Genetic Variation in Neurotransmitter Receptors Generates Behavioral Diversity

Variation in behavior among individuals is both remarkable and of great significance to society. People differ in locomotor skills, in sleep patterns, in their willingness to take risks, and in how they relate to other people. Whereas diversity enriches society, extreme behavioral deviations can be pathological, so it is important to identify the causes of behavioral variability. It is clear that both the environment and genetics contribute to behavioral diversity in all animals, but the nature of the specific genes involved is only beginning to emerge. The nematode worm Caenorhabditis elegans is a good animal model to study the genetic and neuronal bases of behavioral variation, as there are large differences in behavior between naturally-occurring strains, and powerful tools exist to characterize these differences. One example of the behavioral diversity of C. elegans is the existence of different thresholds for exploration–exploitation tradeoffs: some strains decide to exploit resources more thoroughly, while others decide to abandon resources earlier and explore other options. Using quantitative genetic tools I have found that genetic variation in the adrenergic receptor tyra-3 affects this exploration– exploitation decision. tyra-3 responds to the neurotransmitter tyramine, which is related to vertebrate adrenaline and noradrenaline. tyra-3 modifies the activity of sensory neurons that detect food cues and that regulate the decision to abandon depleting food resources. In strains that are more prone to exploration tyra-3 is expressed at lower levels, and this altered expression modifies the response of the sensory neurons to food. Variation in a gene that affects the response to the environment helps explain how nature and nurture interact to produce behavioral outcomes. In addition to variation in exploratory behavior, C. elegans strains also differ in social behaviors. In most strains animals aggregate with each other, whereas a few strains have evolved a solitary life-style. Variation in the neuropeptide Y receptor homologue npr-1 contributes to social behavior variation, but I found that other genes are also involved in this behavior. Through quantitative genetic analysis I identified polymorphisms in the GABA-gated cation channel exp-1 that generate variation in social behavior. Based on existing behavioral diversity in C. elegans, I discovered genetic variation in two neurotransmitter receptors and characterized the way in which this variation modifies the neuronal circuits that generate behavior. Consistent with findings in other systems, my results suggest that genetic variation in neurotransmitter receptors is a common way of generating behavioral diversity in animals

Parent‐offspring inference in inbred populations

Genealogical relationships are fundamental components of genetic studies. However, it is often challenging to infer correct and complete pedigrees even when genome-wide information is available. For example, inbreeding can obscure genetic differences between individuals, making it difficult to even distinguish first-degree relatives such as parent-offspring from full siblings. Similarly, genotyping errors can interfere with the detection of genetic similarity between parents and their offspring. Inbreeding is common in natural, domesticated, and experimental populations and genotyping of these populations often has more errors than in human data sets, so efficient methods for building pedigrees under these conditions are necessary. Here, we present a new method for parent-offspring inference in inbred pedigrees called specific parent-offspring relationship estimation (spore). spore is vastly superior to existing pedigree-inference methods at detecting parent-offspring relationships, in particular when inbreeding is high or in the presence of genotyping errors, or both. spore therefore fills an important void in the arsenal of pedigree inference tools

Parent-offspring inference in inbred populations

Genealogical relationships are fundamental components of genetic studies. However, it is often challenging to infer correct and complete pedigrees even when genome-wide information is available. For example, inbreeding can obfuscate genetic differences between individuals, making it difficult to even distinguish first-degree relatives such as parent-offspring from full siblings. Similarly, genotyping errors can interfere with the detection of genetic similarity between parents and their offspring. Inbreeding is common in natural, domesticated, and experimental populations and genotyping of these populations often has more errors than in human datasets, so efficient methods for building pedigrees under these conditions are necessary. Here, we present a new method for parent-offspring inference in inbred pedigrees called SPORE (Specific Parent-Offspring Relationship Estimation). SPORE is vastly superior to existing pedigree-inference methods at detecting parent-offspring relationships, in particular when inbreeding is high or in the presence of genotyping errors, or both. SPORE therefore fills an important void in the arsenal of pedigree inference tools.Author SummaryKnowing the genealogical relationships among individuals is critical for genetic analyses, such as for identifying the mutations that cause diseases or that contribute to valuable agricultural traits such as milk production. Although many tools exist for establishing pedigrees using genetic information, these tools fail when individuals are highly inbred, such as in domesticated animals, or in groups of people in which consanguineous matings are common. Furthermore, existing tools do not work well when genetic information has errors at levels observed in modern datasets. Here, we present a novel approach to solve these problems. Our method is significantly more accurate than existing tools and more tolerant of errors in the genetic data. We expect that our method, which is simple to use and computationally efficient, will be a useful tool in a diversity of settings, from the studies of human and natural populations, to agricultural and experimental settings

Post-mating parental behavior trajectories differ across four species of deer mice

Among species, parental behaviors vary in their magnitude, onset relative to reproduction, and sexual dimorphism. In deer mice (genus Peromyscus), while most species are promiscuous with low paternal care, monogamy and biparental care have evolved at least twice under different ecological conditions. Here, in a common laboratory setting, we monitored parental behaviors of males and females of two promiscuous (eastern deer mouse P. maniculatus and white-footed mouse P. leucopus) and two monogamous (oldfield mouse P. polionotus and California mouse P. californicus) species from before mating to after giving birth. In the promiscuous species, females showed parental behaviors largely after parturition, while males showed little parental care. In contrast, both sexes of monogamous species performed parental behaviors. However, while oldfield mice began to display parental behaviors before mating, California mice showed robust parental care behaviors only postpartum. These different parental-care trajectories in the two monogamous species align with their socioecology. Oldfield mice have overlapping home ranges with relatives, so infants they encounter, even if not their own, are likely to be closely related. By contrast, California mice disperse longer distances into exclusive territories with possibly unrelated neighbors, decreasing the inclusive fitness benefits of caring for unfamiliar pups before parenthood. Together, we find that patterns of parental behaviors in Peromyscus are consistent with predictions from inclusive fitness theory

Catecholamine receptor polymorphisms affect decision-making in C. elegans.

Innate behaviours are flexible: they change rapidly in response to transient environmental conditions, and are modified slowly by changes in the genome. A classical flexible behaviour is the exploration-exploitation decision, which describes the time at which foraging animals choose to abandon a depleting food supply. We have used quantitative genetic analysis to examine the decision to leave a food patch in Caenorhabditis elegans. Here we show that patch-leaving is a multigenic trait regulated in part by naturally occurring non-coding polymorphisms in tyra-3 (tyramine receptor 3), which encodes a G-protein-coupled catecholamine receptor related to vertebrate adrenergic receptors. tyra-3 acts in sensory neurons that detect environmental cues, suggesting that the internal catecholamines detected by tyra-3 regulate responses to external conditions. These results indicate that genetic variation and environmental cues converge on common circuits to regulate behaviour, and suggest that catecholamines have an ancient role in regulating behavioural decisions