Comprehensive transcriptomic analysis of the process of gonadal sex differentiation in the turbot (Scophthalmus maximus)

The turbot is a flatfish with a ZW/ZZ sex determination system but with a still unknown sex determining gene(s), and with a marked sexual growth dimorphism in favor of females. To better understand sexual development in turbot we sampled young turbot encompassing the whole process of gonadal differentiation and conducted a comprehensive transcriptomic study on its sex differentiation using a validated custom oligomicroarray. Also, the expression profiles of 18 canonical reproduction-related genes were studied along gonad development. The expression levels of gonadal aromatase cyp19a1a alone at three months of age allowed the accurate and early identification of sex before the first signs of histological differentiation. A total of 56 differentially expressed genes (DEG) that had not previously been related to sex differentiation in fish were identified within the first three months of age, of which 44 were associated with ovarian differentiation (e.g., cd98, gpd1 and cry2), and 12 with testicular differentiation (e.g., ace, capn8 and nxph1). To identify putative sex determining genes, ∼4.000 DEG in juvenile gonads were mapped and their positions compared with that of previously identified sex- and growth-related quantitative trait loci (QTL). Although no genes mapped to the previously identified sex-related QTLs, two genes (foxl2 and 17βhsd) of the canonical reproduction-related genes mapped to growth-QTLs in linkage group (LG) 15 and LG6, respectively, suggesting that these genes are related to the growth dimorphism in this species.

Quantitative analysis of the variability of nucleolar organizer regions in Salmo trutta

A quantitative analysis combined with Ag staining was carried out to study the size variation of the main nucleolar organizer region (NOR) bearing chromosome pair 11 of Salmo trutta. A standardized NOR size measurement was developed by comparing the length of the short arm (NOR-bearing region) to the total chromosome length. Statistical procedures support arguments for the existence of a large and structural polymorphism within this species for this chromosome region. A minimum of five different chromosome classes were identified, which account for the total variation found. Size variation among classes was due both to changes in the number of NOR clusters as well as to the amount of rDNA genes within each cluster. NOR size values were normally distributed in the sample analyzed.

Usefulness of bronchial reactivity analysis in the diagnosis of bronchial asthma in patients with bronchial hyperresponsiveness

We examined the usefulness of some bronchial reactivity indices to identify bronchial asthma in patients with airway hyperresponsiveness. Eighty-eight consecutive patients with positive response to histamine bronchial challenge (> or = 20% fall in FEV1) were included in the study. Dose-response curves were characterised by their sensitivity (PD20) and reactivity. Dose-response slope, continuous index of responsiveness (CIR) and bronchial reactivity index (BRI) with respect to baseline and post-diluent baseline values were determined as reactivity indices. The clinical diagnosis remaining in the case history 2 years after the bronchial challenge was considered the definitive diagnosis. Asthmatic patients had higher baseline BRI (12.121+/-0.412 vs. 11.615+/-0.201; P<0.001) and post-diluent baseline BRI (12.054+/-0.368 vs. 11.563+/-0.531; P = 0.003) than other subjects. Area beneath their receiver operating characteristic (ROC) curve was 82.68% (standard error: 0.77) for the baseline BRI and 81.73 (standard error: 0.76). By multiple logistic regression analysis, baseline BRI was the only independent variable identified as a predictor for diagnosis of bronchial asthma (r = 0.387, P = 0.0007). A cut-off of 11.76 for baseline BRI reached an 87.2% sensitivity and an 80% specificity for bronchial asthma diagnosis. In conclusion, BRI calculated with respect to baseline FEV1 should be useful in identifying asthmatic patients among subjects with airway hyperresponsiveness.

Prothymosin alpha, a mammalian c-myc-regulated acidic nuclear protein, provokes the decondensation of human chromosomes in vitro

Prothymosin (ProT alpha) is an acidic nuclear protein, widely distributed in mammalian cells, whose expression is regulated by c-myc and linked to cell proliferation. ProT alpha interacts with histone H1 via its acidic domain, and its overexpression provokes the unfolding of chromatin fibers. Here we show that incubation of human native metaphase chromosomes with ProT alpha induces their extensive unravelling suggesting a function of this protein in chromosome decondensation.

Identification and mutation analysis of a cochlear-expressed, zinc finger protein gene at the DFNB7/11 and dn hearing-loss loci on human chromosome 9q and mouse chromosome 19

The DFNB7/11 locus for autosomal recessive non-syndromic hearing loss (ARNSHL) has been mapped to an approx. 1.5 Mb interval on human chromosome 9q13-q21. We have determined the cDNA sequence and genomic structure of a novel cochlear-expressed gene, ZNF216, that maps to the DFNB7/11 interval. The mouse orthologue of this gene maps to the murine dn (deafness) locus on mouse chromosome 19. The ZNF216 gene is highly conserved between human and mouse, and contains two regions that show homology to the putative zinc linger domains of other proteins. To determine it mutations in ZNF216 might be the cause of hearing loss at the DFNB7/11 locus, we screened the coding region of this gene in DFNB7/11 families by direct sequencing. No potential disease-causing mutations were found. In addition, Northern blot analysis showed no difference in ZNF216 transcript size or abundance between dn and control mice. These data Suggest that the ZNF216 gene is unlikely to be responsible for hearing loss at the DFNB7/11 and dn loci.

Localization of rDNA genes in European eel (Anguilla anguilla) by FISH

A probe containing most of the transcription unit of the major ribosomal genes of Xenopus laevis has been used to localize the rDNA cluster of European eel (Anguilla anguilla) by fluorescence in situ hybridization (FISH). Only on NOR-bearing chromosome pair has been found. The results obtained with this technique confirm the size polymorphism of the NOR revealed previously by other classical cytogenetic techniques.

A new EcoRI family of satellite DNA in lampreys

Satellite DNA sequences have been studied in several groups of organisms. However, until now this type of sequence has not been characterized in cyclostomata, an evolutionarily important class of vertebrates. In the present work, we report the molecular characterization of a new family of satellite DNA in lampreys (Petromyzon marinus). Digestion of lamprey DNA with EcoRI identified a series of very abundant AT-rich (60% A+T) repeating units, with short stretches of AT, that are multimers of 370 bp. Southern blot analysis and comparison with the satellite DNA sequences deposited in the databases indicate that this new family of satellite DNA is exclusive to lampreys. The distribution of this EcoRI satellite DNA on lamprey chromosomes was analyzed by in situ hybridization. The evolutionary origin of this satellite is briefly discussed.

Characterization of an atypical NOR site polymorphism in brown trout (Salmo trutta) with Ag- and CMA3-staining, and fluorescent in situ hybridization

We have analyzed by Ag- and CMA3-staining, and rDNA fluorescent in situ hybridization an unusual NOR site polymorphism in a population of Salmo trutta from Mino basin (Northwestern Spain). A multichromosomal Ag-NOR distribution largely different from standard individuals both in the number and position of Ag-NORs, as well as in the pattern of activity, was revealed. Atypical Ag-NORs consist of rDNA genes, as evidenced by rDNA FISH, and are capable of constituting their own nucleolus. In spite of the large number of available NORs per individual, the mean number of Ag-NOR per cell was less than 3 in most individuals, which suggests a regulation mechanism to adjust the ribosomal production. The new rDNA clusters detected seem to be stably integrated, however, some characteristics of the NOR pattern observed suggest that this polymorphism is an unstable phenomenon.

Differential digestion of the centromeric heterochromatic regions of the 5-azacytidine-decondensed human chromosomes 1, 9, 15, and 16 by NdeII and Sau3AI restriction endonucleases

A study on the factors involved in chromosome digestion by restriction endonuclease was carried out on 5-azacytidine treated and untreated human chromosomes 1, 9, 15 and 16 by using NdeII and Sau3AI isoschizomers. After treatment with 5-azacytidine, chromosomes 1, 9, 15, and 16 showed two differentiated areas at the centromeric regions: the centromere, fully condensed, and the pericentromeric heterochromatin, decondensed. Chromosomes not treated with 5-azacytidine after digestion with Sau3AI and NdeII showed all the centromeric regions undigested, except pair number 1, digested at the pericentromeric area. Digestion of the 5-azacytidine decondensed chromosomes with Sau3AI and NdeII showed the centromeres undigested in the four chromosome pairs while the pericentromeric heterochromatin appeared largely digested. Other factors, different to target distribution, are necessary to explain the pattern of restriction endonuclease digestion observed in this communication.

Induction of G-bands on Anguilla anguilla chromosomes by the restriction endonucleases HaeIII, HinfI, and MseI

Fixed metaphase chromosomes of the eel Anguilla anguilla were treated with the restriction enzymes HaeIII, HinfI, and MseI. All three restriction endonucleases are capable of inducing a G-band-like pattern if the incubation time and enzyme concentration are controlled. The results are discussed in relation to the main factors involved in the appearance of serial G-bands. Chromatin organization, rather than DNA composition, seems to account for the interstitial G-band pattern exhibited by these eel chromosomes.

Analysis of the structure and variability of nucleolar organizer regions of Salmo trutta by C-, Ag-, and restriction endonuclease banding

Nucleolar organizer regions (NORs) of brown trout were investigated using C-, Ag-, and restriction endonuclease banding. The presence of constitutive heterochromatin was confirmed by C-banding. Giemsa-staining, C-banding, and Ag-banding revealed great variability in the size of the short arm of the NOR-bearing chromosome. This size variation was due in some cases to NOR duplication. Restriction endonuclease digestion induced a specific banding pattern for AluI, DdeI, HaeIII, MboI, and HinfI, indicating some features about the sequence composition of the NOR-associated heterochromatin.