A new DNA marker (D4S90) is located terminally on the short arm of chromosome 4, close to the Huntington disease gene

Genetic linkage studies have mapped Huntington's disease (HD) to the distal portion of the short arm of chromosome 4 (4p16.3), 4 cM distal to D4S10 (G8). To date, no definite flanking marker has been identified. A new DNA marker, D4S90 (D5), which maps to the distal region of 4p16.3, is described. The marker was used in a genetic linkage study in the CEPH reference families with seven other markers at 4p16. The study, together with knowledge of the physical map of the region, places D4S90 as the most distal marker, 6 cM from D4S10. A provisional linkage study with HD gave a maximum lod score of 2.14 at a θ of 0.00 and no evidence of linkage disequilibrium. As D4S90 appears to be located terminally, it should play an important role in the accurate mapping and cloning of the HD gene.     

Isotopic evidence of partial mycoheterotrophy in the Gentianaceae: Bartonia virginica and Obolaria virginica as case studies

? Premise of the study: An estimated 10% of plant species have evolved to steal C from their symbiotic fungal partners (mycoheterotrophy), and while physiological evidence for full and partial mycoheterotrophy is well developed in the Orchidaceae and Ericaceae, it is lacking for the majority of other mycoheterotrophic taxa. The family Gentianaceae not only contains several lineages of achlorophyllous mycoheterotrophs, but also contains species that are putative partially mycoheterotrophic. The North American genera Bartonia and Obolaria (Gentianaceae) are green but have leaves reduced to scales or foliose bracts and so have ambiguous mycoheterotrophic status. ? Methods: We investigated the natural abundance (13)C and (15)N profiles of both genera along with total N and chlorophyll content and investigated mycorrhizal infection using light microscopy. ? Key results: The shoots of B. virginica were significantly more enriched in (15)N than the surrounding vegetation but not in (13)C. In contrast, the shoots of O. virginica are not enriched in (15)N compared to the surrounding vegetation but were significantly enriched in (13)C. Total N concentrations were significantly higher than the surrounding vegetation in B. virginica, while the collaroid roots of both species were infected by arbuscular mycorrhizal fungi. ? Conclusions: This microscopic evidence coupled with the natural abundance stable isotope profiles strongly suggests that both species are partially mycoheterotrophic. However, differences in the root-shoot stable isotopic patterns relative to surrounding vegetation between B. virginica and O. virginica are suggestive of the utilization of different physiological pathways or extent of commitment to mycoheterotrophic C gain.     

Assessment of lake sturgeon (Acipenser fulvescens) recruitment in a regulated spawning tributary of Rainy Lake,Ontario

Continued study of the relationship between lake sturgeon (Acipenser fulvescens) recruitment and hydroelectric dams and operations, in a variety of river systems and habitat types is needed to improve the ability to predict and monitor impacts of the hydroelectric industry on this species. Herein, we present results of a juvenile lake sturgeon study aimed at addressing concerns over an inferred lack of recruitment resulting from spawning downstream of a hydroelectric generating station (HGS). Two years of sampling (2015 and 2016) were conducted in five sections of a 41 km long reach of the Seine River, Ontario, a lake sturgeon spawning tributary of Rainy Lake. Using an established gillnetting method, deepwater habitat was targeted to capture juvenile lake sturgeon to assess relative abundance, recruitment (cohort strength), and growth. Deepwater habitat, defined as water depths >6 m in this system, comprised only 2.1% of the wetted area in this study area. Within these habitats, a total of 331 lake sturgeon capture events were observed over the 2-years study period. The majority of the lake sturgeon catch (85%) was comprised of age-0 to age-5 individuals (both sampling years combined). Although inter-annual variation in cohort strength was apparent, each cohort between 2006 and 2016 was represented. The spatial distribution of cohorts varied among river reaches with younger individuals (age-0 and age-1) occupying reaches proximal to the Sturgeon Falls HGS, and larger, older individuals (age-2 to age-5) occupying reaches further downstream. The rarity of age-6+ individuals can likely be explained by ongoing downstream redistribution of juveniles over time, out of the Seine River and into Rainy Lake. Growth of juvenile lake sturgeon captured in the Seine River was above average relative to conspecifics from other rivers in the Hudson Bay drainage. Unfortunately, baseline data sets required to facilitate comparisons of contemporary (post-construction Sturgeon Falls HGS) versus historical (i.e. pre- Sturgeon Falls HGS) lake sturgeon recruitment, or to evaluate the influence of the Seine River Water Management Plan (2004) on lake sturgeon recruitment, are lacking. However, juvenile Lake Sturgeon are more abundant in this system than what had been surmised based on recent studies which implemented random sampling. Results indicate that juvenile lake sturgeon may reside in spawning tributaries for several years (age-0 to age-5) prior to seeking alternate habitats and highlights the value of targeted sampling (i.e. by depth) along the flow axis of rivers downstream of spawning areas when assessing lake sturgeon recruitment patterns.     

Cumulus expansion is impaired with advanced reproductive age due to loss of matrix integrity and reduced hyaluronan

Reproductive aging is associated with ovulatory defects. Age-related ovarian fibrosis partially contributes to this phenotype as short-term treatment with anti-fibrotic compounds improves ovulation in reproductively old mice. However, age-dependent changes that are intrinsic to the follicle may also be relevant. In this study, we used a mouse model to demonstrate that reproductive aging is associated with impaired cumulus expansion which is accompanied by altered morphokinetic behavior of cumulus cells as assessed by time-lapse microscopy. The extracellular matrix integrity of expanded cumulus–oocyte complexes is compromised with advanced age as evidenced by increased penetration of fluorescent nanoparticles in a particle exclusion assay and larger open spaces on scanning electron microscopy. Reduced hyaluronan (HA) levels, decreased expression of genes encoding HA-associated proteins (e.g., Ptx3 and Tnfaip6), and increased expression of inflammatory genes and matrix metalloproteinases underlie this loss of matrix integrity. Importantly, HA levels are decreased with age in follicular fluid of women, indicative of conserved reproductive aging mechanisms. These findings provide novel mechanistic insights into how defects in cumulus expansion contribute to age-related infertility and may serve as a target to extend reproductive longevity.     

How propagule size and environmental suitability jointly determine establishment success: a test using dung beetle introductions

Both the size of founding populations (propagule size) and environmental suitability are known to influence whether a species newly introduced to a location will establish a self-sustaining population. However, these two factors do not operate independently: it is the interaction between propagule size and environmental suitability that determines the probability an introduced population will establish. Here I use the example of dung beetle introductions to Australia to illustrate the importance of this interaction. I first describe equations that model establishment success jointly as a function of propagule size and environmental suitability. I then show how these equations provide insight into the different outcomes observed in two dung beetle species widely introduced to Australia. In one species, variation in propagule size had relatively little influence on establishment success due to large variation in environmental suitability, leading to an essentially bimodal outcome: sites were either very suitable for establishment and introductions succeeded, or sites were unsuitable and introductions failed regardless of propagule size. For the second species, there was much less variation among locations in environmental suitability, leading to propagule size having a strong influence on establishment success. These examples highlight how the interplay between environmental suitability and founding population size is central to determining the probability an introduced species will establish.     

Aerobic Growth of Escherichia coli Is Reduced,and ATP Synthesis Is Selectively Inhibited when Five C-terminal Residues Are Deleted from the ? Subunit of ATP Synthase

F-type ATP synthases are rotary nanomotor enzymes involved in cellular energy metabolism in eukaryotes and eubacteria. The ATP synthase from Gram-positive and -negative model bacteria can be autoinhibited by the C-terminal domain of its ϵ subunit (ϵCTD), but the importance of ϵ inhibition in vivo is unclear. Functional rotation is thought to be blocked by insertion of the latter half of the ϵCTD into the central cavity of the catalytic complex (F₁). In the inhibited state of the Escherichia coli enzyme, the final segment of ϵCTD is deeply buried but has few specific interactions with other subunits. This region of the ϵCTD is variable or absent in other bacteria that exhibit strong ϵ-inhibition in vitro. Here, genetically deleting the last five residues of the ϵCTD (ϵΔ5) caused a greater defect in respiratory growth than did the complete absence of the ϵCTD. Isolated membranes with ϵΔ5 generated proton-motive force by respiration as effectively as with wild-type ϵ but showed a nearly 3-fold decrease in ATP synthesis rate. In contrast, the ϵΔ5 truncation did not change the intrinsic rate of ATP hydrolysis with membranes. Further, the ϵΔ5 subunit retained high affinity for isolated F₁ but reduced the maximal inhibition of F₁-ATPase by ϵ from >90% to ∼20%. The results suggest that the ϵCTD has distinct regulatory interactions with F₁ when rotary catalysis operates in opposite directions for the hydrolysis or synthesis of ATP.     

Polymorphic analysis of the three MHC-linked HSP70 genes

Three genes encoding members of the M _r 70 000 heat shock protein family (HSP70) are known to lie in the class III region of the human major histocompatibility complex. IN order to determine whether these genes or their protein products exhibit any polymorphism the three genes have been specifically amplified from genomic DNA and sequenced. The HSP70-1 and HSP70-2 genes encode the major heat-inducible HSP70. A comparison of the nucleotide sequences of these genes from B8, SC01, DR3, B18, F1C30, DR3, and B7, SC30, DR2 haplotypes has revelad only very limited sequence variation which is not associated with any amino acid polymorphism. The HSP70-Hom gene encodes a protein that is highly related to HSP70-1, but which is not heat-inducible. Nucleotide sequence analysis of this gene from different haplotypes has revealed a Met Thr amino acid substitution at residue 493 in a number of the haplotypes tested. This variable amino acid lies in the proposed peptide-binding site of the HSP70-Hom protein. Address correspondence and offprint requests to: R. D. Campbell.