Non-Coding Changes Cause Sex-Specific Wing Size Differences between Closely Related Species of Nasonia

The genetic basis of morphological differences among species is still poorly understood. We investigated the genetic basis of sex-specific differences in wing size between two closely related species of Nasonia by positional cloning a major male-specific locus, wing-size1 (ws1). Male wing size increases by 45% through cell size and cell number changes when the ws1 allele from N. giraulti is backcrossed into a N. vitripennis genetic background. A positional cloning approach was used to fine-scale map the ws1 locus to a 13.5 kilobase region. This region falls between prospero (a transcription factor involved in neurogenesis) and the master sex-determining gene doublesex. It contains the 5′-UTR and cis-regulatory domain of doublesex, and no coding sequence. Wing size reduction correlates with an increase in doublesex expression level that is specific to developing male wings. Our results indicate that non-coding changes are responsible for recent divergence in sex-specific morphology between two closely related species. We have not yet resolved whether wing size evolution at the ws1 locus is caused by regulatory alterations of dsx or prospero, or by another mechanism. This study demonstrates the feasibility of efficient positional cloning of quantitative trait loci (QTL) involved in a broad array of phenotypic differences among Nasonia species

Person-Specific Non-shared Environmental Influences in Intra-individual Variability : A Preliminary Case of Daily School Feelings in Monozygotic Twins

Most behavioural genetic studies focus on genetic and environmental influences on inter-individual phenotypic differences at the population level. The growing collection of intensive longitudinal data in social and behavioural science offers a unique opportunity to examine genetic and environmental influences on intra-individual phenotypic variability at the individual level. The current study introduces a novel idiographic approach and one novel method to investigate genetic and environmental influences on intra-individual variability by a simple empirical demonstration. Person-specific non-shared environmental influences on intra-individual variability of daily school feelings were estimated using time series data from twenty-one pairs of monozygotic twins (age = 10 years, 16 female pairs) over two consecutive weeks. Results showed substantial inter-individual heterogeneity in person-specific non-shared environmental influences. The current study represents a first step in investigating environmental influences on intra-individual variability with an idiographic approach, and provides implications for future behavioural genetic studies to examine developmental processes from a microscopic angle

“A fly appeared”: <i>sable</i>, a classic <i>Drosophila</i> mutation, maps to <i>Yippee</i>, a gene affecting body color, wings, and bristles

AbstractInsect body color is an easily assessed and visually engaging trait that is informative on a broad range of topics including speciation, biomaterial science, and ecdysis. Mutants of the fruit fly Drosophila melanogastersable1Yippeesable1YippeeYippeeYippeeYippeesableYippeeYippeesablesuppressor of sabl

Fine-Scale Mapping of the Nasonia Genome to Chromosomes Using a High-Density Genotyping Microarray

Nasonia, a genus of four closely related parasitoid insect species, is a model system for genetic research. Their haplodiploid genetics (haploid males and diploid females) and interfertile species are advantageous for the genetic analysis of complex traits and the genetic basis of species differences. A fine-scale genomic map is an important tool for advancing genetic studies in this system. We developed and used a hybrid genotyping microarray to generate a high-resolution genetic map that covers 79% of the sequenced genome of Nasonia vitripennis. The microarray is based on differential hybridization of species-specific oligos between N. vitripennis and Nasonia giraulti at more than 20,000 markers spanning the Nasonia genome. The map places 729 scaffolds onto the five linkage groups of Nasonia, including locating many smaller scaffolds that would be difficult to map by other means. The microarray was used to characterize 26 segmental introgression lines containing chromosomal regions from one species in the genetic background of another. These segmental introgression lines have been used for rapid screening and mapping of quantitative trait loci involved in species differences. Finally, the microarray is extended to bulk-segregant analysis and genotyping of other Nasonia species combinations. These resources should further expand the usefulness of Nasonia for studies of the genetic basis and architecture of complex traits and speciation. The parasitic wasp genus Nasonia (Insecta: Hymenoptera) is a model system in genetics, particularly evolutionary genetics, the genetics of complex traits, developmental genetics, and host−parasite interactions (Beukeboom and Desplan 2003; Werren and Loehlin 2009). Nasonia consists of four closely related species, Nasonia vitripennis, Nasonia giraulti, Nasonia longicornis, and the recently discovered Nasonia oneida, which are all cross-fertile once cured of their endosymbiotic Wolbachia (Breeuwer and Werren 1995; Raychoudhury et al. 2010). The presence of interfertile species is advantageous for evolutionary genetic research because it allows movement of genetic regions between species for the identification, mapping, and cloning of quantitative trait loci (QTL) involved in species differences. Several additional features make Nasonia an excellent genetic model, including short (2-wk) generation time, ease of laboratory rearing, systemic RNA interference, and haplodiploid sex determination (females are diploid, whereas males are haploid and derived from unfertilized eggs, facilitating mutation screening) (Lynch and Desplan 2006; Werren and Loehlin 2009; Werren et al. 2009). The N. vitripennis−N. giraulti species pair has been used widely to identify QTL involved in a diverse array of phenotypes, including wing size (Gadau et al. 2002; Loehlin et al. 2010a,b; Loehlin and Werren 2012), cuticular hydrocarbons (Niehuis et al. 2011), hybrid incompatibilities (Breeuwer and Werren 1995; Gadau et al. 1999; Gibson et al. 2010; Koevoets et al. 2012; Niehuis et al. 2008; Werren et al. 2010), and host preference (Desjardins et al. 2010). The recent sequencing of the genomes of three Nasonia species (Werren et al. 2010) provides a key resource for advancing this new model system. Using the genome sequence data in conjunction with haploid males from hybrid crosses between N. vitripennis and N. giraulti, a genetic map of the Nasonia genome was generated (Niehuis et al. 2010; Werren et al. 2010). This approach was facilitated by the high level of single-nucleotide polymorphisms (SNPs) between species (average coding sequence difference between N. vitripennis and N. giraulti is 1%). The mapping population consisted of haploid male embryos from F1 hybrid females. The advantage of hybrid haploid males is that for any locus, a hybrid male carries only the allele for one of the parental species. With the use of this strategy, 265 scaffolds (covering 64% of the assembled genome) were mapped onto the five chromosomes of Nasonia (Niehuis et al. 2010). The combination of a genome sequence and genetic map has allowed investigators studying Nasonia to do forward genetics efficiently, i.e., quickly proceed from detection of QTL to positional cloning of QTL and identification of the genetic architecture that underlie phenotypes of interest (Loehlin et al. 2010b; Loehlin and Werren 2012). To further advance Nasonia as a genetic system, a high-resolution genetic map is needed that places more scaffolds onto the linkage map and has a finer scale of resolution. In addition, the availability of a cost-effective tool for high-throughput genotyping and bulk-segregant analysis could help advance studies geared toward investigating the genetic basis of complex adaptive phenotypes, genetic incompatibilities, and species differences. Here, we developed a comparative hybridization genotyping (CGH) microarray that uses clusters of SNPs and insertion-deletions (indels) in a high-density genotyping microarray to differentiate N. vitripennis from N. giraulti sequence at a large number of markers spanning the Nasonia genome. Additional resources being developed for Nasonia include a set of segmental introgression lines (SILs), which contain specific genomic regions from one species (typically N. giraulti) in the genetic background of another (typically N. vitripennis) (Werren and Loehlin 2009). These are produced by performing an interspecific cross followed by repeated backcrossing of hybrid females to males of one species. To “hold onto” the introgressed genetic region during the backcrossing process, either visible mutant markers, phenotypic species-differences (such as wing size), or molecular markers are used. Eventually (usually greater than eight generations depending on the size of the introgressed region) the introgression lines are made homozygous for the “foreign” target region within the other species’ genetic background. SILs already have been used for efficient mapping of genes affecting phenotypic differences between Nasonia species (Loehlin et al. 2010b; Loehlin and Werren 2012). To further develop Nasonia SIL resources for QTL mapping, here we used the microarray to genotype 26 SILs. We also tested the applicability of the microarray to bulk segregant analysis, another useful tool for efficiently identifying genomic regions associated with phenotypes of interest (Michelmore et al. 1991). In bulk segregant analysis, a population is divided into two subsamples based on phenotype, and then allele proportions are estimated for each subsample. It is an alternative to genotyping a large population at the level of individuals, and is an economical way to quickly and efficiently identify genomic regions associated with traits of interest. For example, this approach was used in combination with genotyping to identify regions associated with nuclear-cytoplasmic incompatibility in hybrids of N. vitripennis and N. giraulti (Werren et al. 2010). Here we broadly applied the methodology to mapping phenotypes in Nasonia by using the CGH microarray. The CGH array will be of even greater utility if it can be applied to hybrid crosses involving other Nasonia species, such as N. longicornis and N. oneida, as a number of research groups are currently investigating these species (L. Beukeboom, personal communication; Koevoets 2012). Although the array was not designed for this purpose, the close phylogenetic relationship of both N. longicornis and N. oneida to N. giraulti suggest that their DNA would be more likely to hybridize to the N. giraulti oligo than the N. vitripennis oligo (Raychoudhury et al. 2010). We therefore tested how many markers on the microarray can accurately distinguish between N. vitripennis−N. longicornis and N. vitripennis−N. oneida sequences

Temperament and Problem Behaviour during Early Childhood

Some evidence exists for the phenotypic association of problem behaviour in early childhood with temperament in infancy, but little is known about the genetic and environmental mechanisms mediating this association. At the ages of 14, 20, 24, and 36 months, mothers of twins completed the Colorado Childhood Temperament Inventory (CCTI; Buss &amp; Plomin, 1984; Rowe &amp; Plomin, 1977). At age 4, problem behaviour was assessed using maternal reports on the Child Behavior Checklist (CBCL/4-18; Achenbach, 1991). The temperamental trait of Emotionality at all four prior age points correlated signicantly with the CBCL Total Problem Score at 4 years as well as with the broad-band groupings of Internalising the Externalising. In addition, Shyness at all four ages correlated signicantly with the broad-band grouping of Internalising. Longitudinal behavioural genetic analyses indicated that these phenotypic predictions from early temperament to later behaviour problems are largely due to genetic factors. There is growing interest in clinical and developmental psychology in th