Comparative cytogenetic patterns in Carangidae fishes in association with their distribution range

Carangidae are an important and widespreaded family of pelagic predatory fishes that inhabit reef regions or open ocean areas, some species occupying a vast circumglobal distribution. Cytogenetic comparisons among representatives of its different tribes help to understand the process of karyotype divergence in marine ecosystems due to the variable migratory ability of species. In this sense, conventional cytogenetic investigations (Giemsa staining, Ag-NORs, and C-banding), GC base-specific fluorochrome staining and FISH mapping of ribosomal DNAs were performed. Four species, Elagatis bipinnulata (Quoy et Gaimard, 1825) and Seriola rivoliana (Valenciennes, 1883) (Naucratini), with circumtropical distributions, Gnathanodon speciosus (Forsskål, 1775) (Carangini), widely distributed in the tropical and subtropical waters of the Indian and Pacific oceans, and Trachinotus carolinus (Linnaeus, 1766) (Trachinotini), distributed along the western Atlantic Ocean, were analyzed, thus encompassing representatives of three out its four tribes. All species have diploid chromosome number 2n = 48, with karyotypes composed mainly by acrocentric chromosomes (NF = 50–56). The 18S rDNA/Ag-NORs/GC+ and 5S rDNA loci were located on chromosomes likely homeologs. Karyotypes showed a pattern considered basal for the family or with small variations in their structures, apparently due to pericentric inversions. The migratory capacity of large pelagic swimmers, in large distribution areas, likely restricts the fixation of chromosome changes in Carangidae responsible for a low level of karyotype diversification.

Insights into the Karyotype Evolution of Charinidae, the Early-Diverging Clade of Whip Spiders (Arachnida: Amblypygi)

Whip spiders (Amblypygi) represent an ancient order of tetrapulmonate arachnids with a low diversity. Their cytogenetic data are confined to only a few reports. Here, we analyzed the family Charinidae, a lineage almost at the base of the amblypygids, providing an insight into the ancestral traits and basic trajectories of amblypygid karyotype evolution. We performed Giemsa staining, selected banding techniques, and detected 18S ribosomal DNA and telomeric repeats by fluorescence in situ hybridization in four Charinus and five Sarax species. Both genera exhibit a wide range of diploid chromosome numbers (2n = 42–76 and 22–74 for Charinus and Sarax, respectively). The 2n reduction was accompanied by an increase of proportion of biarmed elements. We further revealed a single NOR site (probably an ancestral condition for charinids), the presence of a (TTAGG)n telomeric motif localized mostly at the chromosome ends, and an absence of heteromorphic sex chromosomes. Our data collectively suggest a high pace of karyotype repatterning in amblypygids, with probably a high ancestral 2n and its subsequent gradual reduction by fusions, and the action of pericentric inversions, similarly to what has been proposed for neoamblypygids. The possible contribution of fissions to charinid karyotype repatterning, however, cannot be fully ruled out.

Comparative genomic mapping reveals mechanisms of chromosome diversification in Rhipidomys species (Rodentia, Thomasomyini) and syntenic relationship between species of Sigmodontinae

Rhipidomys (Sigmodontinae, Thomasomyini) has 25 recognized species, with a wide distribution ranging from eastern Panama to northern Argentina. Cytogenetic data has been described for 13 species with 12 of them having 2n = 44 with a high level of autosomal fundamental number (FN) variation, ranging from 46 to 80, assigned to pericentric inversions. The species are grouped in groups with low FN (46–52) and high FN (72–80). In this work the karyotypes of Rhipidomys emiliae (2n = 44, FN = 50) and Rhipidomys mastacalis (2n = 44, FN = 74), were studied by classical cytogenetics and by fluorescence in situ hybridization using telomeric and whole chromosome probes (chromosome painting) of Hylaeamys megacephalus (HME). Chromosome painting revealed homology between 36 segments of REM and 37 of RMA. We tested the hypothesis that pericentric inversions are the predominant chromosomal rearrangements responsible for karyotypic divergence between these species, as proposed in literature. Our results show that the genomic diversification between the karyotypes of the two species resulted from translocations, centromeric repositioning and pericentric inversions. The chromosomal evolution in Rhipidomys was associated with karyotypical orthoselection. The HME probes revealed that seven syntenic probably ancestral blocks for Sigmodontinae are present in Rhipidomys. An additional syntenic block described here is suggested as part of the subfamily ancestral karyotype. We also define five synapomorphies that can be used as chromosomal signatures for Rhipidomys.

Derived karyotypes in two elephantfish genera (Hyperopisus and Pollimyrus): lowest chromosome number in the family Mormyridae (Osteoglossiformes)

The African weakly electric elephantfish family Mormyridae comprises 22 genera and almost 230 species. Up-to-date cytogenetic information was available for 17 species representing 14 genera. Here we report chromosome number and morphology in Hyperopisus bebe (Lacepède, 1803) and Pollimyrus isidori (Valenciennes, 1847) collected from the White Nile system in southwestern Ethiopia. Both taxa displayed the diploid chromosome number 2n = 40, but they differed in fundamental numbers: FN = 66 in H. bebe and FN = 72 in P. isidori; previously the same diploid chromosome number 2n = 40 was reported in an undescribed species of Pollimyrus Taverne, 1971 (FN = 42) from the same region. Our results demonstrate that not only pericentric inversions, but fusions also played a substantial role in the evolution of the mormyrid karyotype structure. If the hypothesis that the karyotype structure with 2n = 50–52 and prevalence of the uni-armed chromosomes close to the ancestral condition for the family Mormyridae is correct, the most derived karyotype structures are found in the Mormyrus Linnaeus, 1758 species with 2n = 50 and the highest number of bi-armed elements in their compliments compared to all other mormyrids and in Pollimyrus isidori with the highest number of bi-armed elements among the mormyrids with 2n = 40.

Chromosome 9 Inversion: Pathogenic or Benign? A Comprehensive Systematic Review of all Clinical Reports

Background: Inversion of chromosome 9 (inv[9]) is known as one of the most common structural balanced chromosomal variations. Chromosome 9 is highly susceptible to structural rearrangements, specifically to pericentric inversions. Various investigators have posited that inv(9) with different breakpoints could be the cause of several abnormal conditions in individuals, whereas others have considered it a benign variant. To our knowledge, a consensus regarding the effects of this inversion has yet to emerge. Objective: This study aims to discuss the pathogenic/benign effects of inv(9) in all possible clinical conditions detected in the occurrence of this abnormality. Methods: Studies on inv(9) were collected via PubMed, MalaCards, Google Scholar, and NORD, along with the search terms of inv(9), pericentric inv(9), and chromosome 9 variants. Additionally, the incidence of inv(9) and the karyotype and clinical findings of individuals reported with this variant were investigated. Results: The collection of the studies reviewed shows that inv(9) is associated with various conditions such as congenital anomalies, growth retardation, infertility, recurrent pregnancy loss, and cancer. The clinical features associated with this variant in humans vary between growth stages. Further, there have been no shared clinical findings in a specific period. Conclusions: Although there is no conclusive evidence for the pathogenicity of this rearrangement, prenatal genetic counseling on inv(9) and further clinical and molecular studies would be helpful in chromosome 9-related problems.

Trends of karyotype evolution in the Neotropical long-legged crickets Phalangopsidae (Orthoptera, Grylloidea)

Phalangopsids are a diverse group of crickets found in all tropical and subtropical regions, and includes 1044 valid species. Up to now, only 22 species were studied cytologically, with the chromosome number ranging from 2n = 11 to 2n = 21. In this paper we studied the chromosomes of 12 phalangopsid species from different Brazilian biomes (eight of them reported for the first time), and we traced some trends on chromosomal derivation in this group, based on chromosome morphology and fundamental number. We found that in the phalangopsid species the karyotype concentrates a large amount of metacentric chromosomes, the result of successive centric fusions over evolutionary time. Moreover, pericentric inversions and translocations have been also important in the chromosomal derivation of these crickets.

Karyotype evolution of the genus Eranthis Salisb. (Ranunculaceae)

We have conducted comparative study of karyotypes for nine Eranthis Salisb. species: E. bulgarica (Stef.)Stef., E. hyemalis (L.) Salisb., E. longistipitata Regel (section Eranthis), E. byunsanensis B. Y. Sun, E. lobulata W. T.Wang, E. pinnatifida Maxim., E. sibirica DC., E. stellata Maxim., and E. tanhoensis Erst (section Shibateranthis). Thespecies-specifity of karyotypes was established for all species investigated. The chromosomes of each species weremedium or large in size (4–12 µm). Besides E. sibirica and E. tanhoensis, all the investigated specimens had diploidcytotypes with 2n = 16 and the basic chromosome number x = 8. Plants from five E. sibirica populations were tetraploidand hexaploid with x = 7, 2n = 28 and 2n = 42 respectively. Plants from seven E. tanhoensis populations were diploid withx = 7 and 2n = 14. Diploid karyotypes of Eranthis included 4–5 pairs of large equal-armed (metacentric) chromosomes,and 2–4 pairs of unequal-armed chromosomes belonging to different morphological types (submetacentric, subtelocentric,and acrocentric ones). We have revealed B chromosomes in root meristematic cells of E. lobulata and E. tanhoensis forthe first time. We suppose that the key developments in Eranthis karyotype`s evolution were pericentric inversions,polyploidy, and probably translocations.

The role of cytogenetic variation in Akodon cursor species complex speciation (Rodentia: Sigmodontinae)

Chromosome polymorphism in populations of Akodon cursor complex (124 specimens) and the karyotypes of other Akodon species (92 specimens) from Brazil were analyzed. Five species were analyzed: Akodon cursor with 2n = 14, and Akodon aff. cursor with 2n = 16, Akodon montensis with 2n = 24, Akodon paranaensis with 2n = 44 and Akodon serrensis with 2n = 46. Chromosome polymorphism was observed in A. cursor and A. aff. cursor showing pericentric inversions, and also in A. paranaensis and A. montensis presenting supernumerary chromosomes. Pericentric inversion polymorphism affecting two autosomes pairs in A. cursor karyotype was found in Hardy-Weinberg equilibrium. Akodon with 2n = 16 occurred from Bahia to Rio Grande do Norte states and A. cursor with 2n = 14 from Bahia to Paraná states. Molecular analyses showed high genetic distance estimates between such set of samples, suggesting that karyomorphic type 2n = 16 is fixed in the northern part of the distribution of Akodon cursor complex. Captive hybrids males between Akodon [2n = 14] x [2n = 16] are apparently sterile, suggesting these populations may represent two full species.

Chromosomal Aberrations in Pediatric Patients with Developmental Delay/Intellectual Disability: A Single-Center Clinical Investigation

Introduction. Chromosomal microarray analysis (CMA) has currently been considered as the first-tier genetic test for patients with developmental delay/intellectual disability (DD/ID) in many countries. In this study, we performed an extensive assessment of the value of CMA for the diagnosis of children with ID/DD in China. Methods. A total of 633 patients diagnosed with DD/ID in West China Second University Hospital, Sichuan University, were recruited from January 2014 to March 2019. The patients were classified into 4 subgroups: isolated DD/ID, DD/ID with multiple congenital anomalies (MCA), isolated autism spectrum disorders (ASDs), and DD/ID with epilepsy. CMA was performed on Affymetrix 750K platform. Results. Among the 633 patients, 127 cases were identified as having pathogenic copy number variations (pCNVs) with an overall positive rate of 20.06%. Of the 127 cases with abnormal results, 76 cases had 35 types of microdeletion/microduplication syndromes (59.84%) including 5 cases caused by uniparental disomy (UPD), and 18 cases had unbalanced rearrangements (14.17%) including 10 cases inherited from parental balanced translocations or pericentric inversions. The diagnostic yields of pCNVs for the subgroups of isolated DD/ID, DD/ID with MCA, isolated ASD, and DD/ID with epilepsy were 18.07% (60/332), 34.90% (52/149), 3.70% (3/81), and 16.90% (12/71), respectively. The diagnostic yield of pCNVs in DD/ID patients with MCA was significantly higher than that of the other three subgroups, and the diagnostic yield of pCNVs in isolated ASD patients was significantly lower than that of the other three subgroups (p<0.05). Conclusion. Microdeletion/microduplication syndromes and unbalanced rearrangements are probably the main genetic etiological factors for DD/ID. DD/ID patients with MCA have a higher rate of chromosomal aberrations. Parents of DD/ID children with submicroscopic unbalance rearrangements are more likely to have chromosome balanced translocations or pericentric inversions, which might have been missed by karyotyping. CMA can significantly improve the diagnostic rate for patients with DD/ID, which is of great value for medical management and clinical guidance for genetic counseling.