SEARCH · PubMed Health

Results for “Hybridization”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 73 records · Page 4Linked to original sources

PubMed1993

Interspecific hybridization in Daphnia: distinction and origin of hybrid matrilines.

Three coexisting Daphnia species belonging to the D. longispina group (D. galeata, D. hyalina, and D. cucullata) form species-hybrid complexes by producing interspecific hybrids in several lakes in Germany and The Netherlands. To evaluate the genetic consequences of interspecific hybridization, I studied the patterns of mitochondrial DNA (mtDNA) sequence variation. The directionality of interspecific hybridization and divergence of hybrids from parental species was tested, using the DNA sequences of a segment of mtDNA. Via the polymerase chain reaction, it was possible to investigate single animals and even single resting eggs. A species-specific marker was established, using restriction patterns of amplified cytochrome b segments. mtDNA genotypes of hybrids revealed unidirectional mitochondrial gene flow for two hybrids, which were investigated by using multiple clones. No evidence for introgression of mtDNA was found. On the basis of a phylogenetic analysis, the species exhibit considerable distinctness, whereas differences between clones within species and between hybrids and maternal species tend to be very low. These results indicate a recent origin of hybrids and suggest that the radiation of the D. longispina group occurred > 5 Mya.

Amino Acid Sequence↗

PubMed2003

Time course analysis of apoptotic cell death during expression of hybrid lethality in hybrid tobacco cells (Nicotiana suaveolens x N. tabacum).

Hybrid cells from the cross Nicotiana suaveolens x N. tabacum expressed hybrid lethality at 28 degrees C in a thin layer cell culture system. Features characteristic of apoptosis, such as DNA fragmentation, chromatin condensation and nuclear fragmentation, were detected during expression of hybrid lethality. Actinomycin D (ActD) or cycloheximide (CHX) added to the medium suppressed apoptotic cell death during hybrid lethality. This indicates that hybrid lethality requires de novo transcription and translation, and is thus under genetic control. To estimate the time course of apoptotic cell death during the expression of hybrid lethality, we determined when factors controlling hybrid lethality were expressed by observing the point of no return. When cells were exposed to 28 degrees C for 2 h or less in inhibitor-free medium before addition of ActD or CHX, the percentage of dead cells did not increase. However, when cells were exposed to 28 degrees C for 4 h before the addition of inhibitor, the percentage of dead cells increased. When cells were exposed to 28 degrees C for 3 h before the addition of inhibitor, the percentage of dead cells varied from experiment to experiment. These data indicate that the factors controlling hybrid lethality are expressed 3 h after induction of hybrid lethality. In addition, we found a time difference between the expression of cell death and nuclear fragmentation. This suggests that the factor controlling cell death is different from the one controlling nuclear fragmentation.

Apoptosis↗

PubMed1988

Simple genetic method to identify viridans group streptococci by colorimetric dot hybridization and fluorometric hybridization in microdilution wells.

Simple dot hybridization and fluorometric hybridization methods in microdilution wells were designed and established for rapid and routine genetic identification of viridans group streptococci. Reference DNA extracted from each strain of 24 reference Streptococcus species was fixed both on a nitrocellulose filter and in a microdilution well. A 1-ml portion of the bacterial suspension which matched the turbidity of McFarland no. 2 standard was prepared when a streptococcal strain was isolated. It was lysed with achromopeptidase, and the DNA was quickly labeled with photobiotin under a sunlamp for 15 min. Dot hybridization and fluorometric hybridization were then carried out between the labeled DNA of the unknown organism and 24 unlabeled reference DNAs. Hybridized fragments on a nitrocellulose filter were detected by using alkaline-phosphatase-conjugated streptavidin and analyzed with a color graphic analyzer. Hybridized fragments in microdilution wells were quantitatively detected by using an enzyme, streptavidin-conjugated beta-D-galactosidase, and a fluorogenic substrate, 4-methylumbelliferyl-beta-D-galactoside. Strains belonging to each genetically distinct species could be identified by this dot blot hybridization test. However, some clinical strains cross-hybridized with two or more reference species, and then they were difficult to differentiate by dot blot hybridization. In such a case, fluorometric identification provided reliable results because the fluorometric method was more quantitative than dot blot identification. By these methods, it was possible to determine species assignment within the viridans group.

Autoradiography↗

PubMed2000

Utilization of a rate enhancement hybridization buffer system for rapid in situ hybridization for the detection of porcine circovirus in cell culture and in tissues of pigs with postweaning multisystemic wasting syndrome.

A rapid in situ hybridization (ISH) technique for the detection of porcine circovirus (PCV) nucleic acid in cell culture and formalin-fixed paraffin-embedded tissues was developed. A fluorescein-labeled RNA probe was transcribed from a plasmid containing 530 bp of the ORF1 of a PCV isolated from a pig with postweaning multisystemic wasting syndrome (PMWS). Hybridization using standard hybridization buffer was performed at 42 C for 16 hours and was compared to hybridization using rate enhancement hybridization (REH) buffer at 67 C for 2 hours. Hybridization was detected with an alkaline phosphatase-conjugated antifluorescein antibody. In both cultured cells and tissues from pigs with PMWS, the signal intensity and number of labeled cells in sections hybridized with REH buffer were equal to those of sections hybridized with standard hybridization buffer. The total time required for ISH using the REH buffer is 7-8 hours, thus making this protocol suitable for application in routine PCV diagnosis.

Animals↗

PubMed2004

New strategy for efficient selection of dendritic cell-tumor hybrids and clonal heterogeneity of resulting hybrids.

Heterotypic hybrids created between dendritic cells (DC) and tumor cells represent an efficient approach for loading DC with tumor-associated antigens (TAA) and DC-tumor hybrid vaccines have shown promising outcomes in various preclinical and clinical studies. Conventional DC-tumor hybrid preparations, however, are unavoidably contaminated by DC-tumor aggregates and DC loaded with tumor cell debris. Here we describe a new strategy for selecting genuine DC-tumor hybrids. A HAT-sensitive/zeocin-resistant DC clone (XS106-7 Zeo) was fused with a GFP-transduced fibrosarcoma clone (S1509a-GFP) by polyethylene glycol and heterotypic hybrid clones were established by limiting dilution in the presence of HAT and zeocin. CD45 (DC origin) and GFP (tumor origin) were both expressed in 91% (51/56 clones) of the resulting clones, indicating high efficiency of our strategy. Marked heterogeneity was observed among the hybrid clones and only one clone exhibited characteristic features of DC (CD86 and I-A expression, dendritic morphology, T cell-stimulatory capacity and IL-1beta, IL-6 and TNFalpha production), suggesting that only small fractions of DC-tumor hybrids acquire and maintain the properties of parental DC. Finally, vaccination with this hybrid clone protected mice from subsequent growth of S1509a tumor cells, documenting the in vivo activity of DC-tumor hybrids in the complete absence of exogenous TAA.

Animals↗

PubMed1984

Antitumor immunity induced by hybrid tumor cells: comparison between hybrids and the parental tumor.

The ability of hybrid tumor cells to induce antitumor immunity has been evaluated in the line 1 alveolar cell carcinoma (L1) model of BALB/c mice. Hybrid tumor cells were produced by fusing freshly dissociated L1 cells isolated from in vivo tumors with the hypoxanthine:aminopterin:thymidine-sensitive cell line, GM 347, derived from C3H mice. Each hybrid was characterized by DNA content and expression of H-2 antigens using a fluorescence-activated cell sorter. Irradiated L1 cells in the presence or absence of Corynebacterium parvum were capable of immunizing BALB/c mice against a challenge of live L1 cells, provided the challenge dose was small (50% lethal dose was between 6 X 10(4) and 1.2 X 10(5) L1 cells). Testing of five hybrid clones and 1 uncloned hybrid line for their immunizing ability demonstrated a range in immunizing ability with none showing a statistically significant improvement in survival (p less than 0.0018) when compared to untreated controls. However, one hybrid clone, MoHb-L1-C2, was selected in which the survival of mice immunized with it compared to controls had a p value of 0.0255. A tumor (labeled L1/A) which grew in one of the mice immunized with this clone was removed and hybridized with GM 347 to yield a second set of hybrids. Both this variant of L1 cells and a hybrid clone made from it (MoHb-L1A-C18) were capable of immunizing mice against a challenge of live L1/A (p values of 0.0000 and 0.0028, respectively, when compared to controls). However, L1 cells were not able to immunize effectively against L1/A, and MoHb-L1A-C18 did not immunize against L1. This suggests that L1/A is a subpopulation of L1 cells with a different antigenic composition. The limited success of MoHb-L1A-C18 against L1/A is thought to be due to the narrower range of antigenic specificities in L1/A and the ability of MoHb-L1A-C18 to represent an important antigenic subpopulation of L1/A.

Adenocarcinoma, Bronchiolo-Alveolar↗

PubMed1976

Analysis of immunoglobulin genes: DNA/RNA hybridization with immunoglobulin kappa-chain mRNA and isolation and translation of hybridized RNA.

Immunoglobulin kappa-chain mRNA was hybridized with DNA in order to assess the kappa-gene frequency. Kappa-mRNA was purified from membrane-bound ribosomes of mouse myeloma MOPC-41 by poly (U) chromatography and isolation of a 13S RNA by successive sucrose density gradient centrifugations. The RNA coded for kappa-chain precursor molecules in cell-free protein synthesis and essentially no other proteins. MOPC-41 kappa-mRNA hybridized with MOPC-41, MPC-11, and Krebs DNA with the same kinetics: the majority of the hybrids was formed with rare or unique DNA sequences (Cot/2 450 to 900), a small portion with highly repetitive sequences (Cot/2 5--6). The slow hybrids were well matched and the rapid hybrids were mismatched by about 4%, regardless of the DNA used. It was further investigated whether the rapid hybrids contained translatable kappa-mRNA or were due to impurities in the RNA preparations. Kappa-mRNA and globin-mRNA (as an internal standard for a unique transcript) were hybridized with DNA to Cot 20 or 48, the hybridized and unhybridized RNA were isolated by hydroxyopatite-urea chromatography and, after removal of the DNA, translated in a cell-free system. The cell-free products were analyzed by SDS-polyacrylamide gel electrophoresis and immunoprecipitation. It was found that approximately equal quantities of translatable kappa- and globin-mRNA were hybridized maximally 1.7%). The results do not support the hypothesis that kappa-mRNA is a transcript of both repetitive and unique DNA sequences.

Animals↗

PubMed1996

Chimeric hemoglobins--hybrids of human and swine hemoglobin: assembly and stability of interspecies hybrids.

Transgenic swine expressing human HbA contained only one of two types of the anticipated interspecies hybrids, namely H alpha 2 P beta 2 (H = human, P = swine). In an attempt to establish whether the absence of the swine alpha and human beta (P alpha 2 H beta 2) hybrid in vivo is a reflection of the lack of complementarity between the interspecies chains to generate appropriate interfaces, we have undertaken the in vitro assembly of swine alpha and human beta chimeric tetramer. In contrast to the in vivo transgenic swine system, in vitro the hybrid of swine alpha human beta chain is assembled readily and the hybrid exhibits normal cooperative oxygen binding. Both the swine alpha human beta and the human alpha swine beta interspecies hybrids are stable around neutral pH and do not segregate into parent tetramers even when mixed together. On the other hand, nearly complete exchange of P alpha chain of P alpha 2 H beta 2 hybrid occurs in the presence of H alpha chain at pH 6.0 and room temperature, resulting in the formation of HbA. However, very little of such an exchange reaction takes place at pH 7.0. These results suggest that the thermodynamic stability of P alpha 2 H beta 2 hybrid is lower compared to that of HbA. In contrast, P beta chain of H alpha 2 P beta 2 hybrid is refractory to exchange with H beta chain at pH 7.0 as well as at pH 6.0, suggesting that the stability of H alpha 2 P beta 2 is higher compared to that of HbA (H alpha 2 H beta 2). The swine alpha human beta chimeric Hb undergoes subunit exchange reaction with human alpha-chain in the presence of 0.9 M MgCl2, at pH 7.0. This demonstrates the lower thermodynamic stability of the intradimeric interactions of the heterodimer even at neutral pH. A synergistic coupling of the intra- and interdimeric interactions of the swine alpha and human beta chain heterodimer is essential for the thermodynamic stability of the chimeric Hb under the physiological conditions. Accordingly, we speculate that the lower thermodynamic stability of P alpha H beta heterodimer (compared to the homodimers H alpha H beta and P alpha P beta) facilitates its segregation into the homodimers by subunit exchange reaction involving either H alpha or P beta. This molecular aspect by itself or possibly along with other cellular aspects of the swine system results in the absence of P alpha 2 H beta 2 hybrid in transgenic swine expressing HbA.

2,3-Diphosphoglycerate↗

PubMed2003

Assessing hybrid sterility in Oryza glaberrima x O. sativa hybrid progenies by PCR marker analysis and crossing with wide compatibility varieties.

Interspecific crossing of the African indigenous rice Oryza glaberrima with Oryza sativa cultivars is hindered by crossing barriers causing 100% spikelet sterility in F(1) hybrids. Since hybrids are partially female fertile, fertility can be restored by back crossing (BC) to a recurrent male parent. Distinct genetic models on spikelet sterility have been developed predicting, e.g., the existence of a gamete eliminator and/or a pollen killer. Linkage of sterility to the waxy starch synthase gene and the chromogen gene C, both located on chromosome 6, have been demonstrated. We selected a segregating BC(2)F(3) population of semi-sterile O. glaberrima x O. sativa indica hybrid progenies for analyses with PCR markers located at the respective chromosome-6 region. These analyses revealed that semi-sterile plants were heterozygous for a marker (OSR25) located in the waxy promoter, whereas fertile progenies were homozygous for the O. glaberrima allele. Adjacent markers showed no linkage to spikelet sterility. Semi-sterility of hybrid progenies was maintained at least until the F(4) progeny generation, suggesting the existence of a pollen killer in this plant material. Monitoring of reproductive plant development showed that spikelet sterility was at least partially due to an arrest of pollen development at the microspore stage. In order to address the question whether genes responsible for F(1) sterility in intraspecific hybrids ( O. sativa indica x japonica) also cause spikelet sterility in interspecific hybrids, crossings with wide compatibility varieties (WCV) were performed. WCV accessions possess "neutral" S-loci ( S(n)) improving fertility in intraspecific hybrids. This experiment showed that the tested S(n)-loci had no fertility restoring effect in F(1) interspecific hybrids. Pollen development was completely arrested at the microspore stage and grains were never obtained after selfing. This suggests that distinct or additional S-loci are responsible for sterility of O. glaberrima x O. sativa hybrids.

Chimera↗

PubMed2000

Phenolic glycosides and condensed tannins in Salix sericea, S. eriocephala and their F1 hybrids: not all hybrids are created equal.

The performance of hybrids depends upon the inheritance and expression of resistance traits. Secondary chemicals are one such resistance trait. In this study, we measured the concentrations of phenolic glycosides and condensed tannins in parental and F1 hybrid willows to examine the sources of chemical variation among hybrids. S. sericea produces phenolic glycosides, salicortin and 2'-cinnamoylsalicortin, and low concentrations of condensed tannin in its leaves. In contrast, S. eriocephala produces no phenolic glycosides but high concentrations of condensed tannins in its leaves. These traits are inherited quantitatively in hybrids. On average, F1 hybrids are intermediate for condensed tannins, suggesting predominantly additive inheritance or balanced ambidirectional dominance of this defensive chemical from the parental species. In contrast, the concentration of phenolic glycosides is lower than the parental midpoint, indicating directional dominance. However, there is extensive variation among F1 hybrids. The concentration of tannin and phenolic glycosides in F1 hybrid families is either (1) lower than the midpoint, (2) higher than the midpoint, or (3) indistinguishable from the midpoint of the two parental taxa. It appears that the production of the phenolic glycosides, especially 2'-cinnamoylsalicortin, is controlled by one or more recessive alleles. We also observed a two-fold or greater difference in concentration between some hybrid families. We discuss how chemical variation may effect the relative susceptibility of hybrid willows to herbivores.

Journal Article↗

PubMed1991

Characterization of somatic cell hybrids by bivariate flow karyotyping and fluorescence in situ hybridization.

We report on the use of flow karyotyping and fluorescence in situ hybridization (FISH) to characterize the human chromosomes in somatic cell hybrids. The identity, DNA content, and relative frequency of human chromosomes are derived from flow karyotypes, i.e., measurements of Hoechst and chromomycin fluorescence intensities of chromosomes by dual beam flow cytometry. Chromosome integrity is assessed by comparing the peak position of a human chromosome in the flow karyotypes of a hybrid cell line and its human donor. When human donor cells are unavailable, the peak position of a human chromosome in a hybrid line is compared to the range of peak positions among normal individuals. The relative frequency of human chromosomes in subclones or hybrids grown in culture is monitored using the volumes of peaks in flow karyotypes. FISH with biotinylated human genomic DNA or chromosome-specific repeat sequence as probe is used in conjunction with flow karyotyping to confirm the number of human chromosomes in hybrids. Some small rearrangements are detected by flow karyotyping and not by FISH. On the other hand, translocations between human and rodent chromosomes are detected by FISH and not always by flow karyotyping. Flow karyotyping and FISH were used to characterize over 100 hybrid lines donated by other laboratories. A hybrid set useful for the construction of chromosome-enriched gene libraries is presented. In this set, each of the 24 human chromosome types is present and intact, as judged by these techniques, in a line containing little or no other human material.

Animals↗

PubMed1999

Direct measurement of recombination frequency in interspecific hybrids between Hordeum vulgare and H. bulbosum using genomic in situ hybridization.

Two different genotypes of diploid Hordeum vulgare x H. bulbosum hybrids, which differ in their pattern of meiotic metaphase pairing behaviour, were investigated at MI and AI by genomic in situ hybridization (GISH). One hybrid, 102C2, showed a high frequency of bivalents at metaphase I whereas the other, 103K5, showed a high frequency of univalents. The GISH analysis of both hybrids established that pairing occurred only between chromosomes of different parental genomes and revealed that pairing frequency greatly exceeded recombination. Hybrid 102C2 had a significantly higher recombination frequency than 103K5, but in both hybrids recombination involved only distal chromosome regions. However, an interesting finding is that the ratio of recombination to pairing frequency in 103K5 (1:8.9) is twice as high compared with 102C2 (1:17). The hybrids also differed in chromosome stability; little chromosome elimination occurred in 102C2 but 103K5 showed extensive chromosome loss. It appears that the high frequency of bound arms at MI favours retention of H. bulbosum chromosomes and maintains stability of chromosome numbers in PMCs. Various ideas are put forward to explain the discrepancy between meiotic pairing frequency and recombination in these hybrids.

Hordeum↗

PubMed1975

Hemoglobin synthesis in somatic cell hybrids: globin gene expression in hybrids between mouse erythroleukemia and human marrow cells or fibroblasts.

Somatic cell hybrids were generated by fusion of mouse erythroleukemia cells either to mouse L cells (B82), human fibroblasts (W1-18 VA2), or human marrow fractions enriched in erythroblasts. The hybrid cells were examined for globin gene expression by benzidine staining to detect cytoplasmic hemoglobin, and by molecular hybridization of cellular RNA to globin complementary DNA (cDNA) to detect globin messenger RNA (MRNA). The fibroblast (human or mouse) times erythroleukemia cell hybrids grown in monolayer retained most of the chromosomes of each parent. Neither cytoplasmic hemoglobin nor globin mRNA was detected in dimethylsulfoxide-treated fibroblast times erythroleukemia hybrid cells, indicating extinction of hemoglobin synthesis prior to the formation of cytoplasmic mRNA. The human marrow times mouse erythroleukemia hybrid cells grown in suspension culture contained only a few human chromosomes and exhibited low levels of hemoglobin synthesis which were amplified by 2% dimethylsulfoxide. Mouse (but not human) globin mRNA was demonstrated in these hybrid cells. The results suggest that somatic cell hybrids may be useful in searching for genetic factors which regulate activity of the globin genes.

Bone Marrow Cells↗

PubMed2002

Painting of parental chromatin in Beta hybrids by multi-colour fluorescent in situ hybridization.

Sugar beet (Beta vulgaris L.) is a relatively young crop and has a narrow gene pool. In order to introduce genetic variability into the crop, interspecific hybrids, selected from crosses with wild beets of the sections Corollinae and Procumbentes, have been generated. The introgressed B. procumbens chromatin carries resistance genes to beet cyst nematode Heterodera schachtii Schm. These lines are important for breeding of nematode-resistant sugar beet, while Corollinae species are potential donors of tolerance to biotic and abiotic stresses such as drought or saline soils. We have used in situ hybridization of genomic DNA to discriminate the parental chromosomes in these interspecific hybrids. Suppression of cross-hybridization by blocking DNA was not necessary indicating that the investigated Beta genomes contain sufficient species-specific DNA enabling the unequivocal determination of the genomic composition of the hybrids. Interspecific hybrid lines with an additional chromosome (2n = 18 + 1), chromosome fragment (2n = 18 + fragment) or translocation of B. procumbens (2n = 18) were analysed by genomic in situ hybridization (GISH) at mitosis and meiosis. Species-specific satellites and ribosomal genes used in combination with genomic DNA or in rehybridization experiments served as landmark probes for chromosome identification in hybrid genomes. The detection of a B. procumbens translocation of approx. I Mbp demonstrated the sensitivity and resolution of GISH and showed that this approach is a powerful method in genome analysis projects of the genus Beta.

Animals↗

PubMed2006

Fluorescence in situ hybridization and comparative genomic hybridization.

This chapter discusses the complementary methodologies of fluorescence in situ hybridization and comparative genomic hybridization. Fluorescence in situ hybridization uses fluorescently labeled DNA probes (whole chromosomes, centromere, or locus-specific sequences) to visualize complementary DNA sequences in the target DNA (metaphase chromosomes or interphase nuclei). Comparative genomic hybridization is essentially a modified in situ hybridization, whereby the whole genome can be screened for gains and losses in a single experiment. Tumor and normal DNA are differentially fluorescently labeled and competitively co-hybridized to normal metaphase spreads. Both techniques require multiple steps in their preparation. These can be divided into preparation of the target, preparation of the probes, hybridization, post-hybridization washes, and image acquisition and analysis, each of which will be described in detail. Success of each experiment is dependent on all of these steps, but where steps are of critical importance to particular techniques, they will be highlighted, together with notes on how to optimize the process.

Breast Neoplasms↗

PubMed1990

Application of a subtraction hybridization technique involving photoactivatable biotin and organic extraction to solution hybridization analysis of genomic DNA.

We have adapted a subtraction hybridization technique involving photoactivatable biotin, streptavidin binding, and organic extraction for solution hybridization analysis of mammalian genomic DNA. By combining maximal hybridization conditions of high salt, dextran sulfate, and formamide with successive hybridization steps and sequence enrichment by agarose gel electrophoresis, up to 97% of tracer DNA can be reproducibly driven to hybridize with photobiotinylated driver DNA. We demonstrate that the fractionation of hybridized from unhybridized sequences by this technique differs from hydroxyapatite chromatography with respect to the handling of nondenatured tracer, foldback sequences, and tracer-tracer hybrids. Strategies are presented to control the contribution of these species to the final subtracted product thereby making this technology a useful adjunct to solution hybridization approaches such as deletion cloning.

Azides↗

PubMed2002

Improved detection of simian immunodeficiency virus RNA by in situ hybridization in fixed tissue sections: combined effects of temperatures for tissue fixation and probe hybridization.

In situ hybridization detection of viral RNAs in formaldehyde-fixed tissue specimens is used frequently to characterize the extent of viral replication within host tissues. The ability to determine the level of expression of viral RNAs in situ is dependent upon many factors including the extent of cross-linking during fixation, the pretreatment regimen utilized to relieve the effects of cross-linking, and the hybridization and wash protocols. In efforts to improve our ability to detect cells infected productively by simian immunodeficiency virus (SIV) in rhesus macaque tissues, the effects of unconventionally high (40 degrees C) and more standard low (4 degrees C) temperature fixation in 4% paraformaldehyde/phosphate buffered saline were tested empirically on in situ hybridization signals. In addition, hybridization temperatures ranging between 37 and 75 degrees C were utilized to determine the optimal hybridization conditions for detection of SIV productively infected cells. Fixation conditions of 40 degrees C and hybridization conditions of 50-55 degrees C were identified as providing the greatest sensitivity for detecting RNA(+) cells and for quantitating the signal per cell, while still allowing antigenic epitopes to be detected by immunohistochemical staining. These data indicate that the signal intensity following in situ hybridization for viral RNAs is dependent upon the combined effects of tissue fixation and in situ hybridization temperatures.

Animals↗

PubMed1997

The developmental genetics of hybrid inviability: a mitotic defect in Drosophila hybrids.

We report studies of the developmental basis of hybrid inviability in the Drosophila melanogaster complex. The pathology of these hybrids closely resembles that of mitotic mutants in D. melanogaster. We use mosaic and cytological analyses to show that hybrid male inviability is associated with, and probably caused by, a defect in mitotic cell division. In the mosaic study, we find that male clones produced in otherwise female hybrids are not cell lethal but are very small, probably reflecting defects in mitotic proliferation. Cytological inspection of larval neuroblasts reveals a profound mitotic defect in hybrids: chromosomes show a near-complete failure to condense even after 2 hr of incubation in colchicine. Both the defect in clonal proliferation and in chromatin condensation are rescued by mutations known to rescue normally inviable hybrid males. We present a simple model in which hybrid inviability is partly or entirely caused by a mitotic defect; this defect is, in turn, caused by an interaction between the Hybrid male rescue (Hmr) locus of D. melanogaster and autosomal gene(s) from D. melanogaster's sister species.

Animals↗