Mapping of a congenital microcoria locus to 13q31-q32.

Congenital microcoria is an autosomal dominant disorder characterized by a pupil with a diameter <2 mm. It is thought to be due to a maldevelopment of the dilator pupillae muscle of the iris, and it is associated with juvenile-onset glaucoma. A total genome search for the location of the congenital microcoria gene was launched in a single large family. We found linkage between the disease and markers located on 13q31-q32 (Zmax = 9.79; theta = 0). Haplotype analysis narrowed the linked region to an interval <8 cM between markers D13S1239 proximally and D13S1280 distally.     

Sex chromosome pairing and sex chromatin bodies in W-Z translocation strains of Ephestia kuehniella (Lepidoptera).

Structure and pairing behavior of sex chromosomes in females of four T(W;Z) lines of the Mediterranean flour moth, Ephestia kuehniella, were investigated using light and electron microscopic techniques and compared with the wild type. In light microscopic preparations of pachytene oocytes of wild-type females, the WZ bivalent stands out by its heterochromatic W chromosome strand. In T(W;Z) females, the part of the Z chromosome that was translated onto the W chromosome was demonstrated as a distal segment of the neo-W chromosome, displaying a characteristic non-W chromosomal chromomere-interchromomere pattern. This segment is homologously paired with the corresponding part of a complete Z chromosome. In contrast with the single ball of heterochromatic W chromatin in highly polyploid somatic nuclei of wild-type females, the translocation causes the formation of deformed or fragmented W chromatin bodies, probably owing to opposing tendencies of the Z and W chromosomal parts of the neo-W. In electron microscopic preparations of microspread nuclei, sex chromosome bivalents were identified by the remnants of electron-dense heterochromatin tangles decorating the W chromosome axis, by the different lengths of the Z and W chromosome axes, and by incomplete pairing. No heterochromatin tangles were attached to the translocated segment of the Z chromosome at one end of the neo-W chromosome. Because of the homologous pairing between the translocation and the structurally normal Z chromosome, pairing affinity of sex chromosomes in T(W;Z) females is significantly improved. Specific differences observed among T(W;Z)1-4 translocations are probably due to the different lengths of the translocated segments.     

Genomic evidence for divergence with gene flow in host races of the larch budmoth

Ecological divergence in the face of gene flow has recently become implicated as a potentially important cause of speciation and adaptive radiation. Here, we develop a genomic approach to test for divergent selection in sympatric host races of the larch budmoth Zeiraphera diniana (Lepidoptera: Tortricidae). We analysed hundreds of amplified fragment length polymorphism markers in 92 individuals in sympatric and allopatric populations, and in two backcross broods used to map the markers to individual chromosomes. The results directly confirm the existence of natural hybridization and demonstrate strong heterogeneity between chromosomes in terms of molecular divergence between host races (the average level of divergence was FST = 0.216). However, genomic heterogeneity was not found when we analysed divergence between geographically separated populations of the same host race. We conclude that the variance of the level of sympatric divergence among chromosomes is the footprint of divergent selection acting on a few linkage groups, combined with appreciable gene flow that homogenizes between-race variation at the remaining linkage groups. These results, coupled with other recent multilocus analyses of sister species pairs, demonstrate that selection-driven sympatric phase of genetic divergence in the presence of gene flow is a likely feature of speciation.     

Resolution of sex chromosome constitution by genomic in situ hybridization and fluorescence in situ hybridization with (TTAGG) n telomeric probe in some species of Lepidoptera

We have developed a simple method to resolve the sex chromosome constitution in females of Lepidoptera by using a combination of genomic in situ hybridization (GISH) and fluorescence in situ hybridization with (TTAGG) _n telomeric probe (telomere-FISH). In pachytene configurations of sex chromosomes, GISH differentiated W heterochromatin and telomere-FISH detected the chromosome ends. With this method we showed that Antheraea yamamai has a standard system with a fully differentiated W–Z sex chromosome pair. In Orgyia antiqua, we confirmed the presence of neo-W and neo-Z chromosomes, which most probably originated by fusion of the ancestral W and Z with an autosome pair. In contrast to earlier data, Orgyia thyellina females displayed a neo-ZW₁W₂ sex chromosome constitution. A neo-WZ₁Z₂ trivalent was found in females of Samia cynthia subsp. indet., originating from a population in Nagano, Japan. Whereas another subspecies collected in Sapporo, Japan, and determined as S. cynthia walkeri, showed a neo-W/neo-Z bivalent similar to O. antiqua, and the subspecies S. cynthia ricini showed a Z univalent (a Z/ZZ system). The combination of GISH and telomere-FISH enabled us to acquire not only reliable information about sex chromosome constitution but also an insight into sex chromosome evolution in Lepidoptera.     

The effect of population density on the elimination dynamics of a recessive lethal mutation l(2)M167DTS from experimental populations of Drosophila melanogaster

Dynamics of the elimination of the temperature-sensitive lethal mutation l(2)M167 ^DTS from experimental populations of Drosophila melanogaster under permissive conditions (25°C) was studied. We have shown a rapid elimination of the mutation from the populations, selection for fitness of heterozygous individuals, association of the selection with high larval density and with the direction of the cross that had produced the founder males of the l(2)M167 ^DTS /+ population, and the effect of relative competitive ability of l(2)M167 ^DTS /+ males on the efficiency of the mutation introduction. Modification systems were shown be involved in fitness selection under conditions of high larval density.Translated from Genetika, Vol. 41, No. 3, 2005, pp. 326–333.Original Russian Text Copyright © 2005 by Kulikov, Marec, Mitrofanov.     

Prader-Willi syndrome and polygonosomal abnormalities in males:about a Prader-Willi/47,XYY patient

We herein report a male patient known as having a XYY karyotype. At the age of 26 years a Prader-Willi syndrome (PWS) was diagnosed. Before that time the whole symptomatology was ascribed to the XYY syndrome. This is the first reported association of PWS and polygonosomal abnormality in a male adult (whose height is above average).     

Female hemophilia. Apropos of a homozygote woman

About one homozygote female for haemophilia, authors report circumstances where we can see an haemophilic female: lyonisation, chromosomal abnormalities of X chromosome, and homozygosis. They report the cases of literature.     

Evidence for integrity of parental genomes in the diploid hybridogenetic water frog Pelophylax esculentus by genomic in situ hybridization

The Western Palearctic water frogs Pelophylax ridibundus and P. lessonae were identified as parental (sexual) species and P. esculentus as their interspecific, hybridogenetically reproducing hybrid with hemiclonal heredity. We used genomic in situ hybridization (GISH) to identify parental chromosomes of P.lessonae and P.ridibundus in diploid P. esculentus karyotypes (2n = 26). GISH probes were made by fluorochrome labeling of total genomic DNA extracted from the sexual progenitors. The labeled probe from one species was hybridized to chromosomes of P. esculentus in the presence of excess of unlabeled genomic DNA from the other species. Thus, the P. lessonae probe was blocked by P. ridibundus unlabeled DNA, and vice versa. We successfully discriminated each of the 13 respective parental chromosomes in metaphase complements of the hybrids according to species-specific hybridization signals. GISH enabled us to confirm additional differences between parental chromosomes in size (smaller chromosomes belong to P. lessonae) and in the presence of DAPI-positive centromeric heterochromatin (detected in chromosomes of P. ridibundus, but not in P. lessonae). The fact that no visible intergenomic exchanges were found in metaphase chromosomes of diploid P. esculentus provides important information on the genomic integrity of hemiclonal transmission and supports hybridogenesis as a reproductive mode at the chromosome level for the specimens examined.     

Divergent location of ribosomal genes in chromosomes of fish thorny-headed worms, <Emphasis Type="Italic">Pomphorhynchus laevis</Emphasis> and <Emphasis Type="Italic">Pomphorhynchus tereticollis</Emphasis> (Acanthocephala)

We studied distribution of ribosomal DNA (rDNA) sequences along with chromosomal location of the nucleolar organizer regions (NORs) in males of two fish parasites, Pomphorhynchus laevis and Pomphorhynchus tereticollis (Acanthocephala). Fluorescence in situ hybridization with 18S rDNA probe identified two clusters of rDNA in each species, but revealed a remarkable difference in their location on chromosomes. In P. laevis, the rDNA-FISH signals were found in long arms of the first chromosome pair and in short arms of the second pair. Whereas in P. tereticollis, rDNA clusters were located in long arms of both the first and second chromosome pairs. The divergent location of rDNA clusters in the chromosome No. 2 supports current classification of P. tereticollis, previously considered a synonym of P. laevis, as a separate species. A possible scenario of the second chromosome rearrangement during karyotype evolution of the two species involves two successive pericentric inversions. In both species, one or two prominent nucleoli were apparent within interphase nuclei stained with either silver nitrate or a fluorescent dye YOYO-1. However, a single large nucleolus was observed in early stages of mitosis and meiosis I regardless the number of rDNA clusters. Nevertheless, two bivalents with silver-stained NORs in diakinesis and two silver-stained sites in early prophase II nuclei indicated that all NORs are active. This means that each Pomphorhynchus NOR generates a nucleolus, but the resulting nucleoli have a strong tendency to associate in a large body.     

Mapping of single-copy genes by TSA-FISH in the codling moth, <Emphasis Type="Italic">Cydia pomonella</Emphasis>

Background

We work on the development of transgenic sexing strains in the codling moth, Cydia pomonella (Tortricidae), which would enable to produce male-only progeny for the population control of this pest using sterile insect technique (SIT). To facilitate this research, we have developed a number of cytogenetic and molecular tools, including a physical map of the codling moth Z chromosome using BAC-FISH (fluorescence in situ hybridization with bacterial artificial chromosome probes). However, chromosomal localization of unique, single-copy sequences such as a transgene cassette by conventional FISH remains challenging. In this study, we adapted a FISH protocol with tyramide signal amplification (TSA-FISH) for detection of single-copy genes in Lepidoptera. We tested the protocol with probes prepared from partial sequences of Z-linked genes in the codling moth.

Results

Using a modified TSA-FISH protocol we successfully mapped a partial sequence of the Acetylcholinesterase 1 (Ace-1) gene to the Z chromosome and confirmed thus its Z-linkage. A subsequent combination of BAC-FISH with BAC probes containing anticipated neighbouring Z-linked genes and TSA-FISH with the Ace-1 probe allowed the integration of Ace-1 in the physical map of the codling moth Z chromosome. We also developed a two-colour TSA-FISH protocol which enabled us simultaneous localization of two Z-linked genes, Ace-1 and Notch, to the expected regions of the Z chromosome.

Conclusions

We showed that TSA-FISH represents a reliable technique for physical mapping of genes on chromosomes of moths and butterflies. Our results suggest that this technique can be combined with BAC-FISH and in the future used for physical localization of transgene cassettes on chromosomes of transgenic lines in the codling moth or other lepidopteran species. Furthermore, the developed protocol for two-colour TSA-FISH might become a powerful tool for synteny mapping in non-model organisms.