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Poster Full Abstracts - Evolution and Quantitative Genetics
Poster board number is above title. The first author is the presenter
264
493A
Characterizing the homomorphic sex chromosomes of
Aedes aegypti
.
Melissa A. Toups
1
, Matthew W. Hahn
1,2
. 1) Biology, Indiana University,
Bloomington, IN; 2) School of Informatics and Computing, Indiana University, Bloomington, IN.
Genetic sex-determination has evolved multiple times in both plants and animals. In many species, there is a nonrecombining region surrounding the sex-
determining locus where sexually antagonistic genes accumulate. The size of this nonrecombining region may contain only a small proportion of the sex
chromosome, as in
Aedes aegypti
, or may include the entire sex chromosome, as in
Drosophila melanogaster
and
Anopheles gambiae
. However, why the
extent of this nonrecombining region varies among species is unknown. We investigated this phenomenon in
Aedes aegypti
, which has been demonstrated to
have only a small nonrecombining region for the last 100-150 million years. The sequenced
Aedes aegypti
genome contains over 1500 scaffolds, but only
~250 scaffolds are mapped onto chromosomes. We developed DNA (RAD) tags and used Illumina sequencing to map ~95% of the largest
Ae. aegypt
i
scaffolds to chromosome using an F6 recombinant population. In order to determine which scaffolds map to the nonrecombining region of the X
chromosome, we compared RAD tag read depth for a male and a female mosquito. Those RAD tags that are in the autosomes or the recombining regions of
the sex chromosomes have equal coverage in both males and females. However, RAD tags that have twice the coverage in a female or are found only in
males are in the nonrecombining region of the sex chromosomes. We used the scaffolds containing these RAD tags to explore the genetic content of the non-
recombining region, gene movement on and off these proto-sex chromosomes, and sex-biased expression in and around the non-recombining region.
494B
Methodological studies on development and duplicate datasets revealed new evidence for Meiotic Sex Chromosomal Inactivation.
Maria
Vibranovski
1
, Jun Wang
1
, Timothy Karr
2
, Manyuan Long
1
. 1) Ecology & Evolution, Univ Chicago, Chicago, IL; 2) Biodesign Institute, Arizona State
University, Tempe, AZ.
The role of the Meiotic Sex Chromosome Inactivation (MSCI) during spermatogenesis proposed initially by Lifschytz and Lindsley [1] has recently
attracted a lot of interest to test if it is an evolutionary force on the chromosomal distribution of sex-biased genes in
Drosophila
. Besides the evidence from
gene expression in spermatogenesis [2,3], here we report our methodological studies on two sets of new supporting data. First, we analyzed the recently
generated data on transcriptional profiling of testis development [4], which took advantage of the spermatogenesis timeline and obtained RNA from the first
wave of germline differentiation in larva testis. In this nicely designed system, the amount of meiotic cells increases with developmental stages. Our
statistical study showed a significant lower expression of X-linked genes in meiosis in comparison to autosomal genes in later developmental phases, which
provided new evidence in support of the MSCI model. Second, our Bayesian models on the expression profile of DNA-based gene duplication in
spermatogenesis using the stage-specific database [3] detected significant new signals from MSCI. If MSCI acts as a general force affecting gene
distribution, it should affect the distribution of both RNA- and DNA-based duplication. Here we confirmed this prediction. These new lines of evidence, in
addition to recent genetic analysis of MSCI and dosage compensation [5], built up further support of the MSCI hypothesis. We reviewed and discussed
related experimental and statistical methods and the application of Bayesian models in testing the MSCI hypothesis. 1.Lifschytz and Lindsley. PNAS USA
1972. 2.Hense et al. PLoS Biol 2007. 3.Vibranovski et al. PLoS Genetics 2009. 4.Mikhaylova and Nurminsky. BMC Biol. 2011. 5.Deng et al. Nature Genet.
2011.
495C
Conservation and expression pattern of overlapping genes in the
Drosophila
genome.
Luyi Wo
1,2
, Yihan Li
3
, Stephen Schaeffer
1,2
. 1) Department of
Biology, Penn State University, University Park, PA 16802; 2) Intercollege Program of Genetics, Penn State University, University Park, PA 16802; 3)
Department of Statistics, Penn State University, University Park, PA 16802.
Drosophila
has compact genome among which 30 % of protein coding genes overlap with each other in a variety of arrangements including straight-
overlapping genes, embedded genes within a parental gene, polycistronic genes and interdigitated genes with straight-overlapping genes and parent-
embedded genes dominating the categories. The comparison of gene structure of overlapping genes among the 12
Drosophila
genomes was used to
determine the selective constraint on these arrangements. In general, overlapping genes are not strictly conserved although the degree of conservation is
consistent with evolutionary distance. Straight overlapping genes are the most conserved type and embedded genes evolve the fastest. Annotation artifacts do
not seem to confound the inference of conservation level. Levels of gene expression of overlapping genes were examined to determine if gene organization
affects levels of expression and dictates levels of conservation. The expression pattern of different types of overlapping cases revealed from microarray data
of
D. melanogaster
seems to be concordant with conservation analysis. Straight overlapping genes overall are expressed universally across various tissues
and developmental stages while embedded genes have a much lower average expression and tend to be expressed in a tissue or developmentally specific
manner. Moreover, median expressions of two counterparts of straight overlapping pair, particularly parallel straight-overlapping pair, are significantly
coupled, while those of parent-embedded pair tend to be inversely related. These data suggest that gene organization can influence levels of gene expression.
Our analysis indicates that there may be transcriptional interference between genes when one gene is embedded within another gene.
496A
Insights into the Mechanisms of Intron Gain and Loss Using Drosophila Genomes.
Paul Yenerall
1
, Leming Zhou
2,3
. 1) Department of Biological
Sciences; 2) Department of Health Information Management; 3) Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA.
Recently it has been shown that intron density may vary among orthologous genes and that the rate of intron gain and loss can vary dramatically in
different species. However, identifying the exact mechanism(s) that generate these structural modifications has proved challenging. Introns are known to
affect gene expression and harbor various non-coding RNAs. Therefore, identifying the mechanism(s) of intron gain and loss will provide novel insight into
the evolution of greater regulation and complexity in eukaryotes. Using 11 Drosophila species and an outlier, Anopheles gambiae, we identified 189 intron
gain and 287 intron loss events. We then analyzed these events to determine what mechanism(s) may have been responsible for these changes. These
analyses enabled us to identify the first documented case of intron gain via transposon insertion in an animal and the first documented case of intron loss via
non-homologous end joining. Our data also suggest that a novel mechanism of intron gain that relies upon or is enabled by transcription may operate in
Drosophila. Furthermore, we have collected all intron gain and loss events reported in the literature that appear to have occurred via a previously proposed