Acrocentric Chromosomes Research Articles

Features of the chromosome set of representatives of smoothnosed bats of the North Caucasus

Aim. The aim of this work was to study the chromosome set of some representatives of smooth-nosed bats of the North Caucasus.Material and Methods. Various research methods were used to achieve this goal, including that of dried preparations (the main method for obtaining chromosomal preparations) and that of constructing karyograms.Results. A comparative analysis of the karyological data of 11 species of smooth-nosed bats of the North Caucasus was undertaken and the karyological characteristics of the species accepted in the latest reports on the fauna of Russia and the Caucasus were clarified. The similarity of G -bands in large pairs of meta- and submetacentric chromosomes in Myotis blythi, Myotis mystacinus, Pipistrellus pipistrellus, Pipistrellus kuhli and Vepertilio murinus with bands in small and medium-sized acrocentric chromosomes such as in Eptesicus seotinus may indicate the evolution of the karyotype of the first species by Robertsonian translocation, i.e. compounds of acrocentric chromosomes of Eptesicus serotinus in various combinations. When comparing karyotypes in the family Vespertilionidae, it was found that the karyotype of Eptesicus serotinus is "archaic" (2n=50, NFa=48). With the help of karyological data, the authors composed schemes of phylogenetic relationships of genera in the family Vespertilionidae, which differ to a certain extent from the schemes compiled by taxonomists for representatives of this family.Conclusions. Based on the results obtained, we can conclude that the karyotype of Eptesicus serotinus is the most primitive among the representatives of the order of bats. The primary role in the evolution of this group was played by Robertsonian rearrangements and pericentric inversions (reduction of NFa and 2n from 50 to 38).

A new opilioacarid species (Parasitiformes: Opilioacarida) from Crete (Greece) with notes on its karyotype

A new species of opilioacarid mite, Opilioacarus thaleri n. sp., is described from mid-level elevation close to the seashore in Crete (Greece). It was found on moister sites, under stones or inside stone accumulations in phrygana vegetation. The peak of activity was found to be in early May. The diagnostic morphological characters include 7–8 eugenital setae (female), 5/7 setae on each sclerite at pregenital and genital areas, 11 setae on genital area (male), anterior dorsal shield with two pairs of eyes and 60–70 stout, ribbed setae, 5 (female) or 6 (male) leaf setae plus one pectinate seta on the palp tarsus, and the "simple" type of ovipositor with two pairs of glands, a pair of ducts plus a basal structure. The female karyotype comprises 16 monocentric chromosomes, predominantly with acrocentric morphology. Comparison with data of the ixodids and mesostigmatids indicates that a low number of chromosomes and predomination of acrocentric chromosomes could be plesiomorphies of the parasitiform mites.

Revisiting the Karyotypes of Alligators and Caimans (Crocodylia, Alligatoridae) after a Half-Century Delay: Bridging the Gap in the Chromosomal Evolution of Reptiles.

Although crocodilians have attracted enormous attention in other research fields, from the cytogenetic point of view, this group remains understudied. Here, we analyzed the karyotypes of eight species formally described from the Alligatoridae family using differential staining, fluorescence in situ hybridization with rDNA and repetitive motifs as a probe, whole chromosome painting (WCP), and comparative genome hybridization. All Caimaninae species have a diploid chromosome number (2n) 42 and karyotypes dominated by acrocentric chromosomes, in contrast to both species of Alligatorinae, which have 2n = 32 and karyotypes that are predominantly metacentric, suggesting fusion/fission rearrangements. Our WCP results supported this scenario by revealing the homeology of the largest metacentric pair present in both Alligator spp. with two smaller pairs of acrocentrics in Caimaninae species. The clusters of 18S rDNA were found on one chromosome pair in all species, except for Paleosuchus spp., which possessed three chromosome pairs bearing these sites. Similarly, comparative genomic hybridization demonstrated an advanced stage of sequence divergence among the caiman genomes, with Paleosuchus standing out as the most divergent. Thus, although Alligatoridae exhibited rather low species diversity and some level of karyotype stasis, their genomic content indicates that they are not as conserved as previously thought. These new data deepen the discussion of cytotaxonomy in this family.

Unusual chromosomal polymorphism of the common shrew, Sorex araneus L., in southern Belarus.

Analysis of the frequency of karyotypes and chromosomal rearrangements in the distributional ranges of four metacentric races of Sorex araneus Linnaeus, 1758 has revealed features that are not typical for polymorphic populations of this species. The frequency of the acrocentric karyotype and heterozygotes for fusion of acrocentric chromosomes turned out to be significantly higher than expected in case of random crossing. As an explanation for the unusual polymorphism, it has been suggested that metacentric races may hybridize with acrocentric populations that remained from the ancient chromosomal form.

Pseudoscopas carbonelli n. sp. (Orthoptera: Acrididae: Melanoplinae) from southern Brazil, including chromosome complement.

New species of Pseudoscopas (Orthoptera, Acrididae, Melanoplinae). Pseudoscopas carbonelli n. sp. from São Francisco de Paula, State of Rio Grande do Sul, Brazil is described, and a key to the species of Pseudoscopas Hebard, 1931 is added. Morphological descriptions are provided together with illustrations emphasizing the most significant diagnostic features of external morphology and male genitalia. Pseudoscopas carbonelli n. sp. differs from the other species known by epiproct with six protuberances in the median region, and extremities of the apical region of the epiproct sclerotized, as well as the lophi with sclerotization. Chromosome analyses were performed using standard staining procedures, showing diploid number of 2n = 23, X0♂/24, XX♀, and the karyotype made up of exclusively acrocentric chromosomes, including a medium-size megameric chromosome. Information is given about type specimens, material examined and geographic distribution.

About Cryptic Acrocentric Pericentromeric Abnormalities in Infertile

Cryptic balanced chromosomal aberrations can be an underlying cause of infertility. In 2003 Cockwell and coworkers highlighted the relevance of euchromatic pericentric regions of acrocentric chromosomes that may be a yet ignored genomic region hosting cryptic rearrangements. Here we offer the first follow-up study to further explore this idea. Two specific molecular cytogenetic probe sets were established to elucidate such cryptic rearrangements together with chromosomal heteromorphisms of acrocentric centromeres. In 28 infertile couples and 20 controls, the rate of centromeric heteromorphisms was almost comparable in both groups and one heteromorphism was noted in ~30% of the cases, and two heteromorphisms in ~15% and three heteromorphisms 5%. However, none of the studied groups revealed any cryptic euchromatic pericentromeric abnormalities of the acrocentrics. Nonetheless, in parallel an infertile case with an inv(13)(p12q12.1?2) was uncovered, being not part of the systematically studied group of infertile. As unbalanced products of meiosis with such or similar karyotypes can potentially contribute to abortions, the existence of rare, cryptic pericentromeric euchromatic abnormalities in the acrocentrics thus needs to be still expected in banding cytogenetic diagnostics. Accordingly, this study reflected that suspicious acrocentric short arms in infertile need special attention and further characterization by fluorescence in situ hybridization.

Identification of satellited markers by microdissection and fluorescence in situ hybridization: a clinical case of isodicentric chromosome 22

BackgroundThe presence of small supernumerary marker chromosomes (sSMCs) in a karyotype leads to diagnostic questions because the resulting extra material may cause abnormal development depending on the origin of the duplication/triplication. Because SMCs are so small, their origin cannot be determined by conventional cytogenetic techniques, and new molecular cytogenetic methods are necessary. Here, we applied a target approach to chromosome rearrangement analysis by isolating a chromosome of interest via microdissection and using it in fluorescence in situ hybridization (FISH) as a probe in combination with whole-chromosome painting probes. This approach allows to identify origins of both the euchromatin and repeat-rich regions of a marker.Case presentationWe report a case of an adult male with congenital atresia of the rectum and anus, anotia, and atresia of the external auditory canal along with hearing loss. Karyotyping and FISH analysis with whole-chromosome painting probes of acrocentric chromosomes and the constructed microdissection library of the marker chromosome reliably identified an additional chromosome in some metaphases: mos 47,XY,+idic(22)(q11.2)[14]/46,XY [23].ConclusionWe propose to use whole-chromosome libraries and microdissected chromosomes in FISH to identify SMCs enriched with repeated sequences. We show that the methodology is successful in identifying the composition of a satellited marker chromosome.

Trisomy 5p with bilateral congenital diaphragmatic hernia: a\xa0case report

BackgroundBilateral congenital diaphragmatic hernia (CDH) is very rare. A few studies have reported the pathogenic role of 5p in CDH.Case presentationA 23-year-old primigravida Japanese woman was referred for the following abnormal findings at 33 weeks of gestation: polyhydramnios, macroglossia, talipes equinovarus, and levocardia. A marker chromosome was detected by amniocentesis. Fluorescence in situ hybridization with whole chromosome paint 5 and nucleolus organizer region probes confirmed its origin from chromosome 5 and an acrocentric chromosome. The karyotype of the fetus was diagnosed as 47, XY, +mar. ish +mar(WCP5+). At 39 + 5 weeks, a 2462 g male infant was delivered, with a specific facial configuration. Bilateral CDH, hypoplasia of the corpus callosum, atrial septal defect, and hypothyroidism were also detected in the baby. The karyotype of the peripheral blood was consistent with that of the amniocentesis.ConclusionGenes coded on 5p might be associated with the pathogenesis of CDH; however, further investigation is required.

Human nucleoli comprise multiple constrained territories, tethered to individual chromosomes.

It is unknown how ribosomal gene (rDNA) arrays from multiple chromosomal nucleolar organizers (NORs) partition within human nucleoli. Exploration of this paradigm for chromosomal organization is complicated by the shared DNA sequence composition of five NOR-bearing acrocentric chromosome p-arms. Here, we devise a methodology for genetic manipulation of individual NORs. Efficient "scarless" genome editing of rDNA repeats is achieved on "poised" human NORs held within monochromosomal cell hybrids. Subsequent transfer to human cells introduces "active" NORs yielding readily discernible functional customized ribosomes. We reveal that ribosome biogenesis occurs entirely within constrained territories, tethered to individual NORs inside a larger nucleolus.

Chromosome analysis of walking catfish, Clarias magur ( Teleostei, Siluriformes, Clariidae ), using staining, FISH with 18S, 5S and BAC probes

The chromosomal characteristics of Clarias magur were examined using conventional (Giemsa-staining, Ag-impregnation and CMA3 + DAPI fluorescence) and molecular/ FISH (18S & 5S rDNA probes + one BAC DNA probe) cytogenetic tools. The diploid chromosome number was 50 and the karyotype consisted of 14 metacentric, 20 sub-metacentric, 8 sub-telocentric, 8 acrocentric chromosomes with 84 chromosome arms without any heteromorphic pair. The C-heterochromatic blocks were located on centromeric position of 13 pairs of chromosomes. The NOR sites, visualized by AgNO3- and CMA3- staining, were situated at p arms of chromosome pair No. 21, which also corresponded to 18S rDNA site visualized by FISH. The FISH signal of ICF_001_D19 clone probe was observed on 18th chromosome pair. The findings of the present study on C. magur provided valuable markers for the chromosome identification and locations of genes of the BAC clone on the chromosome will lead to the construction of physical map of genome of this species.

A long reads-based de-novo assembly of the genome of the Arlee homozygous line reveals chromosomal rearrangements in rainbow trout.

Currently, there is still a need to improve the contiguity of the rainbow trout reference genome and to use multiple genetic backgrounds that will represent the genetic diversity of this species. The Arlee doubled haploid line was originated from a domesticated hatchery strain that was originally collected from the northern California coast. The Canu pipeline was used to generate the Arlee line genome de-novo assembly from high coverage PacBio long-reads sequence data. The assembly was further improved with Bionano optical maps and Hi-C proximity ligation sequence data to generate 32 major scaffolds corresponding to the karyotype of the Arlee line (2 N = 64). It is composed of 938 scaffolds with N50 of 39.16 Mb and a total length of 2.33 Gb, of which ∼95% was in 32 chromosome sequences with only 438 gaps between contigs and scaffolds. In rainbow trout the haploid chromosome number can vary from 29 to 32. In the Arlee karyotype the haploid chromosome number is 32 because chromosomes Omy04, 14 and 25 are divided into six acrocentric chromosomes. Additional structural variations that were identified in the Arlee genome included the major inversions on chromosomes Omy05 and Omy20 and additional 15 smaller inversions that will require further validation. This is also the first rainbow trout genome assembly that includes a scaffold with the sex-determination gene (sdY) in the chromosome Y sequence. The utility of this genome assembly is shown through the improved annotation of the duplicated genome loci that harbor the IGH genes on chromosomes Omy12 and Omy13.

Chromosomal Diversity in Two Allopatric Populations of Farlowella hahni Meinken 1937 (Teleostei: Siluriformes): Cytogenetics and Cytochrome b Analyses

Farlowella is the second richest genus in Loricariinae, broadly distributed in freshwater streams and rivers of South America. In this article, we aimed to expand on the cytogenetic and molecular data available for two allopatric populations of Farlowella hahni. Both populations had diploid chromosome number 58, but with karyotype differences, indicative of chromosomal rearrangements. C-banding showed large heterochromatic blocks at telomeric regions in acrocentric chromosomes in both populations. Fluorescence in situ hybridization (FISH) revealed a single 18S rDNA site in both populations and a single 5S rDNA site for individuals from lower Paraná River basin (native region) and multiple 5S rDNA sites for individuals from upper Paraná River basin (non-native region). Mitochondrial sequence analyses did not separate the two F. hahni populations. The cytogenetic and molecular data obtained are relevant in a preliminary study and suggested the existence of cryptic diversity and the hypothesis that at least two Farlowella lineages may coexist in the Paraná basin.

Two telomeric ends of acrocentric chromosome play distinct roles in homologous chromosome synapsis in the fetal mouse oocyte.

In mammalian oocytes, proper chromosome segregation at the first meiotic division is dictated by the presence and site of homologous chromosome recombination, which takes place in fetal life. Our current understanding of how homologous chromosomes find each other and initiate synapsis, which is prerequisite for homologous recombination, is limited. It is known that chromosome telomeres are anchored into the nuclear envelope (NE) at the early meiotic prophase I (MPI) and move along NE to facilitate homologous chromosome search and pairing. However, the mouse (Mus musculus) carries all acrocentric chromosomes with one telomeric end close to the centromere (subcentromeric telomere; C-telomere) and the other far away from the centromere (distal telomere; D-telomere), and how C- and D-telomeres participate in chromosome pairing and synapsis during theMPI progression is not well understood. Here, we found in the mouse oocyte that C- and D-telomeres transiently clustered in one area, but D-telomeres soon separated together from C-telomeres and then dispersed to preferentially initiate synapsis, while C-telomeres remained in clusters and synapsed at the last. In the Spo11 null oocyte, which is deficient in SPO11-dependent DSBs formation and homologous synapsis, the pattern of C- and D-telomere clustering and resolution was not affected, but synapsis was more frequently initiated at C-telomeres. These results suggest that SPO11 suppresses the early synapsis between C-telomeres in clusters.

Meiotic synapsis of homeologous chromosomes and mismatch repair protein detection in the parthenogenetic rock lizard Darevskia unisexualis.

Parthenogenetic species of Caucasian rock lizards of the genus Darevksia are important evidence for reticulate evolution and speciation by hybridization in vertebrates. Female-only lineages formed through interspecific hybridization have been discovered in many groups. Nevertheless, critical mechanisms of oogenesis and specifics of meiosis that provide long-term stability of parthenogenetic species are still unknown. Here we report cytogenetic characteristics of somatic karyotypes and meiotic prophase I nuclei in the diploid parthenogenetic species Darevskia unisexualis from the new population "Keti" in Armenia which contains an odd number of chromosomes 2n = 37, instead of the usual 2n = 38. We revealed 36 acrocentric chromosomes and a single metacentric autosomal chromosome, resulting from Robertsonian translocation. Comparative genomic hybridization revealed that chromosome fusion occurred between two chromosomes inherited from the maternal species, similar to another parthenogenetic species D. rostombekowi. To trace the chromosome behaviour in meiosis, we performed an immunocytochemical study of primary oocytes' spread nuclei and studied chromosome synapsis during meiotic prophase I in D. unisexualis based on analysis of synaptonemal complexes (SCs). We found meiotic SC-trivalent composed of one metacentric and two acrocentric chromosomes. We confirmed that the SC was assembled between homeologous chromosomes inherited from two parental species. Immunostaining of the pachytene and diplotene nuclei revealed a mismatch repair protein MLH1 loaded to all autosomal SC bivalents. Possible mechanisms of meiotic recombination between homeologous chromosomes are discussed.

High chromosomal evolutionary dynamics in sleeper gobies (Eleotridae) and notes on disruptive biological factors in Gobiiformes karyotypes (Osteichthyes, Teleostei).

The order Gobiiformes is made up of more than 2200 species, representing one of the most diverse groups among teleost fishes. The biological causes for the tachytelic karyotype evolution of the gobies have not yet been fully studied. Here we expanded cytogenetic data for the Eleotridae family, analyzing the neotropical species Dormitator maculatus, Eleotris pisonis, Erotelis smaragdus, and Guavina guavina. In addition, a meta-analytical approach was followed for elucidating the karyotype diversification versus biological aspects (habitat and egg type) of the Gobiiformes. The species E. smaragdus and E. pisonis present 2n = 46 acrocentric chromosomes (NF = 46), D. maculatus 2n = 46 (36sm + 4st + 6a; NF = 86), and G. guavina, the most divergent karyotype, with 2n = 52 acrocentric chromosomes (NF = 52). Besides numeric and structural diversification in the karyotypes, the mapping of rDNAs and microsatellites also showed noticeable numerical and positional variation, supporting the high chromosomal evolutionary dynamism of these species. In Gobiiformes, karyotype patterns which are more divergent from the basal karyotype (2n = 46a) are associated with characteristics less effective to dispersion, such as the benthic habit. These adaptive characteristics, connected with the organization of the repetitive DNA content in the chromosomes, likely play a synergistic role in the remarkable karyotype diversification of this group.

Analysis of sperm chromosomes in six carriers of rare and common Robertsonian translocations*

Summary Introduction Robertsonian translocation (RobT) is the central fusion of the long arms of two acrocentric chromosomes, leading to 45 chromosomes in humans. The most common ones are rob(13;14) and rob(14;21) (91%). Other types of RobT are so-called rare cases. In the general population RobTs occur with a frequency of approximately 0.123%, but among men with reproductive failure this value rises 9-fold. Infertility in RobT carriers is associated with the formation of unbalanced spermatozoa resulting from segregation of the chromosomes involved in trivalent during the meiotic prophase. In spermatozoa of many RobT carriers an increased level of chromosomal aneuploidy is observed. Materials and Methods We examined the hyperhaploidy level of chromosomes 7, 9, 18, 21, 22, X and Y in spermatozoa of 6 RobT unrelated carriers: two carriers with rare rob(13;15), one with rare rob(13;22), and three of the common rob(13;14). Results were compared with the control data from a group of 7 fertile men with a normal karyotype. Fluorescent in situ hybridization (FISH) was applied. Results We found an increased level of sperm aneuploidy regarding at least one of the analyzed chromosomes in each of the carriers, while in rare RobTs interchromosomal effect (ICE) was observed. Meiotic segregation pattern of a rare rob(13;15) carrier revealed the 76% of normal /balanced spermatozoa. Disucussion Due to the relatively high population frequency of RobTs, their influence on reproductive failure, hight risk of imbalancement in prenatal diagnosis (7%), and small amount of data for rare RobTs, each newly characterized case is valuable in genetic counseling.

Contributions to the taxonomy of Trachelyopterus (Siluriformes): comparative cytogenetic analysis in three species of Auchenipteridae

ABSTRACT Auchenipteridae is divided into subfamilies Centromochlinae and Auchenipterinae. Parauchenipterus is included in the latter and is subject of taxonomic discussions concerning its validation or synonymization with Trachelyopterus. Herein, three species from two hydrographic basins were cytogenetically analyzed: Parauchenipterus striatulus from Doce River and two sympatric species, P. galeatus and Trachelyopterus coriaceus, from the Araguaia River. Diploid number of 58 chromosomes was verified for all species, but P. striatulus has different karyotype formula from the others. The three species have heterochromatin located in terminal regions of almost all chromosomes and in pericentromeric region on acrocentric chromosomes. Simple NORs was verified on a subtelocentric chromosome for all species. 5S rDNA sites were detected in three submetacentric chromosome pairs in P. striatulus; in a metacentric chromosome pair and submetacentric pair in T. coriaceus; and in one metacentric chromosome pair in P. galeatus. The similarities found in the karyotypes of the three species suggest the existence of only one genus, Trachelyopterus; therefore, our data refutes the validation of Parauchenipterus. Moreover, the differences in 5S rDNA distribution in P. galeatus in comparison with other populations already studied, indicate the existence of a new taxonomic unit, which suggests a species complex in P. galeatus.

Chromosome Polymorphism and Human Pathology: About 27 Cases of Chromosome 9 Inversion in the Beninese Population

The chromosomal polymorphism defined by variations of some chromosomal regions of a person (the constitutive heterochromatin and the short arms of the acrocentric chromosomes (13 to 15 and 21 - 22)) sometimes highlighted problems with regard to their safety and their pathogenicity. Polymorphisms are usually found in the same family and transmitted in the dominant Mendelian. Chromosome 9 inversion is a frequent phenomenon that some cytogeneticists consider as a variant of normal. Despite its classification as a minor chromosome rearrangement which does not correspond to abnormal phenotypes, many reports have raised conflicting opinions as well, and its complete safety is controversial. 27 cases of inversion of chromosome 9 were identified in our laboratory. The main indications for karyotype of the case of inv (9) were congenital cardiopathy (18.5%), sex development disorders of (18.5%), down syndrome (18.5%), and infertility (14.8%). This study stood out the observations of many authors who highlighted the involvement of inv (9) in the genesis of several pathologies.

A Study of Constitutive Heterochromatin and NOR Banding in Three Species of Puntius from the State of Haryana, India

The purpose of the present study was to investigate and compare the karyotypes of three species of Puntius viz. Puntius sarana (Hamilton, 1822), Puntius sophore (Hamilton, 1822) and Puntius ticto (Hamilton, 1822) belonging to family Cyprinidae in terms of chromosomal architecture, banding pattern and number of chromosomes from aquatic ecosystems of Haryana, India. Diploid chromosome no. 50 was observed in all 3 species of Puntius. The chromosomes of 3 species of Puntius showed constitutive heterochromatin at telomeric and centromeric regions of chromosomes.The Ag-NOR (Argyrophilic-Nucleolus Organizer Region) bands were observed on homologous chromosome pair nos. 2, 8 and 14 in P. sophore, pair nos. 2, 9 and 14 in P. ticto. The diploid chromosome number in P. sarana was found to be 2n = 50, 2 pairs of metacentric chromosomes, 3 pairs of subtelocentric and 20 pairs of acrocentric chromosomes. Chromosomal studies on the P. sophore revealed the diploid chromosome number to be 2n = 50, showed 16 pairs of metacentric chromosomes, 5 pairs of submetacentric, 2 pairs of subtelocentric and 2 pairs of acrocentric chromosomes. The diploid chromosome number in P. ticto was found to be 2n = 50, with 15 pairs of metacentric chromosomes, 6 pairs of submetacentric, 2 pairs of subtelocentric and 2 pairs of acrocentric chromosomes. No heteromorphic sex chromosomes were cytologically detected. Variations in chromosomes are observed with respect to earlier studies which may be due to variation in habitat conditions as a result of anthropogenic activities.

Türkiye’deki Turna Balığı, Esox lucius (Esocidae)’un Bantlı Karyotipleri

In this study, cytogenetic properties of E. lucius in Sakarya River were investigated using standard Giemsa staining, C- and Ag-NOR banding techniques. The number of diploid chromosomes (2n) of individuals studied is 50 and karyotype consists of 50 acrocentric chromosomes with decreasing sizes. Secondary constriction was observed on the third autosomal pair in the karyotype. Morphologically distinguishable sex chromosomes were not detected in male and female individuals. Some chromosomes were centromeric C-positive, while some chromosomes were negative. Active NOR is localized in the pericentromeric region of the third autosomal pair and it is related to C-heterochromatin. Our results are similar to those of other studies and this result shows that the cytogenetic properties of the species are quite stable. Moreover, these results may contribute to the cytogenetic and phylogenetic studies of the Esox species in the future.