Many populations of lake sturgeon Acipenser fulvescens have decreased in size throughout the Great Lakes basin. To implement management strategies such as stocking, it is important to understand the genetic structure of lake sturgeon spawning populations. Lake sturgeon from 27 spawning locations (25 from the Great Lakes basin and 2 from the Hudson Bay drainage) were analyzed using 12 microsatellite loci. Population structure was detected at different spatial scales. At the largest scale, consistent genetic breaks were observed among three clusters of spawning populations: (1) Hudson Bay–northern Lake Superior, (2) southern Lake Superior, and (3) the rest of the Great Lakes. These clusters were identified using a Bayesian approach that does not define the populations a priori. Within each of the three clusters, sublevels of genetic structure were detected. These sublevel clusters accounted for 8.82% of the genetic variation (P < 0.000), while differences among populations within the clusters accounted for 3.72% of the genetic variation (P < 0.000). At the smallest scale, significant genetic differentiation was detected between most sampled locations through pairwise genetic differentiation index (FST) tests and pairwise contingency tests. Lake sturgeon showed greater genetic differentiation in Lake Superior than elsewhere, which could be due to the lake's bathymetry. The lower genetic resolution observed elsewhere in the Great Lakes could be due to more recent colonization events. The results can be used to delineate management units and to select appropriate donor populations for supplementation or reintroductions.

Here we present a high-resolution cytogenomic analysis of chicken microchromosome 16. We established the location of the major histocompatibility complex (MHC)-B and -Y subregions relative to each other and to the nucleolus organizer region (NOR) encoding the 18S-5.8S-28S ribosomal DNA. To do so, we employed multicolor fluorescence in situ hybridization using large-insert bacterial artificial chromosome clones with fully sequenced inserts or repetitive sequence probes specific for the subregion of interest. We show that the MHC-Y and -B regions are located on the same side of the NOR, rather than opposite ends, as previously proposed. On the q arm, the MHC-Y is closely adjacent to the NOR, whereas the MHC-B is distal near the q-terminus. A relatively large GC-rich region separates the 2 MHC subregions and includes a specialized structure, a secondary constriction. We propose that the GC-rich large physical distance is the basis for the lack of genetic linkage between the NOR and MHC-B and between the MHC-Y and -B. An integrated model for GGA 16 is presented that incorporates gene complex order in the context of key architectural features including p and q arms, primary (centromere) and secondary constrictions, telomeres, as well as AT- and GC-rich regions.

Marek's disease virus (MDV) is an oncogenic α-herpesvirus that induces Marek's disease characterized by fatal lymphomas in chickens. Here, we explored the timing during pathogenesis when the virus integrates into the host genome, the cell type involved, the role of viral integration on cellular transformation, and tumor clonality. Three immune organs of chicken (thymus, bursa, and spleen) were extracted following infection with either an oncogenic or a non-oncogenic strain of MDV. Using molecular cytogenetics, cells were investigated for viral integration at key time points throughout pathogenesis. Integration profiling of tumors (early to late stage) was conducted. Virus integration was widespread in B and T lymphocytes based on their abundance in bursa and thymus, respectively. Viral replication was detected early after infection as was viral integration into the host genome. Integration is a natural part of the MDV herpesvirus life cycle. In addition, our data using a non-oncogenic virus establish that although integration is a hallmark of tumor cell populations, integration alone is not sufficient for cellular transformation. Our results provide evidence for progression of lineage clonality within tumors. Understanding the features of integration provides insight into the mechanisms of herpesvirus pathology which could lead to disease mitigation strategies.

BackgroundHerpesviruses are a major health concern for numerous organisms, including humans, causing both acute and chronic infections recurrent over an individual's lifespan. Marek's disease virus (MDV) is a highly contagious herpesvirus which causes a neoplastic condition in chicken populations. Several vertebrate-infecting herpesviruses have been shown to exist in an integrated state during latent periods of infection. However the status of MDV during latency has been a topic of debate.ResultsHere we employed high-resolution multi-color fluorescence in situ hybridization (FISH) to show integration of MDV at the telomeres of chicken chromosomes. Cytogenomic mapping of the chromosomal integrations allowed us to examine the clonal relationships among lymphomas within individuals, whereas analysis of tumors from multiple individuals indicated the potential for chromosomal preferences.ConclusionsOur data highlight that substantive genome-level interactions between the virus and host exist, and merit consideration for their potential impact and role in key aspects of herpesvirus pathobiology including infection, latency, cellular transformation, latency-breaks and viral evolution.

Trisomy mapping is a powerful method for assigning genes to chicken microchromosome 16 (GGA 16). The single chicken nucleolar organizer region (NOR), the 2 major histocompatibility complex regions (MHC-Y and MHC-B), and CD1 genes were all previously assigned to GGA 16 using trisomy mapping. Here, we combined array comparative genomic hybridization with trisomy mapping to screen unassigned genomic scaffolds (consigned temporarily to chrUn_random) for sequences originating from GGA 16. A number of scaffolds mapped to GGA 16. Among these were scaffolds that contain genes for olfactory (OR) and cysteine-rich domain scavenger (SRCR) receptors, along with a number of genes that encode putative immunoglobulin-like receptors and other molecules. We used high-resolution cytogenomic analyses to confirm assignment of OR and SRCR genes to GGA 16 and to pinpoint members of these gene families to the q-arm in partially overlapping regions between the centromere and the NOR. Southern blots revealed sequence polymorphism within the OR/SRCR region and linkage with the MHC-Y region, thereby providing evidence for conserved linkage between OR genes and the MHC within birds. This work localizes OR genes to the vicinity of the chicken MHC and assigns additional genes, including immune defense genes, to GGA 16.

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Well-characterized molecular and cytogenetic maps are yet to be established in Japanese quail (Coturnix japonica). The aim of the current study was to cytogenetically map and determine linkage of specific genes and gene complexes in Japanese quail through the use of chicken (Gallus gallus) and turkey (Meleagris gallopavo) genomic DNA probes and conduct a comparative study among the three genomes. Chicken and turkey clones were used as probes on mitotic metaphase and meiotic pachytene stage chromosomes of the three species for the purpose of high-resolution fluorescence in situ hybridization (FISH). The genes and complexes studied included telomerase RNA (TR), telomerase reverse transcriptase (TERT), 5S rDNA, 18S-5.8S-28S rDNA (i.e., nucleolus organizer region (NOR)), and the major histocompatibility complex (MHC). The telomeric profile of Japanese quail was investigated through the use of FISH with a TTAGGG-PNA probe. A range of telomeric array sizes were confirmed as found for the other poultry species. Three NOR loci were identified in Japanese quail, and single loci each for TR, TERT, 5S rDNA and the MHC-B. The MHC-B and one NOR locus were linked on a microchromosome in Japanese quail. We confirmed physical linkage of 5S rDNA and the TR gene on an intermediate-sized chromosome in quail, similar to both chicken and turkey. TERT localized to CJA 2 in quail and the orthologous chromosome region in chicken (GGA 2) and in turkey (MGA 3). The cytogenetic profile of Japanese quail was further developed by this study and synteny was identified among the three poultry species.

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