Cytogenetic and Genome Research

doi: 10.1159/000338576pmid: N/A

Klein, E.; Rocchi, M.; Ovens-Raeder, A.; Kosyakova, N.; Weise, A.; Ziegler, M.; Meins, M.; Morlot, S.; Fischer, W.; Volleth, M.; Polityko, A.; Ogilvie, C. Mackie; Kraus, C.; Liehr, T.

doi: 10.1159/000336648pmid: 22377933

Since the first report in 1993, an ectopic centromere, i.e. neocentromere formation, has been reported in more than 100 small supernumerary marker chromosomes (sSMC), in 7 instances of centromere repositioning, and in about a dozen cases with more complex chromosomal rearrangements. Here we report 2 new cases with centromere repositioning and 3 neocentric sSMC consisting exclusively of heterochromatic material. Yet, no centromere formation was reported for the regions 18q22.1 and Xq27.1∼27.2 as it was observed in the 2 cases with centromere repositioning here; in both cases, cytogenetically an inversion was suggested. Two of the 3 neocentric sSMC were derived from a short arm of an acrocentric chromosome. The remainder neocentric sSMC case was previously reported and was stainable only by material derived from itself.

Milani, D.; Bedeschi, M.F.; Iascone, M.; Chiarelli, G.; Cerutti, M.; Menni, F.

doi: 10.1159/000336979pmid: 22398643

We describe the case of a 6-year-old boy with a de novo deletion of the long arm of chromosome 1 encompassing band 1q31.1–q32.1, minor facial anomalies, mild developmental delay, and behavioral disorders. His postnatal karyotype was normal. Using array-comparative genomic hybridization, we identified and characterized a de novo 1q interstitial deletion of about 15.6 Mb, which partially overlaps those of other reported cases. We considered the gene content of the deleted region in an attempt to compare the clinical features of our patient with these other cases, even though they were not characterized molecularly in detail. The most remarkable difference was the absence of microcephaly. To the best of our knowledge, this is the first report of a de novo 1q31.1–q32.1 deletion. Moreover, it illustrates how molecular delineation associated with fine clinical characterization can improve the genotype-phenotype correlations of classical cytogenetic abnormalities.

Chen-Shtoyerman, R.; Josefsberg Ben-Yehoshua, S.; Nissani, R.; Rosensaft, J.; Appelman, Z.

doi: 10.1159/000336201pmid: 22327880

We describe 7 cases of abnormal karyotypes involving chromosomes Y and 15 in Ethiopian Beta Israel patients: 46,XX, der(15)t(Y;15)(q12;p12) and 46,XY,der(15)t(Y;15)(q12;p12). Six cases were incidentally found in amniocentesis performed for various indications; the indication for karyotyping in 1 case was recurrent abortions. To the best of our knowledge, this is the first report of this translocation in a specific ethnic group. We conclude that the derivative chromosome 15 with chromosome Y is probably a normal variant in Ethiopian Beta Israel occurring at an estimated frequency of 4/74 (5.4%). The prenatal diagnosis of this translocation in this population probably does not require further parental testing.

Dumas, F.; Houck, M.L.; Bigoni, F.; Perelman, P.; Romanenko, S.A.; Stanyon, R.

doi: 10.1159/000336976pmid: 22488112

We hybridized human chromosome paints on metaphases of the pygmy tree shrew (Tupaia minor, Scandentia). The lack of the ancestral mammalian 4/8 association in both Primates and Scandentia was long considered a cytogenetic landmark that phylogenetically linked these mammalian orders. However, our results show that the association 4/8 is present in Tupaia along with not previously reported associations for 1/18 and 7/10. Altogether there are 11 syntenic associations of human chromosome segments in the pygmy tree shrew karyotype: 1/18, 2/21, 3/21, 4/8, 7/10, 7/16, 11/20, 12/22 (twice), 14/15 and 16/19. Our data remove any cytogenetic evidence that Scandentia has a preferential phylogenetic relationship with Primates.

Zhang, H.Z.; Xu, F.; Seashore, M.; Li, P.

doi: 10.1159/000336978pmid: 22398511

A ring chromosome replacing a normal chromosome could involve variable structural rearrangements and mitotic instability. However, most previously reported cases lacked further genomic characterization. High-resolution oligonucleotide array comparative genomic hybridization with single-nucleotide polymorphism typing (aCGH+SNP) was used to study 2 unrelated cases with a ring chromosome 21. Case 1 had severe myopia, hypotonia, joint hypermobility, speech delay, and dysmorphic features. aCGH detected a 1.275-Mb duplication of 21q22.12–q22.13 and a 6.731-Mb distal deletion at 21q22.2. Case 2 showed severe growth and developmental retardations, intractable seizures, and dysmorphic features. aCGH revealed a contiguous pattern of a 3.612- Mb deletion of 21q22.12–q22.2, a 4.568-Mb duplication of 21q22.2–q22.3, and a 2.243-Mb distal deletion at 21q22.3. Mitotic instability was noted in 13, 30, and 76% of in vitro cultured metaphase cells, interphase cells, and leukocyte DNA, respectively. The different phenotypes of these 2 cases are likely associated with the unique genomic structure and distinct mitotic behavior of their ring chromosome 21. These 2 cases represent a subtype of ring chromosome 21 probably involving somatic dicentric ring breakage and reunion. A cytogenomic approach is proposed for characterizing the genomic structure and mitotic instability of ring chromosome abnormalities.

Cernohorska, H.; Kubickova, S.; Vahala, J.; Rubes, J.

doi: 10.1159/000336248pmid: 22327909

For a clade that includes Antilope, Gazella,Nanger and Eudorcas (Antilopinae), X;BTA5 translocation is a synapomorphy. Using a combination of fluorescence in situ hybridization (FISH) probes and polymerase chain reaction techniques, we provide (i) the first insight into the X;BTA5 architecture which differs in the species under study: Antilope cervicapra (genus Antilope), Gazella leptoceros (genus Gazella) and Nanger dama ruficollis (genus Nanger), (ii) determination of interstitial satellite DNA at the X;BTA5 junctions, and (iii) determination of repetitive sequences occupying constitutive heterochromatin of Xp arms in the studied species. The distribution of 2 repetitive DNA families in the centromeric regions of all chromosomes has been investigated by FISH with probes representing satellite I and satellite II DNA in all studied species. In this context, we discuss a markedly smaller centromere in the BTA5 (Y2) unfused chromosomes in males in the XY1Y2 determining system in comparison with other acrocentrics. An analysis of karyotypic data described in current published studies revealed a disparity with the data determined by FISH. In this report, we document chromosomal fusions in the 3 species mentioned resulting from FISH with painting probes prepared from cattle (Bos taurus). The number and chromosomal location of nucleolus organizer regions were determined by FISH. In the present study, we emphasize the importance of chromosomal rearrangement verification, particularly, if they are used for phylogenetic analysis.

Bakloushinskaya, I.Yu.; Matveevsky, S.N.; Romanenko, S.A.; Serdukova, N.A.; Kolomiets, O.L.; Spangenberg, V.E.; Lyapunova, E.A.; Graphodatsky, A.S.

doi: 10.1159/000336459pmid: 22343488

A comparative genomic analysis was carried out in the mole vole sibling species Ellobius tancrei and E. talpinus. Performing fluorescent in situ hybridisation (Zoo-FISH) using chromosome paints from the field vole Microtus agrestis showed no differences in the allocation of syntenic groups in the karyotypes of these sibling species. The only difference between their karyotypes was the position of the centromere in one pair of chromosomes, which is assumed to be the result of an inversion. To verify this hypothesis, we analysed chromosome synapsis in prophase I of meiosis. We utilised a synaptonemal complex (SC) surface-spreading technique to visualise the process of chromosome synapsis in the spermatocytes and oocytes of first-generation hybrids and back-crosses of these sibling species. In prophase I of meiosis, immunocytochemical and electron microscopy analyses revealed that all bivalents had been fully adjusted. Even in the case of a submetacentric-acrocentric bivalent with different centromere locations, synapsis of SC lateral elements was fulfilled along the entire length of the chromosomes and the formation of an inversion loop was not observed. We hypothesise that a possible mechanism leading to the change in centromere position is the repositioning and/or generation of a neocentromere. Despite the great similarity in the karyotypes of these sibling species, they exhibited significant genomic diversification, which manifested as hybrid sterility and parous female death.

Dutrillaux, A.-M.; Dutrillaux, B.

doi: 10.1159/000336694pmid: 22377972

The aim of this study was the identification of the ancestral location of the nucleolus organizer region (NOR) in the Scarabaeoidea superfamily, and its evolutive trends in the karyotypes. For this purpose, the mitotic and meiotic chromosomes at pachynema of 82 species belonging to 4 families and 8 subfamilies, including 49 species without any published data, were examined after Giemsa staining, C-banding and NOR staining. It could be perceived that most karyotypes are composed of 18 nonacrocentric autosomes, an acrocentric X and a punctiform Y. NORs are frequently located on the X independent of its morphology. In contrast, autosomal NORs are frequently on the rare acrocentric short arms. Thus, it could be shown that the ancestral karyotype was very probably composed of 18 metacentric/submetacentric autosomes, an NOR carrier acrocentric X and a punctiform Y. The NOR translocation on autosomes parallels the passage to their acrocentric morphology. It is proposed that the frequent location of the NOR on the X of beetles, and possibly other insects, is made possible by their mode of dosage compensation of the X chromosome, consisting in the overexpression of the unique X of the males.

Xu, H.; Yin, D.; Li, L.; Wang, Q.; Li, X.; Yang, X.; Liu, W.; An, D.

doi: 10.1159/000336478pmid: 22354334

To develop a set of molecular markers specific for the chromosome arms of rye, a total of 1,098 and 93 primer pairs derived from the expressed sequence tag (EST) sequences distributed on all 21 wheat chromosomes and 7 rye chromosomes, respectively, were initially screened on common wheat ‘Chinese Spring’ and rye cultivar ‘Imperial’. Four hundred and fourteen EST-based markers were specific for the rye genome. Seven disomic chromosome addition lines, 10 telosomic addition lines and 1 translocation line of ‘Chinese Spring-Imperial’ were confirmed by genomic in situ hybridization and fluorescencein situ hybridization, and used to screen the rye-specific markers. Thirty-one of the 414 markers produced stable specific amplicons in ‘Imperial’, as well as individual addition lines and were assigned to 13 chromosome arms of rye except for 6RS. Six rye cultivars, wheat cultivar ‘Xiaoyan 6’ and accessions of 4 wheat relatives were then used to test the specificity of the 31 EST-based markers. To confirm the specificity, 4 wheat-rye derivatives of ‘Xiaoyan 6 × German White’, with chromosomes 1RS, 2R and 4R, were amplified by some of the EST-based markers. The results indicated that they can effectively be used to detect corresponding rye chromosomes or chromosome arms introgressed into a wheat background, and hence to accelerate the utilization of rye genes in wheat breeding.