Patterning the Mud Snail Ilyanassa obsoleta: The Role of Cell Signaling and Asymmetric Protein Localization

The polar lobe of Ilyanassa is asymmetrically partitioned into the D lineage of cells. Two of these cells, 3D and 4d, induce proper axial cell fate patterning in the embryo. Based on known embryological data in Ilyanassa, I hypothesized that Notch signaling would be required for this induction. I found that Notch signaling is required for cell fates induced by 4d and is temporally required well after 4d induction. Based on these results, I hypothesize that Notch signaling is involved in a reciprocal induction between the micromeres and the macromeres (endoderm) resulting in the maintenance of micromere fate induction and endoderm specification.Loss of the polar lobe results in the loss of cell fate induction by 3D/4d. Therefore, I hypothesized that proteins are asymmetrically bequeathed to the inducing D lineage cells by the polar lobe. To test this hypothesis, I compared global protein differences between two cell stage intact embryos, lobeless embryos, and isolated polar lobes by 2-Dimensional Electrophoresis analysis. I found several (12) quantitative differences between these samples including four spots enriched in the polar lobe isolates. I identified voltage-dependent anion-selective channel (VDAC) as one of the candidate proteins enriched in polar lobe isolates. I propose that VDAC is asymmetrically distributed by the polar lobe to the D cell and that it may function in D cell induction and mesendoderm fate specification.Lastly, I identify an acetylated tubulin antigen as a marker for cilia. I describe the pattern of cilia differentiation in the developing larvae that results in the formation of two ciliary bands, the prototroch and the metatroch, required for locomotion and feeding. These ciliary bands are conserved among annelid and mollusc larvae. Interestingly, the metatroch is derived from third quartet derivatives in the annelid Polygordius and from second quartet derivatives in the mollusc Crepidula. I provide evidence that the metatroch is derived from the first quartet derivatives in the mollusc Ilyanassa. Thus while the larval metatroch is conserved, its clonal origin is not. Based on these results, I provide support for the hypothesis that the metatroch is not homologous between annelids and molluscs or even among molluscs

Correction: Type 2 Diabetes Risk Allele Loci in the Qatari Population.

[This corrects the article DOI: 10.1371/journal.pone.0156834.]

Type 2 Diabetes Risk Allele Loci in the Qatari Population.

The prevalence of type 2 diabetes (T2D) is increasing in the Middle East. However, the genetic risk factors for T2D in the Middle Eastern populations are not known, as the majority of studies of genetic risk for T2D are in Europeans and Asians.All subjects were ≥3 generation Qataris. Cases with T2D (n = 1,124) and controls (n = 590) were randomly recruited and assigned to the 3 known Qatari genetic subpopulations [Bedouin (Q1), Persian/South Asian (Q2) and African (Q3)]. Subjects underwent genotyping for 37 single nucleotide polymorphisms (SNPs) in 29 genes known to be associated with T2D in Europeans and/or Asian populations, and an additional 27 tag SNPs related to these susceptibility loci. Pre-study power analysis suggested that with the known incidence of T2D in adult Qataris (22%), the study population size would be sufficient to detect significant differences if the SNPs were risk factors among Qataris, assuming that the odds ratio (OR) for T2D SNPs in Qatari's is greater than or equal to the SNP with highest known OR in other populations.Haplotype analysis demonstrated that Qatari haplotypes in the region of known T2D risk alleles in Q1 and Q2 genetic subpopulations were similar to European haplotypes. After Benjamini-Hochberg adjustment for multiple testing, only two SNPs (rs7903146 and rs4506565), both associated with transcription factor 7-like 2 (TCF7L2), achieved statistical significance in the whole study population. When T2D subjects and control subjects were assigned to the known 3 Qatari subpopulations, and analyzed individually and with the Q1 and Q2 genetic subpopulations combined, one of these SNPs (rs4506565) was also significant in the admixed group. No other SNPs associated with T2D in all Qataris or individual genetic subpopulations.With the caveats of the power analysis, the European/Asian T2D SNPs do not contribute significantly to the high prevalence of T2D in the Qatari population, suggesting that the genetic risks for T2D are likely different in Qataris compared to Europeans and Asians

Type 2 Diabetes Risk Allele SNPs.

<p>Type 2 Diabetes Risk Allele SNPs.</p

Population risk allele frequencies.

<p>Population risk allele frequencies (RAF) in <b>A.</b> all Qataris, and <b>B.</b> Q1 and Q2 genetic subpopulations combined, compared to European RAF (obtained from Hapmap [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156834#pone.0156834.ref023" target="_blank">23</a>]) for 37 SNPs previously associated with T2D, with the straight line indicating the regression line of best fit of the data.</p

Comparison of Qatari haplotypes in the regions flanking known single nucleotide polymorphisms (SNPs) associated with type 2 diabetes (T2D) or nearby tag SNPs to the relevant haplotypes of European, Asian, African, or Admixed 1000 Genomes populations.

<p>Admixture deconvolution was used to determine if Qatari haplotypes flanking 64 ‘T2D SNPs’ matched the populations where these SNPs were discovered. Haplotypes were inferred for 100 deeply sequenced Qatari genomes (n = 60 Bedouin Q1, n = 20 Persian Q2, n = 20 African Q3), and divided into 2000 SNP (0.5 cM) intervals. For each interval, SupportMix [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156834#pone.0156834.ref012" target="_blank">12</a>] was used to infer the population with the most similar haplotype, using 1000 Genomes Project Phase 1 as a reference (Admixed = ASW, PUR, CLM, MXL; Asian = CHB, CHS, JPT; African = LWK, YRI; European = TSI, IBS, CEU, FIN, GBR). For each interval containing a T2D risk SNP (n = 64, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0156834#pone.0156834.s003" target="_blank">S1 Table</a>), the percentage of Qatari haplotypes assigned to European, Asian, African, or Admixed was determined. Shown is a heatmap of the results, where each column represents a SNP, and each row represents a 1000 Genomes group. Scaled from blue (0%) to tan (100%), colors represent the % of haplotypes for the SNP that are most similar to each Qatari population (Q1, Q2, or Q3).</p