Toward an objective measure of functional disability in dysferlinopathy.

INTRODUCTION: Understanding the natural history of dysferlinopathy is essential to design and quantify novel therapeutic protocols. Our aim in this study was to assess, clinically and functionally, a cohort of patients with dysferlinopathy, using validated scales. METHODS: Thirty-one patients with genetically confirmed dysferlinopathy were assessed using the motor function measure (MFM), Modified Rankin Scale (MRS), Muscle Research Council (MRC) scale, serum creatine kinase (CK) assessment, baseline spirometry data, and echocardiographic and electrophysiologic studies. RESULTS: MFM and MRC scores showed a significant negative correlation with disease duration and inverse correlation with MRS, but not with onset age, clinical phenotype, or CK levels. Percent forced vital capacity (%FVC) correlated negatively with disease duration and onset age. Eight known pathogenic mutations were identified recurrently, 4 of which accounted for 79% of the total. CONCLUSIONS: The results suggest that MFM is a reliable outcome measure that may be useful for longitudinal follow-up in dysferlinopathy. Recurrent mutations suggest a founder effect in the Chilean population.

Interaction and integration among behaviors of adult Drosophila in nature.

Living in environments whose ecologies vary in periods as short as 24 h is a challenge for animals as Drosophila species that inhabit pear and apple orchards. These orchards have sunny and shady sections. The size and shape of these habitats change daily according to the position of the sun in the sky. Sunny areas are related to dryness and water loss, and shady places have lower temperatures and higher humidity. The presence of heterospecific flies may lead to competition for space and food. In sunny habitats we did not find adult Drosophila. In shady sections we found conspecific groups D. melanogaster, D. simulans, D. immigrans, D. subobscura, and the Chilean endemic D. pavani perched on grasses and herbs at 8-10 cm from fruits that had fallen on the ground. In the fruits, 99% of the adults were females and they were not grouped. The way in which daily changes in the size and shape of shady habitats together with the presence of heterospecific adults influence the selection of places to live is poorly understood in Drosophila. Our experiments show that adults of the five species prefer dark areas. The experimental results show that the odors of each species: i) influence conspecifics to select similar perch sites and decrease mobility, and ii) increase mobility in heterospecific adults and modify their perch site preferences. Attractions between conspecifics, the repulsions between species, and preferences for shaded areas matter in choosing a place to live in the five Drosophila species. These behaviors seem to have evolved as coordinated routines, contributing to the coexistence of the five Drosophila species in the apple and pear orchards examined.

Plasticity and genotype × environment interactions for locomotion in Drosophila melanogaster larvae.

Locomotion is a primary means by which animals interact with the world. To understand the contribution of genotype × environment interactions to individual differences in D. melanogaster larval locomotion we investigated phenotypic sensitivity to environmental changes in four strains of this species and their F1 hybrids. We also investigated to what extent flexibility and plasticity of locomotion depend upon larval age. Specifically, we examined larval locomotion at 48 and 96 h of development on three different substrates. Locomotion was influenced by the structure of the substrate, but this depended on both the genotype and larval age. At 48 h of larval development phenotypic variation in locomotion was attributable to both genotype × environment interactions and genotypic differences among the larvae, while at 96 h of age, differences were mainly due to genotype × environment interactions. An analysis of variance of the 4 × 4 diallel cross made at 48 and 96 h of development showed, depending on the cross, either dominance to increase/decrease locomotion, overdominance to increase/decrease locomotion, or no dominance to increase/decrease locomotion. Furthermore, the diversity of behavioral responses in the F1 hybrids was greater at 96 than at 48 h of larval development. Our results demonstrate that genotype × environment interactions result in plasticity of D. melanogaster larval locomotion, which makes sense in light of the fact that larvae, in the wild, develop in heterogeneous and rapidly changing environments.

Biogeographic origin and thermal acclimation interact to determine survival and hsp90 expression in Drosophila species submitted to thermal stress.

The relationship between thermal tolerance and environmental conditions has been extensively studied in Drosophila. However, comparisons of thermal tolerance of laboratory-bred flies derived from distinct geographic locations have produced puzzling results. We studied the differential expression of heat shock protein (HSP) after heat (34 °C) and cold (-4 °C) temperature treatments in two species of Drosophila flies, with distinct biogeographic origins (tropical = D. melanogaster and Andean = D. gaucha), previously exposed to sublethal acclimation temperatures (10, 20 and 30 °C). Also we evaluated the relationship between thermal acclimation and survival value as a proxy of fitness. We found a positive relationship between thermotolerance and the patterns of hsp90 transcript expression in both species. Nevertheless, in the cases in which hsp90 mRNA expression does not match thermotolerance induction, the biogeographic origin of the species could explain such mismatches. Survival at upper and lower experimental temperatures were also related with species origin.

Effect of laboratory acclimation on the variation of reproduction-related characters in Drosophila melanogaster.

The natural variation of sex-specific characters between populations can favor their behavioral isolation, eventually leading to the formation of new species. Marked variations for male courtship, mating and the production of sex pheromones - three complex characters potentially inducing sexual isolation - were found between Drosophila melanogaster populations of various origins acclimated for many generations in research laboratories. However, the natural variation of these three characters between natural populations and their evolution after long-term acclimation in the laboratory remains unknown. We measured many traits involved in these characters in six stocks initiated with distinct populations sampled in a restricted geographic area. Several sex-specific traits varied between stocks freshly brought back to the laboratory. After 100 generations spent in the laboratory without any experimental selection, traits varied in a strain-dependent manner. This variation was not related to a reduction of their variance except for copulation duration. This indicates that reproduction-related characters can diverge between neighboring D. melanogaster populations, and differently adapt to stable laboratory conditions.

Germline Variants in Driver Genes of Breast Cancer and Their Association with Familial and Early-Onset Breast Cancer Risk in a Chilean Population.

The genetic variations responsible for tumorigenesis are called driver mutations. In breast cancer (BC), two studies have demonstrated that germline mutations in driver genes linked to sporadic tumors may also influence BC risk. The present study evaluates the association between SNPs and SNP-SNP interaction in driver genes TTN (rs10497520), TBX3 (rs2242442), KMT2D (rs11168827), and MAP3K1 (rs702688 and rs702689) with BC risk in BRCA1/2-negative Chilean families. The SNPs were genotyped in 489 BC cases and 1078 controls by TaqMan Assay. Our data do not support an association between rs702688: A>G or rs702689: G>A and BC risk. The rs10497520-T allele was associated with a decreased risk in patients with family history of BC or early-onset BC (OR = 0.6, p < 0.0001 and OR = 0.7, p = 0.05, respectively). rs2242442-G was associated with a protective effect and rs11168827-C was associated with increased BC risk in families with a strong history of BC (OR = 0.6, p = 0.02 and OR = 1.4, p = 0.05, respectively). As rs10497520-T and rs2242442-G seemed to protect against BC risk, we then evaluated their combined effect. Familial BC risk decreased in a dose-dependent manner with the protective allele count, reflecting an additive effect (p-trend < 10-4). To our knowledge, this is the first association study of BC driver gene germline variations in a Chilean population.

Genetics analysis of larval foraging behavior in Drosophila funebris.

To understand the genetics and evolution of foraging in larvae of Drosophila funebris, we examined two strains reared at different breeding sites in the wild. Larvae of the Til-Til strain breed in necrotic cactus tissue, while those of the Pelequén strain rear in necrotic prickly pear cladodes. We measured feeding, locomotion, turning behavior, and latency of D. funebris. Til-Til and Pelequén larvae, at 8 days of age show very similar rates in all behaviors. Crosses between Til-Til and Pelequén strains decrease feeding rate and increase locomotion, turning, and latency in F(1) and F(2) larvae. Backcross larvae show a behavior similar to that of their parental strains. The behavioral similarities observed between the Til-Til and Pelequén strains are product of two different co-adapted gene pools. Epistasis and dominance are the principal sources upon which adaptation of the gene pools of each population are based.

The behavior of adult Drosophila in the wild.

Little is known about how Drosophila adults behave in the wild, including mating, allocation of food and space, and escape from predators. This lack of information has negative implications for our ability to understand the capabilities of the nervous system to integrate sensory cues necessary for the adaptation of organisms in natural conditions. We characterized a set of behavioral routines of D. melanogaster and D. simulans adults in three ecologically different orchards: grape, apple and prickly pear. We also investigated how the flies identify conspecifics and aliens in the wild to better understand relationships between group formation and adaptation of Drosophila to breeding sites. We characterized the locations by recording in each orchard humidity, temperature, illumination conditions, pH of fruits, the presence/absence of other Drosophila species and the predator ant Linepithema humile. Our findings suggest that the home range of these species of Drosophila includes decaying fruits and, principally, a variety of microhabitats that surround the fruits. The ecological heterogeneity of the orchards and odors emitted by adult D. melanogaster and D. simulans influence perch preferences, cluster formation, court and mating, egg-laying site selection, and use of space. This is one of the first large examinations of the association between changing, complex environments and a set of adult behaviors of Drosophila. Therefore, our results have implications for understanding the genetic differentiation and evolution of populations of species in the genus Drosophila.

The genetics and development of mandibles and hypopharyngeal sclerite and cornua in larvae of Drosophila gaucha.

The genetics and epigenetic processes associated with morphological organization are a principal aim of biology, ranging from cohesion between cells to shape and size of organisms. We investigate the post-embryonic development of Hypopharyngeal sclerite and cornua HPC and mandibles M of Drosophila gaucha larva. Integrated functioning of these Cephalopharyngeal skeleton parts of D. gaucha larva is essential for food acquisition, participating in locomotion and microhabitat selection. We examined two isolates by recording the growth of the HPC and M every 24 h for 8 days in parental, F1, F2 and backcross larvae. In F1 larvae, the HPC and M growth was similar to the parental. In F2 and backcross larvae, the growth was slower. Epistasis and dominance are the principal sources upon which the growth of HPC and M are based. Pleiotropic genes seem also to be involved in integrating the development of M and HPC. Our data suggest that hybridization of the isolates modified epigenetic processes involved in the development of those morphological structures of D. gaucha larva.

The Identification of Congeners and Aliens by Drosophila Larvae.

We investigated the role of Drosophila larva olfactory system in identification of congeners and aliens. We discuss the importance of these activities in larva navigation across substrates, and the implications for allocation of space and food among species of similar ecologies. Wild type larvae of cosmopolitan D. melanogaster and endemic D. pavani, which cohabit the same breeding sites, used species-specific volatiles to identify conspecifics and aliens moving toward larvae of their species. D. gaucha larvae, a sibling species of D. pavani that is ecologically isolated from D. melanogaster, did not respond to melanogaster odor cues. Similar to D. pavani larvae, the navigation of pavani female x gaucha male hybrids was influenced by conspecific and alien odors, whereas gaucha female x pavani male hybrid larvae exhibited behavior similar to the D. gaucha parent. The two sibling species exhibited substantial evolutionary divergence in processing the odor inputs necessary to identify conspecifics. Orco (Or83b) mutant larvae of D. melanogaster, which exhibit a loss of sense of smell, did not distinguish conspecific from alien larvae, instead moving across the substrate. Syn97CS and rut larvae of D. melanogaster, which are unable to learn but can smell, moved across the substrate as well. The Orco (Or83b), Syn97CS and rut loci are necessary to orient navigation by D. melanogaster larvae. Individuals of the Trana strain of D. melanogaster did not respond to conspecific and alien larval volatiles and therefore navigated randomly across the substrate. By contrast, larvae of the Til-Til strain used larval volatiles to orient their movement. Natural populations of D. melanogaster may exhibit differences in identification of conspecific and alien larvae. Larval locomotion was not affected by the volatiles.

The neuro-ecology of Drosophila pupation behavior.

Many species of Drosophila form conspecific pupa aggregations across the breeding sites. These aggregations could result from species-specific larval odor recognition. To test this hypothesis we used larval odors of D. melanogaster and D. pavani, two species that coexist in the nature. When stimulated by those odors, wild type and vestigial (vg) third-instar larvae of D. melanogaster pupated on conspecific larval odors, but individuals deficient in the expression of the odor co-receptor Orco randomly pupated across the substrate, indicating that in this species, olfaction plays a role in pupation site selection. Larvae are unable to learn but can smell, the Syn97CS and rut strains of D. melanogaster, did not respond to conspecific odors or D. pavani larval cues, and they randomly pupated across the substrate, suggesting that larval odor-based learning could influence the pupation site selection. Thus, Orco, Syn97CS and rut loci participated in the pupation site selection. When stimulated by conspecific and D. melanogaster larval cues, D. pavani larvae also pupated on conspecific odors. The larvae of D. gaucha, a sibling species of D. pavani, did not respond to D. melanogaster larval cues, pupating randomly across the substrate. In nature, D. gaucha is isolated from D. melanogaster. Interspecific hybrids, which result from crossing pavani female with gaucha males clumped their pupae similarly to D. pavani, but the behavior of gaucha female x pavani male hybrids was similar to D. gaucha parent. The two sibling species show substantial evolutionary divergence in organization and functioning of larval nervous system. D. melanogaster and D. pavani larvae extracted information about odor identities and the spatial location of congener and alien larvae to select pupation sites. We hypothesize that larval recognition contributes to the cohabitation of species with similar ecologies, thus aiding the organization and persistence of Drosophila species guilds in the wild.

Chemical cues influence pupation behavior of Drosophila simulans and Drosophila buzzatii in nature and in the laboratory.

In the wild, larvae of several species of Drosophila develop in heterogeneous and rapidly changing environments sharing resources as food and space. In this scenario, sensory systems contribute to detect, localize and recognize congeners and heterospecifics, and provide information about the availability of food and chemical features of environments where animals live. We investigated the behavior of D. simulans and D. buzzatii larvae to chemicals emitted by conspecific and heterospecific larvae. Our goal was to understand the role of these substances in the selection of pupation sites in the two species that cohabit within decaying prickly pear fruits (Opuntia ficus-indica). In these breeding sites, larvae of D. simulans and D. buzzatii detect larvae of the other species changing their pupation site preferences. Larvae of the two species pupated in the part of the fruit containing no or few heterospecifics, and spent a longer time in/on spots marked by conspecifics rather than heterospecifics. In contrast, larvae of the two species reared in isolation from conspecifics pupated randomly over the substrate and spent a similar amount of time on spots marked by conspecifics and by heterospecifics. Our results indicate that early chemically-based experience with conspecific larvae is critical for the selection of the pupation sites in D. simulans and D. buzzatii, and that pupation site preferences of Drosophila larvae depend on species-specific chemical cues. These preferences can be modulate by the presence of larvae of the same or another species.

Organization of foraging behavior in larvae of cosmopolitan, widespread, and endemic Drosophila species.

To explore the evolution of higher order behavioral traits we investigated the organization of foraging patterns in first instar larvae of natural populations of Drosophila. We examined Drosophila simulans (cosmopolitan); D. mauritania (widespread); D. pavani, and D. gaucha (endemic). Larvae of these four species share the same behavior components that comprise foraging (locomotion, feeding, bending, and turning). D. simulans and D. mauritania larvae show uncoupled foraging patterns organized into partially independent behavioral elements. Larvae of D. pavani and D. gaucha exhibit coupled foraging behaviors based on a dependency between behavioral components. Hybrid larvae obtained from crosses of natural populations of D. simulans and D. mauritania show an organization of foraging patterns similar to that of the parental lines. In contrast, hybridization disrupts the organization of foraging patterns in D. pavani and D. gaucha intra- and inter-specific hybrid larvae. This suggests genetic co-adaptation for linkage between the behavioral components that comprise foraging. The organization of larval foraging patterns of the endemic species D. pavani seems readily affected by hybridization. The absence of linkage between behavioral components, as in the case of larval foraging patterns of D. simulans and D. mauritania could lead to an increase in the variability of organization of this higher order behavior. The possibility that larvae may use a variable and flexible behavioral integration of foraging patterns could contribute to their development and feeding in a diversity of substrates and climates.

Hybrid disadvantage in the larval foraging behaviour of the two neotropical species of Drosophila pavani and Drosophila gaucha.

Flies from two populations of the Chilean endemic neotropical species Drosophila pavani and two populations of its sibling species Drosophila gaucha were crossed reciprocally to obtain intra- and interspecific hybrids. The developmental pathways of locomotor activity and feeding rate were analysed for eleven of twelve possible genotype groups. The hybrids showed reduced fitness indicated by a decrease in the measured traits. Hybrid disadvantage was strongest in interspecific hybrids, especially with respect to feeding behaviour. This evidence supports the contention that D. pavani and D. gaucha have evolved different coadapted gene pools controlling the developmental pathways for behavioural traits expressed during larval foraging; but genetic divergence affecting these behaviours has also taken place between locally adapted populations within each species.

Conservation and divergence of the genetic structure of larval foraging behaviour in two species of the Drosophila simulans clade.

Larvae of the sibling species Drosophila simulans and D. mauritiana have rates of locomotor and feeding activity that are closely similar. Comparisons of the trait means for intra- and interspecific hybrids show that significant epistatic interactions affect both characters when the genomes of the two species are combined. The phenotypic variances of progenies obtained by backcrossing the interspecific hybrids to their respective parent species show that appreciable genetic turnover affecting foraging behaviour has occurred since their two phylogenetic lines diverged.