A new case of 17p13.3p13.1 microduplication resulted from unbalanced translocation: clinical and molecular cytogenetic characterization

Copy number gain 17 p13.3p13.1 was detected by chromosomal microarray (CMA) in a girl with developmental/speech delay and facial dysmorphism. FISH studies made it possible to establish that the identified genomic imbalance is the unbalanced t(9;17) translocation of maternal origin. Clinical features of the patient are also discussed. The advisability of using the combination of CMA and FISH analysis is shown. Copy number gains detected by clinical CMA should be confirmed using FISH analysis in order to determine the physical location of the duplicated segment. Parental follow-up studies is an important step to determine the origin of genomic imbalance. This approach not only allows a most comprehensive characterization of an identified chromosomal/genomic imbalance but also provision of an adequate medical and genetic counseling for a family taking into account a balanced chromosomal rearrangement.

Identification of regions of constitutive heterochromatin and sites of ribosomal DNA (rDNA) in Rhogeessa hussoni (Genoways & Baker, 1996) (Chiroptera; Mammalia; Vespertilionidae)

There is scarce information about the geographical distribution, biological and cytogenetic data from the Rhogeessa hussoni. This study aims to characterize its chromosome composition through chromosome bandings to visualize regions of constitutive heterochromatin (CGB bands) and sites of ribosomal DNA (rDNA) in R. hussoni’s karyotype. A female specimen of R. hussoni was collected in the “Parque Municipal Mário Viana” Conservation Unit, Nova Xavantina, Mato Grosso, Central-West region of Brazil. The karyotype constitution was 2n=52 and NF=54. The CBG bands evidenced a sex X chromosome nearly completely constituted by heterochromatin. The Rhogeessa hussoni has two sites of rDNA located in a single pair (pair 25) of autosomal chromosomes. We carried out the first cytogenetic characterization of R. hussoni, supplementing knowledge about regions of heterochromatin and ribosomal DNA in this species, thus contributing to future elucidations about the genetic diversification in the genus Rogheessa.

First cytogenetic characterization of the Amazon Catfish Leiarius marmoratus (Gill, 1870) and its hybrid with Pseudoplatystoma reticulatum (Eigenmann & Eigenmann, 1889)

This study reports the first cytogenetic characterization of the Amazonian catfish Leiarius marmoratus (“jandiá”) and its F1 (first generation) hybrid “cachandiá” with Pseudoplatystoma reticulatum (“cachara”). A diploid number of 56 chromosomes and a single argyrophilic nucleolus organizer region (Ag-NOR) in the short arm of two sub-telocentric chromosomes were observed for both L. marmoratus and P. reticulatum, but with differences in the karyotype formula and the size of the chromosome pair with NORs. The hybrid showed 2n = 56 chromosomes with an intermediate karyotype when compared to the parental species. A single Ag-NOR was maintained in the hybrid but located in two chromosomes with marked differences in size and presenting intraindividual variation in NOR activity (nucleolar dominance). For L. marmoratus and the hybrid, heterochromatic bands were predominately distributed in the terminal, centromeric, and sub-centromeric regions of some chromosomes and 5S rDNA sites located in two distinct sub-telocentric chromosomes, similar to the previously described for P. reticulatum. The data suggested that the hybrid karyotype might be insufficient for a precise discrimination of hybrids, however, Ag-NOR can be used as a chromosome marker to differentiate “cachandiá” from L. marmoratus and P. reticulatum. The current study also provides insights into the chromosomal features of L. marmoratus and contributes with novel cytogenetic information of this native Amazonian catfish included in the Pimelodidae family.

Karyotype Variation in Eight Cultivars of Indian Dessert Banana (Musa acuminata L.) of Section Eumusa From Odisha, India

Banana (Musa spp.) cultivars especially dessert banana are important cash crop with high market demand all over the world as an integral part of the diet. The need for assessment of cytogenetic characters in Musa cultivars is inevitable as out of thousands of cultivars, cytogenetic characterization of most of them remains unresolved due to difficulties like small chromosome size, diversity in ploidy levels and high cultivar diversity which behave differently to standardized cytogenetic protocols. In this report, somatic chromosome number, detailed karyotype analysis including total chromosome length, volume, form percentage, Interphase Nuclear Volume (INV) were accessed on eight dessert type of Musa accessions from different places of Odisha. All the cultivars studied were found triploid (2n = 33) with a basic chromosome number of x=11. The karyotype formulae were assigned to each cultivar by grouping the chromosome according to their shared characteristics. The total chromosome length ranged from 54.95 µm in cv. Robusta to 81.5 µm in cv. Kathia with symmetric karyotype in all the studied cultivar. Karyotype formula revealed structural alteration of chromosome with Total Form percentage (TF%) variation from 35.65% in cv. Amritapani to 41.68% in cv. Patakpura that confirms more number of nearly median constricted chromosome as compared to sub-median chromosome. The total chromosome volume recorded from 10.78 µm3 in cv. Robusta to 15.99 µm3 in cv. Khatia and the INV varied from 1336.44 µm3 in cv. Dwarf Cavendish to 2048.37 µm3 in cv. Patakpura. The recorded structural variation might be due to differential genome specific condensation of chromosome. Chromosome length and volume found statistically significant among the cultivars.

Molecular cytogenetic characterization of natural hybrids of Roegneria stricta and Roegneria turczaninovii (Triticeae: Poaceae)

Hybridization is an important part of species evolution. The hybrid progeny population had rich genetic and phenotypic variation, which made the boundaries between them and their parents blurred and difficult to distinguish. There was little research on the origin of natural hybrids of Triticeae. In this study, we found a large number of putative hybrids of Roegneria in West Sichuan Plateau, China. The hybrid plants showed strong heterosis in plant height, tiller number and floret number. Morphologically, the putative hybrids showed intermediate of Roegneria stricta Keng and Roegneria turczaninovii (Drob.) Nevski. Hybrids had 28 chromosomes corresponding to that of R. stricta and R. turczaninovii (2n=4x=28). Meiotic pairing in hybrids were less regular than those of R. stricta and R. turczaninovii. GISH analysis showed that the hybrid plants had the same genome as that of R. stricta and R. turczaninovii (StY). Phylogenetic analysis based on the single copy nuclear gene DMC1 and chloroplast gene rps16 showed the plants were closely related to R. stricta and R. turczaninovii. This study indicated that the plants were hybrids of R. stricta and R. turczaninovii. The results provided data for the utilization of hybrid. This study provided a case study of natural hybrids.