and on the q arm of the pair n°14 Staining with Ag-NOR marked the only telomeric region of the chromosome n°1 p arm. After PCR, the 5S rDNA in this species was cloned, sequenced and analyzed. In the 665bp 5S rDNA sequence of P.ornatipinnis, a conserved 120bp gene region for the 5S rDNA was identified, followed by a non-transcribed variable spacer (NTS) which included simple repeats, microsatellites and a fragment of a non-LTR retrotransposon R-TEX. FISH with 5S rDNA marked the subtelomeric region of the q arm of the chromosome pair n°14, previously marked by CMA3. FISH with 18S rDNA marked the telomeric region of the p arm of the pair n°1, previously marked both by Ag-NOR and CMA3. The (GATA)7 repeats marked the telomeric regions of all chromosome pairs, with the exclusion of the n°1, n°3 and n°14; hybridization with telomeric probes (TTAGGG)n showed signals at the end of all chromosomes. Karyotype evolution in Polypterus genus was finally discussed, including the new data obtained. © 2010 Elsevier B.V.

Although considerable progress has been made in elucidating the relationships within the Chondrichthyes, there is no agreement as it concerns the systematics of Batoidea, the most derived superorder among cartilaginous fishes, and many different interpretations exist. Our investigation provides the first assessment of relationships among the described batoid species using sequences from both mtDNA and nuclear genes as well as karyological morphology. Our work consists primarily in reconstructing the phylogenetic relationships of Batoidea by examining the mtDNA (16S) and nuclear gene (18S) sequences from 11 batoid species. The three analytical methods (NJ, MP and Bayesian analysis) grouped Rajiformes, Myliobatiformes and Rhinobatiformes. In these trees the two torpedoes diverge from the other batoid fishes. We also compare the molecular data with the available karyological evidence, which consist of the diploid number and the karyotype morphology of eight species belonging to the four orders examined. The results show that the karyological structure in the different species is generally consistent with the various phylogenetical trees, and that Torpediniformes confirm their unique genome organization. © 2006 Elsevier B.V. All rights reserved.