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The average genome size (GS) of bats, which are the only mammals capable of powered flight, is approximately 18% smaller than that of closely related mammalian orders. The low nuclear DNA content of Chiroptera is comparable to that of birds, which are also characterized by a high metabolic rate. Only a few chiropteran taxa possess notable amounts of constitutive heterochromatin. Here, we studied the karyotypes of two non-related vesper bat species with unusually high amounts of constitutive heterochromatin: Hesperoptenus doriae and Philetor brachypterus. Conventional staining methods and whole-chromosome painting with probes derived from Myotis myotis (2n = 44), showing a karyotype close to that of the presumed ancestor of Vespertilionidae, revealed Robertsonian fusions as the main type of rearrangement leading to the exceptionally reduced diploid chromosome number of 2n = 26 in both species. Moreover, both karyotypes are characterized by large blocks of pericentromeric heterochromatin composed of CMA-positive and DA-DAPI-positive segments. In H. doriae, the heterochromatin accumulation has resulted in a genome size of 3.22 pg (1C), which is 40% greater than the mean genome size for the family. For P. brachypterus, a genome size of 2.94 pg was determined, representing an increase of about 28%. Most notably, in H. doriae, the presence of additional constitutive heterochromatin correlates with an extended mitotic cell cycle duration in vitro. A reduction in diploid chromosome number to 30 or lower is discussed as a possible cause of the accumulation of pericentromeric heterochromatin in Vespertilionidae. [ABSTRACT FROM AUTHOR]

Background: Defining factors that contributed to the fixation of a high number of underdominant chromosomal rearrangements is a complex task because not only molecular mechanisms must be considered, but also the uniqueness of natural history attributes of each taxon. Ideally, detailed investigation of the chromosome architecture of an organism and related groups, placed within a phylogenetic context, is required. We used multiple approaches to investigate the dynamics of chromosomal evolution in lineages of bats with considerable karyotypic variation, focusing on the different facets contributing to fixation of the exceptional chromosomal changes in Tonatia saurophila. Integration of empirical data with proposed models of chromosome evolution was performed to understand the probable conditions for Tonatia's karyotypic evolution. Results: The trajectory of reorganization of chromosome blocks since the common ancestor of Glossophaginae and Phyllostominae subfamilies suggests that multiple tandem fusions, as well as disruption and fusions of conserved phyllostomid chromosomes were major drivers of karyotypic reshuffling in Tonatia. Considerable variation in the rates of chromosomal evolution between phyllostomid lineages was observed. Thirty-nine unique fusions and fission events reached fixation in Tonatia over a short period of time, followed by ~12 million years of chromosomal stasis. Physical mapping of repetitive DNA revealed an unusual accumulation of LINE-1 sequences on centromeric regions, probably associated with the chromosomal dynamics of this genus. Conclusions: Multiple rearrangements have reached fixation in a wave-like fashion in phyllostomid bats. Different biological features of Tonatia support distinct models of rearrangement fixation, and it is unlikely that the fixations were a result of solely stochastic processes in small ancient populations. Increased recombination rates were probably facilitated by expansion of repetitive DNA, reinforced by aspects of taxon reproduction and ecology. [ABSTRACT FROM AUTHOR]

Robertsonian (centric) fusion or fission is one of the predominant modes of chromosomal rearrangement in karyotype evolution among mammals. However, in karyotypes composed of only bi-armed chromosomes, creation of new chromosomal arm combinations in one step is possible only via whole-arm reciprocal translocation (WART). Although this type of rearrangement has often been proposed to play an important role in chromosomal evolution, direct observations of WARTs remained rare, and, in most cases, were found in hybrids of chromosomal races in the genera Mus and Sorex. For the first time, we present the karyotype of the horseshoe bat species Rhinolophus sedulus (2n = 28, FNa = 52), where a WART between 2 metacentric autosomes was detected by G-banding and confirmed by FISH with painting probes of the vespertilionid bat Myotis myotis. Among the 6 specimens analyzed, 2 showed the heterozygous condition of the WART, 1 showed the presumed ancestral, and 3 specimens showed the derived homozygous state. As the existence of a hybrid zone at the sampling locality is thought to be rather improbable, the WART may indicate ongoing karyotype evolution in this taxon. © 2014 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background New World leaf-nosed bats, Phyllostomidae, represent a lineage of Chiroptera marked by unprecedented morphological/ecological diversity and extensive intergeneric chromosomal reorganization. There are still disagreements regarding their systematic relationships due to morphological convergence among some groups. Their history of karyotypic evolution also remains to be documented. Results To better understand the evolutionary relationships within Phyllostomidae, we developed chromosome paints from the bat species Macrotus californicus. We tested the potentials of these paints as phylogenetic tools by looking for chromosomal signatures in two lineages of nectarivorous phyllostomids whose independent origins have been statistically supported by molecular phylogenies. By examining the chromosomal homologies defined by chromosome painting among two representatives of the subfamily Glossophaginae (Glossophaga soricina and Anoura cultrata) and one species from the subfamily Lonchophyllinae (Lonchophylla concava), we found chromosomal correspondence in regions not previously detected by other comparative cytogenetic techniques. We proposed the corresponding human chromosomal segments for chromosomes of the investigated species and found two syntenic associations shared by G. soricina and A. cultrata. Conclusion Comparative painting with whole chromosome-specific paints of M. californicus demonstrates an extensive chromosomal reorganization within the two lineages of nectarivorous phyllostomids, with a large number of chromosomes shared by M. californicus and G. soricina. We show that the evolution of nectar-feeding bats occurs mainly by reshuffling of chiropteran Evolutionary Conserved Units (ECUs). Robertsonian fusions/fissions and inversions seem to be important modifiers of phyllostomid karyotypes, and autapomorphic character states are common within species. Macrotus californicus chromosome paints will be a valuable tool for documenting the pattern of karyotypic evolution within Phyllostomidae radiation. [ABSTRACT FROM AUTHOR]

Abstract: GTG-banded karyotypes are presented for Scotoecus hirundo (; ), Rhogeessa alleni (; ), Scotophilus kuhlii (; ) and Scotophilus leucogaster (; ). These three genera belong to the family Vespertilionidae and have previously been placed into the tribe “Nycticeiini” (Tate 1942). Karyological analysis, however, points to a close relationship of Scotoecus hirundo to the tribes Pipistrellini and Vespertilionini (sensu Volleth and Heller 1994). Rhogeessa (Baeodon) alleni, a member of the karyologically diverse genus Rhogeessa, has two fusion chromosomes in common with the genus Plecotus. Together with morphological (Hill and Harrison 1987) and molecular-genetic results (Hoofer and Van Den Bussche 2003), chromosome analysis suggests a closer relationship of Plecotini and Rhogeessa. The two species examined of the genus Scotophilus show differences only in two small autosomal pairs and the Y chromosome. Chromosomal data did not reveal closer relationships of this genus to any other vespertilionid tribe. [Copyright &y& Elsevier]

Reports on the role of chromosomal characteristics in the analysis of the phylogenetic relationships of the plecotine bats. Comparison of results from morphological and chromosomal data with those from morphology only.

In bush-crickets, males produce a calling song to announce their presence to females. Females ready to mate respond either by a phonotactic approach or signal their presence acoustically by establishing a kind of duet. This duetting behaviour is typical of phaneropterid bush-crickets, of which many species in Europe are flightless. In the long-winged genus Phaneroptera, the females also respond acoustically to the male calling song, which is quite similar in the three west European species in this genus. After acoustical contact, however, the behaviour of males and females of the three species differ markedly. In P. nana, males and females engage in a duet in which the female responds to each syllable of the male song (and he approaches her). In P. falcata, the female only responds to certain elements of the male song that are produced at long intervals. However, after her response the male does not change its song or its position, but often increases its singing activity (and the female approaches him). In P. sparsa the female only responds to particular, very complicated and soft elements of the male song, which are typically repeated at intervals of several to many minutes. After hearing the response, the male drastically changes its song by producing only the soft elements. These parts of the song contain syllables with a unique spectral composition and others that may threaten eavesdropping rivals. In this species both sexes probably move towards each other during mate localization. At present, we can only speculate about the adaptive nature of the different strategies. [ABSTRACT FROM AUTHOR]

In bush-crickets, males produce a calling song to announce their presence to females. Females ready to mate respond either by a phonotactic approach or signal their presence acoustically by establishing a kind of duet. This duetting behaviour is typical of phaneropterid bush-crickets, of which many species in Europe are flightless. In the long-winged genus Phaneroptera, the females also respond acoustically to the male calling song, which is quite similar in the three west European species in this genus. After acoustical contact, however, the behaviour of males and females of the three species differ markedly. In P. nana, males and females engage in a duet in which the female responds to each syllable of the male song (and he approaches her). In P. falcata, the female only responds to certain elements of the male song that are produced at long intervals. However, after her response the male does not change its song or its position, but often increases its singing activity (and the female approaches him). In P. sparsa the female only responds to particular, very complicated and soft elements of the male song, which are typically repeated at intervals of several to many minutes. After hearing the response, the male drastically changes its song by producing only the soft elements. These parts of the song contain syllables with a unique spectral composition and others that may threaten eavesdropping rivals. In this species both sexes probably move towards each other during mate localization. At present, we can only speculate about the adaptive nature of the different strategies. [ABSTRACT FROM AUTHOR]

Chiroptera is the second largest order among mammals, with over 1300 species in 21 extant families. The group is extremely diverse in several aspects of its natural history, including dietary strategies, ecology, behavior and morphology. Bat genomes show ample chromosome diversity (from 2n = 14 to 62). As with other mammalian orders, Chiroptera is characterized by clades with low, moderate and extreme chromosomal change. In this article, we will discuss trends of karyotypic evolution within distinct bat lineages (especially Phyllostomidae, Hipposideridae and Rhinolophidae), focusing on two perspectives: evolution of genome architecture, modes of chromosomal evolution, and the use of chromosome data to resolve taxonomic problems. [ABSTRACT FROM AUTHOR]

Noonan syndrome (NS), the most common among RASopathies, is caused by germline variants in genes encoding components of the RAS-MAPK pathway. Distinct variants, including the recurrent Ser257Leu substitution in RAF1, are associated with severe hypertrophic cardiomyopathy (HCM). Here, we investigated the elusive mechanistic link between NS-associated RAF1S257L and HCM using three-dimensional cardiac bodies and bioartificial cardiac tissues generated from patient-derived induced pluripotent stem cells (iPSCs) harboring the pathogenic RAF1 c.770 C > T missense change. We characterize the molecular, structural, and functional consequences of aberrant RAF1–associated signaling on the cardiac models. Ultrastructural assessment of the sarcomere revealed a shortening of the I-bands along the Z disc area in both iPSC-derived RAF1S257L cardiomyocytes and myocardial tissue biopsies. The aforementioned changes correlated with the isoform shift of titin from a longer (N2BA) to a shorter isoform (N2B) that also affected the active force generation and contractile tensions. The genotype-phenotype correlation was confirmed using cardiomyocyte progeny of an isogenic gene-corrected RAF1S257L-iPSC line and was mainly reversed by MEK inhibition. Collectively, our findings uncovered a direct link between a RASopathy gene variant and the abnormal sarcomere structure resulting in a cardiac dysfunction that remarkably recapitulates the human disease. Studies on 3D bioartificial cardiac tissues reveal the impacts of hypertrophic cardiomyopathy-associated RAF1 mutations on sarcomere structure, contractile behavior, Ca2+ handling, and intracellular signaling. [ABSTRACT FROM AUTHOR]

The possibility to generate cardiomyocytes from pluripotent stem cells in vitro has enormous significance for basic research, disease modeling, drug development and heart repair. The concept of heart muscle reconstruction has been studied and optimized in the rat model using rat primary cardiovascular cells or xenogeneic pluripotent stem cell derived-cardiomyocytes for years. However, the lack of rat pluripotent stem cells (rPSCs) and their cardiovascular derivatives prevented the establishment of an authentic clinically relevant syngeneic or allogeneic rat heart regeneration model. In this study, we comparatively explored the potential of recently available rat embryonic stem cells (rESCs) and induced pluripotent stem cells (riPSCs) as a source for cardiomyocytes (CMs). We developed feeder cell-free culture conditions facilitating the expansion of undifferentiated rPSCs and initiated cardiac differentiation by embryoid body (EB)-formation in agarose microwell arrays, which substituted the robust but labor-intensive hanging drop (HD) method. Ascorbic acid was identified as an efficient enhancer of cardiac differentiation in both rPSC types by significantly increasing the number of beating EBs (3.6 ± 1.6-fold for rESCs and 17.6 ± 3.2-fold for riPSCs). These optimizations resulted in a differentiation efficiency of up to 20% cTnTpos rPSC-derived CMs. CMs showed spontaneous contractions, expressed cardiac markers and had typical morphological features. Electrophysiology of riPSC-CMs revealed different cardiac subtypes and physiological responses to cardio-active drugs. In conclusion, we describe rPSCs as a robust source of CMs, which is a prerequisite for detailed preclinical studies of myocardial reconstruction in a physiologically and immunologically relevant small animal model. [ABSTRACT FROM AUTHOR]

5-Methylcytosine-rich heterochromatic regions were demonstrated in metaphase chromosomes of 5 species of Chiroptera by indirect immunofluorescence using a monoclonal anti-5-methylcytosine antibody. These species belong to 4 genera and 2 families and are characterized by divergent karyotypes. One species (Glauconycteris beatrix) has an extremely low diploid chromosome number of 2n = 22 with only meta- to submetacentric elements and remarkably large amounts of constitutive heterochromatin located in the centromeric and pericentromeric regions of all chromosome pairs. Two species (G. beatrix and Neoromicia cf. guineensis) possess X-autosome translocations. In all species, the hypermethylated chromosome segments correspond to constitutive heterochromatin, and the numbers and positions of hypermethylated chromosome segments in the karyotypes are constant and species-specific. In some species (Pipistrellus hesperidus, Neoromicia cf. somalicus), there are several smaller chromosome pairs in which the bright anti-5-methylcytosine antibody labeling is not restricted to constitutively heterochromatic regions but is observed along the whole lengths of these chromosomes. The nature of these additional hypermethylated regions is discussed. The analysis of 5-methylcytosine-rich chromosome regions elucidates valuable data for chiropteran cytogenetics and reflects the high pace of evolution of the repetitive DNA fraction in their genomes. [ABSTRACT FROM AUTHOR]

In Europe, 2 different diploid chromosome numbers, 2n = 54 and 2n = 56, have been described in the lesser horseshoe bat (Rhinolophus hipposideros) . The eastern form with 2n = 56 extends from the Czech Republic to Greece. To date, specimens with 54 chromosomes have been reported only from Spain and Germany. This study expands the distributional area of the western variant to Ireland. Strikingly, this distribution of European chromosomal variants is in contrast to the available molecular data that indicate little genetic differentiation of R. hipposideros populations spanning Northwestern to Central Europe. Further, we have developed an optimized protocol for establishing fibroblast cell cultures, suitable for karyotype analyses, from 3-mm wing membrane biopsies. This is a useful technique for cytogenetic studies of endangered bat species, as this nonlethal sampling method imposes only minimum stress to the animal without lasting adverse effects and is routinely used to sample tissue probes for molecular genetic studies in bats. [ABSTRACT FROM AUTHOR]

Background Complex small supernumerary marker chromosomes (sSMC) constitute one of the smallest subgroups of sSMC in general. Complex sSMC consist of chromosomal material derived from more than one chromosome; the best known representative of this group is the derivative chromosome 22 {der(22)t(11;22)} or Emanuel syndrome. In 2008 we speculated that complex sSMC could be part of an underestimated entity. Results Here, the overall yet reported 412 complex sSMC are summarized. They constitute 8.4% of all yet in detail characterized sSMC cases. The majority of the complex sSMC is contributed by patients suffering from Emanuel syndrome (82%). Besides there are a der(22)t(8;22)(q24.1;q11.1) and a der(13)t(13;18)(q11;p11.21) or der(21)t(18;21)(p11.21;q11.1) = der(13 or 21)t(13 or 21;18) syndrome. The latter two represent another 2.6% and 2.2% of the complex sSMC-cases, respectively. The large majority of complex sSMC has a centric minute shape and derives from an acrocentric chromosome. Nonetheless, complex sSMC can involve material from each chromosomal origin. Most complex sSMC are inherited form a balanced translocation in one parent and are non-mosaic. Interestingly, there are hot spots for the chromosomal breakpoints involved. Conclusions Complex sSMC need to be considered in diagnostics, especially in non-mosaic, centric minute shaped sSMC. As yet three complex-sSMC-associated syndromes are identified. As recurrent breakpoints in the complex sSMC were characterized, it is to be expected that more syndromes are identified in this subgroup of sSMC. Overall, complex sSMC emphasize once more the importance of detailed cytogenetic analyses, especially in patients with idiopathic mental retardation. [ABSTRACT FROM AUTHOR]

Background: Heterochromatic variants of pericentromere of chromosome 9 are reported and discussed since decades concerning their detailed structure and clinical meaning. However, detailed studies are scarce. Thus, here we provide the largest ever done molecular cytogenetic research based on >300 chromosome 9 heteromorphism carriers. Results: In this study, 334 carriers of heterochromatic variants of chromosome 9 were included, being 192 patients from Western Europe and the remainder from Easter-European origin. A 3-color-fluorescence in situ hybridization (FISH) probe-set directed against for 9p12 to 9q13~21.1 (9het-mix) and 8 different locus-specific probes were applied for their characterization. The 9het-mix enables the characterization of 21 of the yet known 24 chromosome 9 heteromorphic patterns. In this study, 17 different variants were detected including five yet unreported; the most frequent were pericentric inversions (49.4%) followed by 9qh-variants (23.9%), variants of 9ph (11.4%), cenh (8.2%), and dicentric- (3.8%) and duplication-variants (3.3%). For reasons of simplicity, a new short nomenclature for the yet reported 24 heteromorphic patterns of chromosome 9 is suggested. Six breakpoints involved in four of the 24 variants could be narrowed down using locus-specific probes. Conclusions: Based on this largest study ever done in carriers of chromosome 9 heteromorphisms, three of the 24 detailed variants were more frequently observed in Western than in Eastern Europe. Besides, there is no clear evidence that infertility is linked to any of the 24 chromosome 9 heteromorphic variants. [ABSTRACT FROM AUTHOR]

Chromosome 16 contains multiple copy number variations (CNVs) that predispose to genomic disorders. Here, we differentiate pathogenic duplications of 16p11.2-p12.2 from microscopically similar euchromatic variants of 16p11.2. Patient 1 was a girl of 18 with autism, moderate intellectual disability, behavioural difficulties, dysmorphic features and a 7.71-Mb (megabase pair) duplication (16:21 521 005-29 233 146). Patient 2 had a 7.81-Mb duplication (16:21 382 561-29 191 527), speech delay and obsessional behaviour as a boy and, as an adult, short stature, macrocephaly and mild dysmorphism. The duplications contain 65 coding genes of which Polo-like kinase 1 (PLK1) has the highest likelihood of being haploinsufficient and, by implication, a triplosensitive gene. An additional 1.11-Mb CNV of 10q11.21 in Patient 1 was a possible modifier containing the G-protein-regulated inducer of neurite growth 2 (GPRIN2) gene. In contrast, the euchromatic variants in Patients 3 and 4 were amplifications from a 945-kb region containing non-functional immunoglobulin heavy chain (IGHV), hect domain pseudogene (HERC2P4) and TP53-inducible target gene 3 (TP53TG3) loci in proximal 16p11.2 (16:31 953 353-32 898 635). Paralogous pyrosequencing gave a total copy number of 3-8 in controls and 8 to >10 in Patients 3 and 4. The 16p11.2-p12.2 duplication syndrome is a recurrent genomic disorder with a variable phenotype including developmental delay, dysmorphic features, mild to severe intellectual disability, autism, obsessive or stereotyped behaviour, short stature and anomalies of the hands and fingers. It is important to differentiate pathogenic 16p11.2-p12.2 duplications from harmless, microscopically similar euchromatic variants of proximal 16p11.2, especially at prenatal diagnosis. [ABSTRACT FROM AUTHOR]

The discovery of copy number variations (CNV) in the human genome opened new perspectives on the study of the genetic causes of inherited disorders and the aetiology of common diseases. Here, a single-cell-level investigation of CNV in different human tissues led us to uncover the phenomenon of mitotically derived genomic mosaicism, which is stable in different cell types of one individual. The CNV mosaic ratios were different between the 10 individuals studied. However, they were stable in the T lymphocytes, immortalized B lymphoblastoid cells, and skin fibroblasts analyzed in each individual. Because these cell types have a common origin in the connective tissues, we suggest that mitotic changes in CNV regions may happen early during embryonic development and occur only once, after which the stable mosaic ratio is maintained throughout the differentiated tissues. This concept is further supported by a unique study of immortalized B lymphoblastoid cell lines obtained with 20 year difference from two subjects. We provide the first evidence of somatic mosaicism for CNV, with stable variation ratios in different cell types of one individual leading to the hypothesis of early embryonic chromosome instability resulting in stable mosaic pattern in human tissues. This concept has the potential to open new perspectives in personalized genetic diagnostics and can explain genetic phenomena like diminished penetrance in autosomal dominant diseases. We propose that further genomic studies should focus on the single-cell level, to better understand the aetiology of aging and diseases mediated by somatic mutations. [ABSTRACT FROM AUTHOR]

Rubinstein–Taybi syndrome (RSTS) is a well-known autosomal dominant mental retardation syndrome with typical facial and skeletal abnormalities. Previously, we have reported two patients presenting with RSTS and additional clinical features including failure to thrive, seizures, and intractable infections (Bartsch et al. in Eur J Hum Genet 7:748–756, ). Recently we identified a third patient with this condition, termed here severe RSTS, or chromosome 16p13.3 deletion syndrome. The three patients died in infancy, and all displayed a specific mutation, a chromosomal microdeletion including the 3′-end of the CREBBP gene. Using fluorescence in situ hybridization and closely spaced DNA probes, we characterized the deletion intervals in these patients and in three individuals with a deletion of CREBBP and typical RSTS. The deleted DNA segments were found to greatly vary in size, spanning from ∼40 kb to >3 Mb. Four individuals, including the patients with severe RSTS, exhibited deletions containing gene/s in addition to CREBBP. The patients with severe RSTS all had deletions comprising telomeric neighbor genes of CREBBP, including DNASE1, a dominant gene encoding a nuclease that has been associated with systemic lupus erythematodes. Our findings suggest that severe RSTS is distinct from RSTS and represents a novel true contiguous gene syndrome (chromosome 16p13.3 deletion syndrome). Because of the risk of critical infections and high mortality rate, we recommend that the size of the deletion interval should be determined in CREBBP deletion-positive patients with RSTS, especially in young children. Further studies are needed to delineate the clinical spectrum of the new disorder and to clarify the role of DNASE1. [ABSTRACT FROM AUTHOR]

The article provides insight on a study pertaining to the cytogenic and bioinformatic models of hereditary genomes. It has been concluded that the conflict between the models of ancestral genome reflect on limited animal groups having natural relations models in the bioinformatic analysis. The study further presumed that the increased availability of genomic files from a wider spectrum of species and the growth of more complex algorithm, bioinformatic and the cytogenetic models will likely merged as one.

Small supernumerary marker chromosomes (SMCs) are present in about 0.05% of the human population. In approximately 30% of SMC carriers (excluding the ~60% SMC derived from one of the acrocentric chromosomes), an abnormal phenotype is observed. The clinical outcome of an SMC is difficult to predict as they can have different phenotypic consequences because of (1) differences in euchromatic DNA-content, (2) different degrees of mosaicism, and/or (3) uniparental disomy (UPD) of the chromosomes homologous to the SMC. Here, we present 35 SMCs, which are derived from all human chromosomes, apart from chromosome 6, as demonstrated by the appropriate molecular cytogenetic approaches, such as centromere-specific multicolor fluoresence in situ hybridization (cenM-FISH), multicolor banding (MCB), and subcentromere-specific multicolor FISH (subcenM-FISH). In nine cases without an aberrant phenotype, neither partial proximal trisomies nor UPD could be detected. Abnormal clinical findings, such as psychomotoric retardation and/or craniofacial dysmorphisms, were associated with seven of the cases in which subcentromeric single-copy probes were proven to be present in three copies. Conversely, in eight cases with a normal phenotype, proximal euchromatic material was detected as partial trisomy. UPD was studied in 12 cases and subsequently detected in two of the cases with SMC (partial UPD 4p and maternal UPD 22 in a der(22)-syndrome patient), indicating that SMC carriers have an enhanced risk for UPD. At present, small proximal trisomies of 1p, 1q, 2p, 6p, 6q, 7q, 9p, and 12q seem to lead to clinical manifestations, whereas partial proximal trisomies of 2q, 3p, 3q, 5q, 7p, 8p, 17p, and 18p may not be associated with significant clinical symptoms. With respect to clinical outcome, a classification of SMCs is proposed that considers molecular genetic and molecular cytogenetic characteristics as demonstrated by presently available methods. [ABSTRACT FROM AUTHOR]

A thorough study of the heterochromatin organisation in the pericentromeric region and the proximal long (q) and short (p) arms of human chromsome 9 (HSA 9) revealed homology between 9p12 and 9q1321.1, two regions that are usually not distinguishable by molecular cytogenetic techniques. Furthermore, the chromosomal regions 9p12 and 9ql 3-21.1 showed some level of homology with the short arms of the human acrocentric chromosomes. We studied five normal controls and 51 clinical cases: 48 with chromosome 9 heteromorphisms, one with an exceptionally large inversion and two with an additional derivative chromosome 9. Using fluorescence in situ hybridisation (FISH) with three differentially labelled chromosome 9-specific probes we were able to distinguish 12 heteromorphic patterns in addition to the most frequent pattern (defined as normal). In addition, we studied one inversion 9 case with the recently described multicolour banding (MCB) technique. Our results, and previously published findings, suggest several hotspots for recombination in the pericentromeric heterochromatin of HSA 9. They also demonstrate that constitutional inversions affecting the pericentromeric region of chromosome 9 carry breakpoints located preferentially in 9p12 or 9q13-21.1 and less frequently in 9q12. [ABSTRACT FROM AUTHOR]

Mosaicism is present in more than 50% of the cases with small supernumerary marker chromosomes (sSMCs) and karyotype 47,XX,+mar/46,XX or 47,XY,+mar/46,XY. Recently we provided first evidence that the mitotic stability of sSMC is dependent on their structure, i.e. their shape. Thus, here we performed a long term in vitro study on 12 selected cell lines from the Else Kröner–Fresenius-sSMC-cellbank ( http://ssmc-tl.com/ekf-cellbank.html ) to test mitotic sSMC stability systematically. The obtained results showed that inverted duplicated shaped and also the so-called complex sSMCs (group 1) are by far more stable, than centric-minute- or ring-shaped sSMCs (groups 2). Generally speaking, the percentage of cells with group-1-sSMCs remained stable over 90 days of cell culture, while that of group-2-sSMCs in parts dramatically decreased. In one group-2-cell line the sSMC was even lost completely after 30 days of in vitro culture, in others the sSMC was depleted in up to 40% of the cells. Still the highest rate of sSMC loss was recorded during EBV-transformation. Overall, the major difference between groups 1 and 2 was the number of telomeres per sSMC. In group 1 the sSMCs had “original” telomeres at both of their ends; in group 2 the sSMCs had either no, possibly secondary acquired and/or only one original telomere. This absence of protective telomeric sequences in group 2 seems to make sSMC more susceptible for loss during cell division. Still, also a growth advantage of cells without sSMC cannot be neglected entirely. [ABSTRACT FROM AUTHOR]

A contiguous deletion encompassing the genes for dystrophin, cytochrome b(-245) beta-subunit (CYBB), retinitis pigmentosa GTPase regulator (RPGR), and OTC was detected in a female patient only suffering from OTC deficiency while symptoms of the other conditions were not present. [ABSTRACT FROM AUTHOR]